Transformation temperatures and microstructural evolution of an ausformed NiTi shape memory alloy using equal channel angular extrusion Conference Paper uri icon

abstract

  • In this study, the thermomechanical properties of Ti-50.8 at% Ni alloy severely deformed using Equal Channel Angular Extrusion (ECAE) are investigated. Solutionized NiTi bars were deformed at different temperatures above austenite finish temperature (Af). The aim was to investigate the effects of ausforming (plastic deformation above Af) on shape memory characteristics of NiTi such as transformation temperatures and microstructure. The unique findings were 1) martensite stabilization in the samples deformed at room temperature (ECAE at RT), 2) the observation of highly organized, twin related B2 austenite nanograins (100 nm in size) and thin twins in B2 austenite matrix after low temperature annealing of ECAE at RT samples, and 3) simultaneous observation of strain induced B19' martensite and deformation twins in the samples deformed at 450°C (ECAE at 450°C). This was attributed to the heavy deformation and to the accumulation of dislocations mainly along the twin-twin and martensite variant boundaries which caused the stabilization.

author list (cited authors)

  • Kulkarni, A. V., Karaman, I., Luo, Z. P., & Chumlyakov, Y. I.

publication date

  • July 2004