Investigation of physical metallurgy characteristics of two-way shape memory effect in TiNi alloy

The two-way shape memory effect (TWSME) represents a behaviour in which a r eversible temperature change of a "memory alloy" is accompanied with sponta neous reversible macroscopic deformations. It was generally accepted that i nternal defects, which are introduced during the so called training procedu re, are responsible for this phenomenon. The formation of ghost martensite may contribute to the enhanced reversibility of binary TiNi system without R-phase formation. The aim of this study is to investigate TiNi materials i n which R-phase formation occurs. The trained specimens contain dislocation array, stabilised martensite and ghost martensite. It is expected, owing t o the specific crystallographic relation, that ghost martensite formation c an facilitate both the R-phase formation as well as B 19' martensite format ion and in this way support the reversible memory of TiNi alloys.