Hierarchically Structured Ultrafine Grained Magnesium Alloys

摘要

The intrinsic low density of magnesium drives research towards high-performance magnesium alloys. Hierarchically structured ultrafine grained magnesium alloys possess exceptional strength-ductility combination and eliminate many of the traditional drawbacks like low strength, high yield strength asymmetry, poor formability, and limited superplasticity. In this overview presentation, friction stir processed microstructures are used as examples to discuss the microstructural paradigms that can exhibit excellent balance of mechanical properties. These show the possibilities of exceeding 500 MPa strength with good work hardening and >10% ductility. Use of micron-sized boron carbide (B_4C) and nano-sized yttria (Y_2O_3) powder can simultaneously enhance modulus-strength-ductility combination. High-strength ultrafine grained magnesium alloys also show high strain rate superplasticity which can provide pathways for overcoming poor formability. An example of friction stir additive manufacturing will be used to discuss possibilities of implementing such microstructures at component level with emerging solid-state additive manufacturing techniques.