Stress-induced detwinning and martensite transformation in an austenite Ni–Mn–Ga alloy with martensite cluster under uniaxial loading

Abstract

Stress-induced martensitic detwinning and martensitic transformation during step-wise compression in an austenite Ni–Mn–Ga matrix with a martensite cluster under uniaxial loading have been investigated by electron backscatter diffraction, focusing on the crystallographic features of microstructure evolution. The results indicate that detwinning occurs on twins with a high Schmid factor for both intra-plate and inter-plate twins in the hierarchical structure, resulting in a nonmodulated (NM) martensite composed only of favourable variants with [001]NM orientation away from the compression axis. Moreover, the stress-induced martensitic transformation occurs at higher stress levels, undergoing a three-stage transformation from austenite to a twin variant pair and finally to a single variant with increasing compressive stress, and theoretical calculation shows that the corresponding crystallographic configuration is accommodated to the compression stress. The present research not only provides a comprehensive understanding of martensitic variant detwinning and martensitic transformation under compression stress, but also offers important guidelines for the mechanical training process of martensite.

Computational and materials structural science

“…Another fascinating area of nanoscience is illustrated by the article of Chiu et al (2019), which describes the formation of gyroid-structured Au nanonetworks, fabricated through the development of Au nanoparticles. A schematic of the resulting structures is shown in Fig 1. Alloy structural science continues to be a widely explored theme, with computational methods being used by Han et al (2019) to predict new Heusler alloys and studies of stress-induced detwinning and phase transformations in ternary alloys by Hou et al (2019). Ternary alloys are also the subject of an intriguing investigation by Martino et al (2018) of a new compound, Sr 2 Pt 8 À x As, which is prepared by high-pressure synthesis and has a high concentration of vacancies which are incommensurately ordered.…”