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"Paduan aluminium banyak digunakan di industri manufaktur karena sifatnya yang ringan, mudah di cor, dan tahan korosi. Oleh karena itu, penggunaan paduan aluminium sebagai material turbin Organic Rankine Cycle (ORC) diharapkan mampu meningkatkan efisiensi kerjanya. Untuk meningkatkan kekuatan mekanis aluminium perlu dilakukan penambahan elemen paduan seperti Si, Mg, dan Cu. Selain itu paduan Al-Si-Mg-Cu dapat ditingkatkan sifat mekanisnya dengan melakukan pengerasan penuaan atau pengerasan presipitasi. Studi ini dilakukan untuk mengetahui pengaruh elemen paduan Cu sebesar 0,38, 3,82, dan 6 wt.% pada paduan Al-7Si-4Mg dan mengamati respon paduan terhadap pengerasan penuaan dengan melakukan solution treatment pada temperatur 495°C selama 2 jam, pendinginan cepat, dan penuaan (ageing) pada temperatur 130°C. Karakterisasi yang dilakukan yakni pengujian kekerasan, pengamatan struktur mikro dengan mikroskop optik dan Scanning Electron Microscope (SEM) dilengkapi Energy Dispersive X-Rays Spectroscopy (EDX), dan pengujian Simultaneous Thermal Analysis (STA). Hasil penelitian menunjukkan peningkatan kekerasan as-cast seiring dengan penambahan Cu. Proses pengerasan penuaan juga meningkatkan kekerasan paduan hingga kekerasan puncak sebesar 64,47, 65,8, dan 70,1 HRB pada penambahan Cu berturut- turut 0,38, 3,82, dan 6 wt.%. Penambahan Cu mampu membentuk fasa kedua Al2Cu dan Al5Cu2Mg8Si6 yang akan meningkatkan kekerasan. Pembentukan presipitat GP-zone, θ'', dan θ' terjadi pada temperatur 48, 240, dan 296°C dan tidak ada pengaruh penambahan Cu terhadap temperatur tersebut.

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Aluminum alloys have been used in manufacturing industries because of their light-weight, high castability, and high corrosion resistant. Therefore, the use of aluminum alloys for turbine impeller of Organic Rankine Cycle (ORC) is expected to increase the efficiency. The addition of alloying elements such as Si, Mg, and Cu are necessary to improve mechanical properties. Further improvement of the properties can be achieved through age hardening or precipitation strengthening.

This study was aimed to determine the effect of Cu addition of 0.38, 3.82 and 6 wt.% in Al-7Si-4Mg alloy on hardness and age hardening response. The alloys were solution treated at 495°C for 2 hours, quenched and aged at 130°C. Characterization included hardness test, microstructural observation by an optical microscope and Scanning Electron Microscope (SEM) combined with Energy Dispersive X-Rays Spectroscopy (EDX), as well as Simultaneous Thermal Analysis (STA) testing.

The results showed an increase in as-cast hardness along with the addition of Cu. Peak hardness increased to 64.47, 65.8 and 70.1 HRB by addition of 0.38, 3.82 and 6 wt.% Cu, respectively. The addition of Cu promoted the formation of Al2Cu and Al5Cu2Mg8Si6 which contibuted to higher as-cast hardness. Formation of GP-zone, θ'' dan θ' was observed at 48, 240 and 296°C, respectively and no effects of Cu on these temperatures."

"Aluminium memiliki sifat yang ringan dan tahan korosi, sehingga banyak digunakan di bidang manufaktur. Penggunaan material aluminium sangat efektif untuk meningkatkan efisiensi turbin pembangkit tenaga listrik Organic Rankine Cycle (ORC). Aluminium seri 7xx (Al-Zn) merupakan pilihan yang diperhitungkan pada turbin ORC karena memiliki kekuatan yang tinggi dibanding seri lainnya. Untuk lebih meningkatkan kekuatan Al-Zn, ditambahkan unsur Mg dan Cu serta pemberian laku pengerasan penuaan. Penelitian kali ini mempelajari pengaruh penambahan Cu sebesar 0, 1, 3 dan 5 wt.% pada paduan Al-9Zn-4Mg (wt.%). Paduan dibuat dengan proses investment casting pada cetakan berbentuk impeller turbin. Pada paduan dilakukan proses laku pelarutan pada temperatur 460°C selama 2 jam dan dilanjutkan proses penuaan pada temperatur 130°C. Karakterisasi meliputi pengujian kekerasan untuk mengamati respon pengerasan penuaan, pengamatan struktur mikro dan pengujian Differential Scanning Calorimetry (DSC). Struktur mikro diamati menggunakan mikroskop optik dan Scanning Electron Microscope (SEM) yang dilengkapi dengan Energy Dispersive Spectroscopy (EDS). Hasil penelitian menunjukkan bahwa penambahan Cu ke dalam paduan Al-9Zn- 4Mg menurunkan kekerasan awal (2 jam) akibat segregasi kompeks Cu-V ke batas butir yang akan melunakkan dan memperlebar batas butir, Namun kandungan penambahan Cu meningkatkan kekerasan puncak, walau tidak terlalu signifikan akibat tingginya kandungan Zn dan Mg. Selama pengerasan penuaan terjadi reaksi eksotermik yaitu pembentukan GP zone, presipitat η’ (MgZn2) dan presipitat η (MgZn2) serta reaksi endotermik dari dissolution GP zone dan presipitat η. Sementara, fasa kedua yang ditemukan adalah MgZn2 dan Al7Cu2Fe di batas butir.

