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"Selongsong peluru adalah salah satu komponen yang terpenting dalam peluru karena merupakan tempat mesiu, proyektil, dan primer. Material yang digunakan untuk membuat selongsong peluru adalah paduan cartridge brass (Cu-Zn) dengan kandungan seng dalam rentang 28 ? 32 wt.%. Selongsong peluru difabrikasi dengan melewati beberapa tahap yaitu pengecoran, canai dingin, deep drawing, dan anil. Persen deformasi yang diberikan saat proses fabrikasi mencapai lebih dari 70 %, maka dari itu agar dapat melalui seluruh proses fabrikasi diatas dibutuhkan paduan kuningan yang memiliki keuletan tinggi dan perilaku rekristalisasi yang dapat dikontrol. Penambahan unsur Mn diharapkan dapat meningkatkan keuletan dari paduan cartridge brass tanpa mengorbankan kekuatan dari paduan tersebut. Pada penelitian ini, paduan Cu-31Zn dengan penambahan 9 wt.% Mn difabrikasi dengan pengecoran gravitasi. Untuk memperoleh paduan dengan komposisi kimia yang homogen maka dilakukan perlakuan panas homogenisasi pada temperatur 800 oC selama 2 jam. Kemudian paduan dilakukan canai dingin dengan deformasi 20, 40, dan 70 %. Selanjutnya paduan dengan deformasi 70 % dilakukan perlakuan panas anil dengan variasi temperatur 300, 400, dan 600 oC selama 30 menit. Karakterisasi material yang dilakukan pada penelitian ini meliputi analisis struktur mikro dengan mikroskop optik dan Scanning Electron Microscope (SEM) ? Energy Dispersive Spectroscopy (EDS), dan pengujian kekerasan microvickers. Hasil penelitian menunjukkan bahwa peningkatan derajat deformasi sebesar 20, 40, dan 70 % menyebabkan pemipihan fasa kedua dengan L/T ratio masing-masing sebesar 4, 11,6, dan 18. Selain itu juga terjadi peningkatan kekerasan paduan yaitu sebesar 68, 147, 171, dan 205 HV. Sementara proses anil dengan variasi temperatur 300, 400, dan 600 oC menyebabkan terjadinya fenomena recovery, rekristalisasi (dgrain ~ 5 μm), dan grain growth (dgrain ~ 40 μm) yang ditandai dengan penurunan kekerasan spesimen yaitu sebesar 201, 128, dan 171 HV. Penambahan Mn menyebabkan pertumbuhan fasa kedua mengandung sedikit Zn dan Mn akibat kecenderungan ordering Cu dan Mn yang meningkatkan nilai kekerasan dan memperlambat laju rekristalisasi, sehingga dibutuhkan temperatur anil dan/atau waktu yang lebih tinggi untuk mencapai rekristalisasi sempurna pada paduan cartridge brass dengan penambahan Mn.

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Cartridge shell is one of the most important components in a bullet because it contains gunpowder, projectiles, and primer. The material used to make cartridge shells are cartridge brass alloys (Cu-Zn) with the zinc content in the range of 28 ? 32 wt.%. Bullet casings are manufactured by passing through several stages fabrication, which are casting, cold rolling, deep drawing, and annealing. The degree of deformation during the fabrication process reaches 70 % or more. Therefore in order to be able to go through the whole process of fabrication it is required to use brass alloys that have high ductility and recrystallization behavior that can be controlled. The addition of Mn is expected to improve the ductility of the cartridge brass alloy without sacrificing its strength.

In this study, the characteristics of Cu-31Zn alloy with the addition of 9 wt.% Mn fabricated by gravity casting was observed. To obtain alloys with homogeneous chemical composition, homogenizing heat treatment was carried out with the temperature of 800 °C for 2 hours. Then the alloys were cold rolled with degree of deformation of 20, 40, and 70 %. Furthermore, the specimens with 70 % degree of deformation were annealed with temperature variation of 300, 400, and 600 °C for 30 minutes. Characterization of material carried out in this study included the analysis of the microstructure by optical microscopy and Scanning Electron Microscope (SEM) - Energy Dispersive Spectroscopy (EDS), and microhardness testing.

