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"The present study investigated the mechanical properties and microstructure of ultrafine grained (UFG) brass processed by four passes of equal channel angular pressing (ECAP) and annealed at elevated temperatures. The mechanical properties of all samples were assessed using tensile and micro-hardness tests. Microstructure analysis was performed using optical microscopy (OM) and scanning electron microscopy (SEM). Ultimate tensile strengths (UTS) and yield strengths (YS) of 878 and 804 MPa, respectively, ductility of 15%, and hardness of 248 HV were obtained for samples processed by four passes of ECAP with equivalent true strain of 4.20. Annealing at 300°C caused UTS and YS to decrease significantly, to 510 and 408 MPa, respectively, ductility to increase to 28%, and hardness to decrease to 165 HV. Fractography analysis of un-annealed samples after four ECAP passes showed small brittle fractures with shallow dimpling. Ductile failures were found on annealed samples. After four ECAP passes, the microstructure of un-annealed samples was UFG and dominated by lamellar grain with shear band. In contrast, after annealing, the microstructure changed due to recrystallization, showing nucleation and grain growth."

"The presentstudy investigated the mechanical properties and microstructure of ultrafinegrained (UFG) brass processed by four passes of equal channel angular pressing(ECAP) and annealed at elevated temperatures. The mechanical properties of allsamples were assessed using tensile and micro-hardness tests. Microstructureanalysis was performed using optical microscopy (OM) and scanning electronmicroscopy (SEM). Ultimate tensile strengths (UTS) and yield strengths (YS) of878 and 804 MPa, respectively, ductility of 15%, and hardness of 248 HV wereobtained for samples processed by four passes of ECAP with equivalent truestrain of 4.20. Annealing at 300°C caused UTS and YS to decrease significantly,to 510 and 408 MPa, respectively, ductility to increase to 28%, and hardness todecrease to 165 HV. Fractography analysis of un-annealed samples after fourECAP passes showed small brittle fractures with shallow dimpling. Ductilefailures were found on annealed samples. After four ECAP passes, themicrostructure of un-annealed samples was UFG and dominated by lamellar grainwith shear band. In contrast, after annealing, the microstructure changed dueto recrystallization, showing nucleation and grain growth."

"In the present study, natural fibers located in thick outer woody rinds of the metroxylon sago (MS) tree were investigated. The investigation focused on measuring the mechanical properties and observing the microstructures of MS fibers before and after treatment with 5% sodium hydroxide. A scanning electron microscope was used to observe the microstructure of MS fiber, and the results showed that there was a decrease in fiber diameter after mercerization. A porous structure in the cross-section area of untreated fibers was clearly seen, and it was highly compressed after mercerization. The strength of MS fiber increased significantly after it was treated by 5% NaOH solution for two hours. The average ultimate strength of untreated MS fiber was recorded as 46 MPa; treatment with sodium hydroxide resulted in a significant increase in average ultimate strength to 163 MPa. Additionally, the elastic modulus of treated fiber was greater than that of untreated fiber."

"The definition of the physical and mechanical properties of sugarcane trash pellets were necessary for the design considerations relating to storage, handling and processing equipment. The mixing ratios of ground sugarcane trash:cassava starch:water content (1.0:0.25:0.85 and 1.0:0.25:1.40 by weight) and pelleting speeds (100, 120, 140, and 160 rpm) were considered to determine their effects on bulk density, true density, porosity, durability and compressive strength. The results show that the mixing ratio by weight of 1.0:0.25:0.85 and pelleting speed of 120 to 140 rpm were optimum for producing the sugarcane trash pellets. At the moisture content of 12.01% (wb), the bulk density, true density, durability and compressive strength of biomass pellets were in the range of 330.93 to 365.00 kg/m3, 860.38 to 918.43 kg/m3, 99.34 to 99.46 % and 5.15 to 6.43 MPa, respectively."