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Aluminium is a light-weight material and possesse high corrosion resistance, so that it is widely used in manufacturing industries. Aluminium alloy is a candidate to be used as turbine impeller in an Organic Rankine Cycle (ORC) power plant system. Al 7xx series (Al-Zn) has the highest strength compared to other aluminium series, therefore it is suitable for ORC turbine. To futher increase the strength of Al-Zn alloys, Mg and Cu are added as well as age hardening treatment.

This research studied Al-9Zn-4Mg alloys with Cu content of 0, 1, 3 and 5 wt.%. The alloys were produced through investment casting taking the shape of turbine impeller. The samples were solution treated at 460°C for 2 hours and then aged at 130°C. The characterization included hardness testing to observed response of age hardening, microstructural observation and Differential Scanning Calorimetry (DSC) testing. Microstructural observation was conducted by optical microscope and Scanning Electron Microscope (SEM) which was combined with Energy Dispersive Spectroscopy (EDS).

The results showed that addition of Cu initially decreased the hardness during early ageing ( 2 hours) due to segregation of Cu-V complexes toward the grain boundaries which then decrease the hardness and enlarge the grain boundaries. However, the peak hardness is increased by addition of Cu although not as significant due to high concentration of Zn and Mg. exothermic reaction of formation of GP zone, η’ (MgZn2) and η (MgZn2) was found during precipitation process while endothermic reaction were observed due to dissolution of GP zone and η (MgZn2). Presence of MgZn2 and Al7Cu2Fe were also observed in grain boundaries."

"Aluminium komposit merupakan material yang dikembangkan untuk aplikasi balistik dengan tujuan untuk memperoleh pada penggunaan material yang lebih ringan sebagai pengganti baja. Untuk aplikasi balistik dibutuhkan material dengan kekerasan yang tinggi namun tidak mengorbankan ketangguhannya, sehingga dia mampu memecah dan menahan penetrasi peluru. Untuk itu, aluminium yang memiliki kekuatan yang rendah perlu ditambahkan dengan unsur-unsur paduan dan penguat SiC. Selain itu komposit aluminium dilakukan proses pengerasan penuaan untuk mendapatkan kekuatan material yang lebih baik.Penelitian kali ini menggunakan paduan Al-8Zn-4Mg berpenguat 15 vol. % SiC dengan variasi 0, 1 dan 3 wt. % Cu hasil squeeze casting. Selanjutnya pada komposit dilakukan proses laku pelarutan pada temperatur 500 oC selama satu jam dan dilanjutkan proses penuaan pada temperatur 200 oC. Karakterisasi yang dilakukan meliputi pengujian kekerasan untuk membuat kurva penuaan, impak, analisis mikrostruktur dan pengujian balistik tipe III berkaliber 7.62 mm.Hasil penelitian ini menunjukkan bahwa dengan penambahan Cu akan meningkatkan kekerasan puncak akibat adanya presipitat selama proses pengerasan penuaan. Semua sampel mencapai kekuatan puncak dalam waktu 2 jam dengan kekerasan bervariasi dari 83.36 sampai 91.17 HRB. Hal ini tidak sama dengan harga impak dimana mengalami penurunan seiring dengan penambahan Cu dari 45440.86 sampai 38533.40 Joule/m2. Hasil pengujian balistik menunjukkan bahwa semua pelat komposit tidak mampu menahan penetrasi peluru pada pengujian balistik tipe III.

