一种超高强度的Mg-Al-Ca-Zn-Mn 变形镁合金的研究

Abstract

An ultra-high strength and low-cost magnesium wrought alloy, Mg-1Al-1Ca-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%. 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-disk Al2Ca phases can be further precipitated, which results in the alloy still maintaining the ultra-high 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.