Effect of Microstructure Variations on the Formation of Deformation-Induced Martensite and Associated Tensile Properties in a #beta# Metastable Ti Alloy

摘要

This article focuses on the effect of themicrostructure on the activity of different deformationmechanisms and the resulting mechanical behavior of ametastable #beta# Ti alloy (#beta#-Cez). Various types ofmicrostructures were produced, with given volume fractions of#beta# phase (100 or 90 pct). These microstructures differed inthe size of their #beta# grains as well as in the distribution,shape, and size of the primary a particles. A statistical approachwas also developed to characterize small variations in chemistryof the #beta# phase between the various microstructures. It isshown that, even for similar volume fractions of #beta# phase,changes in the microstructure strongly affect the mechanicalresponse of the alloy. The mechanical, response is controlled bythe interplay between the two deformation modes operating inthis alloy: formation of #alpha#" deformation-inducedmartensite and activation of slip. The easier formation of stress-induced martensite leads to lower apparent yield stresses and abetter work-hardening response. On the contrary, very limitedwork hardening is obtained when slip is activated solely. Thedifferences in the ability of the martensitic transformation tooccur can be understood by considering the effect on M_S andT_0 of both the chemistry of the #beta# phase and ofconstraining effects due to grain sizes and dislocations.