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Aluminium composite materials are widely developed for ballistic application to obtain the use of lighter materials as a substitute for steel. Ballistic application requires, materials with high strength and good toughness, so they are able to break the tip of bullets and resist penetration. Therefore, aluminium with low hardness and strength is combined with alloying elements and SiC to produce high strength materials. Age hardening is also conducted to further improve its toughness.

This research studied Al-8Zn-4Mg alloy with varied content of 0,1 and 3 wt. % Cu and reinforced by 15 % SiC produced by squeeze casting methode. The composite was solution treated at 500 oC for 1 hour and then aged at 200 oC. The characterization included hardness testing to construct ageing curves, impact testing, microstructure observation and ballistic testing (type III bullets of 7.62 mm).

The result shows that the addition of Cu increasing the peak hardness due to the presence of precipitates. All samples reached peak hardess within 2 hours with the value of 83.36 to 91.17 HRB. However, impact strength decreases with the addition of Cu. Ballistic testing showed that all composite plates with varied Cu content could not stop the bullets."

"Aluminium dan paduannya tengah dikembangkan sebagai sudu turbin Organic Rankine Cycle (ORC) dalam sistem pembangkit listrik karena sifatnya yang ringan, mudah dibentuk dan tahan korosi. Paduan aluminium 7XXX yang mengandung Zn dan Mg dapat ditingkatkan sifat mekanisnya melalui proses pengerasan penuaan. Penambahan Ti dapat semakin meningkatkan kekerasan melalui mekanisme penguatan batas butir.Penelitian ini bertujuan untuk mengetahui pengaruh penambahan 0, 0.02, 0.05 dan 0.25 wt.% Ti dalam paduan Al-10Zn-6Mg. Pembuatan paduan dilakukan dengan proses squeeze casting. Proses homogenisasi dilakukan pada pada temperatur 400 °C selama 4 jam. Peningkatan kekerasan dilakukan dengan pengerasan pengendapan yaitu laku pelarutan pada temperatur 440 °C selama 4 jam, pencelupan cepat dan penuaan pada temperatur 130 °C selama 200 jam. Karakterisasi meliputi pengujian kekerasan untuk mengamati respon pengerasan penuaan dengan Rockwell B, pengujian impak, pengamatan struktur mikro dan pengujian Simultaneous Thermal Analysis (STA). Struktur mikro diamati menggunakan mikroskop optik dan Scanning Electron Microscope (SEM) yang dilengkapi dengan Energy Dispersive Spectroscopy (EDS).Hasil penelitian menunjukkan bahwa penambahan Ti sebesar 0, 0.02, 0.05 dan 0.25 wt.% Ti meningkatkan kekerasan as-cast sebesar 49.72, 49.92, 52.02 dan 53.08 HRB akibat pengecilan secondary dendrite arm spacing (SDAS) menjadi 22.78, 22.69, 19.56 dan 16.55µm. Penuaan pada temperatur 130 ºC meningkatkan kekerasan, namun penambahan Ti tidak menunjukkan pengaruh signifikan terhadap kekerasan puncak dan harga impak. Fasa kedua yang terbentuk selama proses solidifikasi adalah T (Mg32(Al,Zn)49, β (Al8Mg5) dan TiAl3 sementara penuaan menghasilkan endapan GP Zone, ƞ? dan ƞ (MgZn2).

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Aluminum alloys are being developed as turbin impeller of Organic Rankine Cycle (ORC) in power plant generation system, due to lightweight, formable and corrosion resistant. Al 7xxx series with Zn and Mg alloying elements are one options because of increase the mechanical properties in high temperatures due to age hardening. Ti as grain refiner was added to further improve hardness through grain boundary strengtening mechanism.

This research aimed to find out the effects of 0, 0.02, 0.05 and 0.25 wt.% Ti addition in the Al-10Zn-6Mg alloys. The alloys were produced by squeeze casting process. Homogenization was conducted at 400°C for 4 hour followed by solution treatment at 440 °C for 1 hour, quenching and ageing at 130 °C for 200 hour. Age hardening response was followed by Rockwell B hardness testing. Other characterization included impact testing, Simultaneous Thermal Analysis (STA) and microstructural analysis by using optical microscopy and Scanning Electron Microscope (SEM) with EnergyDispersive X-ray (EDX).

The result showed that addition of 0, 0.02, 0.05 and 0.25 wt.% Ti increased the as-cast hardness of Al-10Zn-6Mg to 49.72, 49.92, 52.02 and 53.08 HRB due to decreasing of secondary dendrite arm spacing (SDAS) to 22.78, 22.69, 19.56 and 16.55µm, respectively. Ageing at 130 ºC increased the hardness of the alloys, but addition of Ti did not affect the peak hardness and the impact values. The second phases formed during solidification were found to be T (Mg32(Al,Zn)49, β (Al8Mg5) dan TiAl3, while the precipitates formed during ageing were GP Zone, ƞ? and ƞ (MgZn2)."

