In-situ EBSD study of the multiple deformation modes of a TiNb/Nb/NiTi multilayer composite

Abstract

In the current work, a Ti72.8Nb27.2/Nb/Ni50.9Ti49.1 multilayer composite was fabricated to elucidate the contribution of multiple deformation modes to the mechanical properties with respect to the material. The composite, which consists of a TiNb component, intermediate Nb layers and NiTi component, shows a well-bonded metallurgical interface. The in-situ EBSD results indicated that B2 and β-Nb experienced elastic deformation at macroscopic strains below 1.3% during loading. As the strain range increased from 1.3% to 9.5%, B2 underwent stress-induced martensitic transformations (SIMTs) from B2 to B19′, while β-Nb experienced mainly plastic deformation. In the case of β-TiNb, the process of elastic deformation, plastic slip, and deformation twinning occur within the macroscopic strain ranges of 0%–2.5%, 2.5%–5.3%, and 5.3%–9.5%, respectively. The deformed composite, comprising of B19′ martensite, β-TiNb/Nb, TiNb twins, and B2 parent phases, exhibited both elastic recovery (ranging from 9.5% to 8.8%) and partially reversible B19′ to B2 SIMTs (ranging from 9.5% to 7.8%). Once unloaded, a significant macroscopic residual strain is retained at 7.8%, since the partially reversible B19′ → B2 SIMTs, potential plastic deformation and deformation twinning.