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"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 propertiesand 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 infiber diameter after mercerization. A porousstructure 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 wastreated 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 significantincrease in average ultimate strength to 163 MPa. Additionally, the elastic modulus of treated fiber was greater than that of untreated fiber."

"Magnesium memiliki nilai massa jenis lebih ringan diantara logam-logam komoditi penyuplai industri otomotif lainnya yaitu 1,74 gr/cm3. Berat magnesium sendiri lebih ringan 30% terhadap aluminium dan 70% terhadap baja. Perbaikan sifat-sifat mekanik dan ketahanan korosi pada paduan Mg-Al-Zn dapat dilakukan secara intrinsic melalui penambahan unsur paduan, perlakuan panas dan modifikasi teknik fabrikasi. Peningkatan sifat mekanik pada paduan (90-x)Mg9AlZnxCa dilakukan dengan penambahan unsur Ca yang divariasikan konsentrasi (0; 1; 1,5 dan 2 % berat) dengan Teknik fabrikasi pembuatan paduan (90-x)Mg-9Al-1Zn-xCa melalui proses semi-solid casting metoda Thixoforming menjadi parameter penting untuk menghasilkan suatu produk komponen otomotif. Sampel yang diuji memiliki multi fasa yaitu fasa a-Mg struktur kristal Hexagonal space group P63/mmc, fasa kedua β-Mg17Al12 struktur kristal kubik space group I-m43 m dan fasa Al2Ca termasuk dalam struktur kristal kubik dengan space grup Fd-3m. Hasil SEM-EDS menunjukkan terbentuknya fasa Al2Ca pada batas butir dapat menghambat pertumbuhan butir baru dan mengurangi terbentuknya fasa β-Mg17Al12.Pada sampel as-cast penambahan Ca 1 wt.% terjadi penurunan fraksi massa fasa a-Mg dan peningkatan fraksi massa fasa β-Mg17Al12. Pada sampel dengan penambahan Ca 1,5 dan 2 wt.% menunjukkan penurunan fraksi massa fasa a-Mg dan fasa β-Mg17Al12 serta adanya pembentukan fasa baru yaitu fasa Al2Ca. Pada sampel 1 wt.% Ca hasil proses thixoforming mengakibatkan penurunan fraksi massa fasa a-Mg, sedangkan fraksi massa fasa β-Mg17Al12 terjadi peningkatan yang signifikan. Pada sampel dengan penambahan Ca 1,5 dan 2 wt.% menunjukkan penurunan fraksi massa fasa a-Mg dan fasa β-Mg17Al12 serta adanya peningkatan pembentukan fasa baru yaitu fasa Al2Ca. Kekerasan tertinggi dihasilkan pada sampel 1 % berat Ca setelah dilakukan proses thixoforming dan ageing (T6) selama 20 jam sebesar 92,48 BHN. Pada pengukuran butir dengan metoda Jeffries teridentifikasi terjadi penghalusan butir sampai 17µm.

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Magnesium has a lighter density value than other commodity metals supplying the automotive industry, namely 1.74 gr/cm3. The weight of magnesium itself is 30% lighter for aluminum and 70% for steel. Improvement of mechanical properties and corrosion resistance of Mg-Al-Zn alloys can be made intrinsically by adding alloying elements, heat treatment, and modification of fabrication techniques. The improvement of the mechanical properties of the alloy (90-x)Mg9AlZnxCa was carried out by adding elements of Ca with varying concentrations (0; 1; 1.5 and 2% by weight) with the fabrication technique of making alloys (90-x)Mg-9Al-1Zn-xCa through Thixoforming metal casting semi-solid process is a vital parameter to produce an automotive component product. The samples tested had multiple phases: the a-Mg phase with the Hexagonal space group P63/mmc crystal structure, the second phase β-Mg17Al12 cubic crystal structure with the space group I-m43 m, and the Al2Ca phase included in the cubic crystal structure with the space group Fd-3m. The SEM-EDS results show that the formation of the Al2Ca phase at the grain boundaries can inhibit the growth of new grains and reduce the formation of the β-Mg17Al12 phase.