"[Stainless steel merupakan material yang paling banyak digunakan dalam pembuatan turbin pembangkit tenaga listrik Organic Rankine Cycle (ORC), karena densitasnya yang tinggi, membuat kinerja turbin menjadi kurang efisien. Salah satu alternatif penggantinya adalah paduan aluminium seri 7xx.x (Al-Zn-Mg) yang memiliki sifat mekanik terbaik dibandingkan dengan seri yang lainnya. Sifat mekanik paduan tersebut dapat ditingkatkan dengan penambahan Cr serta perlakuan pengerasan penuaan. Pada penelitian ini dipelajari pengaruh penambahan Cr sebesar 0, 0.03, 0.1 dan 0.46 wt. % pada paduan Al-10Zn-6Mg. Paduan dibuat dengan proses squeeze casting dengan tekanan sebesar 76 MPa. Pelat selanjutnya dihomogenisasi pada temperatur 400 oC selama 4 jam dan dilakukan proses pengerasan penuaan dengan melakukan solution treatment pada temperatur 440 oC selama 2 jam, pendinginan cepat, dan penuaan pada temperatur 130 oC. Karakterisasi yang dilakukan diantaranya adalah pengujian kekerasan Rockwell B, pengujian impak, pengamatan struktur mikro dengan mikroskop optik dan Scanning Electron Microscope (SEM) dilengkapi dengan Energy Dispersive X-Rays (EDX), dan Simultaneous Thermal Analysis (STA). Hasil penelitian menunjukkan bahwa penambahan Cr sebesar 0.03, 0.1 dan 0.46 wt. % meningkatkan kekerasan paduan Al-10Zn-6Mg menjadi 50.9, 52.8, 53.2 HRB yang diakibatkan oleh pengecilan ukuran SDAS, pembentukan larutan padar Cr di dalam matriks serta pembentukan fasa kedua (CrFe)Al7 dan CrAl7 pada penambahan 0.46 wt. % Cr. Penambahan Cr belum memberikan pengaruh yang signifikan terhadap proses pemanasan.

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Stainless steel is most widely used in manufacturing of turbine impeller of Organic Rankine Cycle (ORC). However, due to its high density, the performance of turbine becomes less efficient. One alternative to substitute stainless steel is 7xx.x series aluminum alloys (Al-Zn-Mg) which have good mechanical properties compared to other series. Their mechanical properties can be improved by the addition of Cr as well as precipitation hardening process. This research studied the effect of addition of Cr with variation of 0, 0.03, 0.1 and 0.46 wt. % in Al-10Zn-6Mg alloys. The samples were made by squeeze casting process with pressure of 76 MPa. The plate was then homogenized at 400 ° C for 4 hours, followed by precipitation hardening process which consisted of solution treatment at 440 ° C for 2 hours, water quenching and ageing 130 ° C. Characterization was done by Rockwell B hardness testing, impact testing, microstructure observation by using optical microscope and Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-rays (EDX) and Simultaneous Thermal Analysis (STA). The results showed that addition of Cr 0.03, 0.1 and 0.46 wt. % increase the hardness of Al-10Zn-6Mg aloys to 50.9, 52.8, 53.2 HRB respectively, which were due to reduction of SDAS, solid solution strengthening of Cr in the matrix and the formation of (CrFe)Al7 and CrAl7 second phases when 0.46 wt. % Cr was added. During ageing process also increased hardness alloys, but Cr were not have a significant impact on the transformation phase. The addition of Cr not have a significant influence on the heating process.