The results showed that the addition of Mn up to 9 wt.% to cartridge brass alloy led to the formation of second phase particles that are less rich in Zn and Mn content due to ordering tendency of Cu and Mn. The increase in the degree of deformation of 20, 40, and 70 % led to the decrease of second phase L/T ratio, each for 4, 11.6, and 18. There were also increase in the alloy hardness with the values of 68, 147, 171, and 205 HV respectively. The annealing process with temperature variation of 300, 400, and 600 °C led to the phenomena of recovery, recrystallization (dgrain ~ 5 μm), and grain growth (dgrain ~ 40 μm) that resulted in the decrease of hardness with the values of 201, 128, and 171 HV respectively. The effect of Mn addition in the cartridge brass alloy is to increase the hardness by solid solution and dispersion strengthening mechanisms and to decrease the rate of recrystallization, so it required higher annealing temperature and / or longer annealing time to reach full recrystallization."

"[Salah satu komponen terpenting pada peluru adalah selongsong yang memuat bubuk mesiu, primer, dan proyektil. Material yang umum digunakan untuk memfabrikasi selongsong peluru adalah cartridge brass (kuningan) yang mengandung 26-32 wt.% Zn. Selongsong peluru diproduksi dengan proses metalurgi yang kontinu, yang terdiri atas pengecoran, pencanaian, dan deep drawing. Dalam proses deep drawing biasanya ditemukan beberapa masalah mayor, seperti keretakan dan perobekan. Untuk meminimalisir masalah tersebut, pengembangan material dengan keuletan yang lebih baik menjadi penting untuk digunakan sebagai selongsong peluru. Mangan digunakan sebagai unsur paduan pada kuningan untuk meningkatkan keuletannya. Pada penelitian ini, paduan Cu-28Zn dengan penambahan 3,2 wt.% Mn difabrikasi dengan pengecoran gravitasi. Untuk menghomogenisasi komposisi kimia, paduan diberi perlakuan panas pada 800 oC selama 2 jam. Kemudian spesimen dicanai dingin dengan deformasi 20, 40, dan 70 % reduksi. Proses anil selanjutnya dilakukan setelah pencanaian dingin sebesar 70 % dengan temperatur 350, 400, dan 450 oC selama 15 menit. Karakteriasi material yang dilakukan pada penelitian ini terdiri dari analisis struktur mikro menggunakan mikroskop optik dan Scanning Electron Microscope (SEM) - Energy Dispersive Spectroscopy (EDS), serta pengujian kekerasan mikro. Hasil penelitian menunjukkan bahwa peningkatan derajat deformasi sebesar 20, 40, dan 70 % menyebabkan butir menjadi semakin pipih dengan L/D ratio masing-masing bernilai sekitar 0,7, 2,2, 7,7, dan 14,1. Selain itu juga terjadi peningkatan nilai kekerasan spesimen, yakni sebesar 56, 127, 145, dan 207 HV secara berurutan. Sementara proses anil setelah canai dingin sebesar 70 % pada temperatur 350, 400, dan 450 oC menyebabkan terjadinya peristiwa stress relieve yang ditandai dengan fenomena recovery, diikuti dengan rekristalisasi (dgrain ~ 7 μm), hingga grain growth (dgrain ~ 14 μm). Selain itu juga terjadi penurunan nilai kekerasan spesimen, yakni sebesar 204, 131, dan 100 HV secara berurutan. Pengaruh penambahan unsur Mn di dalam paduan cartridge brass adalah meningkatkan nilai kekerasan dan memperlambat laju rekristalisasi, dibutuhkan temperatur anil yang lebih tinggi untuk mencapai rekristalisasi sempurna pada paduan cartridge brass dengan penambahan Mn.