In the sample addition of Ca one wt.%, there was a decrease in the mass fraction of the a-Mg phase and an increase in the mass fraction of the β-Mg17Al12 phase. The samples with the addition of Ca 1.5 and 2 wt.% showed a decrease in the mass fraction of the a-Mg and β-Mg17Al12 phases and the formation of a new phase, namely the Al2Ca phase. In the sample of 1 wt.% Ca, the thixoforming process resulted in a decrease in the mass fraction of the a-Mg phase, while the mass fraction of the β-Mg17Al12 phase experienced a significant increase. The sample with the addition of Ca 1.5 and 2 wt.% showed a decrease in the mass fraction of the a-Mg and β-Mg17Al12 phases and an increase in the formation of a new phase, namely the Al2Ca phase. The highest hardness produced in 1% by weight of Ca sample after thixoforming and aging (T6) for 20 hours was 92.48 BHN. In the grain measurement using the Jeffries method, the grains are refined to 17µm"

"Penelitian ini didasari oleh terjadinya fenomena crack pada komponen bucket tooth, yang yang menggunakan material baja HSLA, setelah 1 bulan diproduksi, yang disebut dengan delayed crack. Penelitian ini akan berfokus terhadap proses perlakuan panas, khususnya tempering setelah normalisasi. Tempering dilakukan selama 1 jam dengan variabel temperatur tempering pada temperatur 527, 577, 627, dan 677°C. Sampel pengujian awalnya berupa keel block hasil normalisasi, yang kemudian dipotong menjadi balok dengan dimensi 4 x 1 x 4 cm. Karakterisasi dilakukan pada sampel as-normalize dan setelah ditempering, dimulai dari pengamatan struktur mikro menggunakan mikroskop optik, Scanning Electron Microscope (SEM), dan pengujian kekerasan mikro dan makro. Didapatkan bahwa tempering setelah normalisasi tidak hanya menghomogenisasi struktur mikro, tetapi juga mentransformasi fasa dari upper bainite menjadi granular bainite. Semua variabel temperatur tempering menghasilkan bentuk struktur mikro yang sama, berupa granular bainite. Seiring meningkatnya temperatur tempering setelah normalisasi, struktur mikro akan semakin membulat, ketajamannya akan semakin berkurang, kekerasan makro akan menurun dari 389 HVN menjadi 257 HVN, dan kekerasan mikro akan menurun dari 371 HVN menjadi 247 HVN.

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This study is based on the occurrence of a phenomenon of crack on a bucket tooth component that used HSLA steel as a material after 1 month being produced, which is called delayed crack. This study will be focusing on its heat treatment process, especially tempering after normalizing. Tempering was carried out for 1 hour with variable tempering temperatures at 527, 577, 627, and 677°C. Initially, the sample was a normalized keel block, which was then cut into blocks with dimensions of 4 x 1 x 4 cm. Characterization was carried out on as normalize and after tempering samples, such as observing microstructure using Optical Microscopy (OM), Scanning Electron Microscope (SEM), microhardness and macro hardness testing. It was found that tempering after normalizing not only homogenized the microstructure, but also transformed the phase from upper bainite to granular bainite. All tempering temperature variables produced the same microstructure, that is granular bainite. As the tempering temperature after normalizing increases, the microstructure will be increasingly rounded, the sharpness will be decreased, macro hardness decreased from 389 HVN to 257 HVN, and microhardness decreased from 371 HVN to 247 HVN."

"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."

"ABSTRAKPenambahan nano SiC pada aluminium A356 bertujuan untuk meningkatkan sifat mekanisaluminium A356 dengan densitas yang tetap rendah. Penambahan nano SiC padapenelitian ini sebesar 0.10, 0.15, 0.20, 0.25, dan 0.30 %berat. Penggunaan nano SiCditujukan untuk menjaga keuletan dari material. Ikatan antar fasa yang baik diperlukanagar pengaruh nano SiC pada aluminium A356 berfungsi dengan baik. Untuk membuatikatan antar fasa yang baik diberikan penambahan magnesium, Mg, sebanyak 1 %berat.Proses fabrikasi yang digunakan adalah metode pengecoran aduk dimana pengecoran adukadalah metode yang ekonomis dan mudah untuk dioptimalkan. Sifat mekanis yangdidapatkan adalah optimum pada penambahan nano SiC sebanyak 0.25 %berat dimanakekuatan tarik sebesar 175.57 MPa yang meningkat 21.87%, kekerasan sebesar 60.8 HREyang meningkat 50.59%, harga impak sebesar 0.0287 Joule/mm3 yang meningkat 14.8%,dan ketahanan aus sebesar 1.75 x 10-5 mm3/mm yang lebih rendah 21.13% dibandingkansifat mekanis aluminiun A356. Proses dan komposisi yang tepat merupakan hal yangpenting dalam pembuatan komposit.

