High strength, nano-structured Mg–Al–Zn alloy

The mechanical behavior and microstructure of nanocrystalline (nc) Mg AZ80 alloy, synthesized via a cryomilling and spark plasma sintering (SPS) approach are reported and discussed. The effects of cryomilling processing on chemistry, particle morphology, and microstructure of the Mg alloy powder are described and discussed. The experimental results show that cryomilling for 8 h yields nc Mg agglomerates, approximately 30 μm in size, with an internal average grain size of approximately 40 nm. The mechanisms that are thought to be responsible for deformation twins that were observed in the cryomilled AZ80 powder are discussed. The cryomilled Mg powder was subsequently consolidated using SPS at 250, 300 and 350 °C. The consolidated material consisted of a bimodal microstructure with nc fine and coarse grains formed in the SPS’ed Mg AZ80 microstructure. Inside of the coarse grains, nano-sized Mg17Al12 precipitates were observed. A maximum microhardness of 140 HV, compressive yield strength of 442.3 MPa, and ultimate strength of 546 MPa are measured, which compare favorably to published values for conventional Mg alloys.