EBSD study of variant selection in red gold alloys during phase transformation under four point bending

The A₀→L1₀ phase transformation, which appears in red gold alloys with compositions close to Au-Cu, is well known as diffusive. However, a shape memory effect has been reported in these alloys, which must involve variant selection during a displacive transformation. Therefore, in this work, the variant selection is studied by EBSD in a polycrystalline red gold alloy heat treated under 4-point bending. For the first time, the L1₀ domains could be identified by EBSD despite their c/a ratio close to unity and their nanometric scale. The orientation relationship between parent and daughter phases was determined and the mechanical work of the variant formation calculated from both the lattice distortion and the experimental orientations. The maximal work criterion, initially introduced for variant selection in martensitic transformations, was applied on large-scale areas with statistical data and it provided quantitative results on the degree of variant selection in both tension and compression.