Effect of heat treatment on deformation mechanisms in Mg–10Gd during tensile load studied by acoustic emission tests

One of the most promising materials for temporary bone implants is magnesium alloyed with rare-earth elements. Its degradation behaviour strongly depends on the microstructure, which is determined by material processing. Since future bone implants must withstand mechanical loading, understanding their deformation and failure mechanisms is essential. In this study, two microstructural states of Mg–10Gd, serving as a model system for the Mg–xGd alloys, are investigated: as-cast and heat-treated. Although the heat-treated state exhibits superior mechanical performance, both states show the same fundamental deformation mechanisms, raising the question of how they differ under loading. However, very large grain sizes make common investigation techniques, such as electron backscattered diffraction or X-ray diffraction, challenging. Therefore, the question arises whether acoustic emission (AE) testing followed by microstructural investigations could be sufficient to understand microstructural differences in deformation behaviour. The samples are investigated by tensile tests combined with in situ AE tests. Subsequently, additional analysis involves optical microscopy and micro computed tomography. It was observed that the strain rate sensitivity is more pronounced in the as-cast state due to precipitates and dendrites, with only small differences between the two processing conditions. The results show that, for well-understood materials, AE testing with microstructural investigations is sufficient to understand deformation behaviours.