Precipitation hardening by nanoscale Ti2Ni phase in high Ti-rich Ti52.6Ni46.8Si0.6 melt-spun ribbon

摘要

A high Ti-rich Ti52.6Ni46.8Si0.6 ribbon was investigated to reveal the precipitation hardening effect caused by the nano-scale Ti2Ni precipitates. TEM observations revealed only nano-scale Ti2Ni second phase in the ribbon after aging treatment, which induced the R phase transformation detected in DSC tests. Nanoindentation measurements demonstrated the increment of hardness from 2.43 GPa to 2.98 GPa, an increment of about 22%, in the first 3 h of aging treatment at 500 degrees C. The pseudoelasticity (PE) of the ribbon, evaluated by depth and energy recovery ratios of nanoindentation tests, also revealed that 3 h-aged ribbon had the best recovery performance. The shape memory effect (SME) of the 3 h-aged ribbon exhibited the best performance with a recoverable strain of 3.5% and an irrecoverable strain smaller than 0.1%. Both PE and SME tests demonstrated that the precipitation hardening effect of nano-scale Ti2Ni precipitates can effectively improve the shape memory properties of high Ti-rich TiNi shape memory ribbons. (C) 2019 Elsevier B.V. All rights reserved.