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Ultrahigh strength is achieved in low-cost Mg-4Sm-0.6Zn-0.4Zr alloy by a traditional extrusion process, with tensile yield strength over 450 MPa, which exceeds the majority of heavy rare-earth (RE) alloyed Mg-RE extrusion alloys. The alloy showed a typical bimodal microstructure, consisting of fine recrystallized grains with random orientations and coarse hot-worked grains with strong basal texture. And profuse Mg 3 Sm particles were dynamically precipitated in recrystallized grains boundary as well as hot-worked grains interior during extrusion. The ultrahigh yield strength of the alloy is closely related to the combined effect of fine recrystallized grains, highly textural hot-worked grains, and numerous nanoscale particles, independent of the accepted age-hardening in those heavy RE containing Mg alloys. Low cost, high strength, and simple extrusion process make the present alloy gets more fantastic potential in industrial applications than other Mg-RE extrusion alloys. [ABSTRACT FROM AUTHOR]

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 Al 2 Ca 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 Al 2 Ca and AlMn 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. • Ultra-high strength of ~449 MPa was achieved in the low-cost Mg-1Ca-1Al-0.3Zn-0.4Mn (wt%) wrought alloy. • Ultra-fine grain size (300–500 nm) was achieved due to ther fine-precipitates distributing at the new grain boundaries. • A higher number density of nano-precipitations could afford extra precipitation hardening effect after heat treatment. [ABSTRACT FROM AUTHOR]

In this work, the trace Ce atoms have been added into the low-alloyed Mg-Al-Ca matrix, and the microstructure and mechanical properties have been investigated. For the Mg-Al-Ca ternary alloy, the tensile yield strength (TYS) would be decreased from ~ 321 MPa at 260 °C (extrusion temperature) to ~ 294 MPa at 290 °C. In contrast, the Mg-Al-Ca-Ce alloy can still exhibit the high YS of ~ 350 MPa and elongation of ~ 12.1% at higher extrusion temperature of 290 °C. Microstructure characterization shows that the Ce addition can effectively induce the solute segregations along both dislocations and grain boundaries in Mg-Al-Ca-Ce alloy, which thus leads to the finer grain size of 0.7 ~ 0.8 µm at a wide range of extrusion temperature. Formation of subgrain with strong texture, residual dislocations due to segregation and profuse nano-precipitations can together contribute to the high yield strength of Mg-Al-Ca-Ce alloy. More importantly, the trace Ce atoms can promote the activation of non-basal dislocations in Mg matrix and also the weakened texture in DRXed grains. As a result, the ductility is also simultaneously improved by the trace addition of Ce atom into Mg-Al-Ca based alloy. The relevant results can shed light on designing the new high strength and low-alloyed Mg alloys. • Simultaneous improvement of strength and ductility is achieved through trace Ce addition into dilute Mg-Al-Ca alloys. • Solute segregations along both dislocations and grain boundaries can be achieved by the addition of Ce. • Finer grain size of 0.7–0.8 µm at a wide range of extrusion temperature is obtained in the new Mg-Al-Ca-Ce alloy. [ABSTRACT FROM AUTHOR]