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One of the most important part of bullet is its cartridge shell which contains gun powder, primer, and projectile altogether. Common material used to fabricate bullet shell is cartridge brass which contains 26-32 wt.% Zn. Cartridge shell is produced by a continuous metallurgical processes, which are casting, rolling, and deep drawing. In deep drawing process, some major problems are typically found, such as cracking and tearing. In order to minimize these problems, it is essential to develop materials with enhanced ductility to be used as cartridge shell. Manganese is used as an alloying element of cartridge brass to increase its ductility. In this research, Cu-28Zn alloy with addition of 3,2 wt.% Mn were fabricated by gravity die casting. To homogenize the chemical composition, the alloy was heated at 800 °C for 2 hours. Afterwards, the specimens were cold-rolled with deformation of 20, 40, and 70 %. Subsequent annealing process after 70 % cold-rolled with temperature of 350, 400, and 450 oC for 15 minutes was carried out. Material characterizations consisted of microstructure analysis using optical microscope and Scanning Electron Microscope (SEM) - Energy Dispersive Spectroscopy (EDS), and microvickers hardness testing. The result showed that higher degree of deformation of 20, 40, and 70 % led to more elongated grains with L/D ratio of 0.7, 2.2, 7.7, and 14.1, respectively. Moreover, the hardness of material increased with the increase in the level of deformation, with the values of 56.1, 126.6, 144.6, and 206.7 HV, respectively. Meanwhile, annealing at the temperatures of 350, 400, and 450 oC to specimens with prior deformation of 70 %, resulted in recovery and stress relieve, followed by recrystallization (dgrain ~ 7 μm), and finally grain growth (dgrain ~ 14 μm). Furthermore, the hardness of material decreased with the increase in level of annealing temperature, with the values of 204, 131, and 100 HV, respectively. The roles of Mn in the cartridge brass is to increase the hardness and to slower the recrystallization rate. In general, addition of Mn in cartridge brass increased the annealing temperatures needed to achieve full recrystallization.;One of the most important part of bullet is its cartridge shell which contains gun powder, primer, and projectile altogether. Common material used to fabricate bullet shell is cartridge brass which contains 26-32 wt.% Zn. Cartridge shell is produced by a continuous metallurgical processes, which are casting, rolling, and deep drawing. In deep drawing process, some major problems are typically found, such as cracking and tearing. In order to minimize these problems, it is essential to develop materials with enhanced ductility to be used as cartridge shell. Manganese is used as an alloying element of cartridge brass to increase its ductility. In this research, Cu-28Zn alloy with addition of 3,2 wt.% Mn were fabricated by gravity die casting. To homogenize the chemical composition, the alloy was heated at 800 °C for 2 hours. Afterwards, the specimens were cold-rolled with deformation of 20, 40, and 70 %. Subsequent annealing process after 70 % cold-rolled with temperature of 350, 400, and 450 oC for 15 minutes was carried out. Material characterizations consisted of microstructure analysis using optical microscope and Scanning Electron Microscope (SEM) - Energy Dispersive Spectroscopy (EDS), and microvickers hardness testing. The result showed that higher degree of deformation of 20, 40, and 70 % led to more elongated grains with L/D ratio of 0.7, 2.2, 7.7, and 14.1, respectively. Moreover, the hardness of material increased with the increase in the level of deformation, with the values of 56.1, 126.6, 144.6, and 206.7 HV, respectively. Meanwhile, annealing at the temperatures of 350, 400, and 450 oC to specimens with prior deformation of 70 %, resulted in recovery and stress relieve, followed by recrystallization (dgrain ~ 7 μm), and finally grain growth (dgrain ~ 14 μm). Furthermore, the hardness of material decreased with the increase in level of annealing temperature, with the values of 204, 131, and 100 HV, respectively. The roles of Mn in the cartridge brass is to increase the hardness and to slower the recrystallization rate. In general, addition of Mn in cartridge brass increased the annealing temperatures needed to achieve full recrystallization., One of the most important part of bullet is its cartridge shell which contains gun powder, primer, and projectile altogether. Common material used to fabricate bullet shell is cartridge brass which contains 26-32 wt.% Zn. Cartridge shell is produced by a continuous metallurgical processes, which are casting, rolling, and deep drawing. In deep drawing process, some major problems are typically found, such as cracking and tearing. In order to minimize these problems, it is essential to develop materials with enhanced ductility to be used as cartridge shell. Manganese is used as an alloying element of cartridge brass to increase its ductility.

In this research, Cu-28Zn alloy with addition of 3,2 wt.% Mn were fabricated by gravity die casting. To homogenize the chemical composition, the alloy was heated at 800 °C for 2 hours. Afterwards, the specimens were cold-rolled with deformation of 20, 40, and 70 %. Subsequent annealing process after 70 % cold-rolled with temperature of 350, 400, and 450 oC for 15 minutes was carried out. Material characterizations consisted of microstructure analysis using optical microscope and Scanning Electron Microscope (SEM) - Energy Dispersive Spectroscopy (EDS), and microvickers hardness testing.

The result showed that higher degree of deformation of 20, 40, and 70 % led to more elongated grains with L/D ratio of 0.7, 2.2, 7.7, and 14.1, respectively. Moreover, the hardness of material increased with the increase in the level of deformation, with the values of 56.1, 126.6, 144.6, and 206.7 HV, respectively. Meanwhile, annealing at the temperatures of 350, 400, and 450 oC to specimens with prior deformation of 70 %, resulted in recovery and stress relieve, followed by recrystallization (dgrain ~ 7 μm), and finally grain growth (dgrain ~ 14 μm). Furthermore, the hardness of material decreased with the increase in level of annealing temperature, with the values of 204, 131, and 100 HV, respectively.

