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Hot deformation behavior of high-strength Mg-2.5Nd-0.2Zn-1.0Zr (in wt.%) alloy was investigated by the aid of tensile tests at the temperatures ranging from 200 to 400°C and strain rates varying from 0.001 to 1 s−1. The constitutive relationship of the alloy was modeled by a hyperbolic sine equation based on experimental result. A processing map of the alloy was designed by dynamic material model, which formed a domain of instability at inferior degree of deformation temperature (200-300°C) and relatively large strain rate (1-0.02 s−1). Accordingly, a domain of stability was developed implying the maximum efficiency of power dissipation as high as 46.2%, and relating a couple of optimum parameter values to deformation process, i.e., deformation temperature of 380 °C and strain rate of 0.006 s−1, respectively. Different morphological features of the fracture surface on tensile sample were revealed varying from quasi-cleavage to ductile fracture by decreasing strain rate and simultaneously increasing deformation temperature. [ABSTRACT FROM AUTHOR]

High-quality Mg-Nd-Zn-Zr magnesium alloy billets with diameter of 200 mm were successfully prepared by direct chill (DC) casting. The results show that microstructures of the as-cast billet prepared by DC casting are mainly composed of equiaxed a-Mg and Mg 12 Nd eutectic compound distributing along the grain boundaries. The average grain size decreases along the radius of the billet. And the alloying elements of Nd and Zn distribute homogeneously across the large billet. The optimum process parameters for DC casting of the Mg-Nd-Zn-Zr magnesium alloy billet with diameter of 200 mm have been experimentally determined as follows: casting temperature 710 °C and casting speed 80 mm/min. [ABSTRACT FROM AUTHOR]

Large size seamless tubes of Mg-3.0Nd-0.4Zn-0.4Zr alloy (NZ30K, in weight percent) were prepared by integrating backward extrusion with forward extrusion. Microstructure, mechanical properties, aging behavior and texture of the tubes were investigated. The microstructure of as-extruded tube is characterized by the blend of considerably elongated grains and fine equiaxed grains. The maximum values of yield strength and ultimate tensile strength, i.e., 191 and 245 MPa, were obtained in the as-extruded tubes, and these values were increased to 212 and 267 MPa in the peak-aged tubes (T5), implying an increasing ratio of 9 and 11%, respectively. The peak value of the Vickers’ micro-hardness of the NZ30K tubes extruded at 673, 723 and 753 K are 66, 64 and 60 (kilogram-force per square millimeter), respectively. The texture of NZ30K tube is weak, the primary mechanism behind which is suggested to be the particle-induced nucleation responsible for the promotion of recrystallization. [ABSTRACT FROM AUTHOR]

Creep-resistant Mg-4Al-4Ca (AX44) alloy was solidified under different growth/cooling rates using a directional solidification (DS) technique. The solidification behavior and microsegregation of the alloying elements in the castings was investigated. Computational thermodynamics calculations of phase equilibria and experimental observations confirm that the solidification microstructure in this alloy consists of α-Mg, C36-(Mg,Al)Ca, and C14-MgCa phases. A relationship was established between the primary dendrite arm spacing and the cooling rate, which can be used to predict mechanical properties such as yield strength and creep. The microsegregation of alloying elements (Al and Ca) predicted by the Scheil model in AX44 agrees well with the electron probe microanalysis (EPMA) measurements, suggesting that the Scheil model can be used in microstructure simulation of magnesium castings. [ABSTRACT FROM AUTHOR]

Abstract: The plastic flow behavior of a newly developed high strength magnesium alloy, Mg–3Nd–0.2Zn–0.4Zr (NZ30K, wt.%), was investigated by tensile testing in the temperature range of 25–400°C and a strain rate range of 1×10−4–1×10−2. The constitutive relationship for this alloy deformed at elevated temperatures was determined by plotting the experimental data according to the Arrhenius and hyperbolic sine models. The results show that both equations fit the experimental data reasonably well. The effect of deformation parameters on the microstructure and deformation mechanisms of the alloy was also examined using optical metallography and electron backscattered diffraction (EBSD) techniques. The results suggest that basal slip and twinning are the main deformation mechanisms at temperatures up to 200°C; and that recrystallization occurs at deformation temperatures above 200°C. Dynamic recrystallization (DRX) was shown to be the main softening mechanism at temperatures above 400°C. [Copyright &y& Elsevier]

