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"Paduan ingat bentuk berbasis tembaga adalah salah satu alternatif yang lebih murah dan mudah untuk difabrikasi dibandingkan dengan paduan ingat bentuk komersial berbasis Ni-Ti. Penggunaan paduan Cu-Zn-Al sebagai paduan ingat bentuk memiliki kelemahan berupa sifat ingat bentuk rendah dan kecenderungan membentuk stabilitas martensit yang dapat dihindari dengan perlakuan panas dan metode pencelupan. Maka, penelitian ini mempelajari pengaruh metode pencelupan terhadap karakteristik fasa martensit yang terbentuk dan pemulihan regangan dari paduan dengan komposisi Cu-25,8Zn-4,8Al wt.%. Sampel paduan hasil fabrikasi pengecoran gravitasi diberikan perlakuan panas berupa homogenisasi pada temperatur 850 oC dengan tujuan mendapatkan struktur mikro fasa yang lebih homogen sebelum dilakukan betatizing pada temperatur 850oC selama 30 menit diikuti dengan proses pencelupan dengan variasi pencelupan langsung (direct quench, DQ) dan pencelupan naik (up-quench, UQ). Karakteriasi komposisi paduan dilakukan menggunakan Optical Emission Spectroscopy (OES), observasi struktur mikro fasa yang terbentuk menggunakan mikroskop optik dan Scanning Electron Microscope- Energy Dispersive X-Ray Spectroscopy (SEM-EDS), pengujian X-ray Diffractory (XRD), pengujian kekerasan microvickers, pengujian Differential Scanning Calorymetry (DSC) untuk mendapatkan temperatur transformasi, serta pengujian bending untuk mendapatkan nilai pemulihan regangan. Struktur mikro paduan hasil pengecoran dan homogenisasi terdiri atas dua fasa yaitu α [A1] dan β[D03]. Metode pencelupan langsung dan pencelupan naik menghasilkan struktur mikro dengan dua fasa β’ [M18R] dan α[A1]. Nilai pemulihan regangan yang didapatkan dari pencelupan langsung dan pencelupan naik masing-masing adalah 29.6% dan 40%.

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Copper-based shape memory alloys are one of the cheaper and easier alternatives to fabricate compared to commercial shape memory Ni-Ti alloys. Usage of copper-based memory alloy such as Cu-Zn-Al ternary alloy includes several disadvantages such as low shape memory effect and the tendency to form martensite stabilization which can be nullified using heat treatment and varying quenching method. Thus, this research studied the effects of quenching method on the characteristics of the formed martensitic phase and the strain recovery of Cu-25,8Zn-4,8Al wt.%. As-cast samples formed by gravitation casting were given heat treatment homogenization at 850 ᵒC for 2 hours before solution treated at 850 ᵒC for 30 minutes followed by quenching with varying method such as direct quenching (DQ) and up-quenching (UQ). Characterization the alloys composition were done using Optical Emission Spectroscopy (OES), microstructural observartion using optical microscope and Scanning Electron Microscope- Energy Dispersive X-Ray Spectroscopy (SEM-EDS), X-ray Diffractory (XRD) test, microvickers hardness test, Different Scanning Calorymetry (DSC) test to obtain temperature transformation, and bending test to observe the strain recovery. As-cast and as-homogenized microstructure consist of binary phase α [A1] and β[D03]. Direct quenching and up-quenching method resulted in a microstructure with two phases [M18R] and [A1]. The strain recovery values obtained from direct quenching and up-quenching were 29.6% and 40%, respectively."

"Penelitian ini mengkaji penggunaan model Jaringan Saraf Tiruan (Artificial Neural Networks - ANN) untuk memprediksi temperatur awal transformasi martensit (Ms) pada paduan Cu-Al-Mn. Model ANN yang terdiri dari satu lapisan input, dua lapisan tersembunyi, dan satu lapisan output ini menggunakan metode gradient descent digunakan dalam proses pelatihan secara iteratif. Dengan memanfaatkan data dari Shape Memory Materials Database yang disediakan oleh NASA GRC secara open access, studi ini mengembangkan model regresi linear yang memprediksi suhu transformasi martensit awal (Ms) pada paduan Cu-Al-Mn. Evaluasi efektivitas dan akurasi model dilakukan dengan menggunakan dua paduan, yaitu paduan Cu- 24,12Al-3,13Mn (% atomik) dan Cu-25,92Al-3,6Mn (% atomik), dimana temperatur transformasi martensit awal (Ms) dari kedua paduan ini telah diperoleh. Secara khusus, studi ini menghasilkan sebuah persamaan yang bisa digunakan untuk memprediksi Ms. Persamaan yang diperoleh dari hasil pelatihan model ANN dengan validasi menggunakan data paduan yang spesifik, telah menunjukkan kemampuannya dalam mengkorelasikan variabel yang relevan dengan hasil yang diinginkan namun dengan beberapa limitasi.

