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In this work, the role of manganese (Mn) addition in tuning microstructure and mechanical properties of the Mg-1.0Al-0.4Ca-xMn (x = 0.6, 1.0, 1.34 wt.%) alloys are studied. When enhancing the Mn content from 0.6 to 1.0 wt.%, the nano-precipitates of Al2Ca/Al8Mn5 phase becomes much finer, which can effectively refine the dynamical recrystallized (DRXed) grain size and also the subgrain lamellae. However, further increasing Mn content to 1.34 wt.%, the amounts of nano-Al2Ca and Al8Mn5 phases in the grain interiors are obviously decreased since more Al atoms are attracted to form the micron-sized Al8Mn5 phases, and average DRXed grain size in AXM102 alloy is thus largely increased. As a result, the as-extruded Mg alloy can exhibit the optimal mechanical property with yield strength (YS) of ~ 379 MPa and elongation of ~ 7.6%, only when the added Mn atom is controlled at ~ 1.0 wt.%. The relevant results can shed light on the further designing of novel high-strength and low-alloyed Mg wrought alloys. [ABSTRACT FROM AUTHOR]

This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy. The results showed that yield strength of the as-extruded Mg-1.2 wt.% Ca alloys decrease from ∼ 360 MPa to ∼ 258 MPa as the ram speed increases from 0.4 mm/s to 2.4 mm/s, and the elongation increases from ∼ 3.9% to ∼ 12.2%. The microstructure changes from bimodal grain feature to the complete dynamical recrystallization (DRX) with increase of the extrusion speed. The ultrafine DRXed grains in size of ∼0.85 µm, the numerous nano-Mg 2 Ca particles dispersing along the grain boundaries and interiors, as well as the high density of residual dislocations, should account for the high strength. It is believed that the high degree of dynamic recrystallization and the resulting texture randomization play the critical roles in the ductility enhancement of the high-speed extruded Mg alloys. [ABSTRACT FROM AUTHOR]

Effect of different rolling reductions on the microstructure and mechanical properties of Mg-6Al-3Zn-0.1Mn wt.% alloys were investigated by means of scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that after rolling the as-extruded Mg-Al-Zn-Mn alloy, more second phases are dynamically precipitated. The grains are also gradually refined with increasing the total reduction due to the dynamic recrystallization, and the average grain sizes are estimated to be ∼7.2 μm, ∼3.7 μm, ∼1.2 μm for the as-extruded Mg alloy, ∼34% and ∼60% rolled samples, respectively. On the other hand, the high-density contraction twins have been activated in as-rolled Mg samples, which can effectively separate the Mg matrix and a similar grain refinement effect can be afforded. Moreover, the dislocations are significantly multiplied during the rolling process. Consequently, the tensile strength of the Mg alloy is gradually increased, and the ∼60% rolled Mg alloy exhibits the optimal mechanical properties, with the ultimate tensile strength (UTS) of ∼363 MPa and the elongation of ∼7.2%. • Ultra-fined grain size of ∼1.2 μm was produced in AZM630 alloy by combining extrusion and rolling. • The tensile yield strength of as-rolled Mg alloy is up to 327 MPa with high elongation of 7.2%. • Dislocation tangles and contraction twin boundaries effectively improved both the strength and ductility. [ABSTRACT FROM AUTHOR]

In this work, the neutron poison element of boron (B) has been successfully added into the AlNbTiZr based multiprincipal element alloy (MPEA) via the arc melting method, and a new class of nuclear fuel materials based on the MPEAs with both high strength, and neutron poison property has been developed. The mechanical results show that both the AlNbTiZr and AlNbTiZrB samples exhibit the high yield strength of 790 ~ 800 MPa under compressive condition, and 720 ~ 750 MPa under tension. With a minor addition of B element, the ductility of AlNbTiZrB sample is largely deteriorated, exhibiting the compressive ductility of ~ 35 % and tensile ductility of only ~ 1 %. The X-ray diffraction (XRD), Calculation of Phase Diagram (CALPHAD) and transmission electron microscopy (TEM) characterizations demonstrate the formation of numerous feather-like TiB precipitates in AlNbTiZrB sample, which lead to the largely deteriorated tensile ductility in B-containing sample. Despite of that, the compressive ductility can yet reach as high as ~ 35 %, and excellent yield strength can be also obtained. Consequently, the present B-containing MPEA can act as a new promising candidate for future nuclear-fuel materials. • A new boron-containing AlNbTiZrB multiprincipal element alloy (MPEA) has been successfully developed. • AlNbTiZrB samples exhibit the high yield strength of ~ 800 MPa under compression, and also ~ 720 MPa under tension. • The poor tensile ductility in AlNbTiZrB can be ascribed to the existence of numerous feather-like TiB precipitates. • The present B-containing MPEA can act as a new promising candidate for future nuclear-fuel materials. [ABSTRACT FROM AUTHOR]

In this work, the microstructure and mechanical properties of the as-extruded and as-annealed Mg-0.8Ca-xMn-0.2Ce (x = 0.4, 0.7) wt% alloys, which are named as XME04 and XME07, have been investigated. An ultra-high strength of ~428 MPa can be achieved in as-extruded XME04 sample due to the high proportion of as-deformed grains and also high density of residual dislocations. The high Mn addition in as-extruded XME07 alloy can promote the dynamical recrystallization and induce more nano-precipitations. More nano-Mn precipitates in XME07 alloy can effectively hinder grain growth during extrusion and contribute to the finer grains. As a result, more precipitation of nano-phases, finer grains, and lower density of residual dislocations together account for the higher thermal stability in XME07 alloy than that in XME04 alloy. A novel Mg-0.8Ca-0.7Mn-0.2Ce wt% alloy with an excellent thermal stability has been developed. After annealing at 300 °C for 6 h, the yield strength of this alloy can still maintain at ~322 MPa. The relevant results can provide important guidance for developing novel Mg wrought alloys with both ultra-high strength and also high thermal stability. • Ultra-high strength of ~428 MPa was achieved in the low-cost Mg-0.8Ca-0.4Mn-0.2Ce (wt%) wrought alloy. • The Mn addition can promote dynamical recrystallization and induce more nano-precipitations. • A novel Mg-0.8Ca-0.7Mn-0.2Ce wt% alloy with an excellent thermal stability has been produced. [ABSTRACT FROM AUTHOR]