Effect of Al incorporation for Co on the gamma-beta phase boundary of rapidly solidified CoNiAl ferromagnetic shape memory alloys

Abstract

The alloys Co64xNi36Alx(at%, X¼23,24,26 and 28)prepared through melt spinning technique revealed β- and γ-phase structure at room temperature. A monotonous increase in β-phase and simultaneous decrease in γ-phase has been observed with increasing Al content.The synergistic competition between β- and γ-phase influence β(B2)-L10 martensitic transformation. Therefore transformation broadening has been observed with Alcontent.Consequently, martensitic transformation temperature decreases and austenite transformation temperature increases.The γ-rich alloys showed magnetically soft phase, with high initial susceptibility and enhanced saturation magnetization.These alloys also revealed large magneto-strain values which are also supported by micro-structural morphology.