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This study examined the use of an Artificial Neural Network (ANN) model to predict the Martensite Start (Ms) transition temperatures in Cu-Al-Mn alloys. The ANN model which consisted of an input layer, two hidden layers, and an output layer, utilized the gradient descent method for iterative training processes. Utilizing data from the Shape Memory Materials Database provided by NASA GRC with open access, this study developed a linear regression model that predicts the starting temperature of martensitic transformation (Ms) in Cu-Al-Mn alloys. The effectiveness and accuracy of the model were evaluated using two alloys, namely the Cu-24.12Al-3.13Mn (at. %) and Cu-25.92Al-3.6Mn (at. %) alloys, from which the Martensite Start (Ms) transition temperature were obtained. Specifically, this study produced a linear regression equation that can be used to predict Ms. The equation, derived from the ANN model training results with validation using specific alloy data, has demonstrated its capability to correlate relevant variables with the desired outputs under various limitations."

"Disertasi ini membahas mengenai pengembangan baja fasa ganda untuk mendukung kebutuhan akan material baja bodi mobil. Diharapkan dengan penelitian yang menarik di mana terdapat potensi kebutuhan material bodi mobil. Baja fasa ganda adalah salah satu baja yang canggih, industri otomotif telah lama memakai untuk komponen kendaraan yang memerlukan bobot ringan dan keamanan dalam berkedaraan. Benda uji dipanaskan hingga mencapai temperatur austenit pada berbagai derajat panas, yaitu 900, 920, 960 dan 1000oC dengan waktu tahan selama 30 menit, kemudian di kuens pada air (10oC) sehingga menghasilkan fasa martensit. Selanjutnya material tersebut di anil interkritis pada temperatur 750C dengan variasi lamanya waktu penahanan, yaitu 2, 5, 10, 20, 30, 40, 50 dan 60 menit, kemudian di kuens air pada temperatur kamar (30oC) sehingga diperoleh struktur mikro fasa ganda ferit dan martensit. Dalam penelitian ini diselidiki pembentukan struktur fasa ganda dengan berbagai fraksi volume martensit pada baja paduan rendah JIS G.3125 selama proses anil intarkritis. Ditemukan bahwa temperatur austenisasi dan anil interkritis serta waktu penahanan dapat mempengaruhi struktur mikro dan sifat mekanik baja karbon paduan mikro fasa ganda. Dari hasil penelitian tersebut diperoleh persamaan :

fvα’ = 12,905 ln ( 1 √𝑡̇ ) + 59,78 dimana :

t, adalah waktu fvα’, adalah fraksi volume martensit

Persamaan empiris hubungan sifat mekanik dengan volume fraksi martensit adalah:

σu = 0,0185 (fvα’) 3 - 2,1011 (fvα’) 2 + 81,427 (fvα’) – 500

σy = 0,0135 (fvα’)3 - 1,4543 (fvα’)2 + 54,99 (fvα’) - 335,38

ε = -0,0012 (fvα’) 3 + 0,1507 (fvα’) 2 - 6,3783 (fvα’) + 121,05 HV = 4,2539 (fvα’) + 418,96

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This dissertation discusses the development of dual-phase steel to support the need for car body steel materials. It is hoped that there will be interesting research where there is a potential need for car body materials. Dual-phase steel is one of the advanced steels, the automotive industry has long used it for vehicle components that require lightweight and safety in driving. The test object is heated until it reaches the austenite temperature at various degrees of heat, namely 900, 920, 960, and 1000C with a holding time of 30 minutes, then quenched in water to produce a martensite phase. Next, the material is intercritically annealed at a temperature of 750oC with varying lengths of holding time, namely 2, 5, 10, 20, 30, 40, 50 and 60 minutes, then quenched in water at room temperature to obtain a dual phase microstructure of ferrite and martensite. In this study, the formation of dual phase structures with various martensite volume fractions in low alloy carbon steel JIS G.3125 during the intercritical annealing process was investigated. It was found that the intercritical annealing temperature and holding time can affect the microstructure and mechanical properties of dual-phase micro alloy steel. The results of this research obtained the equation:

fvα’ = 12,905 ln ( 1 √𝑡̇ ) + 59,78

Where:

t, is time

fvα’, is fraction volume martensite

The empirical equation for the relationship between mechanical properties and martensite volume fraction is:

