Effect of Post-Deformation Annealing on Structure and Properties of Nickel-Enriched Ti-Ni Shape Memory Alloy Deformed in Various Initially Deformation-Induced Structure States

The effect of post-deformation annealing (PDA) of nickel-enriched Ti-50.9 at.% Ni shape memory alloy deformed in various initially deformation-induced structure states on the structure and properties was studied. The phase composition, temperature ranges of martensitic transformations and structure were studied using X-ray diffractometry and TEM. Mechanical and functional properties were determined using Vickers hardness tests and thermomechanical method using a bending mode for recovery strain inducing. The PDA at 430 degrees C (1 h) of the nickel-enriched Ti-Ni SMA with the dynamically recovered, dynamically polygonized or dynamically recrystallized structures after compressing deformation leads to the precipitation of finely dispersed (nanosized) Ti3Ni4 particles. The most significant increase of the completely recoverable strain (from 8.8 to 11.8%) and shape recovery rate (from 88 to 100%) as compared to the reference treatment is observed after PDA of the alloy with the dynamically polygonized structure.