;Stainless steel is most widely used in manufacturing of turbine impeller of Organic Rankine Cycle (ORC). However, due to its high density, the performance of turbine becomes less efficient. One alternative to substitute stainless steel is 7xx.x series aluminum alloys (Al-Zn-Mg) which have good mechanical properties compared to other series. Their mechanical properties can be improved by the addition of Cr as well as precipitation hardening process. This research studied the effect of addition of Cr with variation of 0, 0.03, 0.1 and 0.46 wt. % in Al-10Zn-6Mg alloys. The samples were made by squeeze casting process with pressure of 76 MPa. The plate was then homogenized at 400 ° C for 4 hours, followed by precipitation hardening process which consisted of solution treatment at 440 ° C for 2 hours, water quenching and ageing 130 ° C. Characterization was done by Rockwell B hardness testing, impact testing, microstructure observation by using optical microscope and Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-rays (EDX) and Simultaneous Thermal Analysis (STA). The results showed that addition of Cr 0.03, 0.1 and 0.46 wt. % increase the hardness of Al-10Zn-6Mg aloys to 50.9, 52.8, 53.2 HRB respectively, which were due to reduction of SDAS, solid solution strengthening of Cr in the matrix and the formation of (CrFe)Al7 and CrAl7 second phases when 0.46 wt. % Cr was added. During ageing process also increased hardness alloys, but Cr were not have a significant impact on the transformation phase. The addition of Cr not have a significant influence on the heating process.

, Stainless steel is most widely used in manufacturing of turbine impeller of Organic Rankine Cycle (ORC). However, due to its high density, the performance of turbine becomes less efficient. One alternative to substitute stainless steel is 7xx.x series aluminum alloys (Al-Zn-Mg) which have good mechanical properties compared to other series. Their mechanical properties can be improved by the addition of Cr as well as precipitation hardening process. This research studied the effect of addition of Cr with variation of 0, 0.03, 0.1 and 0.46 wt. % in Al-10Zn-6Mg alloys. The samples were made by squeeze casting process with pressure of 76 MPa. The plate was then homogenized at 400 ° C for 4 hours, followed by precipitation hardening process which consisted of solution treatment at 440 ° C for 2 hours, water quenching and ageing 130 ° C. Characterization was done by Rockwell B hardness testing, impact testing, microstructure observation by using optical microscope and Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-rays (EDX) and Simultaneous Thermal Analysis (STA). The results showed that addition of Cr 0.03, 0.1 and 0.46 wt. % increase the hardness of Al-10Zn-6Mg aloys to 50.9, 52.8, 53.2 HRB respectively, which were due to reduction of SDAS, solid solution strengthening of Cr in the matrix and the formation of (CrFe)Al7 and CrAl7 second phases when 0.46 wt. % Cr was added. During ageing process also increased hardness alloys, but Cr were not have a significant impact on the transformation phase. The addition of Cr not have a significant influence on the heating process.

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"[ABSTRAKMaterial yang digunakan pada kendaraan balistik harus memiliki kekerasan yang tinggi, namun tidak mengorbankan sifat ketangguhannya.Komposit aluminium berpotensi untuk digunakan sebagai material pengganti bajapada kendaraan balistikkarena ringan dan sifat mekanis aluminium sebagai matriks mampu ditingkatkan dengan penambahan unsur-unsur paduan dan partikel penguat SiC. Selain itu, dapat dilakukan pengerasan penuaan pada komposit aluminium untuk meningkatkan kekuatan.Penelitian kali ini menggunakan paduan Al-6Zn-6Si-5Mg berpenguat 10 vol. % SiC dengan variasi penambahan 0, 1, dan 3 wt % Cu hasilsqueeze castingyang berbentuk pelat berketebalan 25 mm. Pelat hasil cor kemudiandihomogenisasi pada temperatur 440 °C selama 24 jam untuk menyeragamkan butir. Selanjutnya dilakukan laku pelarutan dan pengerasan penuaan terhadap pelat komposit ini pada temperatur 200 °C.Karakterisasi komposit aluminium berpenguat SiC tersebut meliputi pengujian kekerasan untuk membuat kurva penuaan, pengujian impak, pengamatan struktur makro dan mikro dengan mikroskop optik dan SEM, serta pengujian balistik tipe III berkaliber 7.62 mm.Hasil penelitian ini menunjukkan bahwa penambahan kandungan Cu menyebabkan peningkatan kekerasan pada kondisi as-cast. Penambahan Cu tidak memberi pengaruh terhadap respons pengerasan penuaan, disebabkan oleh tingginya kadar Zn, Mg, dan Si pada paduan ini. Penambahan kandungan Cu sebesar 0, 1 dan 3 wt.% menghasilkan kekerasanpuncak senilai 49.94, 52.92 dan 54.89 HRB berturut-turut selama 4 jam pada temperatur penuaan 200 °C. Penambahan kandungan Cu dari 0, 1 dan 3 wt.%menghasilkan harga impak 18.7 x 10-3, 26.6 x 10-3, dan 25.5 x 10-3J/mm2. Hasil pengujian balistik menunjukkan bahwa semua pelat komposit belum mampu menahan penetrasi peluru pada pengujian balistik tipe III.

