Effect of temperature and strain rate on the tensile properties related to hot cracking of Csf/AZ91D composites

The ultimate tensile strength (σUTS) and fracture strain (εf) of Csf/Mg composites at temperatures just below and above the incipient melting temperature with different strain rates were determined by modified semi-solid tensile tests using a partial remelting approach. The variations of σUTS and εf were analyzed combining the discussion of damage mechanism. It was concluded that εf is more sensitive to the temperature and stain rate compared with σUTS. The maximum εf was achieved at the onset temperature for partial melting and at low strain rate, when the liquid fraction rose to 6%, the liquid phase at grain boundaries and interfaces played a dominant role in the deformation, and the composites exhibited very low ductility. The cavity initiation sites were closely related to the test temperature and strain rate, and the favored direction of crack propagation was highly dependent upon the strain rate.