The roles of Mn in the cartridge brass is to increase the hardness and to slower the recrystallization rate. In general, addition of Mn in cartridge brass increased the annealing temperatures needed to achieve full recrystallization.]"

"Selongsong peluru dibuat dari cartridge brass, yang terdiri dari 28-30% wt. % Zn. Proses fabrikasi selongsong peluru terdiri dari : canai dingin, deep drawing, dan annealing. Deformasi yang terjadi pada proses fabrikasi selongsong peluru melebihi 70%. Cartridge brass memiliki 3 mekanisme deformasi: slip (deformasi 20%), twin ( 40%), dan shear (> 40%). Bi mulai digunakan untuk menggantikan Pb dalam kuningan karena racun yang lebih rendah.Pada penelitian ini, Cu-29Zn-0.6Bi dilakukan pengecoran gravitasi, dihomogenisasi dengan temperatur 800 °C selama 2 jam, dan dicanai dingin dengan variasi deformasi 20, 40, dan 70%. Pada 70%, proses anil dilakukan pada temperatur 350, 400, dan 450 °C. Semua sampel lalu dikarakterisasi nilai kekerasan dan struktur mikronya. Meningkatnya % deformasi akan menghasilkan peningkatan kekerasan. Pada deformasi 70%, ditemukan adanya retak permukaan. Segregasi Bi terdapat baik di dalam butir maupun batas butir.Bi meningkatkan kekerasan pada cartridge brass dengan mekanisme grain boundary strengthening (pengecilan ukuran butir) dan dispersoid strengthening. Nukleasi pada temperatur 350 °C dimulai pada shear band dan batas butir, dan selesai pada 400 °C, sedangkan grain growth terjadi pada 450 °C (semua dalam 15 menit). Bi mempercepat proses rekristalisasi cartridge brass.

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Bullet case is made of cartridge brass, which consists of 28-30% content of Zinc. Bullet case's fabrication consists of cold rolling, deep drawing, and annealing. Deformation which occurs in bullet case?s fabrication gets higher than 70%. Cartridge brass has 3 deformation mechanism: slip (20% deformation), twin (40% deformation), and shear (> 40% deformation). Bi is used nowadays to substitute Pb in cartridge Brass due to lower toxicity. In this research, Cu-29Zn-0.6Bi is gravity casted, homogenized at 800 °C for 2 hours, and then cold rolled with variation of percent deformation 20, 40, and 70%. At 70% cold rolled cast is annealed with temperatures 350, 400 and 500 °C. The samples then are characterized for hardness properties and structures.Increasing % deformation generates higher hardness. In 70% deformation, a crack is found on a surface. Bi segregation tends to be immersed both in bulk grain or grain boundaries.Bi increases cartridge brass? hardness with grain boundary strengthening (grain refining), and dispersoid strengthening. Nucleation in 350 °C started at shear bands region and grain boundaries, finished in 400 °C; besides, grain growth occurred in 450 °C (all in 15 minutes). Bi exceeds recrystallization process in cartridge brass."

"ABSTRAKSelongsong merupakan salah satu bagian penting pada munisi tempat dimana bubuk mesiu, primer, dan peluru. Material yang digunakan untuk fabrikasi selongsong adalah paduan Cu-28Zn atau cartridge brass. Selongsong munisi dibuat dengan beberapa proses diantaranya adalah pengecoran, canai, dan penarikan dalam. Sering terjadi retak dan robek pada tahap fabrikasi. Telah dilakukan beberapa penambahan unsur paduan, tetapi hasilnya belum optimal. Dibutuhkan unsur paduan untuk meningkatkan kekuatan paduan cartridge brass tanpa mengorbankan keuletan. Aluminium dipilih sebagai unsur paduan tersebut.Pada penelitian ini, paduan cartridge brass dengan penambahan 1.9, 5.7, dan 6.2 wt. % Al dihasilkan dengan pengecoran gravitasi. Paduan tersebut kemudian dihomogenisasi pada 800 °C selama 2 jam. Karakterisasi material meliputi analisis struktur mikro menggunakan mikroskop optik dan Scanning Electron Microscope (SEM) - Energy Dispersive X-Ray (EDX), serta uji kekerasan Rockwell B, mikro Vickers, dan uji tarik.Hasil pengujian menunjukkan bahwa penambahan Al meningkatkan sifat mekanis paduan Cu-28Zn. Kekerasan, kekuatan tarik, dan tegangan luluh meningkat, sedangkan nilai elongasi menurun seiring penambahan Al. Peningkatan sifat mekanis disebabkan penambahan unsur Al mempromosi fasa beta dan memfasilitasi fasa gama dengan penambahan berlebih. Secara keseluruhan fasa gama yang terbentuk meningkatkan sifat mekanis paduan dengan mekanisme penguatan dispersi.

