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"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."

"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."

"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."

"Material penyusun badan pelindung kendaraan militer umumnya terbuat dari baja. Dengan densitasnya yang tinggi, dilakukan pengembangan berupa penggantian material penyusunnya yang ringan dan tetap mampu menahan penetrasi peluru, yakni aluminium komposit. Penelitian sebelumnya telah berhasil membuat komposit berpenguat SiC yang dapat menahan peluru tipe III, namun masih mengalami retak di pelat bagian belakang. Oleh karena itu, pada penelitian ini, SiC diganti dengan ZrO2 yang memiliki ketangguhan retak lebih tinggi dan matriksnya dimodifikasi menggunakan Sr yang juga untuk meningkatkan ketangguhan. Komposit dengan matriks Al-9Zn-4Mg-3Si berpenguat ZrO2 sebanyak 5 vol.% dengan variasi kadar Sr sebesar 0, 0,0006, 0,0008, dan 0,01 wt.% difabrikasi menggunakan metode squeeze casting. Guna meningkatkan ketangguhan, komposit tersebut diberi laku pelarutan pada temperatur 450 oC selama 1 jam, dilanjutkan dengan laku penuaan pada temperatur 200 oC selama 1 jam. Dilakukan karakterisasi pada komposit, yakni pengujian komposisi kimia dengan Optical Emission Spectroscopy (OES), pengujian kekerasan dengan metode Rockwell B, pengujian impak dengan metode Charpy, pengamatan struktur mikro menggunakan mikroskop optik dan Scanning Electron Microscope (SEM) yang dilengkapi dengan Energy Dispersive X-Ray Spectroscopy (EDS) dan X-Ray Mapping. Hasil pengujian menunjukkan dengan peningkatan kadar Sr dari 0 % menjadi 0,0006 % terjadi penurunan kekerasan disebabkan fraksi porositas yang meningkat. Peningkatan kadar Sr dari 0,0006 menjadi 0,01 % terjadi peningkatan kekerasan disebabkan kemampuan Sr dalam memodifikasi fasa Mg2Si. Peningkatan kadar Sr menyebabkan terjadinya penurunan harga impak diperkirakan karena Sr memodifikasi fasa α-AlFeSi menjadi β-AlFeSi yang getas. Hasil analisa dengan SEM-EDS menunjukkan termodifikasinya fasa Mg2Si yang chinese script menjadi granul yang lebih halus dan poligonal tak beraturan akibat ko-segregasi Sr ke dalam fasa tersebut.

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Materials for military vehicle are usually made of steel. Steel has high density that results in high weight and high energy consumption. Therefore, it needs to be replaced by lighter materials such as aluminum composites. Previous research has successfully produced SiC-strengthened aluminum composites that were able to withstand type III bullets. However, cracks remained at the back of the plate. To increase toughness, in this research SiC was replaced by ZrO2 and the matrix was modified by Sr addition.

The studied composites used Al-9Zn-4Mg-3Si as matrix and 5 vol.% ZrO2 as reinforcement with Sr addition of 0, 0,0006, 0,0008, and 0,01 wt.% which is fabricated with squeeze casting method. To improve toughness, the composite was solution treated at 450 oC for 1 hour, and then aged at 200 oC for 1 hour.

Material characterization consisted of chemical composition using Optical Emission Spectroscopy (OES), hardness testing by using Rockwell B method, and impact testing by using Charpy method, microstructural analysis by using optical microscope and Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-Ray Spectroscopy (EDS) dan X-Ray Mapping.

The results showed that addition of Sr from 0 to 0.0006 % decreased the hardness because of the increased in porosity. Increasing Sr addition from 0.0006 to 0.01 % increased the hardness because the ability of Sr to modify microstructures. Increasing Sr addition that induce decreasing impact properties is analyzed because of Sr modified α-AlFeSi to β-AlFeSi phase.

The result of microstructure analysis with SEM-EDS detected co-segregation of Sr with Mg2Si, which then modify the morphology from chinese script to fine granule and irregular polygonal."

