The temperature-dependence of the mechanical properties of unidirectionally solidified silver-germanium eutectic

Work-hardening curves of the unidirectionally solidified silver-germanium eutectic have been determined by tensile deformation between room temperature and 615° C. The transition stress, ₀ between elastic and plastic deformation of the germanium platelets, exhibits the same temperature dependence (₀ exp Q/KT) over the whole temperature range. ₀ is determined, however, by two effects: the temperature-dependent critical shear stress of germanium and the lowering of the shear strength, , of the phase interfaces. Estimates of yield 14 kg mm^–2 at room temperature and <0.12 kg mm^–2 at 615° C. At low temperatures (<400° C), the composite fracture is initiated by the fracture of fibres (platelets), whereas at higher temperatures, the matrix fails first. As long as the interface shear strength is sufficiently large, the composite fracture is retarded resulting in a pronounced maximum of the fracture strain at 550° C.