Abstract: Hot deformation and associated structural changes were studied in compression of a
magnesium alloy AZ31 with initial grain sizes (D0) of 22 µm and 90 µm at a temperature of 573K. D0 influences significantly the flow curve and the kinetics of grain refinement during hot deformation. For D0 = 22 µm, grain fragmentation takes place due to frequent formation of kink bands initially at corrugated grain boundaries and then in grain interiors in low strain, followed by full development of new fine grains in high strain. For D0 = 90 µm, in contrast, twinning takes place in coarser original grains, and then kink bands and new fine grains are formed mainly in finer ones at low strains. Then new grains are formed in necklace along the boundaries of coarse original grains, followed by their development into the grain interiors. Grain refinement in the Mg alloy can be concluded to result from a series of deformation-induced continuous reactions, they are essentially similar to continuous dynamic recrystallization (cDRX).
Abstract: In this paper, diffusion bonding of ZK60 superplastic material is investigated according to atom diffusion law. Gleeble-1500 testing machine is used in the diffusion bonding processing on the superplastic ZK60. In additional, shear tests of bonding joints are carried out on electronic universal testing machine. The optimized diffusion bonding conditions are obtained: a bonding time of 90 min at 653K at a pressure of 20MPa. The microstructures of the joints are observed through OM and SEM. It is concluded that the mechanism of diffusion bonding of the ZK60 superplastic material is the slide of original grain boundaries caused by atom diffusion and the grain growth, and sound joints with high shear strength are obtained through sufficient diffusion of the interface atoms.
Abstract: Effects of variable La/Ce ratio on microstructure and mechanical properties of
Mg-5Al-0.3Mn-1RE alloys were investigated. The results indicated that pure La or pure Ce can improve ultimate strength and yield strength of AM50 effectively without obvious decrease of elongation, and the effect of La is better than that of Ce. However, addition of La and Ce together deteriorates the mechanical properties of AM50, and the valley of mechanical properties mostly appears on La:Ce= 1:1. The existence of coarse skeleton-like phase and less amount of Mg17Al12 phase is responsible for this.
Abstract: A new series of magnesium-rare earth master alloys have been developed by the
electrowinning method with subsidence cathode in the KCl•NaCl-RECl3 system. The electrolysis conditions were studied. Experimental results showed that the optimum for electrolyte at 850oC and 10~20wt% RECl3 content in the molten salt system. The current efficiency of electrolyte increased with increasing the rare earth content and reach the maximum at the content of 20% RECl3. The current efficiency gradually decreased with increasing cathode current density. The component of
master-alloys was analyzed using ICP-MS and chemical method. A series of magnesium-rare earth master-alloy, Mg-Y, Mg-Nd, Mg-Ce, Mg-La, Mg-Nd-rich and Mg-LPC were successfully prepared and the content of rare earth is adjustable between 5 – 20%.
Abstract: In the present work Mg-Li-X alloys with different alloying are investigated and the
studies are focus on the stability of microstructures and properties of β base Mg-13Li-X alloys. The alloying elements concerned are aluminum, zinc, zirconium, rare earth. The microstructure and corresponding mechanical properties are examined with the aid of DSC analyses, X-ray diffraction and OM observation. The results showed that the hardening effect and the stability of the alloys varied with different
addition of aluminum, zinc, zirconium, rare earth elements. The mechanical properties of the alloys greatly depend on the additional elements.
Abstract: Morphologies of precipitation phases along grain boundaries of the as-cast Mg-6.0Zn-0.45Zr, Mg-6.0Zn-1.2Y and Mg-6.0Zn-0.6Zr-1.0Y alloys were investigated. The experimental results indicated that the main precipitation phase along grain boundary of the as-cast Mg-6.0Zn-0.45Zr was a Mg-Zn binary compound. There were two kinds of precipitation phases along grain boundaries for Mg-6.0Zn-1.2Y and Mg-6.0Zn-0.6Zr-1.0Y alloys. One grew at triangular grain boundary, which was fish-bone -like in shape and a Mg-Zn binary compound. The other distributed mainly around the grain, which was net-like in shape and a Mg-Zn-Y ternary compound. In addition, there were lots of granular phases, extending to the interior of the grain, at the rim of grain boundary phases. Y was found to affect obviously morphology of precipitation phases along grain boundary of the as-cast Mg-Zn-Zr (ZK60) alloys.
Abstract: Bulk AZ91HP rods with a diameter of 8mm were prepared by copper mould casting. The microstructure and mechanical properties have been studied. The compressive strength, yield strength, elongation and microhardness of the rapidly solidified AZ91HP alloy are 392MPa, 183 MPa, 3.6% and HV87, respectively. It results from grain refinement and reinforcement of β-Mg17Al12 phase.
Abstract: Mg2Sn is a well known anode material used in rechargeable lithium batteries, and a
principal component of low melting tin-based alloys. In order to improve its anodic as well as anti corrosion performance, alloying of selected metals like aluminum into Mg2Sn was recommended in the literature. In this research,phase stability of a series of tin based (MgxAl1-x)2Sn alloys was studied by DFT calculations. Structural and thermodynamic properties of Al in Mg2Sn was disclosed, which may be of interest to the design of new anode materials or low melting alloys for industrial
Abstract: Effects of solution and aging treatment on microstructure and mechanical properties of rolled AM50+xCa alloys(x=0, 1, 2 wt. %) were studied. The results indicated that, with increasing solution time i, the secondary phase Mg17Al12 was dissolved into the Mg matrix and Al2Ca became thinner and shorter, then gradually broken and spheroidized.With an increase of aging time, Mg17Al12 precipitated from the Mg matrix in the form of particles and Al2Ca changed a little. After solution treatment, hardness and tensile properties of the alloy’s decreased. After the aging treatment, the alloy’s hardness increased first and decreased later while the tensile properties increased little. The solution and aging treatment can increase the ductility of AM50 and AM50+1Ca alloys. For AM50+2Ca alloy, the ductility increased after solid solution treatment and decreased after aging treatment.
Abstract: Particle-stimulated nucleation (PSN) was investigated in magnesium alloy AZ31 to study the effect of the evolution of second-phases during extrusion and other metal forming processes. Compression tests were carried out on samples taken from coarse-grained as-cast magnesium alloy billets containing a lamellar Mg17All2 eutectic phase and (Al, Mn) particles. These revealed that particle-stimulated DRX nucleation (PSN) was taking place during hot deformation and that this is facilitated by the fragmentation of the Mg17All2. When Mg17All2 dissolves into the matrix at about 350°C, the (Al, Mn) particles remain effective in producing PSN at temperatures up to at least 400°C. This suggests that alloy design leading to a suitable distribution of second-phase particles can improve the properties and formability of wrought magnesium alloys.