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ABSTRACTCartridge case is an important part of bullet where the gun powder, primer, and bullet take place. Common material that is used to make cartridge case is Cu-28Zn alloy or known as cartridge brass. Cartridge case is made by some processes, that include casting, rolling, and deep drawing. Cracking and torning are often found in the fabricating process. Many kind of alloying elements were added in order to minimize those problems, but the results obtained are still unsatisfying. Another alloying element is needed that could improve the cartridge case without sacrificing the ductility. Aluminum is chosen to be thataforementioned alloying element.In this research, cartridge brass alloy with addition of 1.9, 5.7, and 6.2 wt.%Al were fabricated by gravity die casting. To homogenize the composition, the alloy was heated at 800 °C for 2 hours. Material characterizations consisted ofmicrostructural analysis using optical microscope and Scanning Electron Microscope (SEM) - Energy Dispersive X-Ray (EDX), Rockwell B, Microvicker hardness testing, and tensile testing.The result obtained shows that Al addition improved the mechanical properties of Cu-28Zn alloy. Hardness, tensile strength, and yield strength increased, but the elongation decreased due to addition of Al. Increasing of Al composition in Cu-28Zn promotes beta phase and facilitates gamma phase with excessive addition. Overall, the gamma phase enhances the mechanical properties of Cu-28Zn alloy with dispersion strengthening mechanism."

"Selongsong peluru terbuat dari cartridge brass Cu-Zn , yang mengandung 28 32 wt. Zn. Material ini di fabrikasi melalui berbagai tahap, dimulai dari canai dingin, penekanan dalam, dana nil. Deformasi yang terjadi pada saat fabrikasi selongsong peluru mencapai lebih dari 90 , dan proses rekristalisasi selesai pada temperatur 450 500 oC selama 30 menit. Pada penelitian sebelumnya, penambahan Bi kedalam paduan cartridge brass menyebabkan penggetasan karena adanya segregasi Bi ke batas butir. Sedangkan pada penambahan Mn, peningkatan sifat mekanik paduan hanya terjadi hingga penambahan 3.52 wt. Mn. Maka dari itu, pada penelitian ini dilakukan penambahan Al untuk meneliti pengaruhnya terhadap sifat mekanik dan perilaku anil nya. Pada penelitian ini, pembuatan paduan Cu-28Zn-5.5Al dilakukan dengan pengecoran gravitasi, dihomogenisasi pada temperatur 800 oC selama 2 jam, kemudian dicanai dingin dengan variasi deformasi 5, 10, dan 20 . Untuk derajat deformasi canai dingin 20 , dilakukan proses anil pada temperatur 300, 400, dan 600 oC selama 30 menit. Lalu, sampel dilakukan karakterisasi nilai kekerasan dan struktur mikronya. Peningkatan derajat deformasi akan menghasilkan peningkatan kekerasan. Al meningkatkan kekerasan cartridge brass dengan mekanisme penguatan solid solution dan grain boundary strengthening, yang menghalangi pergerakan dislokasi. Nukleasi parsial terjadi pada daerah dekat permukaan pada temperatur 300 oC, begitu juga dengan temperatur 400 oC. Proses anil pada temperatur 400 oC menyebabkan munculnya presipitasi fasa gamma yang terjadi melalui mekanisme dekomposisi fasa beta. Rekristalisasi terjadi homogen terjadi pada temperatur 600 oC pada batas butir. Pengaruh Al secara umum adalah menyebabkan terjadinya penurunan temperatur rekristalisasi paduan.