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ABSTRACTBallistic application requires materials with high strength and good toughness. Aluminium composite materials is potential to subsitute steel as a material for ballistic vehicle due to its light weight and improved properties by addition of alloying elements and SiC reinforced particles. Age hardening can also applied to this material to improve its properties.This research studied Al-6Zn-6Si-5Mgreinforced by 10 vol. %SiC with varied content of 0, 1, and 3 wt % Cu with 25 mm thickness produced bysqueeze casting. The composite was homogenized at 440 °C for 24 hours, followed by solution treatment at 460 °C for 1 hour and then aged at 200 °C. The characterization included hardness testing to construct the ageing curve, impact testing, microstructure observation by using optical microscope and SEM, as well astype III ballistic testing.The results showed that the addition of Cu increased hardness in as-cast condition. However, addition of Cu did not give any increased response to age hardening due to high content of Zn, Mg, and Si. The peak hardness of 0, 1 and 3 wt. % Cu added composites was 49.94, 52.92 and 54.89 HRB, respectively, achieved after 4 hours at 200 °C. Impact strength decreased with the addition of Cu. Type III ballistic testing type III results showed that all plates could not stop the bullets penetration, Ballistic application requires materials with high strength and good toughness. Aluminium composite materials is potential to subsitute steel as a material for ballistic vehicle due to its light weight and improved properties by addition of alloying elements and SiC reinforced particles. Age hardening can also applied to this material to improve its properties.This research studied Al-6Zn-6Si-5Mgreinforced by 10 vol. %SiC with varied content of 0, 1, and 3 wt % Cu with 25 mm thickness produced bysqueeze casting. The composite was homogenized at 440 °C for 24 hours, followed by solution treatment at 460 °C for 1 hour and then aged at 200 °C. The characterization included hardness testing to construct the ageing curve, impact testing, microstructure observation by using optical microscope and SEM, as well astype III ballistic testing.The results showed that the addition of Cu increased hardness in as-cast condition. However, addition of Cu did not give any increased response to age hardening due to high content of Zn, Mg, and Si. The peak hardness of 0, 1 and 3 wt. % Cu added composites was 49.94, 52.92 and 54.89 HRB, respectively, achieved after 4 hours at 200 °C. Impact strength decreased with the addition of Cu. Type III ballistic testing type III results showed that all plates could not stop the bullets penetration]"

"ABSTRAKBatasan rasio komposisi Cu : Mg yang mengalami fenomena rapid hardening pada paduan Al-Cu-Mg masih belum diketahui secara pasti. Selain itu juga, pengaruh komposisi Cu dan Mg pada rentang yang lebar terhadap respons penuaan belum pernah diamati dengan rinci. Penelitian ini mengamati pengaruh variasi komposisi Cu dan Mg pada fenomena rapid hardening dan respons penuaan pada paduan Al-Cu-Mg. Karakterisasi meliputi pengujian kekerasan Vickers dan pengamatan mikrostruktur dengan menggunakan mikroskop optik, SEM/EDS (Scanning Electron Microscopy/Energy Dispersive Spectroscopy), dan TEM (Transmission Electron Microscopy). Hasil menunjukkan bahwa peningkatan komposisi Cu dan Mg memperkecil ukuran butir dan meningkatkan fraksi volume partikel intermetalik yang terbentuk. Pada rentang komposisi Cu (1.1-3.0 at.%) dan Mg (1.7-3.5 at.%) yang lebar, pada paduan Al-Cu-Mg, batas rasio terjadinya fenomena rapid hardening belum dapat ditentukan dengan tepat. Komposisi dimana terjadi fenomena rapid hardening pada penuaan temperatur 170 oC ternyata fluktuatif. Pada saat rapid hardening (waktu penuaan 60 detik), loop dislokasi merupakan satu-satunya mikrostruktur yang ditemukan, sementara pada saat kekerasan puncak, ditemukan presipitat fasa S.

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ABSTRACTThe range of Cu : Mg ratio in Al-Cu-Mg alloy which undergoes rapid hardening has not been clearly understood. The ageing response on this alloy with wide Cu : Mg ratio has not been fully evaluated. This study observed the effect of Cu : Mg ratio on rapid hardening and ageing response of Al-Cu-Mg alloys. Characterization included Vickers Hardness Testing and Microstructural Observation by using Optical Microscope, SEM/EDS (Scanning Electron Microscopy/Energy Dispersive Spectroscopy), and TEM (Transmission Electron Microscopy). The results showed that the higher the Cu and Mg content, the smaller the grain size and the higher the volume fraction of intermetallic particles. Within the range of 1.1-3.0 at.% Cu and 1.7-3.5 at.% Mg, the Cu : Mg ratio at which rapid hardening occurred, was not able to define. The data was fluctuative at the ageing temperature of 170 oC. After rapid hardening (for 60 seconds of ageing), dislocation loops were observed. While at the peak hardness, the microstructure was strengthened by S precipitates."

