Yield-stress anomalies and high-temperature mechanical properties of intermetallics and disordered alloys

Metals and alloys sometimes exhibit an increase of yield-stress with increasing temperature, called ‘yield-stress anomaly’ (YSA). YSA allows a combination of high strength at high temperature and sufficiently good fracture toughness at low temperature in some materials for industrial applications. YSA seem a priori difficult to analyse because they can be observed in various situations. They, however, originate from well-understood dislocation locking mechanisms in two cases: cross-slip leading to the formation of ‘incomplete’ Kear–Wilsdorf locks in Ni3Al and diffusion in several other situations. The second origin that relies on less constraining hypotheses is proposed to be the prevalent one. YSA in other materials are then tentatively interpreted on this basis.