Persistence of variant selection in red gold alloys

Abstract

Recently, a new thermally activated distortion with amplification (TADA) effect has been reported in red gold alloys caused by the A1 → L10 phase transformation. The macroscopic amplification is due to the persistence of variant selection nucleated under stress but growing in stress-free condition. In this work, we show that the TADA effect can generate a compressive force whose absolute value exceeds 40 MPa in bending and uniaxial loading. Complementary EBSD analyses indicate that the compressive force has no influence on the variant selection initiated under tension. This result confirms that the A1 → L10 disorder-order phase transformation is diffusive, thermodynamically of 1st order, displacive and crystallographically continuous. The TADA force may be exploited for actuators.