Characterization of the microstructure and mechanical properties of a 50.3Ni–29.7Ti–20Hf shape memory alloy

The alloy 50.3Ni–29.7Ti–20Hf (at.%) exhibits attractive high-temperature shape memory properties. To determine the effect of aging on the behavior of this alloy, isothermal constant strain rate compression testing was performed at temperatures above the austenite finish temperature. This revealed that the alloy strength and the temperature range for pseudoelasticity vs. austenite plasticity was strongly influenced by aging. Electron microscopy has revealed precipitates rich in hafnium with a novel ordered structure relative to the B2 austenite phase form during aging.