The role of matrix microstructure in the creep behaviour of discontinuous fiber-reinforced AZ 91 magnesium alloy

Constant stress tensile creep tests were conducted to failure at temperatures of 423 and 473 K on an AZ 91 (Mg–9wt.%Al–1wt.%Zn) alloy reinforced with 20 vol.% Al2O3 short fibres and on an unreinforced AZ 91 matrix alloy. The creep resistance of the reinforced material was considerably improved by comparison with the matrix alloy. A microstructural investigation revealed that the most frequent morphology of the β-phase precipitates in the composite is continuous Mg17Al12 platelets. Detailed investigations using transmission electron microscopy indicate that the matrix microstructure has no significant influence on the creep properties of these two materials. This result confirms the proposal that the creep strengthening of the composite is controlled by an effective load transfer between the matrix and the fibres.