σu = 0,0185 (fvα’) 3 - 2,1011 (fvα’) 2 + 81,427 (fvα’) – 500

σy = 0,0135 (fvα’)3 - 1,4543 (fvα’)2 + 54,99 (fvα’) - 335,38

ε = -0,0012 (fvε = -0,0012 (fvα’) 3 + 0,1507 (fvα’) 2 - 6,3783 (fvα’) + 121,05

HV = 4,2539 (fvα’) + 418,96

 

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"This study tries to reveal the process of socio - economic transformation and its impact on rural communicaties in Pendoworejo village. This research is aimed at describing the effects of the socio-economic transformation on the quality of human resources, particularly the efforts of residents in the village of Pendoworejo to improve the quality of life, in depth. The techniques of collecting data are observation, interviews, documentation and FGD to all Pendoworejo stakeholders. Then, the data obtained were analyzed qualitatively by taking an interpretative approach and then summed up. From the analysis, it is concluded that the socio-economic transformation has led to the improvement of the quality of human resources through learning process in the interaction among the citizens, especially through the process of urbanization. The society has changed a lot in terms of quality of life, but less followed by the institutionalization of these changes, thus weakening local instutions in the village. In the case of Pendoworejo village, the changes are influeced by two main factors, namely : (1) intrnal - rural conditions with the change in the local community's orientation or in their rational domain of awareness that has drastically changed , (2) the influence of supra - village (external conditions), which can come from the government (the state) and the expension of capital that tends to dominate."

"ABSTRACTPaduan memori bentuk berbasis tembaga adalah bahan alternatif untuk menggantikan paduan Ni-Ti komersial karena paduannya ekonomis dan mudah dibuat. Penggunaan paduan memori bentuk berbasis tembaga seperti paduan terner Cu-Zn-Al biasanya memiliki beberapa kendala seperti stabilisasi fase yang dapat dihindari dengan menggunakan metode pendinginan alternatif. Oleh karena itu, penelitian ini mempelajari efek metode pendinginan pada karakteristik martensit dan pemulihan regangan paduan Cu-28Zn-3.5Al (wt.%). Plat as-cast dihomogenisasi pada 850 oC selama 2 jam sebelum larutan diperlakukan pada 850 oC selama 30 menit diikuti dengan pendinginan menggunakan direct quench (DQ), up quench (UQ) dan metode step quench (SQ). Karakterisasi pada paduan dilakukan dengan menggunakan uji komposisi OES, pengamatan struktural menggunakan mikroskop optik dan SEM, analisis mikro EDS, uji XRD, uji kekerasan, uji DSC, dan uji tekuk untuk mengamati pemulihan regangan. As - cast dan as - homogenisasi terdiri dari α [A1] dan β [D03] fase biner dengan α [A1]: β [D03] rasio 46:54, bersama dengan kekerasan fase α [A1] dari 106.73 HV dan β [D03] kekerasan fase 195,82 HV. Perlakuan panas langsung (DQ) dan naik (UQ) menghasilkan β ′ [M18R] dengan jarak interlamelar 9,08 dan 6,08, masing-masing, sedangkan pendinginan langkah menghasilkan fasa β [D03] dan α [A1] dengan β [D03]: α [ A1] dari 94: 6. Kekerasan paduan pada pendinginan langsung, pendinginan naik dan pendinginan adalah 175,46 HV, 186,90 HV, dan 195,49 HV. Sedangkan regangan pemulihan quench langsung, quench dan step quench adalah 52,76, 58,4 dan 5,86%. Up quench memiliki suhu transformasi austenit dan martensit yang selesai dalam periode yang lebih pendek daripada pendinginan langsung yang karenanya mengakomodasi sifat memori bentuk yang lebih baik.

