Formation of stress-induced martensite in the presence of γ-phase, in a Cu–Al–Ni–Mn–Fe shape memory alloy

✍ Scribed by S. Stanciu; L.G. Bujoreanu

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 853 KB
• Volume: 481-482
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/j.msea.2007.01.174

✦ Synopsis

The structure of a Cu-13.67Al-4.28Ni-0.54Mn-0.14Fe (wt.%) shape memory alloy was analyzed in the initial condition, during a heating-cooling cycle, and during a room temperature loading-unloading mechanical cycle. A fully reversible martensitic transformation was revealed which was associated with a shape recovery degree reaching a saturation value at 97.7% for a relative permanent deflection of 90 %. By X-ray diffraction, the occurrence of a reduced amount of β 1 stress-induced martensite (SIM) accompanied by the precipitation of the hard ␥ 2 -phase was noticed both during the heating of a martensitic specimen and during the air-cooling of the alloy in the austenitic state. It was assumed that a possible cause for the formation of β 1 SIM during heating or cooling could be the strains caused by the volume increase of hard ␥ 2 -phase that deformed the softer martensitic or the austenitic matrix. The irreversible formation of β 1 SIM at 100 MPa was revealed by X-ray diffraction in elongated condition and confirmed by OM at room temperature, after unloading.