Microstructure and Mechanical Properties of As-extruded Spray Forming Mg12Al1.5Zn6.5Ca1Nd Alloy

The Mg12A11.5Zn6.5CalNd alloy was prepared by spray forming. The microstructure and mechanical properties of the as-extruded experimental alloy were investigated by XRD, SEM, TEM and EDS. The results show that the microstructure of the experimental alloy consists of a-Mg and Al2Ca, the microstructure is equiaxial grain, and the grain size is about 2 mu m. The size of dispersive Al2Ca phase is less than 1 pm, which distributes mainly along the grain boundaries of the primary Mg. The dislocation pile-up in matrix Mg and twin structure in Al2Ca are observed by TEM. The sigma(b), sigma(0.2) and delta of the alloy reach 470 MPa, 350 MPa and 4.7%, respectively. The main strengthening methods are fine grain strengthening, dispersion strengthening and solid solution strengthening. The fracture morphologies indicate the micro cracks nucleate between the impurity at the bottom of holes or the hard phase around the holes and the matrix. Holes are formed through micropores aggregation in the fracture. The fracture mechanism is microporous polymeric intergranular fracture.