The mechanical properties (σb,σ0.2,and δ) and fracture behavior of tensile specimens of the refined A356 alloys were investigated as a function of the addition level of Al-Ti-B master alloy under both as-cast and T...The mechanical properties (σb,σ0.2,and δ) and fracture behavior of tensile specimens of the refined A356 alloys were investigated as a function of the addition level of Al-Ti-B master alloy under both as-cast and T6 heat-treated conditions. The results show that as the addition level of Al-5Ti-1B master alloy increases from 0.1 wt.% to 5.0 wt.%,the mechanical properties of refined A356 alloys improve steadily and then decrease slightly under both as-cast and T6 heat-treated conditions. Also,they display exc...展开更多
The macrosegregation formation in an ingot and the influence of rotating mould upon it were analysed on the basis of interdendritic flow.When the ingot mould rotates unidirectionally,the centrifugal volume force acts ...The macrosegregation formation in an ingot and the influence of rotating mould upon it were analysed on the basis of interdendritic flow.When the ingot mould rotates unidirectionally,the centrifugal volume force acts on all inner parts,and when the ingot mould rotates alternately, the tangential alternate force is also formed,and both have various influences on the different modes of interdendritic flow.It is shown that as the ingot mould rotates unidirectionally or alternately with a moderate angular speed,the interdendritic unstable flow may be controlled effectively and the formation of segregation may be restrained.Thus,it seems to be significant for reducing the segregation such as A-type etc.,in the steel ingot.展开更多
The influence of fluid flow on the dendritic growing tips in region close to the growth interface have been studied quantitatively.The effect of asymmetrical parabola tips and the crossover of diffusion-convection tra...The influence of fluid flow on the dendritic growing tips in region close to the growth interface have been studied quantitatively.The effect of asymmetrical parabola tips and the crossover of diffusion-convection transport mechanisms on crystal growth behaviour have been found for the first time.展开更多
Through phase transformation kinetic analysis and experimental observation,the δ/γtransformation occurring in the non-equilibrium peritectic Fe-4.33at.%Ni alloys was systematically investigated.According to JMA soli...Through phase transformation kinetic analysis and experimental observation,the δ/γtransformation occurring in the non-equilibrium peritectic Fe-4.33at.%Ni alloys was systematically investigated.According to JMA solid-state transformation ki-netic theory,the Time-Temperature-Transformation(TTT)curves of the δ/γtrans-formation in peritectic Fe-Ni alloy were calculated.On this basis,the physical cor-relation between the δ/γtransformation and the initial undercooling of melt(T)was elucidated.The results indicate that the change of T can alter not only the overall δ/γtransformation pathways but also the transformation fraction with re-spect to each transformation mechanism.展开更多
A solution entropy model was developed for the undercooled binary eutectic alloy systems. As an ex-tension of Taylor and Fidler et al.'s model, the present model considered the change of phase compo-sition with th...A solution entropy model was developed for the undercooled binary eutectic alloy systems. As an ex-tension of Taylor and Fidler et al.'s model, the present model considered the change of phase compo-sition with the increase of undercooling. Furthermore, the sub-regular solution model and the interac-tion parameter (IAB) were also introduced. In this paper, the extended model is used to calculate the solution entropy for binary eutectic phases under the undercooled condition, and the application scope of the model is also extended. Not only the growth manner of eutectic phases, but also the transition of morphologies may be predicted and explained by calculating the solution entropy of eutectic phases under the non-equilibrium condition with the developed model. Experimental results show that the developed model is valid for the undercooled Ni-Si and Ni-Sn eutectic alloy systems.展开更多
基金the National Natural Science Foundation of China (No. 50571081)the Aeronautical Science Foundation of China (No. 04G53042) for financial support
文摘The mechanical properties (σb,σ0.2,and δ) and fracture behavior of tensile specimens of the refined A356 alloys were investigated as a function of the addition level of Al-Ti-B master alloy under both as-cast and T6 heat-treated conditions. The results show that as the addition level of Al-5Ti-1B master alloy increases from 0.1 wt.% to 5.0 wt.%,the mechanical properties of refined A356 alloys improve steadily and then decrease slightly under both as-cast and T6 heat-treated conditions. Also,they display exc...
文摘The macrosegregation formation in an ingot and the influence of rotating mould upon it were analysed on the basis of interdendritic flow.When the ingot mould rotates unidirectionally,the centrifugal volume force acts on all inner parts,and when the ingot mould rotates alternately, the tangential alternate force is also formed,and both have various influences on the different modes of interdendritic flow.It is shown that as the ingot mould rotates unidirectionally or alternately with a moderate angular speed,the interdendritic unstable flow may be controlled effectively and the formation of segregation may be restrained.Thus,it seems to be significant for reducing the segregation such as A-type etc.,in the steel ingot.
文摘The influence of fluid flow on the dendritic growing tips in region close to the growth interface have been studied quantitatively.The effect of asymmetrical parabola tips and the crossover of diffusion-convection transport mechanisms on crystal growth behaviour have been found for the first time.
基金the National Natural Science Foundation of China (Grant Nos. 50395103,50501020 and 50431030)the Fundamental Research Project of National Defense of China (Grant No. A2720060295)+3 种基金the New Century Excellent Person Supporting Project (Grant No. NCET-05-870)the Doctorate Foundation of Northwestern Polytechnical University (Grant No. CX200604)the Scientific and Technological Creative Foundation of Youth in Northwestern Polytechnical University,the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education of China (Grant No. N6CJ0002) the Natural Science Foundation of Shaanxi Province,China (Grant No. 2004E108)
文摘Through phase transformation kinetic analysis and experimental observation,the δ/γtransformation occurring in the non-equilibrium peritectic Fe-4.33at.%Ni alloys was systematically investigated.According to JMA solid-state transformation ki-netic theory,the Time-Temperature-Transformation(TTT)curves of the δ/γtrans-formation in peritectic Fe-Ni alloy were calculated.On this basis,the physical cor-relation between the δ/γtransformation and the initial undercooling of melt(T)was elucidated.The results indicate that the change of T can alter not only the overall δ/γtransformation pathways but also the transformation fraction with re-spect to each transformation mechanism.
基金Supported by the National Natural Science Foundation of China (Grant No. 50395103)Doctorate Foundation of Northwestern Polytechnical University (Grant No. CX200506)
文摘A solution entropy model was developed for the undercooled binary eutectic alloy systems. As an ex-tension of Taylor and Fidler et al.'s model, the present model considered the change of phase compo-sition with the increase of undercooling. Furthermore, the sub-regular solution model and the interac-tion parameter (IAB) were also introduced. In this paper, the extended model is used to calculate the solution entropy for binary eutectic phases under the undercooled condition, and the application scope of the model is also extended. Not only the growth manner of eutectic phases, but also the transition of morphologies may be predicted and explained by calculating the solution entropy of eutectic phases under the non-equilibrium condition with the developed model. Experimental results show that the developed model is valid for the undercooled Ni-Si and Ni-Sn eutectic alloy systems.
