The effect of partial crystallization on elevated temperature flow stress and room temperature hardness of a bulk amorphous Mg60Cu30Y10 alloy Original Research Article

Partially crystallized samples of the bulk amorphous alloy Mg60Cu30Y10 were prepared by annealing amorphous samples slightly above Tg. After partial crystallization, the alloy is a nanocomposite consisting of equiaxed Mg2Cu crystallites with an average diameter of 100 nm homogeneously distributed in an amorphous matrix. The flow stress of the nanocomposites was measured as a function of strain rate above Tg. For fixed strain rate, the flow stress increases monotonically as a function of degree of crystallinity, increasing most rapidly for low degrees of crystallinity. A variety of models describing the rheological properties of composites are compared with the flow stress measurements. In all cases, a significant discrepancy is found between the model predictions and experimental observations. A linear relationship was also found between hardness at room temperature and the degree of crystallinity, consistent with a recently proposed model.