Effect of TiB2 Addition on Microstructure and Mechanical Properties in Conventional Cast TiAl-Based Alloy

摘要

Effects of TiB2 addition on microstructures and mechanical properties of Ti-48Al-2Cr-2Nb fabricated by induction skull melting (ISM) process were investigated.The results show that TiB2 additives were completely dissolved in the melt and consequently re-precipitated during solidification.The re-precipitated borides were identified to be TiB2 with flake,plate and block morphologies.The microstructure of ingots was evidently refined by the TiB2 addition.The grain size was reduced to about 100μm and transformation of fine equiaxed lamellar colonies appeared in alloys containing 0.4 at.％ and 1.0 at.％ TiB2 addition.Grain refinement is attributed to more α nucleation sites provided by β,which is interleaved with secondary TiB2.Fine equiaxed lamellar colonies and results from fine β dendrites,which are caused by high boron concentration induced constitutional undercooling and heterogeneous nucleation of β phase on primary TiB2.Alloy containing 1.0 at.％ TiB2 exhibits much better tensile strength and non-deteriorated ductility than TiAl matrix.