Failure mechanism of as-cast Mg-6Zn-2Er alloy during tensile test at room temperature

Tensile test of the as-cast Mg-6Zn-2Er alloy was conducted at room temperature. The results indicate that the alloy is inclined to failure when the strain reaches 5.6%. The coarse secondary phases are responsible for the failure, especially for the Mg3Zn3Er2 phase (W-phase). It is indicated that the existence of the W-phase activates the stress concentrations due to the incapacity of W-phase for the load transfer, which results in the void at the inner of the W-phase. In comparison, the interface between the matrix and the secondary phase is stable. In conclusion, the characters of the secondary phases with respect to size, distribution, morphology and type, play an important role in the plastic deformation behavior of the alloy.