The three-stage B2-R-B19-B19′ and shape memory characteristics in Ti–Ni–Cu–Fe alloys

Transformation behavior of Ti–(45.0 − x)Ni–5.0Cu–xFe (at.%) (x = 1.0–2.5) alloys were investigated by means of electrical resistivity measurements and X-ray diffraction. The one-stage B2-B19′ transformation occurred in a Ti–44.0Ni–5.0Cu–1.0Fe alloy, while the two-stage B2-B19-B19′ transformation occurred in a Ti–43.5Ni–5.0Cu–1.5Fe alloy. The three-stage B2-R-B19-B19′ transformation behavior was found in Ti–43.3Ni–5.0Cu–2.0Fe and Ti–43.0Ni–5.0Cu–2.5Fe alloys. The Fe content dependence of TR(the B2-R transformation start temperature), M ′ s (the R-B19 transformation start temperature) and Ms (the B19-B19′ transformation start temperature) were 100, 80 and 20 K/at.%Fe, respectively.