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ABSTRACTNano SiC addition on the aluminum A356 aims to improve the mechanical properties ofaluminum A356 with remains low density. The addition of nano SiC in this study at 0.10,0.15, 0.20, 0.25, and 0.30 %wt. The use of nano sized SiC intended to maintain theductility of the material. Good interfacial bonding is required to get nano SiC effect on thealuminum A356 is functioning properly. To create a good bonding between phases, giventhe addition of magnesium, Mg, 1% by weight. Fabrication process used is stir castingmethod which is an economical and easy to optimized method. The mechanical propertiesobtained optimum on addition of nano SiC as much as 0.25 %wt where the tensile strengthis 175.57 MPa which is increased by 21.87%, hardness is 60.8 HRE which is increased50.59%, the toughness is 0.0287 Joules/mm3 which is increased 14.8%, and the wearresistance is 1.75 x 10-5 mm3/mm lower 21.13% of aluminiun A356 mechanical properties.The right process and composition is important in the manufacture of composites with stircasting."

"ABSTRAKKomposit aluminium 6061 dengan partikel penguat nano SiC sudah banyak dikembangkan untuk aplikasi yang membutuhkan sifat mekanis yang baik dengan densitas yang rendah. Dalam rangka mencapai performa yang lebih baik, perlakuan panas T6 diberikan untuk meningkatkan sifat mekanis material komposit. Pada penelitian ini dilakukan proses perlakuan panas T6 dengan variasi waktu aging 2 jam, 4 jam, 6 jam, 8 jam, dan 10 jam pada temperatur 175 oC. Solution treatment dilakukan pada temperatur 440 oC selama 1 jam. Hasil penelitian menunjukkan bahwa waktu optimum aging adalah 10 jam yang ditandai dengan hasil kekerasan paling tinggi yaitu sebesar 66,22 HRB dan laju aus paling rendah yaitu sebesar 1,09 x 10-6 mm3/mm. Pengaruh perlakuan panas T6 terhadap hasil uji tarik sangat rendah akibat adanya porositas. Hasil struktur mikro dari mikroskop optik dan SEM menunjukkan adanya fasa α-Al, Mg2Si biner (Al+Mg2Si), dan fasa intermetalik β-Al2Mg3.

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ABSTRACTAluminum 6061 composites reinforced by SiC nanoparticles has been widely used for high performance applications with low denstity. In order to obtain a better performance, artificial aging is conducted to improve mechanical properties of composite. In this study, aging treatment was done with varying aging time: 2h, 4h, 6h, 8h, and 10h at 175 oC with solution treatment at 440 oC for 1h. The results showed that the optimum aging time was achieved by 10h with the highest hardness up to 66,22 HRB and wear rate reached the lowest value by 1,09 x 10-6 mm3/mm. Heat treatment process did not show a strong influence to tensile strength due to a porosity. OM and SEM observation exhibit α-Al and binary Mg2Si (Al+Mg2Si) phases, and intermetallic phases of β-Al2Mg3."

"In this study, friction stir processing (FSP) was attempted to produce SiCp/AA6061 surface composite in order to address the challenges presented by liquid state fabrication processes. SiC particles of 400-grit size were added into a groove machined on the surface of AA6061 plates. FSP was performed by means of a manual milling machine with a tapered, cylindrical tool rotating at 1225 rpm and with a feed rate of 35 mm/min. The effect of the tool tilt angle and the number of FSP passes on the microstructures and mechanical properties was investigated. The tool tilt angles were varied between 0° and 3°, in increments of 1°. The number of passes was varied at 1, 3, and 5 passes. High resolution optical microscopic analysis was performed to investigate the microstructural evolution of each specimen. Mechanical properties were explored through Vickers microhardness test, the results of which were also utilized to estimate the tensile strength at localized areas using an empirical relationship. The results exhibited significant improvement in the microstructures, where refined grains were obtained as a result of the dynamic recrytallization and severe plastic deformation generated by the FSP. Microhardness and ultimate tensile strength of the FSPed surface composite improved by up to 62.2% compared to the base metal.

