Multistage martensitic transformation in high temperature aged Ti48Ni52 shape memory alloy
Journal
Intermetallics
Journal Volume
67
Pages
12-18
Date Issued
2015
Author(s)
Abstract
Abstract Aging effects on the transformation behavior of Ti48Ni52 SMA aged at 600 C and 550 C were investigated. The transformation evolution of specimens aged at 600 C and at 550 C can be classified into three and two periods, respectively. During aging at 600 C, the specimens undergo B2虠M1 in period I, B2虠M1 + B2虠M2 in period II, and B2虠M2 in period III (M represents the B19′ martensite). During aging at 550 °C, the specimens undergo B2→R→M1/M1→B2 in periods I and II, and an additional B2虠M2 in period II. In period I, only Ti3Ni4 precipitates (ppts) form in the B2 matrix. In period II, Ti3Ni4 and Ti2Ni3 ppts coexist, and Ti3Ni4 depletion zones occur around Ti2Ni3 plates, inducing B2虠M2. In period III, only Ti2Ni3 plates exist. The occurrence of B2→R→M1 or B2→M1 in period I is related to whether the Ti3Ni4 ppts have a coherent interface or not. Schematic diagrams for periods I ∼ III are proposed to interpret the observed transformation behavior. The difference in Ni-content in the matrix near the Ti3Ni4 and Ti2Ni3 ppts affects the transformation temperatures of B2虠B19′.
Publisher
Elsevier Ltd
Type
journal article