Effects of Thermomechanical Treatment on Phase Transformation of the Ti₅₀Ni₄₉W₁ Shape Memory Alloy

• Main Authors: Tyau-Song Huang, Shih-Fu Ou, Cheng-Hsien Kuo, Cheng-Hsiu Yang
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Metals
• Subjects: shape memory alloy; martensitic transformation; thermomechanical treatments
• Online Access: https://www.mdpi.com/2075-4701/10/4/527
• ISSN: 2075-4701

The Ti₅₀Ni₄₉W₁ alloy has a B2 ↔ 19’ martensitic transformation but slightly lower shape recovery than the Ti₅₀Ni₅₀ alloy. The B19’ martensite structure in the Ti₅₀Ni₄₉W₁ has the lattice parameters <i>a</i> = 0.301 nm; <i>b</i> = 0.423 nm; <i>c</i> = 0.472 nm; and β = 97.5°. The hardness increment and transformation temperature depression of Ti₅₀Ni₄₉W₁ are greater than those of Ti₅₀Ni₅₀ under the same degree of cold rolling and the same number of thermal cycles; owing to the Ti₅₀Ni₄₉W₁; with higher inherent hardness from solidification strengthening of W atoms. Both thermal cycling and cold rolling on Ti₅₀Ni₄₉W₁ also promotes R-phase transformation. The effects of thermal cycling and cold rolling on the martensitic transformation temperature (<i>M</i>_s) of the Ti₅₀Ni₄₉W₁ alloy follow a linear trend; and the <i>M</i>_s decreased with the hardness.