"[Latar Belakang: Magnesium merupakan biomaterial logam yang berpotensi digunakan sebagai material implan tubuh yang dapat terdegradasi. Syarat magnesium dapat digunakan sebagai material implan biodegradasi adalah laju degradasi magnesium harus memiliki kekuatan mekanis yang cukup dalam jangka waktu tertentu, sampai terjadi penyembuhan tulang, kecepatan resorbsi yang sesuai dengan kecepatan penyembuhan tulang. Aplikasi magnesium sebagai implan yang terdegradasi terhambat karena tingkat tinggi degradasi lingkungan fisiologis. Dengan adanya sifat biodegradasi magnesium maka diperlukan cara bagaimana mencegah atau menekan kecepatan laju biodegradasi sehingga dapat disesuaikan dengan proses penyembuhan tulang. Beberapa penelitian tentang magnesium telah dilakukan untuk mengatasi keterbatasan tersebut, antara lain dengan prosedur Equal Channel Angular Pressing ( ECAP), merupakan salah satu prosedur dari grain refinement yang dapat menurunkan laju degradasi dan meningkatkan sifat mekanis magnesium. Tujuan: Menganalisa sifat mekanis magnesium ECAP dalam perendaman dalam larutan DMEM. Metode: Sifat mekanis magnesium ECAP dianalisis setelah dilakukan perendaman dalam larutan DMEM dengan menggunakan masing-masing sepuluh sampel magnesium ECAP untuk uji bending dan sepuluh sampel magnesium ECAP uji keuletan. Sifat mekanis di analisis menggunakan nilai bending pada uji bending dan nilai keuletan pada uji keuletan. Hasil: Terdapat pengaruh waktu perendaman terhadap nilai bending magnesium ECAP, nilai keuletan magnesium ECAP dan penurunan nilai bending juga nilai keuletan magnesium ECAP pada perendaman dalam larutan fisiologis DMEM., Background: Magnesium is a metal biomaterials that could potentially be used as an implant material which can be decomposed body. Requirement of magnesium can be used as an implant material is the biodegradation rate of degradation must possess sufficient mechanical strenght in a certain period of time until the healing bone resorption speed corresponding to speed bone healing, generally magnesium has a rapid rate of degradation, it is undesirable magnesium deficiency. Application of magnesium as the implant is degraded hampered by high levels of physiological environmental degradation. With the biodegradation rate of speed so it can be adapted to the bone healing process. Several studies on magnesium have been made to overcome these limitations. Among others, the ECAP procedure which is one of the grain refinement procedure that can decrease the rate of degradasi and improve the mechanical properties of magnesium. Objective: To analyze the mechanical properties of magnesium ECAP in DMEM solution immersion. Methods: Mechanical properties of magnesium ECAP analyzed after immersion in DMEM solution by using each of the ten samples of magnesium ECAP for bending test and ten samples of magnesium ECAP for ductility test. Result: There is the effect of immersion time on the value of ECAP bending magnesium, magnesium ECAP ductility value and impairment bending ductility also magnesium ECAP on immersion in physiological solution of DMEM.]"

"This work investigates the fresh, mechanical and durability properties of normal, Self-Compacting Concrete (SCC) and Smart Dynamic Concrete (SDC), which are a new generation of concrete with a lower amount of cementitious content. SDC is a low-fine, self-compacting concrete, that combines the benefits of normal concrete (stability) and self-compacting concrete (fresh properties). Fresh properties such as slump flow, L-box and V-funnel tests were investigated to evaluate its self-compacting properties. Mechanical properties such as compressive, splitting tensile and flexural strengths were also examined to compare its effectiveness with normal concrete. In addition to the fresh and hardened properties, the rapid chloride permeability test was also conducted to check the durability of normal, SCC and SDC concrete mixtures. The test results of the fresh properties clearly showed that SDC exhibited superior flowability in the slump flow, L-box and V-funnel tests within the limits of EFNARC (The European Federation of Specialist Construction Chemical and Concrete Systems) guidelines. The mechanical properties of SDC attained higher compressive strength, splitting tensile strength and flexural strength compared with the normal and SCC concrete mixtures. The rapid chloride permeability tests result of SDC clearly showed that SDC exhibited similar and better results than that of normal and SCC concrete mixtures."

"Penelitian ini didasari adanya masalah crack pada produk bucket tooth yang menggunakan material baja HSLA di industri alat berat setelah 2 bulan pengiriman ke pelanggan(delayed crack). Penelitian sebelumnya mengemukakan bahwa delayed crack ini diduga akibat adanya austenite sisa yang bersifat metastabil. Austenite sisa dapat bertransformasi menjadi martensite sehingga terjadi peningkatan volume dan tegangan internal yang menyebabkan delayed crack. Penelitian ini berfokus mengurangi austenite sisa dengan variasi suhu tempering. Suhu temper yang digunakan adalah 155°C, 205°C, 255°C, dan 305°C Mikrostruktur menunjukkan adanya transformation zone yaitu daerah dimana transformasi fasa yang terjadi belum sempurna. Hasil dari penelitian ini menunjukkan jumlah austenite sisa dan nilai kekerasan menurun ketika suhu temper dinaikkan.

