Chemical Ordering induced Strengthening in Lightweight Mg Alloys

The influence of structure and composition on precipitation phenomena in Al-bearing BCC/HCP Mg alloys are studied via diffusion couple technique. Interdiffusion induced by the resultant composition gradient results in a change in crystal structure from HCP to BCC in the diffusion zone. The Vickers hardness in the diffusion zone is much higher than that in the Mg–5.5at.%Al and Mg–38at.%Li, which is attributed to the chemical ordering by nano-sized secondary ordered D0(3)–Mg(3)Al precipitation in the BCC Mg–Li–Al diffusion zone. The reasons for different precipitation in Al-bearing Mg alloys with various matrices are discussed. Generating ordered precipitates can be an effective approach to improve both strength and ductility in HCP Mg alloys.