Abstract: Mg–3.0Nd–0.2Zn–0.4Zr (wt.%, NZ30K) is a newly developed magnesium rare earth alloy with middle strength and high toughness in as-cast state. In this paper the forgeability of the as-cast NZ30K alloy prepared by direct chill (DC) casting was studied. The forgeability of the DC casting NZ30K alloy was firstly modeled by using uniaxial tensile and compression tests at temperatures between 250 and 400°C and strain rates ranging from 0.001 to 10S−1. The results show that the optimum forging temperature of the as-cast NZ30K alloy is between 350 and 400°C and strain rate ranges from 0.01 to 1S−1. Finally, a flange of automobile clutch was tentatively and successfully forged by using the DC casting NZ30K billet. The forged flange possesses desired microstructure and high mechanical properties. The mechanical properties of the product are further enhanced by T5 heat treatment for precipitate strengthening. The maximum ultimate tensile strength, yield strength and elongation of the T5 state alloy are 323.5MPa, 318.2MPa and 11.2%, respectively. The creep strain rates for the NZ30K alloy are 2.0×10−8 and 1.2×10−7 at the 200 and 250°C, respectively. [Copyright &y& Elsevier]

Abstract: Some large Mg–3.0Nd–0.2Zn–0.4Zr (NZ30K) magnesium alloy seamless tubes were prepared by forward extrusion. The as-extruded tubes were cooled in the air or by spraying liquid N2 after extrusion. The formability, mechanical and corrosive properties of the NZ30K magnesium alloy seamless tubes were investigated. The experimental results show that seamless NZ30K tubes with an outer diameter of 110mm and inner diameter of 90mm can be produced by forward extrusion and the tubes have good roundness, concentricity and straightness even without any straightening. The tensile results show that the maximum ultimate tensile strength, yield strength and elongation of the extruded tubes cooled in the air and by spraying liquid N2 are 306.3 and 314.6MPa, 250.4 and 270.3MPa, 14.2% and 15.6%, respectively. The corrosion rates of the as-extruded tubes cooled in the air and by spraying liquid N2 immersed in 5% NaCl solution for 3days are 0.225 and 0.234mgcm−2 day−1, respectively, which are a little inferior to the as-cast, T4 and T6 NZ30K alloys, but much lower than that of AZ91 alloy. Localized corrosion is suggested to be its corrosion pattern. [Copyright &y& Elsevier]

Abstract: Mg–4Al–4Nd–0.5Zn–0.3Mn alloy was prepared by metal mould casting method. Microstructure, aging behavior, mechanical properties and fracture morphology of the alloy were investigated. The results showed that α-Mg, Al11Nd3, Al2Nd and Mg32(Al,Zn)49 phases were the main phases of the as-cast alloy. And the long rod-like Al11Nd3 phase was decomposed to granular Al2Nd through T6 heat treatment. The tensile strength was also enhanced by T6 treatment. The yield strength was increased by 17% and 21% at RT and 150°C, respectively. It was mainly because that the precipitates were refined through T6 treatment and this became more benefit to hinder dislocations slipping. [Copyright &y& Elsevier]

The surface treatment of the metal substrate has a significant effect on the adhesion between the metal sheet and fiber/epoxy prepreg. The effect of the surface treatment methods, including sandpaper abrasion, phosphating treatment, anodizing and plasma electrolytic oxidation (PEO), on the surface morphology, surface energy and shear strength of WE43 magnesium alloy was analyzed in this study. The surface roughness is noted to have a significant effect on the wettability of WE43 magnesium alloy. The roughness and surface energy of the phosphated WE43 magnesium alloy are observed to be the largest among the four surface treatment methods, and the corresponding values are 4.17 and 70.8 mJ/m2, respectively. The lap-shear tensile tests reveal that WE43 magnesium alloy treated by the PEO process possesses the highest shear strength. Overall, the shear strength of the samples after phosphating treatment, anodizing and PEO treatment is noted to improve by 46%, 61% and 116% respectively, as compared with the sample treated by sandpaper abrasion. The observed superior shear properties after PEO treatment have been attributed to the cylindrical pores conducive to the infiltration of the epoxy resin during the curing process, thus, enhancing the adhesion between WE43 magnesium alloy sheet and epoxy resin. Additionally, the shear fracture mechanism was also analyzed in detail. [ABSTRACT FROM AUTHOR]

Abstract: The formability in three-dimensional rectangular cup drawing of AZ31 magnesium alloy sheet is successfully predicted by the Drucker–Prager plasticity (DP model). Numerical results show that the punch corner shoulder is under the condition of high tension bending and the die corner shoulder is on pure bending regardless of constitutive models. The failure is attributed to the competition between the biaxial tension bending induced fracture on the punch corner shoulder and the through-thickness shear induced fracture on other shoulders in the sheet forming. Taking the yield surface asymmetry into consideration, in a way of the friction angle in the coordinate of compressive and tensile strengths in the DP model, the accuracy of plastic strain is improved remarkably. The fracture locates on the punch corner shoulder where the strain reaches its fracture limit earlier than the die corner shoulder''s. The predictions of forming limit and fracture locus in the DP model simulation are in good agreement with the experimental results. [Copyright &y& Elsevier]