Realizing ultra-fine grains and ultra-high strength in conventionally extruded Mg-Ca-Al-Zn-Mn alloys: The multiple roles of nano-precipitations

An ultra-high strength and low-cost magnesium wrought alloy, Mg-1Ca-1Al-0.3Zn-0.4Mn (wt%), has been fabricated by conventional extrusion, with yield strength of -435 MPa, the ultimate tensile strength of -449 MPa and the elongation of -4.2%. Mono-dispersive nano-precipitations, e.g., the Al2Ca phase and AlMn phase, have been induced during extrusion, which can effectively pin pyramidal dislocation motions in grain interiors and thus provide substantial nucleation sites for dynamic recrystallization in present Ca-containing Mg alloys. Simultaneously, these fine-precipitates distributing at the new grain boundaries can prevent their growths, which thus guarantee the ultra-fine grains formation (300?500 nm). After heat treatment, a higher number density of nano Al2Ca and AlMn phases can be further precipitated, which results in the alloy still maintaining the ultrahigh strength of -444 MPa. The multiple roles of the same nano-precipitations in both promoting the ultrafine grains formation and affording precipitation hardening have been clarified in present Mg wrought alloy.

Automated summary

An ultra-high strength and low-cost magnesium wrought alloy, Mg-1Ca-1Al-0.3Zn-0.4Mn (wt%), has been fabricated by conventional extrusion, with yield strength of -435 MPa, the ultimate tensile strength of -449 MPa and the elongation of -4.2%. The mono-dispersive nano-precipitations induced during extrusion play a crucial role in promoting both ultrafine grains formation and providing precipitation hardening in the present Mg wrought alloy.