Tribo-performance of Thixoformed A356-5TiB2 in-situ Composites

摘要

In the current work,thixofonnedA356-5wt%TiB2in-situ composites were subjected to dry sliding wear.Further,the wear surface topography and wear debris was analyzed.The results show that wear rate is significantly influenced by redistribution of TiB2 particles in the matrix,refinement of fine globular α-Al grains and modification of eutectic Si.As expected,the thixoformed composites show better wear resistance than the alloy.Moreover TiB2 particles lower the coefficient of friction when reinforced in A356 alloy,in both gravity cast and thixoformed conditions.Also,it is interesting to note that there exist a linear relationship between wear rate and hardness of composites,irrespective of the processing history.The wear rate in the thixoformed composite is reduced by 48% as compared to gravity cast alloy.The improvement in wear resistance in the present thixoformed composite is not only due to the presence of fine TiB2 particles but also due to refinement of a-Al and eutectic Si caused due to the plastic deformation during thixoforming.In addition,high hardness and strength of thixoformed specimens compared with gravity cast parts has resulted in lower coefficient of friction in thixoformed A356-5TiB2 in-situ composite.