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A bullet case is made of cartridge brass Cu Zn , which consists of 28 32 wt. Zn. This material is fabricated through various kinds of process, starting from cold rolling, deep drawing, and annealing. The deformation occurred along the fabrication of bullet case is more than 90 , and the recrystallization process is completed at 450 500 oC for 30 minutes. In the previous research, addition of Bi into cartridge brass causes mechanical properties degradation due to segregation of Bi. Mn improves mechanical properties only up to 3.52 wt. of addition. Therefore, this research studied the effects of Al addition on mechanical properties and annealing behavior of Cu 28Zn. In this research, fabrication of Cu 28Zn 5.5Al was fabricated by gravity casting, followed by homogenization at 800 oC for 2 hours, then cold rolled with deformation degree varied from 5, 10, to 20 . Annealing was conducted at 300, 400, and 600 oC for 30 minutes. Then, the hardness values and microstructures were characterized. Al improved hardness of Cu 28Zn alloy through solid solution and grain boundary strengthening. Partial nucleation started at 300 oC around the edge of the sampel. Annealing at 400 oC led to the formation of gamma phase due to the beta phase decomposition. Full recrystallization occurred at 600 oC. Al addition into Cu 28Zn alloy decrease the recrystallization temperature."

"Selongsong peluru terbuat dari cartridge brass Cu-Zn , yang mengandung 28-32 wt. seng, dengan melewati beberapa tahap fabrikasi yaitu: canai dingin, deep drawing, dan anil. Pada proses anil akan terjadi pengembalian keuletan paduan melalui mekanisme stress relieve, rekristalisasi, dan pertumbuhan butir. Bismut biasanya digunakan untuk menggantikan Pb pada cartridge brass karena lebih ramah lingkungan. Unsur Bi juga tidak larut pada kuningan dan cenderung bersegregasi ke batas butir. Pada penelitian ini dipelajari pengaruh deformasi canai dingin dan temperatur anil pada karakteristik paduan Cu-28Zn-1.1Bi. Pembuatan paduan Cu-28Zn-1.1Bi dilakukan dengan pengecoran gravitasi. Selanjutnya paduan dihomogenisasi pada temperatur 800 C selama 2 jam, kemudian dicanai dingin dengan variasi deformasi 5, 10, dan 20 . Pada sampel dengan deformasi canai dingin 20 , proses dilanjutkan dengan anil pada temperatur 300, 400, dan 600 C selama 30 menit. Sampel lalu diamati nilai kekerasan dan struktur mikronya. Kehadiran Bi meningkatkan kekerasan cartridge brass dengan mekanisme penguatan dispersoid strengthening, yang menghalangi pergerakan dislokasi. Peningkatan deformasi akan menghasilkan peningkatan kekerasan. Rekristalisasi pada saat anil di temperatur 400 C terjadi pada batas butir dan di sekitar partikel Bi. Rekristalisasi selesai pada 600 C, dan diikuti dengan pertumbuhan butir. Unsur Bi mempercepat proses rekristalisasi pada cartridge brass melalui mekanisme Particle Stimulated Nucleation PSN

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Bullet case is made of cartridge brass Cu Zn , which consists of 28 32 Zinc, through several stages cold rolling, deep drawing, and annealing. During annealing, there will be stress relieve, recrystallization, and grain growth that may restore the ductility of the alloy. Bismuth is used to replace lead in cartridge brass because it is more environmental friendly. Bismuth is also insoluble in brass and preferentially segregates at grain boundaries. This research studied the effects of cold rolling and annealing temperature on the characteristic of Cu 28Zn 1.1Bi.The Cu 28Zn 1.1Bi alloy was gravity casted, followed by homogenization at 800 C for 2 hours, and then cold rolled for 5, 10, and 20 . The samples with 20 deformation were continued to annealing process at 300, 400 and 600 C for 30 minutes. The hardness and microstructures of the alloy were observed to understand the role of bismuth. The presence of Bi increases the hardness of the cartridge brass through dispersoid strengthening mechanism that blocks movement of dislocation. The higher the percentage of deformation, the higher the hardness of the alloy. Recrystallization in 400 C started at grain boundaries and around Bi particles, finished in 600 C, and followed by grain growth. Bismuth exceeds recrystallization process in cartridge brass, because of the Particle Stimulated Nucleation PSN process."

