Semi-solid metal casting and forming is a promising production method for a wide range of metal alloys, In spite of many applications for semi-solid processed light alloys, few works have reported on the semi-solid pr...Semi-solid metal casting and forming is a promising production method for a wide range of metal alloys, In spite of many applications for semi-solid processed light alloys, few works have reported on the semi-solid processing of iron and steel. In this research, an inclined plate was used to change the dendritic structure of iron to globular. The effects of the length and slope of the plate on the casting structure were examined. The results show that the process effectively changes the dendritic structure to globular. A sloped plate angle of 7.5° and length of 560 mm with a cooling rate of 67 K· s^-1 gave the optimum graphite nodu- larity and solid particle globularity. The results also show that the sloped plate more easily prevents inoculant fading since the total time processing is rather short. In addition the semi-solid ductile cast iron prepared using the inclined plate method was reheated to examine the effect of reheating conditions on the microstructure and coarsening kinetics of the alloy. The solid fractions at different reheating temperatures and holding times were used to find the optimum reheating temperature range.展开更多
Two kinds of bi-metal composite parts （Sn-15%Pb and Pb-22%Sn bi-metal system, and Al-7%Si and SiCp/6061 MMC bi-metal system） were prepared by the strain-induced melt activated thixo-forging. The interfaces of the bi...Two kinds of bi-metal composite parts （Sn-15%Pb and Pb-22%Sn bi-metal system, and Al-7%Si and SiCp/6061 MMC bi-metal system） were prepared by the strain-induced melt activated thixo-forging. The interfaces of the bi-metal composites were observed by OM and SEM. The observations show that the semisolid metals keep independence during thixo-forging. The solid phases in the semisolid slurries maintain their original morphologies after thixo-forging. The liquid phases near the interface mix together and form a thin layer. The interfaces are bonded firmly with the metallurgical bonding. No oxide layers are found at the interfaces. Strengths of the interfaces were investigated by the micro-hardness test. The experimental results show that the composite interfaces have high strength. However, the agglomerated enhancing particles cause fine defect on the interface of the Al-7%Si and SiCr/6061 MMC bi-metal composite.展开更多
To meet the demands of continuous stream-line for component production in the thixo-forming industry, billet heating should be of high quality and in a controllable way. A 4-step inductive heating strategy for aluminu...To meet the demands of continuous stream-line for component production in the thixo-forming industry, billet heating should be of high quality and in a controllable way. A 4-step inductive heating strategy for aluminum alloy A356 was performed. Thixotropic testing and microstructure analysis showed that a homogenous temperature distribution was achieved after temperature-power-time optimization. Theoretical analysis was given concerning the thermal conductivity and heat capacity of A356 between conventional and semisolid casting microstructures. The experimental results show that the optimized 4-step strategy could be the best strategy for billet heating during the thixo-forming of aluminum alloy A356.展开更多
文摘Semi-solid metal casting and forming is a promising production method for a wide range of metal alloys, In spite of many applications for semi-solid processed light alloys, few works have reported on the semi-solid processing of iron and steel. In this research, an inclined plate was used to change the dendritic structure of iron to globular. The effects of the length and slope of the plate on the casting structure were examined. The results show that the process effectively changes the dendritic structure to globular. A sloped plate angle of 7.5° and length of 560 mm with a cooling rate of 67 K· s^-1 gave the optimum graphite nodu- larity and solid particle globularity. The results also show that the sloped plate more easily prevents inoculant fading since the total time processing is rather short. In addition the semi-solid ductile cast iron prepared using the inclined plate method was reheated to examine the effect of reheating conditions on the microstructure and coarsening kinetics of the alloy. The solid fractions at different reheating temperatures and holding times were used to find the optimum reheating temperature range.
基金Project(1343-71333000469) supported by the Funding of Graduate Student Training of Central South University,China
文摘Two kinds of bi-metal composite parts （Sn-15%Pb and Pb-22%Sn bi-metal system, and Al-7%Si and SiCp/6061 MMC bi-metal system） were prepared by the strain-induced melt activated thixo-forging. The interfaces of the bi-metal composites were observed by OM and SEM. The observations show that the semisolid metals keep independence during thixo-forging. The solid phases in the semisolid slurries maintain their original morphologies after thixo-forging. The liquid phases near the interface mix together and form a thin layer. The interfaces are bonded firmly with the metallurgical bonding. No oxide layers are found at the interfaces. Strengths of the interfaces were investigated by the micro-hardness test. The experimental results show that the composite interfaces have high strength. However, the agglomerated enhancing particles cause fine defect on the interface of the Al-7%Si and SiCr/6061 MMC bi-metal composite.
基金supported by the National High-Tech Research and Development Program of China (No.2007AA03Z119)the Innovation Programs of China Electronics Technology Group Corporation (No.81AA10042)
文摘To meet the demands of continuous stream-line for component production in the thixo-forming industry, billet heating should be of high quality and in a controllable way. A 4-step inductive heating strategy for aluminum alloy A356 was performed. Thixotropic testing and microstructure analysis showed that a homogenous temperature distribution was achieved after temperature-power-time optimization. Theoretical analysis was given concerning the thermal conductivity and heat capacity of A356 between conventional and semisolid casting microstructures. The experimental results show that the optimized 4-step strategy could be the best strategy for billet heating during the thixo-forming of aluminum alloy A356.