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This research is based on the problem of crack on bucket tooth products using HSLA steel material in heavy equipment industry after 2 months of delivery to customers (delayed crack). Previous studies have suggested that the delayed crack is thought to be due to metastable retained austenite. The retained austenite can be transformed into martensite which causes an increase in internal volume and stress resulting in delayed crack. This research focuses on reducing retained austenite with variations in tempering temperature. Tempering temperatures used were 155°C, 205°C, 255°C, and 305°C. Microstructure shows that there is a transformation zone, which is an area where phase transformation is not yet perfect. The results of this study indicate the amount of remaining austenite and the value of hardness decreases when the temper temperature is raised."

"Aluminium merupakan logam yang mudah untuk dipadukan dengan logam lain. Salah satu paduan aluminium yang sedang banyak dikembangkan adalah seri 7xxx Al-Zn-Mg karena memiliki densitas yang rendah dan sifat mekanis yang baik. Peningkatan sifat mekanis paduan tersebut dapat dilakukan dengan penambahan sejumlah unsur paduan seperti Cr yang dapat memperhalus butir. Selain itu, paduan juga dapat dikeraskan melalui proses pengerasan pengendapan dengan tahapan laku pelarutan, pencelupan cepat, dan penuaan.Untuk memeroleh pengerasan pengendapan yang diinginkan maka tahapan laku pelarutan harus diperhatikan karena akan memengaruhi sejumlah unsur paduan yang dapat larut dan jumlah kekosongan yang terbentuk. Sementara itu, masih sedikit penelitian mengenai pengaruh kombinasi penambahan Cr dan temperatur laku pelarutan pada paduan. Oleh karena itu, penelitian ini bertujuan untuk mengetahui pengaruh penambahan Cr terhadap variasi temperatur laku pelarutan pada paduan Al-4.7Zn-1.7Mg-0.37Cr berat.Paduan dibuat dengan metode squeeze casting. Kemudian dilakukan proses homogenisasi pada temperatur 400 C selama 4 jam. Pada paduan selanjutnya dilakukan proses laku pelarutan pada temperatur 220, 420, dan 490°C yang dilanjutkan dengan pencelupan dalam air. Setelah itu, paduan dilakukan pengerasan penuaan pada temperatur 130°C selama 48 jam. Karakterisasi yang dilakukan berupa pengamatan struktur mikro menggunakan OM Optical Microscope dan SEM-EDS Scanning Electron Microscope - Energy Dispersive Spectroscopy, pengujian kekerasan HRB dan HB, pengujian XRD X-Ray Diffraction, dan STA Simultaneous Thermal Analysis.Hasil penelitian menunjukkan bahwa semakin tinggi temperatur laku pelarutan menyebabkan semakin banyaknya fasa interdendritik yang dapat larut dalam matriks Al. Hal ini dibuktikan dengan fraksi volume fasa interdendritik setelah laku pelarutan 220, 420, dan 490°C yang menurun menjadi 6.67, 4.55, dan 4.14 dari 6.9 setelah homogenisasi. Hasil tersebut menunjukkan bahwa penambahan 0.37 berat Cr tidak berpengaruh terhadap proses pelarutan fasa interdendritik selama laku pelarutan. Sebaliknya, intermetalik Cr seperti Al18Cr2Mg3 dan Cr,Fe Al7 yang terbentuk dapat meningkatkan kekerasan paduan. Kekerasan paduan setelah penuaan pada temperatur 130 C selama 48 jam meningkat menjadi 49.64, 52.54, dan 70.52 HRB pada variasi laku pelarutan 220, 420, 490°C.

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Aluminium is a metal that can be easily alloyed with other metals. One of them is the 7xxx Al Zn Mg series which are the most developed series due to their low density and good mechanical properties. Their mechanical properties can also be strengthened by adding some microalloying element such as Cr which can refine the grain of the alloy. Aside from that, heat treatment such as precipitation hardening through solution treatment, quenching, and ageing can also be done to strengthen its properties. Solution treatment temperature may affect the amount of dissolved interdendritic phase and the number of vacancy, thus it has to be considered in case of getting the desired properties after the precipitation hardening.