"Aluminium dan paduannya tengah dikembangkan sebagai badan pesawat terbang karena sifatnya yang lebih ringan daripada baja dan mudah dibentuk. Paduan aluminium 7XXX yang mengandung Zn dan Mg dapat ditingkatkan sifat mekanisnya melalui proses deformasi. Persentase deformasi yang diberikan akan meningkatkan kekerasan paduan melalui mekanisme penguatan regang. Proses anil yang dilakukan setelah deformasi akan mengembalikan keuletan paduan melalui mekanisme stress relieve, rekristalisasi dan pertumbuhan butir. Penelitian ini bertujuan untuk mengetahui pengaruh persen deformasi dan temperatur anil terhadap rekristalisasi dan sifat mekanik paduan Al-4.7Zn-1.8Mg berat. Pembuatan paduan dilakukan dengan proses squeeze casting. Proses homogenisasi dilakukan pada temperatur 400 oC selama 4 jam. Paduan hasil homogenisasi kemudian diberikan canai dingin dengan persen deformasi 5, 10 dan 20 . Selanjutnya paduan dengan deformasi 20 diberi perlakuan panas anil dengan temperatur 300, 400 dan 500 oC selama 2 jam. Karakterisasi meliputi pengujian kekerasan untuk melihat pengaruh canai dingin dan temperatur anil terhadap sifat mekanik paduan, pengamatan struktur mikro dengan mikroskop optik dan Scanning Electron Microscope SEM yang dilengkapi dengan Energy Dispersive Spectroscopy EDS. Hasil penelitian menunjukkan bahwa peningkatan persen deformasi sebesar menyebabkan terjadinya pemipihan butir. Deformasi 5, 10 dan 20 menghasilkan rasio deformasi butir sebesar 2.19, 3.19 and 4.59 dan meningkatkan kerasan paduan dari 69.5 HV menjadi sebesar 95.3, 100.1 dan 105.4 HV. Perlakuan panas anil pada temperatur 300 oC menyebabkan terjadinya recovery sedangkan rekristalisasi terjadi pada temperatur 400 oC dgrain 290 ?m. Grain growth terjadi pada temperatur 500 oC dgrain 434 ?m yang menyebabkan penurunan kekerasand dari 105.4 HV menjadi 71.5, 96.8 and 95.3 HV berturut turut. Rekristalisasi sempurna diprediksi pada temperature anil 375 ndash; 425 oC selama 2 jam.

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Aluminium alloys are developed as airplane body due to its lighter weight compared to steel and good formability. Aluminium 7XXX series with Zn and Mg alloying elements are commonly used because of its mechanical properties can be improved through deformation process. Deformation such as cold rolling may increase the hardness of an alloy through strain hardening. Annealing process after deformation process will recover ductility through stress relieve, recrystallization and grain growth mechanisms. This research aimed to find out the effect of cold rolling and annealing temperatur on the recrystallization and mechanical properties of Al 4.7Zn 1.8Mg wt. alloy.

The alloy was produced by squeeze casting process. Homogenization was conducted at 400 oC for 4 hours followed by cold rolling with degree of deformation of 5, 10 and 20 . The samples with 20 of deformation were then annealed at 300, 400 and 500 oC for 2 h. Vickers hardness test was performed on the cold rolled and annealed samples to reveal strain hardening effect and subsequent recrystallization process. Microstructure was observed by using optical microscope and Scanning Electron Microscope SEM with Energy Dispersive Spectroscopy EDS.

The results showed that the higher the deformation, the more elongated the grains. Deformation of 5, 10 and 20 led to grain shape ratios of 2.19, 3.19 and 4.59, respectively and increase in the hardness of the alloy from 69.5 HV to 95.3, 100.1 and 105.4 HV, respectively. Annealing at 300 oC resulted in recovery, while at 400 oC, recrystallization occured dgrain 290 m. Grain growth was observed after annealing at 500 oC for 2 h dgrain 434 m. The annealing temperature of 300, 400 and 500 oC decrease the hardness of the alloy from 105.4 HV to 71.5, 96.8 and 95.3 HV, respectively. Full recrystallization was predicted to happen at 375 ndash 425 oC for 2 hours."

