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Inhomogeneity of density and mechanical properties of A357 aluminum alloy backward extruded in semi-solid state

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Transactions of Nonferrous Metals Society of China 2011年第10期21卷 2285-2293页

作者：杜之明陈刚程远胜谢水生哈尔滨工业大学材料科学与工程学院哈尔滨150001 北京有色金属研究总院有色金属制造与加工国家重点实验室北京100088

The inhomogeneity of density and mechanical properties of A357 aluminum alloy in the semi-solid state were *** simulation and backward extrusion were adopted to study the preparation of cup *** results show that the relative density of the wall is the lowest in samples,and that of the base is the *** increasing the billet height,more time is needed for relative density of the corner to reach the maximum value,and the relative densities in every region improve evidently with increasing the *** tensile stress was simulated to be the largest at the corner,and the hot tearings were forecasted to mainly appear at the corner *** employing proper billet height and pressure,the extruded samples consisted of fine and uniform microstructures,and can obtain excellent mechanical properties and Brinell hardness.

关键词： A357 aluminum alloy inhomogeneity semi-solid state backward extrusion numerical simulation

Microscopic characterization of semi-solid aluminium alloys

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International Journal of Minerals,Metallurgy and Materials 2010年第3期17卷 290-296页

作者： Ya-lin Lu Miao-quan Li Xing-cheng Li Xiao-ping Li School of Materials Science and Engineering Northwestern Polytechnical University Xi＇an 710072 China School of Materials Engineering Jiangsu Teachers University of Technology Changzhou 213000 China

The microstructural evolution and element distribution of the Al-4Cu-Mg alloy during semi-solid compression were investigated, and the precipitate behavior and dislocation morphology were discussed. The experimental results show that the microstructure, the number of CuAl2 （θ phase） precipitates, and the dislocation density of the Al-4Cu-Mg alloy depend apparently on the process parameters. More segregation of Cu at the grain boundary happens with an increase of deformatinn temperature and a decrease of strain rate, leading to an increase in the number of θ phase. With an increase of height reduction, Cu segregation at the grain boundary decreases gradually. Moreover, unique dislocation morphologies including helical dislocations and dislocation loops appear at different process parameters and evolve to reduce the stored energy.

关键词： aluminum alloys semi-solid state microstructural evolution dislocation

Behaviors of Oxide Layer at Interface between semi-solid Filler Metal and Aluminum Matrix Composites during Vibration

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Journal of Materials Science & Technology 2011年第8期27卷 746-752页

作者： Lei Shi Jiuchun Yan Yanfei Han Bo Peng state Key Laboratory of Advanced Welding and Joining School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

The joint interface between semi-solid Zn-Al filler metal and SiCp/Al composites with applying vibration for different time was examined. With increasing vibrating time, the oxide layer was disrupted prior at the centre to the periphery of the interface. And the solid grains near the centre of interface in semi-solid filler metal aggregated into two solid regions and compressed the composites during vibration; the solid grains near the periphery of interface moved toward the edge and scraped the composites during vibration. The models of disrupting oxide layer under the vibration condition were developed. At the centre of interface, the oxide layer was tore and stripped during the solid grains in the semi-solid filler metal depressing the composites with a very high compressive stress. At the periphery of interface, the oxide layer was cut and stripped into the filler metal during the solid grains scraping the interface.

关键词： SiCP/Al composites Brazing Oxide layer semi-solid state

Influence of semi-solid isothermal treatment on eutectic carbide in Cr12MoV steel

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China Foundry 2014年第6期11卷 498-502页

作者： Li Qingchun Yang Bo Li Chong Wang Chao Chang Guowei School of Materials Science and Engineering Liaoning University of Technology

In-situ observation of eutectic solidification of Cr12MoV steel was conducted using high temperature confocal laser-scanning microscopy. The semi-solid isothermal treatment temperature of the steel was determined by thermodynamic calculation using Thermo-cal software. At the same time, the influences of isothermal treatment temperature and time on eutectic carbides in the steel were also studied. The results show that when the liquid metal cools at the rate of 47 ℃·min^-1, the eutectic reaction occurs rapidly at 1,214.7 ℃ in one second with the reticular liquid around austenite dendrites, transforming into a network of eutectic structure. After being held at 1,300 ℃ for 30 min, the carbide network is broken due to the impingement of refined primary austenite dendrites and secondary dendrites arms, and the thickness of eutectic structure is reduced.

关键词： semi-solid state isothermal treatment eutectic carbide

Effect of TiB_2 addition on microstructure of spray-formed Si-30Al composite

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Transactions of Nonferrous Metals Society of China 2011年第10期21卷 2242-2247页

作者：甘贵生张磊贝舒瑜卢毅杨滨北京科技大学新金属材料国家重点实验室北京100083 重庆理工大学材料科学与工程学院重庆400050

An in situ reaction and spray forming technique were employed in the synthesis of 2% TiB2/Si-30Al *** formation mechanism of TiB2 particulates was explained based on thermodynamic *** modification of the primary Si in the Si-30Al alloy was interpreted in the light of the knowledge of atomic *** experimental results show that adding 2% TiB2 to the Si-30Al alloy can effectively refine the primary ***,the coarsening and growth of primary Si phase in its semi-solid state was retarded effectively due to the existence of the TiB2 particulates.

关键词： spray forming TiB2 particulate coarsening semi-solid state