Meanwhile, there are very few research on the combined effects of addition of Cr and solution treatment temperature on the properties of this alloy. Therefore, this research is aimed to investigate the effect of Cr and variation of solution treatment temperature on the properties of Al 4.7Zn 1.7Mg 0.37Cr wt. alloy.

The alloy was fabricated by squeeze casting process. Then it was homogenized at 400 C for 4 hours. Three samples were then solutionized at 220, 420, and 490 C for 1 hour and followed by rapid quenching in water. Ageing was then conducted at 130 C for 48 hours. Characterization included microstructure observation by using OM Optical Microscope and SEM EDS Scanning Electron Microscope Energy Dispersive Spectroscopy , hardness testing HRB and HB, XRD X Ray Diffraction, and STA Simultaneous Thermal Analysis.

The results showed that the higher solution treatment temperature increased the dissolution of interdendritic phase to the Al matrix. It was shown by the decreasing of interdendritic volume after solution treatment at 220, 420, and 490°C which became 6.67, 4.55, and 4.14 after 6.9 in the homogenized alloy. The results showed that the 0.37 wt. Cr addition had no effect on the dissolution process of the interdendritic phase. However, the formation of Cr intermetallic such as Al18Cr2Mg3 and Cr,Fe Al7 increased the hardness of the alloy. The hardness of the alloy after ageing at 130°C for 48 hours was increased to 49.64, 52.54, and 70.52 HRB in 220, 420, 490°C solutionized alloy respectively."

"The present work aims to improve the microstructure and hardness related properties of age hardened Al6061-SiC reinforced composites produced by a two stage stir casting method. Three composites with 2, 4, and 6wt. % (35-40?m) of SiC reinforcement are subjected to microstructural examination and hardness test at different locations to analyse the uniform distribution of the reinforcements in the matrix. As-cast composites are solution-treated at 558°C, followed by an aging treatment conducted at 100, 150, and 200°C, during which peak hardness values are noted. The peak aged samples are subjected to hardness and wear tests. In line with the objectives, ranges from 80-100% and 120-145% additional increase in hardness values are observed over as-cast alloy during the aging treatment conducted at 100, 150 and 200°C, respectively. Lower temperature aging shows substantial improvement in hardness and wear resistance over high temperature aging in each respective group. Also higher weight percentages of reinforced composites show excellent wear resistance, due to the presence of eroded iron particles from the counter surface which is regarded as a beneficial effect during the wear test. The presence of SiC particles provides more sites for the nucleation of fine precipitates. These fine precipitates hinder the movement of dislocation and thus increases hardness as well as wear resistance after the precipitation hardening treatment."

"ABSTRAKPenambahan partikel nano SiC kedalam matriks Al6061 menghasilkan material komposit dengan kekuatan mekanis yang tinggi namun tetap mampu mempertahankan sifat ulet. Magnesium sebesar 10% Vf juga ditambahkan sebagai agen pembasah agar didapatkan ikatan yang kuat pada daerah antarmuka. Pada penelitian ini digunakan variasi penambahan partikel nano SiC sebesar 0,05%, 0,10%, 0,15%, 0,20% dan 0,30% untuk mengetahui titik optimal penambahan penguat. Hasil dari penelitian ini menunjukkan penambahan partikel nano SiC optimal di komposisi 0,15%, dengan kekuatan tarik 263,43 MPa, presentase elongasi 7,67%, kekerasan 56,5 HRB, dan harga impak sebesar 0,0550 J/mm2. Peningkatan kekuatan mekanis pada komposit dihasilkan dari kehadiran fasa penguat Mg2Si, distribusi partikel nano SiC yang merata, serta pembasahan yang baik antara matriks dan partikel penguat.

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ABSTRACTThe addition of nano SiC particles to Al6061 matrix has enhancing the mechanical properties of metal matrix composite while the ductility properties still maintained. 10% Vf of magnesium were used as wetting agent to achieve strong interface bonding. In the present work, Al6061 reinforced with various amounts (0,05%, 0,10%, 0,15%, 0,20% and 0,30%) of nano SiC were prepared. Results of this study shows the optimum content of nano SiC in Al6061 matrix were 0,15% Vf, with UTS (Ultimate Tensile Strength) reached 263,43 MPa, 7,67% elongation, hardness up to 56,5 HRB, and 0,0550 J/mm2 impact value. The enhancement of mechanical properties of Al6061/SiC composite were influenced by the presence of Mg2Si phase, good distribution of nano SiC particles, and also good interface bonding between matrix and reinforce.;"