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Dalam studi ini, friction stir processing (FSP) dicoba untuk menghasilkan komposit permukaan SiCp/AA6061 untuk mengatasi tantangan yang disajikan oleh proses fabrikasi keadaan cair. Partikel SiC berukuran 400 grit ditambahkan ke dalam alur yang dikerjakan pada permukaan pelat AA6061. FSP dilakukan dengan menggunakan mesin frais manual dengan pahat berbentuk silinder runcing yang berputar pada kecepatan 1225 rpm dan laju pemakanan 35 mm/menit. Pengaruh sudut kemiringan pahat dan jumlah lintasan FSP pada struktur mikro dan sifat mekanik diselidiki. Sudut kemiringan pahat divariasikan antara 0° dan 3°, dengan penambahan 1°. Jumlah pass divariasikan pada 1, 3, dan 5 pass. Analisis mikroskopis optik resolusi tinggi dilakukan untuk menyelidiki evolusi mikrostruktur masing-masing spesimen. Sifat mekanik dieksplorasi melalui uji kekerasan mikro Vickers, yang hasilnya juga digunakan untuk memperkirakan kekuatan tarik di daerah lokal menggunakan hubungan empiris. Hasilnya menunjukkan peningkatan yang signifikan dalam struktur mikro, di mana butiran halus diperoleh sebagai hasil dari rekristalisasi dinamis dan deformasi plastis parah yang dihasilkan oleh FSP. Kekerasan mikro dan kekuatan tarik tertinggi dari komposit permukaan yang di-FSP meningkat hingga 62,2% dibandingkan dengan logam dasar."

"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."

"Teknologi material yang semakin maju membuat banyak terobosan baru, salah satunya adalah penggunaan magnesium paduan. Magnesium paduan banyak diaplikasikan untuk penggunaan sebagai biomaterial ataupun sebagai EV (Electronic Vehicle). Magnesium memiliki banyak keunggulan dan sifat mekanik yang menguntungkan, magnesium bersifat ringan sehingga bisa meningkatkan efisiensi dalam penggunaan bahan bakar pada EV, magnesium juga bersifat biodegradable dan bersifat non toxic bagi tubuh manusia, memiliki nilai densitas dan juga modulus elastisitas yang paling mirip dengan tulang manusia, bahkan hadir dalam jumlah banyak dalam tubuh manusia sehingga tak heran jika banyak diaplikasikan dalam biomaterial baik sebagai implant ataupun pengganti tulang. Namun sayangnya perubahan sifat mekanik dan struktur mikro akibat perlakuan panas belum dilakukan penelitian secara sistematis.Penelitian ini dilakukan pada lembaran paduan magnesium AZ31B yang diberi perlakuan panas dengan waktu tahan selama 10, 30, 60, dan 120 menit. Didapatkan bahwa struktur mikro paduan magnesium AZ31B yang tidak diberi perlakuan panas memiliki butir yang cukup besar dan tidak homogen, hal ini membuat sifat mekaniknya kurang baik. Perlakuan panas membuat struktur mikronya menjadi lebih homogen dan besar butirnya mengecil, butir yang semakin kecil ini membuat sifat mekaniknya semakin baik, namun semakin lama waktu tahan yang diberikan membuat butir semakin besar dan menurunkan sifat mekanik yang dimiliki, dibuktikan dengan persamaan Hall-petch yang mendukung hasil ini.

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Advancements in material technology have led to numerous breakthroughs, one of which is the use of magnesium alloys. Magnesium alloys are widely applied in biomaterials and electric vehicles (EV). Magnesium possesses many advantageous mechanical properties, being lightweight which enhances fuel efficiency in EVs. Additionally, magnesium is biodegradable and non-toxic to the human body, with a density and elastic modulus closely matching that of human bone. It is also abundant in the human body, making it ideal for applications in biomaterials, such as implants or bone substitutes. However, systematic research on the changes in mechanical properties and microstructure due to heat treatment has not been thoroughly conducted.

This study investigates magnesium AZ31B alloy sheets subjected to heat treatment with holding times of 10, 30, 60, and 120 minutes. It was found that the microstructure of the untreated magnesium AZ31B alloy exhibited relatively large and inhomogeneous grains, resulting in suboptimal mechanical properties. Heat treatment homogenized the microstructure and reduced grain size, leading to improved mechanical properties. However, prolonged holding times caused grain growth, reducing mechanical properties, which is supported by the Hall-Petch relationship."