Determination of martensite structures of the Au7Cu5Al4 and Au7Cu5.7Al3.3 shape-memory alloys

作者：Elcombe Margaret M; Kealley Catherine S; Bhatia Vijay K; Thorogood Gordon J; Carter Damien J; Avdeev Maxim; Cortie Michael B^*

来源：Acta Materialia, 2014, 79: 234-240.

DOI：10.1016/j.actamat.2014.07.039

• X-ray diffraction
• Neutron diffraction
• Shape memory
• Modulated martensite
• Au-Cu-Al

The beta-phase of Au7Cu5Al4 undergoes a reversible shape-memory phase transformation for which several conflicting martensite phases have been reported. Here we show the significance of the cooling temperature used to obtain the martensite. If Au7Cu5Al4 is cooled from the parent phase condition to cryogenic temperatures, e.g. below 200 K, the martensitic phase is orthorhombic (space group Pcmn, a = 4.4841 angstrom, b = 5.8996 angstrom, c = 17.8130 angstrom); however, when this composition is cooled to only similar to 260K it will in general consist of a mixture of orthorhombic and monoclinic phase (the latter has space group P2(I)/m, a = 4.4742 angstrom, b = 5.9265 angstrom, c = 13.3370 angstrom, beta = 91.425 degrees). In contrast, a sample with decreased Al content (Au7Cu5.7Al3.3) transforms fully to monoclinic phase if cooled to similar to 260 K.

• 出版日期2014-10-15