Papers by Keyword: Ageing Treatment

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Authors: Soon Vern Yee, Zuhailawati Hussain, Abu Seman Anasyida, Muhammad Syukron, Indra Putra Almanar
Abstract: This study investigated the effect of severe plastic deformation (SPD) and artificial ageing treatment on mechanical properties of cast Al-Mg-Si alloy. 6061-T6 aluminum alloy was remelted and casted into a rod of 13mm in diameter and 60mm in length. The rod samples were then subjected to equal channel angular pressing (ECAP) for SPD process, up to 2 passes, through Bc route. Cast and ECAPed samples were solution heat treated at 530 °C, quenched in water and held at 180 °C at various ageing time to determine the effect of artificial ageing. Cast alloy consisted of α phase grains that were surrounded by Mg2Si particles locating at the grain boundaries. The hardness increased with accumulative applied strain by 2-pass ECAP process with the value of 99.4 Hv. For heat treated samples, maximum hardness was achieved after 5-hour ageing.
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Authors: Hong Wei Liu, Feng Wang, Bai Qing Xiong, Yon Gan Zhang, Zhi Hui Li, Xi Wu Li
Abstract: In this study, the Al-Zn-Mg-Cu alloy was prepared by spray forming process. The ageing precipitation and strengthening behavior of the spray formed Al-Zn-Mg-Cu alloy were studied by microhardness tests, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) .The results show that the main strengthening precipitates of the spray formed Al-Zn-Mg-Cu alloy are GPI (solute-rich clusters), GPII (vacancy-rich clusters) under peak aging condition. The effect of the microstructure on ageing hardness is controlled by the size and amount of the existing precipitates, and therefore depends critically on the ageing temperature and ageing time. Strength of this alloy is influenced significantly during natural ageing at room temperature, which is related to the dominant formation of GPI. During the initial stage of artificial ageing at 120°C, strong age-strengthening response is due to the formation of GP zones (both GPI and GPII ) .During later stages of artificial ageing , GPII precipitation is accelerated significantly but GPI is not affected clearly.
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Authors: Fan Qing Ran, Zi Yong Chen, Li Hua Chai
Abstract: In this paper, the polished specimens of high Zn content Al-Zn-Mg-Cu alloy after various aging treatments were immersed in 3.5 wt.% NaCl for up to 240 mins. The development of corrosion was monitored using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). There are two stages during the corrosion process, the first stage of attack started with localized corrosion of trenching around the Al-Zn-Mg-Cu particles. In the second stage the pitting corrosion appeared at the grain boundaries, and then developed into intergranular corrosion. This phenomenon is related to the potential difference between the matrix and the precipitates.
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Authors: Kurnia Hastuti, Esah Hamzah, Jasmi Hashim
Abstract: In this study, a commercial Ti-50.7at.%Ni was subjected to solution treatment at 800oC and 900oC for one hour followed by ageing at 300oC, 400oC, 500oC and 600oC for 1 hour, 2 hours and 4 hours respectively. Characterization of the material using optical microscope, XRD, FESEM and EDX has shown that the presence of Ti2Ni and Ti-rich precipitates in the as-received material remained unchanged even after heat treatment. The presence of oxygen in the air condition heat treatment has stabilized Ti2Ni since this condition causing the formation of Ti4Ni2O which is also determined as Ti2Ni due to their same crystal structure. The formation of Ti3Ni4 precipitates during ageing encouraged the establishment of R phase instead of martensite due to the depletion of Ni content in the matrix. Ageing treatment at 300oC generates two steps of R phase transformation due to the differences in Ni composition in the matrix at the grain boundary and grain interior region. However, for samples subjected to ageing at higher temperature, 400-500oC, only one step of R phase transformation occurred because Ni atomic diffusion was not forbidden in the high temperature. Hardness test performed on the samples revealed that increasing the ageing time will increase the hardness of material; however for the sample aged at 600oC, increasing the ageing time would reduce the hardness due to dissolution of Ti3Ni4 precipitaes into the matrix.
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Authors: Esah Hamzah, Kurnia Hastuti, Jasmi Hashim, Chuan Eng Chuah, Muhammad Adil Khattak
Abstract: In this study a plate form of Ti-50.7at.%Ni was subjected to solution annealing at 800°C and 900°C for one hour followed by ageing at 300°C and 400°C for 4 hours respectively in order to investigate the effect of solution annealing and low temperature ageing on the microstructures and superelastic behaviour. It was found that the formation of Ti3Ni4 precipitates on the samples aged at 300°C and 400°C influences superelasticity differently. Increasing the testing temperature up to 38°C generally increases the superelasticity of samples for all heat treatment conditions compared to those tested at 22°C, however the sample solution annealed at 900°C give better superelasticity at 22°C due to excessive plastic deformation at higher temperature.
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Authors: Peng Hui Deng, Tie Cheng Li, Gang Yi Cai
Abstract: In this study, the comprehensive performance of AZ80 magnesium alloy was improved by solution treatment and multi-step ageing treatment. The effects of different thermal processing parameters on the microstructure and mechanical properties of AZ80 magnesium alloy were studied. The experimental results show that the optimal process of solution treatment for AZ80 alloy is heated at 420°C for 5h, which the β phase dissolve thoroughly into the α substrate. After first-stage ageing treatment, the hardness of samples varied as the ageing temperature, and had higher hardeness at temprature 180°C. While in the second-stage ageing treatment, the sample got the ageing peak value at 210°C for 10h. After two-stage treatment, the grains of AZ80 magnesium alloy became homogeneous and fine, and the second phase distributes along the grain boundary and plays an important role of dispersion strengthening. Above all, the optimal heat treatment process of AZ80 magnesium is solution treated at 420°C for 5h, as well as ageing at 180°C, 4h and 210°C, 10h.
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Authors: Shi Xing Zhang, Gang Yi Cai, Hai Hong Wu
Abstract: Comprehensive performance of 6061 aluminum alloy was improved by solution treatment and two-step ageing treatment in this paper . The effects of different thermal processing parameters on the microstructure and mechanical properties of 6061 aluminum alloy were studied. The experimental results show that the optimal process of solution treatment for 6061 aluminum alloy is heated at 500°C for 10min. After first-stage aging, the hardness measurements and microstructure analysis results show that the hardness increased with increasing aging temperature, and reached peak value at temperature 180°C for 10h, while in the second-stage ageing treatment, the sample got the ageing peak value at 220°C for 1h. After two-stage treatment, the grains of 6061 aluminum alloy became uniform and fine and the second phase distributed along the grain boundary and play an important role of dispersion strengthening. Above all, the optimal heat treatment process of 6061 aluminum alloy is solution treated at 500°C for 10min, as well as ageing at 180°C, 10h and 220°C, 1h
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Authors: Yue Jiang, Ying Ying Ai, Qi Ting Wang
Abstract: The changes of precipitation phases and matrix structures in Fe-13Cr-7Ni-4Mo-4Co-2W maraging stainless steel at different temperature were studied by using the Thermo-Calc software. The research was on the microstructures and precipitation behaviors of the maraging stainless steel, the performance is investigated through solution and aging treatment by TEMand SADP. The calculation results were in good agreement with the experiments, which demonstrated that when maraging stainless steel was treated in high temperature, the Laves-Fe2Mo precipitates became totally dissolved as the temperature was above 1050°C, and about 8% of R phase was found during aging. The calculation provides a guiding significant to the establishment of reasonable heat treatment process and the development of new materials.
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