Grain size effect on the structural parameters of the stress induced Ehcp - Martensite in iron-based shape memory alloy

Abstract

The aim of this work was to study the effect of austenitic grain size (GS) reduction on the structural parameters of the εhcp -martensite in stainless shape memory alloy (SMA). Rietveld refinement data showed an expansion in c-axis and a reduction in a and b-axis with thermo-mechanical cycles for all samples analyzed. Samples with 75 ≤ GS (μ) ≤ 129 were analyzed. It was also observed an increase of the unit cell volume in this phase with GS reduction. The smallest grain size sample (GS = 75 μm) presented a c/a ratio of 1.649, and approximately 90% of total shape memory recovery.