Papers by Keyword: Supersaturated Solid Solution

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Authors: Takuro Nakamura, Hiromoto Kitahara, Jung Goo Lee, Nobuhiro Tsuji
Abstract: Pure Al (99%) and pure Fe (99.5%) sheets were mutually stacked and severely deformed up to equivalent strain of 16 by the accumulative roll bonding (ARB) process in an attempt to achieve bulk mechanical alloying. The deformation was carried out at RT. The Al/Fe sheets ARB processed by 1 cycle showed a number of shear bands penetrating the stacked layers. The Fe layers, which were harder than the Al layers, were subdivided by the shear bands into diamond-shaped regions. Dissolution of Fe into Al was observed and a supersaturated solid solution was formed in the specimen ARB processed by 10 cycles. It was also found that local amorphization occurred at interface regions via formation of Al5Fe2 intermetallic compound.
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Authors: Bo Gao, Yi Hao, Gan Feng Tu, Shi Wei Li, Sheng Zhi Hao, Chuang Dong
Abstract: High current pulsed electron beam (HCPEB), a novel high-power energetic beam technology, has been developed as a useful tool for surface modification of materials. In the present work, the effect of HCPEB treatment on microstructure and wear resistance of Al-15Si and ZK60-1Y Mg alloys was investigated. The results show that a supersaturated solid solution of (Al) and (Mg) is formed on top surface of melted layer induced by rapid heating and cooling during HCPEB process. In addition, the melted layer of approximately 5~11μm thickness is obtained on the ZK60-1Y Mg alloy surface. Wear resistance of Al-15Si and ZK60-1Y Mg alloys are significantly improved after HCPEB treatment. It is demonstrated that HCPEB technology has a good application future in enhancing surface properties of Al-Si and Mg alloys.
1204
Authors: Xue Ran Liu, Y. B. Liu, Y. Sun, G.H. Su
Abstract: C/Cu self-lubricating composites were a kind of potentially functional materials. Nanostructured C/Cu composites were prepared by the new technology of mechanical activation-spark plasma sintering (MA-SPS). Microstructures of the as-milled powder and the as-sintered simple were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. These investigations indicated that in Cu-C immiscible system, the nanostructured supersaturated solid solution of carbon in copper was formed at atomic level after milling for 24 h. Microstructures of SPS sintered C/Cu composites still kept the nanostructure. In addition, Cu-C interface bonding was good. It was ascribed to a double activation mechanism in the MA-SPS process, which improved the sintering activity of C/Cu powders. Nanostructured C/Cu composites were obtained by SPS sintered at 600 °C for 3 min.
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Authors: Xiao Dong Zhang, Yue Chi, Zhan Kui Zhao
Abstract: High-silicon aluminum alloys as light-weight structural materials are attractive because of their high wear resistance, low density and low thermal expansion. However, the Si phase in the high-silicon aluminum alloys always has big size, which deteriorates the mechanical properties and machinability of alloys. In this paper, alloy ribbon of high-silicon aluminum alloy with the composition of Al70Si30 was prepared by melt-spinning method. Then alloy ribbon was broken to powder by ball milling. The alloy powers were consolidated by spark plasma sintering (SPS) at different sintering parameters including time and temperature under vacuum atmosphere. The density, hardness and compression property of the compacts were investigated. The sintered samples were characterized by scanning electron microscopy (SEM) and X-ray diffractometry (XRD), and compared with their alloy power and original alloy ribbons. The results showed that the density of Al70Si30 alloy, prepared under the condition of 320 °C and 500 MPa, was above 98%, the grain size was refined to sub-micron, and the wear resistance was good, micro-hardness was 311.70 Hv. It is believed that the existence of local high temperature and discharge plasma can break down and disrupt oxidation film on powder surface, and therefore improving the efficiency of sintering. In the case of large current, short time and low temperature, sintering grain growth was not obvious, there was less supersaturated solid solution precipitation and the rapid solidification microstructure , and the properties can be preferably reserved.
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Authors: Li Jun Wei, Bo Long Li, Liu Yi Guan, Tong Bo Wang, Peng Qi, Zuo Ren Nie
Abstract: Al-Si alloy was widely applied in automobile engine parts to realize weight reduction. The influence of casting temperature on the microstructure of die casting Al-Si-Cu-Mg alloy was studied in this paper. Based on ZL 101 alloy, the strength was improved with addition of 0.8% Cu element. The influence of pouring temperature on microstructure was investigated using optical microscope and electron probe micro-analysis (EPMA), and T1 heat treatment was optimized. The primary α-Al was more coarsened when the pouring temperature rose from 660 ̊C to 690 ̊C. The solid solubility of Cu in α-Al was 0.2406 wt%, analyzed by EPMA. Considering the solid solubility of Cu and avoiding porosity at high-temperature, T1 heat treatment was reasonable and affective. The micro-hardness reached to a peak value of 114 HV during aging at a temperature of 175 ̊C after 10 h. Therefore, 175 ̊C×10h aging was the most appropriate heat treatment process.
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