"Kendaraan taktis (rantis) merupakan kendaraan yang digunakan dalam dunia militer dengan komponen penyusun utama berupa baja yang berat dengan sifat balistik yang baik. Diperlukan material pengganti yang lebih ringan dengan sifat balistik yang endekati. Aluminium komposit merupakan material yang diharapkan mampu menjadi pengganti baja pada kendaraan taktis dikarenakan sifatnya yang ringan, mudah dipadu dan dapat dilaku panas. Penelitian menggunakan paduan Al-12Zn-5Mg-1Cu-1Si dengan variasi penguat ZrO2 sebesar 5, 7,5 dan 10 vol. % hasil squeeze casting dengan proses laku pelarutan pada temperatur 450 oC selama 1 jam kemudian dlakukan pendinginan cepat menggunakan media air pada temperatur ruang dan dilakukan penuaan selama 200 jam. Karakterisasi yang dilakukan berupa pengujian kekerasan, impak, pengamatan struktur makro dan mikro, SEM, EDX dan pengujian balistik tipe IIIA. Hasil penelitian menunjukkan bahwa pengerasan penuaan akan meningkatkan kekerasan komposit. Semakin tinggi kandungan ZrO2 akan menyebabkan turunnya kekerasan dan naiknya harga impak dikarenakan dua faktor yang mempengaruhi, yaitu porositas dan peningkatan ketangguhan oleh penguat ZrO2. Hasil pengujian balistik didapatkan bahwa lapisan pelat ketiga mampu menahan beban peluru akan tetapi pelat mengalami hancur disebabkan harga impak pelat yang rendah dan hadirnya porositas yang mempercepat terjadinya kegagalan.

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Tactical vehicle is used in military need with steel as the main component that is heavy with good ballistic property, so we need a subtitution material which is lighter and having good ballistic property. Aluminium composite is designed to subtitute the use of steel in tactical vehicle due to its low weight and strength.

This study used Al-12Zn-5Mg-1Cu-1Si with the variation of ZrO2 by 5, 7,5 and 10 vol. % that was produced by squeeze casting. The composite were solution treated at 450 oC for 1 hour and then quenched in water at room temperature and aged for 200 oC. The characterization included hardness and impact tests, analysis of microstructure and macrostructure, SEM, EDX and type IIIA of ballistic test.

The results show that by the increase in ZrO2 led to the decrease in hardness and the impact. These were due to two affecting factors, they are porosity and the ZrO2 that will increase the toughness. The ballistic test showed that the third plate could resist the bullet but the plate was broken due to the low impact value and the presence of porosity."

"Paduan aluminium AC4B umum digunakan untuk komponen cylinder head dengan metode Low Pressure Die Casting (LPDC). Penambahan unsur stronsium dan titanium dimaksudkan untuk mengurangi kegagalan yang terjadi pada proses pengecoran akibat cacat, diantaranya penyusutan, porositas, dan misrun. Selain itu, untuk meningkatkan kekerasan dari paduan perlu dilakukan pengerasan penuaan. Faktor yang mempengaruhi pada pengerasan penuaan adalah proses perlakuan pelarutan yang berperan untuk memerangkap vacancy dan melarutkan semua unsur didalam matriks. Kombinasi penambahan Ti dan Sr serta perlakuan pelarutan diamati pada penelitian ini. Penelitian ini mempelajari pengaruh perlakuan pelarutan pada temperatur 480, 500, dan 520 oC dengan waktu tahan 30 dan 120 menit pada paduan AC4B dengan kandungan 0.078 wt. % Ti dan 0.02 wt. % Sr. Dilakukan pengamatan peningkatan kekerasan setelah proses penuaan pada temperatur 200°C untuk waktu hingga 96 jam serta mengamati evolusi struktur mikro pada paduan tersebut. Hasil penelitian menunjukkan dengan meningkatnya temperatur serta waktu tahan lebih lama lebih melarutkan fasa-fasa kedua kedalam matriks. Sehingga pada waktu tahan yang lebih lama melarutkan fasa silikon dan fasa intermetalik yang berbentuk jarum menjadi lebih halus dan terjadi fragmentasi. Pada AC4B dengan kandungan 0.078 wt. % Ti dan 0.02 wt. % Sr setelah proses penuaan memiliki kekerasan yang lebih tinggi pada temperatur pelarutan 520°C selama 30 menit, yakni 63.32 HRB.

