Effects Of Solidification Pressure Difference And Solidification Pressure On The Microstructure And Elevated Temperature Creep Properties Of Vacuum Counter-pressure Casting Aluminum Alloy

With the increasing requirement of elevated temperature property for military products such as aeronautics and astronautics,the elevated temperature property require higher requirements on the structure,microstructure and mechanical properties of the matrix.However,the coarse acicular eutectic structure and dendrite of Al-Si alloy affect the microstructure and elevated temperature creep properties of the castings.Vacuum counter-pressure casting can improve the structure of casting and obtain aluminum alloy products with good creep properties on account of promoting solidification feeding of molten metal.The solidification feeding capacity of molten metal is affected by solidification pressure difference and solidification pressure.Therefore,the effects of solidification pressure difference and solidification pressure on the microstructure and elevated temperature creep properties of vacuum counter-pressure casting aluminum alloy were studied.In this paper,the influence of solidification pressure difference and solidification pressure on the density,microstructure and elevated temperature creep properties of ZL114 A alloy was studied.The results show that the solidification pressure difference and solidification pressure have a significant effect on the elevated temperature creep properties of the specimens.With the increase of solidification pressure difference and solidification pressure,the elevated temperature creep properties of the castings increase.When the solidification pressure difference is 30 kPa and the solidification pressure is 250 kPa or 300 kPa,the specimens rupture at about 30 h,and there is no second stage of creep.When the difference is 90 kPa and the solidification pressure is 350 kPa,the specimens have no fracture at 100h;the steady deformation rate of the second stage of creep increases with the increase of creep stress,the logarithm of creep rate is linear with the logarithm of creep stress.The relationship between creep rate and creep stress of vacuum counter-pressure casting ZL114 A alloy is established,the relational equation of creep rate and creep stress is deduced:lg ε=1.833lgσ-6.979After creep experiments,the microstructure of the samples are refined and the segregation of eutectic silicon is improved.With the decrease of the size of eutectic silicon,the elevated temperature creep property of the sample is improved.When the solidification pressure difference and the solidification pressure increase,the density of the casting increases,and the solidification pressure difference has greater effect on the solidification feeding of molten metal than the solidification pressure.The effect of solidification pressure difference and solidification pressure on the microstructure and elevated temperature creep properties of vacuum counter-pressure casting aluminum alloy is studied in this paper,which provides a new idea for the study of vacuum counter-pressure casting process parameters,and provides the oretical basis and technical support for the production of elevated temperature performance parts.