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The strengthening mechanism and stress corrosion cracking (SCC) behavior of a new Mg-6Zn-1Y-0.5Cu-0.5Zr alloy (given the name "ZWCK6100″) were investigated in this work. The results showed that the microstructure, mechanical properties and stress corrosion resistance were significantly affected by the combined addition of Cu and Y. The alloy consisted of α-Mg, Zn 2 Zr, CuMgZn, rod-shaped MgZn 2 precipitates and I phase (Mg 3 Zn 6 Y), and displayed a balance between strength and ductility, with the yield strength, ultimate tensile strength and elongation being 320.3 MPa, 351.5 MPa and 19.8%, respectively. The main strengthening mechanisms were found to be grain refinement, second phases and texture. In addition, the stress corrosion resistance was assessed by slow strain rate testing and fractography. These tests showed that ZWCK6100 alloy exhibited improved SCC resistance and low SCC sensitivity in 3.5 wt% NaCl solution. The novel ZWCK6100 alloy may serve as a promising magnesium alloy for industrial applications. • A novel ZWCK6100 alloy was developed by combined additions of Y and Cu. • ZWCK6100 alloy exhibited an excellent balance of strength and elongation. • The alloy also displayed low stress corrosion cracking sensitivity in 3.5 wt% NaCl solution. • The alloy may serve as a promising magnesium alloy for industrial applications. [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]

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]

• The WE43 sheets rolled at 370 and 450 °C exhibit non-recrystallized structures. • {10 1 ¯ 1} twins and {10 1 ¯ 1}-{10 1 ¯ 2} twins are formed when rolled at 370 °C. • {10 1 ¯ 2} twins are formed when rolled at 450 °C. • The sheet rolled at 370 °C failures at a considerably low stain. • The low plasticity is caused by the activity of compression and double twins. The WE43 sheets are prepared by single-passed rolling at 370 °C and 450 °C with total reduction of 40% and 50%, and the microstructure and mechanical properties of the sheets are contrastively investigated. The R370-40% and R450-50% alloys both exhibit non-recrystallized structures with high-density dislocations and strong basal texture. Many {10 1 ¯ 1} compression twins and {10 1 ¯ 1}-{10 1 ¯ 2} double twins are formed when rolled at 370 °C, while {10 1 ¯ 2} tensile twins are formed when rolled at 450 °C. The R370-40% alloy failures at a considerably low stain, while the ductility of R450-50% alloy is much higher than that of R370-40%. The orientation of compression twins and double twins is more favorable for the basal < a > slip, then a large deformation occurs inside twins and deformation incompatibility appears at the twin-matrix boundary in the subsequent plastic deformation, leading to the final failure. The low plasticity of R370-40% alloy is mainly caused by the activity of compression twins and double twins. [ABSTRACT FROM AUTHOR]