"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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"Telah dilakukan pembuatan paduan Al Cu dengan proses metalurgi serbuk (powder metallurgy). Bahan diperoleh dari Merck, kemurnian > 98,5 % untuk serbuk Al , sedang serbuk Cu, kemurnian > 99,7 %. Kedua serbuk tersebut dicampur dengan berbagai variasi komposisi persen berat, terdiri dari Al - 90,40% Cu, Al - 70, 19% Cu, Al - 33,33% Cu, Al - 0% Cu, Al - 3% Cu, Al - 5% Cu. Proses pembentukan dilakukan dengan menggerusnya selama 3 jam. Kemudian dilakukan proses pembentukan dengan cara cetak tekan menggunakan hidrolik press dengan tekanan 7 ton dan selanjutnya di Sinter/pembakaran pada temperatur 400°C, 500°C, 600°C. Heat treatment dilakukan selama 1 jam pada temperatur 540°C, quenching dalam media air. Karakterisasi meliputi analisis fasa dengan XRD, kekerasan, densitas serta kandungan unsur paduan dengan XRF. Hasil analisis fasa memperlihatkan adanya fasa Al2Cu yang ditunjukkan oleh puncak difraksi dengan orientasi (220), (310), (130). Fasa Al3Cu2 bidang orientasi (111), (205), (102) sedang fasa Al4Cu9, oleh puncak difraksi (330), (411 ), (600), (442) , pada temperatur sinter >- 500°C, densitas (appaerent density) meningkat dengan bertambahnya prosentase Cu,dan kenaikan temperatur sinter untuk komposisi Cu relatif kecil, nilai densitas :2,23gr/cm3 - 6,44gr/cm3 . Kekerasan cenderung meningkat tajam untuk temperatur sinter 600°C bisa mencapai 797 ,5 HV, khususnya untuk paduan komposisi (Al - 70, 19% Cu), hasil analisis kandungan unsur dengan XRF, semakin tinggi temperatur sinter ternyata prosentasi kandungan Al mengecil, kecuali untuk paduan Al - 0% Cu, kenaikan temperatur sinter menyebabkan kandungan Al justru naik, walaupun kenaikannya relatif kecil."

"[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]"

"Anoda korban paduan Al-5Zn-0,5Cu-0,3Y merupakan salah satu pengembangan anoda korban dengan tegangan yang rendah yang dapat mencegah terjadinya adanya proteksi berlebih yang dapat menimbulkan potensi terjadinya stress corrosion cracking. Namun pada pengaplikasiannya dibutuhkan anoda korban yang memiliki efisiensi yang tinggi untuk memaksimalkan kerja anoda korban. Salah satu peningkatan efisiensi anoda korban yaitu dengan penambahan perlakuan panas. Perlakuan panas yang dilakukan pada penilitan ini yaitu age hardening. Dilakukan proses quenching dari suhu 400°C kemudian dilakukan penuaan pada suhu 220°C dengan variasi waktu penahanan 1 jam, 3 jam, dan 5 jam. Pengujian efisiensi dilakukan dengan menggunakan standar DNV RP-B401 yang dilakukan selama 96 jam. Didapatkan efisiensi dari anoda korban Al-5Zn-0.5Cu-0,3Y as-cast, aging 1 jam, 3 jam, dan 5 jam berturut – turut adalah 67%, 66%, 64%, dan 61%. Perlakuan panas menyebabkan meningkatnya laju korosi dari anoda korban paduan karena adanya pembentukan presipitat yang tumbuh pada batas butir sehingga korosi lebih mudah menyerang. Hal tersebut menunjukkan bahwa semakin lama penahanan waktu perlakuan panas maka akan semakin mengurangi efisiensi dari anoda korban paduan Al-5Zn-0.5Cu-0.3Y.

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Al-5Zn-0,5Cu-0.3Y alloy sacrificial anode is one of the developments of a low-voltage sacrificial anode that can prevent overprotection which that makes stress corrosion cracking. However, its application requires a sacrificial anode that has high efficiency is needed to maximize the function of the sacrificial anode. One way to increase the efficiency of the sacrificial anode is by adding heat treatment. The heat treatment that carried out in this research is age hardening. The quenching process uses 400°C for a temperature and then aging at a temperature of 220°C with variations in holding times of 1 hour, 3 hours, and 5 hours. Efficiency testing was carried out using the DNV RP-B401 standard which was carried out for 96 hours. The efficiency of the sacrificial anode Al-5Zn0.5Cu-0.3Y without heat treatment, or with aging holding time of 1 hour, 3 hours, and 5 hours, respectively, was 67%, 66%, 64%, and 61%. Heat treatment causes an increase in the corrosion rate of the alloy sa crificial anode due to the formation of precipitates that grow at the grain boundaries so that corrosion is easier to attack. This shows that the long holding time will further reduce the efficiency of the Al-5Zn-0.5Cu-0.3Y alloy sacrificial anode."

"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."