" ABSTRAK Paduan aluminum telah dikenal sebagai material utama untuk berbagai aplikasi yang membutuhkan kombinasi antara kekuatan dan massa jenis yang rendah. Paduan aluminium yang sering diaplikasikan yaitu paduan seri 7xxx. Kebanyakan paduan ini digunakan untuk aplikasi pesawat terbang yang membutuhkan kekuatan yang tinggi dan keuletan. Dalam industri penerbangan, paduan Al-Zn-Mg mengalami proses pembentukan untuk menghasilkan produk struktural. Salah satu masalah yang sering muncul dari produk hasil pembentukan adalah peripheral coarse grain PCG dan hot tearing yang dapat mengurangi sifat mekanik dan ketahanan korosi paduan. Penambahan paduan mikro dapat digunakan untuk mengatasi masalah ini. Penambahan kromium Cr pada paduan Al-Zn-Mg dapat menekan pertumbuhan butir dan mengontrol ukuran butir dengan mencegah rekristalisasi lanjutan. Tujuan dari studi ini yaitu untuk mengetahui pengaruh deformasi melalui proses canai dingin pada paduan Al-4.5Zn-1.5Mg-0.9Cr berat dan untuk mengetahui pengaruh kromium terhadap struktur mikro dan sifat mekanik selama rekristalisasi melalui proses anil.Dalam studi ini, paduan dihasilkan melalui squeeze casting. Kemudian, paduan dilakukan homogenisasi selama 4 jam dengan temperatur 400 C. Paduan kemudian dicanai dingin dengan persen deformasi 5, 10 dan 20 . Proses anil dilakukan pada sampel deformasi 20 dengan variasi temperatur 300, 400 dan 500 C selama 2 jam. Karakterisasi yang dilakukan terdiri dari analisis struktur mikro oleh mikroskop optik dan Scanning Electron Microscope SEM - Energy Dispersive Spectroscopy EDS dan pengujian sifat mekanik dengan uji keras Microvickers. Hasilnya, terjadi pemipihan struktur diikuti dengan peningkatan reduksi ketebalan 5, 10 dan 20 dengan nilai rasio butir terdeformasi berturut-turut yaitu, 1.6, 2.84 dan 2.99. Struktur yang semakin pipih ini efektif untuk meningkatkan kekerasan. Selain itu, proses anil hasil canai dingin 20 pada temperatur 300 C dan 400 C belum menunjukkan adanya proses rekristalisasi. Proses rekristalisasi baru terjadi pada proses anil dengan temperatur 500 C. Sementara, pada paduan tanpa Cr, rekristalisasi baru terjadi pada temperatur 400 C. Hal ini dikarenakan adanya dispersoid Cr dalam bentuk Al, Zn 7Cr dengan ukuran kurang dari 1 m menghambat pergerakan dislokasi dan proses rekristalisasi. Hal ini ditandai dengan pembentukan butir baru berawal dari intermetalik Al, Zn 7Cr dengan ukuran lebih dari 1 m yang telah terdeformasi melalui mekanisme particle stimulated nucleation PSN .

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ABSTRACT Aluminum alloys have been known as the main material for various application which requires the combination of strength and low density. One of the alloys that widely used is 7xxx series aluminum alloy. Most of the alloys are commonly used in aircraft industries for their high strength and ductility. In aircraft industries, Al Zn Mg alloys undergo many kinds of forming processes to create structural product. Problems that are usually found in the forming process include peripheral coarse grain PCG and hot tearing which decrease mechanical properties and corrosion resistance of the alloys. Microalloying element can be used to overcome these problems. The addition of chromium Cr in Al Zn Mg alloys can supress the grain growth and control the grain size by preventing excess recrystallization. The aim of this study is to understand the effect of deformation by cold rolling and Cr addition on the microstructure and mechanical properties of Al 4.5Zn 1.5Mg 0.9Cr wt. during recrystallization by annealing process.The Al 4Zn 1.5Mg 1Cr wt. alloy was fabricated by squeeze casting process and was subsequently homogenized at 400 oC for 4 hours. The samples were cold rolled for 5, 10 and 20 . The 20 deformed samples were then annealed at 300, 400 and 500 oC for 2 hours. The material characterization consisted of microstructure analysis by optical microscope and Scanning Electron Microscope SEM Energy Dispersive Spectroscopy EDS and also mechanical testing by Microvickers hardness test. The results showed that the deformed grain ratio was found to be 1.6, 2.84 dan 2.99 in the 5, 10 and 20 deformed samples, rexspectively. The elongated dendrites were effective to increase the hardness of the alloy. No recrystallization was detected during annealing at 300 oC and 400 oC. Recrystallization was observed in the annealing process at 500 oC. Whereas, for the samples without Cr addition, recrystallization occurred at 400 oC. It means the addition of Cr was found to increase the recrystallization temperature of the alloy. It occurred because Cr dispersoid in Al, Zn 7Cr with size less than 1 m impedes the dislocation motion. However, the presence of Al, Zn 7Cr intermetalics with size more than 1 m promote the formation of new grains around them by particle stimulated nucleation PSN mechanism. "