The Influence Of Super Gravity On The Microstructures And Hardness Of Aluminum Alloy

With the development of the aviation industry,the higher requirements on the strength,plastic,wear resistance and corrosion resistance properties of aluminum alloys are put forward.Developing special solidification technologies become hotspots in the research field of aluminum alloy.There is a few reports about that the effect of super gravity solidification on aluminum alloys.The mechanism of super gravity on solidification isn't still very clear.So,It's necessary to explore the influence of super gravity on the microstructure of the aluminum alloy.In this paper,the influence of super gravity on macro segregation,microstructure and hardness of aluminum alloy was investigated by choosing the aluminum-yttrium alloy,aluminum-silicon alloy and ZL205 A alloy for experimental subjects.With the increase of the gravity,it is found that the macro segregation occurs between the core and the edge of the ingot of Al98Y2 alloy.The dispersed shrinkage cavities become concentrated and the primary phase(?-Al)is obviously refined with the increase of the gravity.The size of primary phase(?-Al)decreases from 35?m to 19?m when the gravity increases from 1g to 1200 g.The eutectic structure is changed from irregular form to regular eutectic cell.The proportion of eutectic structure increases gradually with the increase of the gravity.With the increase of the gravity,it is found that the macro segregation occurs between the core and the edge of the ingot of Al-Si alloy.The dispersed shrinkage cavities become concentrated.The shape and the size of eutectic silicon are changed significantly with the increase of the gravity.When solidified under normal gravity,the eutectic silicon is needle-like,Which the diameter is about 1.8 ?m.When the gravity is larger than 600 g,the shape of eutectic silicon is changed from needle to granular,and the size gradually decreases.When the gravity gets 1800 g,the average diameter of the eutectic silicon is only 0.64 ?m.The value of the hardness increases with the increase of the gravity.When the gravity increases from 1g to 4000 g,the value of hardness changes from HV 58 to HV 72.With the increase of the gravity,no macro segregation occurs in the ZL205 A alloy ingot.When solidified under normal gravity,the shape of the grains of the alloy becomes irregular,and the average size of the grains is about 85?m.The grains gradually become equiaxed and small with the increase of the gravity.When the gravity gets 4000 g,the average diameter of the grains is 35?m,and the coarse precipitated phase is refined.The value of the hardness of the alloy increases with the increase of the gravity.When the gravity increases from 1g to 3000 g,the value of hardness changes from HV 64.3 to HV 83.4.