Property and Microstructure of TiNi SMA Prepared Using BaZrO3 Crucible

Abstract:

TiNi shape memory alloy (SMA) is one of the commercially successful shape memory alloys (SMAs) due to its excellent performances. In this work, the 49.3Ti-Ni (at.%) alloy was prepared by vacuum induction melting in 25 kg-grade home-made BaZrO3 crucible, and the cast alloy was turned into wire form (Ф1.0mm). The chemical compositions (including oxygen, nitrogen and carbon) of as-cast alloy were measured and the phase constitution was analyzed by X-ray diffraction (XRD), the microstructures were observed by Optical Microscope (OM) and Scanning Electron Microscope (SEM), the shape memory recovery rate and fatigue life of alloy wires were tested by two home-made test apparatus respectively. Experimental results showed that the contents of oxygen and nitrogen in alloy ingot were 560 ppm and 17 ppm respectively, and the impurities contents in TiNi alloy melted using the BaZrO3 crucible are just eligible to medical devices and surgical implants. The chemical composition melted by the BaZrO3 crucible is more uniform and accurate than by the vacuum arc remelting (VAR). The present presents higher shape memory rate and fatigue life than graphite crucible, the best shape memory recovery can reach 98.62% with 2% deformation and water aging at 550℃ for 20min, and the best average fatigue life can reach 3072 times with water aging at 500℃ for 20min.