Effect of multi-step structural transitions in parent phase on martensitic transformation in Au7.01Cu5.15Al3.77 alloy

The effect of the structural transitions in parent phase on the martensitic transformation in the Au7.01Cu5.15Al3.77 alloy has been investigated by internal friction, DSC and in situ XRD technique. Two phase transitions were observed during heating from room temperature to 680 °C, the first one depressed MS temperature to −13 °C and the later one promoted MS temperature to −1 °C. It was also found that MS temperature declined with the increasing of L21 ordering degree in the Au7.01Cu5.15Al3.77 alloys. The mechanism about the effect of chemical ordering on martensitic transformation was discussed through thermodynamics analysis.

► Beside the B2–L21 ordering transitions, there is another structural transition occurred between 300 °C and 550 °C.
► The unknown structural transition depressed MS temperature to about −13 °C.
► The MS temperature corresponding to B2 ordering structure is about −1 °C.
► The MS temperature declined as the degree of L21 ordering increased in the Au7.01Cu5.15Al3.77 alloy.