Tribology behaviors of Ti-Ni51 .5 at% shape memory alloy with different microstructures and textures

The microstructure characteristics of TiNi alloy were investigated to elucidate the active deformation mechanisms during hot rolling and the corresponding tribology performance. The deformation was mainly dominated by a combination of mechanical twinning involving the {114}(B2) and {112}(B2) twins, dislocations, and stacking faults during the manufacturing process. Moreover, various heat treatments were performed to differentiate the discrepancies in tribological behaviors of hot-rolled and heat-treated alloys. Hot-rolled microstructures with high defect density approximate to nanoscale precipitates through aging as the wear resistance of the alloy improves, albeit it is softer compared to the aged one. As demonstrated by the X-ray diffraction (XRD) results of the wear tracks, microstructures undergo the stress-induced martensitic (SIM) transformation during dry sliding. From differential scanning calorimetry (DSC) analysis, the martensitic transformation temperature is lowered by defects in the austenite phase. The activation of the SIM transformation can be a sluggish process owing to the effect of twinning, where both primary and secondary twins are involved. Furthermore, a reversible transformation that is related to pseudoelasticity causes a decrease in wear volume at room temperature, which is higher than the austenite finish temperature. Meanwhile, abrasive wear advances toward adhesion. Additionally, the hot-rolled sheet with gamma fiber-{111}//ND (normal direction) exhibits better wear resistance compared to the sheet with alpha fiber-{100}//ND.

Automated summary

The microstructure characteristics of TiNi alloy during hot rolling and corresponding tribology performance were investigated. The deformation mechanisms mainly involved mechanical twinning, dislocations, and stacking faults. Different tribological behaviors were observed in hot-rolled and heat-treated alloys. Wear resistance improved with high defect density in microstructures after aging, accompanied by a decrease in hardness.