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AC4B aluminium alloys is commonly used to produce cylinder head with low pressure die casting methode. Strontium and titanium added to reduce reject in casting process, such as shrinkage, porosity, and misrun. To increase their hardness, the alloys are usually precipitation hardened. Crucial factor that affect age hardening respone is the solution treatment process, in which vacancies are trapped and solute elements are dissolved in the matrix. Combination of Ti and Sr addition on solution treatment process was studied.

This research analyzed the solution treatment of 480, 500, and 520 oC with 30 and 120 minutes of holding time on AC4B alloys added with 0.078wt. % Ti and 0.02 wt.% Sr. Age hardening was followed during ageing at 200°C for 96 hours and evolution of microstructure was observed.

Research results showed that the higer the temperature and longer the holding time dissolved more second phases into the matrix. Longer holding time dissolved silicon and intermetalic phases, changing their morphology into finer and fragmented phases. AC4B alloys with 0.078 wt. % Ti and 0.02 wt.% Sr had the higher hardness of 63.32 HRB after solution treatment at 520°C for 30 minutes."

"Baja diketahui merupakan material yang sering digunakan untuk kendaraan tempur. Densitas baja yang berat membuat mobilitas baja sebagai kendaraan tempur menjadi kurang efektif. MMC dengan matriks alumunium belakangan ini telah dikembangkan sebagai material alternatif balistik, karena memiliki berat yang ringan dan sifat mekanis yang baik. Sehingga pada penelitian ini digunakan komposit dengan matriks paduan alumunium berpenguat SiC.Dalam penelitian ini, dikembangkan komposit dengan matriks paduan Al - 8 wt. % Zn dengan variasi 3, 4, dan 5 wt. % Mg berpenguat 15 vol. % SiC hasil squeeze casting. Untuk meningkatkan ketangguhan komposit saat menerima beban balistik, dilakukan laku pelarutan pada suhu 500 oC selama 1 jam kemudian dilakukan pengerasan penuaan pada suhu 200 oC. Karakterisasi material yang dilakukan diantaranya adalah pengujian kekerasan untuk mendapatkan kurva penuaan, pengujian impak, analisis fraktografi dan pengamatan mikrostruktur dengan menggunakan mikroskop optik dan SEM. Sebagai target akhir dari penelitian ini, dilakukan pengujian balistik menggunakan senjata SPR 1 dengan peluru kaliber 7.62 mm.Hasil penelitian ini menunjukkan bahwa kekerasan puncak komposit semakin meningkat dengan bertambahnya kandungan Mg, sementara energi impak dari komposit akan semakin menurun. Nilai kekerasan puncak tertinggi didapatkan pada kandungan 5 wt. % Mg senilai 88.8 HRB. Dan nilai terkecil dari energi impak didapat pada kandungan 5 wt. % Mg senilai 2.83 J. Dengan dilakukan pengerasan penuaan pada komposit, ketangguhan akan meningkat dibandingkan pada komposit hasil pengecoran. Komposit ini tidak mampu untuk menahan penetrasi peluru kaliber 7.62 mm.

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Steel is widely used for armour vehicles. The high density of steel leads to less mobility of the vehicle. MMC with aluminium matrix has recently been developed as an alternative for ballistic material, because of its light weight and good mechanical properties. So this study evaluated alumunium alloy matrix composites strengthened by SiC and precipitation hardening.

This research developed Al - 8 wt. % Zn matrix composite with varied content of 3, 4, and 5 wt. % Mg strengthened by 15 vol. % SiC produced by squeeze casting. To improve the toughness during ballistic loading, composites were solution treated at 500 oC for 1 hour and then aged at 200 oC. Characterizations included hardness testing to construct ageing curves, impact testing, and fractography analysis and microstructure observation using optical microscopy and SEM. As the final target of this research, composite underwent ballistic testing by using SPR 1 rifle gun with of 7.62 mm bullet.

The results show that the higher the Mg content, the higher peak hardness of composite increase, but the lower impact energy. The highest peak hardness of the composite is proceeded by 5 wt. % Mg content with the hardness value 88.8 HRB. The lowest impact energy of the composite is proceeded by 5 wt. % Mg content with the impact energy value 2.83 J. With age hardening, the toughness of the composite higher than that of as cast condition. This composite were not able to resist penetration of projectile with 7.62 mm bullet."