Phase transformation behavior and shape memory characteristics of Ti−Ni−Si alloys

Abstract

Transformation behavior, microstructures and shape memory characteristics of Ti−(50−X)Ni−XSi (X=2, 4, 6 at.%) and (50−X)Ti−Ni−XSi (X=2, 5, 7, 10 at.%) alloys were investigated by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, differential scanning calorimetry, electrical resistivity measurements and constant load thermal cycling tests. Ti 5 Si 3 , Ni 16 Ti 6 Si 7 and Ni 4 Ti 4 Si 7 were formed in Ti−(50−X)Ni−XSi alloys, while Ti 5 Si 4 , Ni 3 Si, Ni 3 Ti 2 and Ni 3 Ti 2 Si were found in (50−X)Ti−Ni−XSi alloys. The total amount of silicides increased with increasing Si content, irrespective of Si content. The B2→B19 transformation occurred in Ti−(50−X)Ni−XSi alloys, and their transformation temperatures appeared to be almost constant. Transformation elongation associated with the B2→B19 transformation decreased with increasing Si content. In contrast to Ti−(50−X)Ni−XSi alloys, a transformation accompanied with structural change did not occur in (50−X)Ti−Ni−XSi alloys.