Outstanding dynamic tensile response of pure Mg and diluted Mg Mn alloy under very high strain rates

Hetero deformation induced (HDI) and bi-modal grain structure induced (BI) hardening are effective ways to increase the performance of magnesium (Mg) alloys. However, loading rate, texture, and microstructure features play a decisive role in achieving the full advantage of these mechanisms. In particular, we reported that the heterogeneous grain structured Mg Mn alloy and bimodal grain structured pure Mg, having low strength and low elongation to fracture (EF) under quasi-static (QS) loading, can show exceptionally high strength and high EF under high strain rate (HSR) loading. To prove it, we have conducted QS ( ε ̇ = 0.001 s − 1 ) and HSR ( ε ̇ = 2400 − 4200 s − 1 ) tensile properties of a bi-modal grain structure extruded Mg and a heterogeneous grain structure extruded Mg Mn alloy having different textures. Subsequently, the ultimate tensile strength (UTS) ∼ 334 MPa is achieved for Mg under HSR loading, which is 110 % higher than the UTS (∼ 159 MPa) under QS loading. Likewise, the Mg Mn alloy also displayed an exceptional UTS of ∼382 MPa, which is ∼105 % higher than the UTS (∼ 185 MPa) of the Mg Mn alloy under QS loading. Most specifically, EF is 2-fold and ∼ 3–4 fold in Mg and Mg Mn alloy under HSR compared to the QS loading. The results also revealed that Mg displayed structure instability, and Mg Mn alloy displayed structure stability. Therefore, Mg Mn alloy displayed a higher UTS ∼ 81 MPa than that of Mg under the same HSR (4100 and 4182 s −1 ). Thus, the maximum advantage of the HDI and BI mechanisms is attained at HSR loading, and the Mg and Mg Mn alloy that were not high strength and ductile under QS loading are high strength and ductile under HSR tensile loading. • Mg andMg-Mn alloy, displayed an exceptional increase in strength and ductility under dynamic loading. • The UTS reached ∼382 MPa in Mg-Mn alloy, which is much higher than pure Mg under the same conditions. • Pure Mg displayed structure instability under dynamic loading, while Mg-Mn alloy displayed structure stability. • The underlying deformation mechanisms in Mg and Mg-Mn alloy were discussed in detail.