Strengthening Mechanisms in Ti-6Al-4V/TiC Composites

摘要

In this study,the compressive behavior of Ti-6Al-4V/TiC composites considered for ballistic applications was examined at strain rates of 0.1,1.0,and 10 s~(-1).As little as 1 vol% of paniculate TiC provided nearly a 25% increase in strength in Ti-6Al-4V/TiC composites over that of the monolithic Ti-6Al-4V,while subsequent additions of TiC did not provide proportional benefit.The mechanisms responsible for such a significant increase in strength were investigated for the first time in this study.Microscopy(optical,SEM,TEM)aided in identifying the possible strengthening mechanisms that are typically important to the strength of metal matrix composites.These mechanisms include grain size and subgrain size refinement and an increase in dislocation density,all of which can occur during processing.Two other important mechanisms are thermal mismatch strains and load transfer from the matrix to the particle;the contribution of these mechanisms to the strength of the composite was evaluated using the Eshelby approach.A quantitative comparison of the mechanisms listed clearly showed that none of them was responsible for the large increase in strength with only lvol%TiC in Ti-6Al-4V.The results from this study show for the first time that carbon in solution is,by far,the most potent strengthening mechanism in the Ti-6Al-4V/TiC particulate composites.