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ABSTRACTCopper-based form memory alloys are an alternative material to replace commercial Ni-Ti alloys because they are economical and easy to make. The use of copper-based form memory alloys such as the Cu-Zn-Al ternary alloy usually has several constraints such as phase stabilization which can be avoided by using alternative cooling methods. Therefore, this study studies the effects of the cooling method on the characteristics of martensite and strain recovery of Cu-28Zn-3.5Al alloys (wt.%). As-cast plates were homogenized at 850 oC for 2 hours before the solution was treated at 850 oC for 30 minutes followed by cooling using direct quench (DQ), up quench (UQ) and step quench (SQ) methods. Characterization of the alloy was carried out using the OES composition test, structural observations using optical microscopy and SEM, EDS micro analysis, XRD test, hardness test, DSC test, and buckling test to observe strain recovery. As-cast and as-homogenization consist of α [A1] and β [D03] binary phase with α [A1]: β [D03] ratio of 46:54, along with α [A1] phase hardness of 106.73 HV and β [D03 ] 195.82 HV phase hardness. Direct heat treatment (DQ) and rise (UQ) produce β ′ [M18R] with interlamatic distances of 9.08 and 6.08, respectively, whereas cooling steps produce phases β [D03] and α [A1] to β [D03] ]: α [A1] of 94: 6. Hardness of the alloy in direct cooling, rising cooling and cooling is 175.46 HV, 186.90 HV, and 195.49 HV. While the direct recovery quench strain, quench and step quench are 52.76, 58.4 and 5.86%. Up quench has austenitic and martensitic transformation temperatures that are completed in a shorter period than direct cooling which therefore accommodates better shape memory properties."

"Paduan ingat bentuk Cu-Al-Mn merupakan material cerdas menjanjikan yang murah biaya; namun, kinerja dan suhu transformasinya sangat sensitif terhadap komposisi paduan. Dalam penelitian ini, pembelajaran mesin Extreme Gradient Boosting (XGBoost) diterapkan untuk memodelkan suhu martensite start (Ms) paduan Cu-Al-Mn. Paduan Cu-26,24Al-7,77Mn (at. %) digunakan untuk memvalidasi model dan menyelidiki pengaruh perlakuan panas terhadap struktur mikro dan sifat memori bentuk. Paduan tersebut dibuat dengan pengecoran gravitasi, dihomogenisasi pada suhu 900 ºC selama 2 jam, dibetatisasi pada suhu 900 ºC selama 30 menit, dan kemudian didinginkan menggunakan metode pencelupan langsung (DQ) dan pencelupan naik (UQ). Model XGBoost yang dikembangkan menghasilkan nilai R2, MAE, RMSE sebesar 0,98, 4,82, dan 10,67, memprediksikan Ms sebesar -174 ºC—mendekati suhu aktual (-190 ºC) yang diperoleh melalui pengujian resistivitas listrik. Hasil pengamatan mikroskop optik dan elektron bersama dengan analisis difraksi x-ray menunjukkan struktur fasa ganda β(L21) + γ dalam sampel as-cast dan setelah homogenisasi sedangkan fasa β(L21) tunggal diamati pada sampel perlakuan DQ dan UQ. Proses perlakuan panas mengakibatkan pertumbuhan butir dan penurunan nilai kekerasan mikrovickers, sesuai dengan persamaan Hell-Petch. Ditemukan bahan pengotor Fe (0,43 at. %) menyebabkan pertumbuhan butir abnormal pada sampel yang diberi perlakuan panas, di mana satu butir abnormal mencapai ukuran hingga ~15 mm. Sampel DQ dan UQ masing-masing mencapai pemulihan regangan 92,1 dan 100%. Perlakuan UQ diperkirakan mengurangi jumlah vakansi yang terperangkap akibat pencelupan dan derajat pinning pada antarmuka martensit.

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Cu-Al-Mn shape memory alloys show great promise as low-cost smart materials; however, their performance and transformation temperatures are sensitive towards alloy composition. In this study, Extreme Gradient Boosting (XGBoost) machine learning was applied to model the martensite start (Ms) temperature of Cu-Al-Mn alloys. Cu-26.24Al-7.77Mn (at. %) alloy was used to validate the model and investigate the influence of heat treatment on microstructure and shape memory properties. The alloy was gravity cast, homogenized at 900 ºC for 2 hours, betatized at 900 ºC for 30 minutes, and quenched using direct quenching (DQ) and up-quenching (UQ) methods. The refined XGBoost model delivered R2, MAE, RMSE scores of 0.98, 4.82, and 10.67, predicting an Ms of -174 ºC— close to the actual - 190 ºC obtained by electrical resistivity measurements. Optical and electron microscopy along with X-ray diffraction analyses revealed a dual-phase β(L21) + γ structure in as-cast and as-homogenized samples while a single β(L21)-phase in DQ and UQ treated samples. The heat treatment process resulted in grain growth of the alloy which also reduced Vickers microhardness values, consistent with the Hell-Petch relation. Notably, Fe (0.43 wt. %) impurity induced abnormal grain growth in heat-treated samples, with an abnormal grain reaching up to ~15 mm. DQ and UQ samples achieved 92.1 and 100% strain recovery, respectively. UQ treatment was thought to reduce the number of quenched-in vacancies and the degree of pinning on the martensite interface."