Mcrostructure and properties of Mg-Zn-Nd-Cd-Zr alloy have been investigated on different solution treatments and artificial aging conditions by optical microscope, SEM (scanning electron microscope) and TEM(transmission electron microscope). The results indicate that the grain boundarys become thinner and the second phases distributed on the grain boundarys become finer by double-stage homogenization at 400°C for 2h plus 460°C for 12h than that of homogenization at 420°C for 24h. Double-stage homogenization brings a greater peak-ageing hardness and longer time to reach peak hardness 20h about., and the ultimate tensile strength is 345MPa at 140°C for 34h, higher 15% than that of as-extruded
The dynamic mechanical analyzer (DMA) was applied to investigate the damping properties of Mg-6Zn-0.6Zr alloys. The results show that the as-cast Mg-6Zn-0.6Zr alloy exhibits higher strain amplitude independent damping performance than that of as-homogenized. The strain amplitude dependent damping of the as-homogenized has the best damping performance with the strain amplitude from 3×10-5 to 6×10-4, and the as-extruded is the lowest. When the strain amplitude exceeded 6×10-4, the as-extruded has the best damping capacity all the time within the experimental strain amplitude, and all the alloys reach the high damping capacity. Two critical strain amplitude points were detected in the alloy as-extruded and as-homogenized. The damping peak value is 0.0192 with the strain amplitude of 1.5×10-3 presented in the alloy as-extruded.
The effective strain size and distribution of Al-5Ti-1B alloy deformed by equal channel angular pressing (ECAP) were investigated through the finite element simulation by the die with outer corner ψ=0°, 20°, 30° and the friction coefficient f=0, 0.2, 0.3. The simulation results show that the effective strains decrease with the increase of the outer corner ψ from 0° to 30° with a constant f; the more uniform deformation were obtained under the conditions of large friction than that of small friction. Al-5Ti-1B alloy was produced by once path ECAP at room temperature under the die with the corner angle φ=90° and ψ=20°. The optical microscope and compressing test machine were performed. The results indicate that the grain size was obviously refined. The yield strength increased by 37.5% from 142.0MPa to 195.3MPa, and hardness increased by 24% from 45.2HV to 55.9 HV.
Hot compression tests of the homogenized Mg-Zn-Nd-Cd-Zr magnesium alloy were performed on Gleeble-1500 at temperatures between 300 °Cand 420 °C and at strain rates ranging from 0.001 to 1 s-1 with maximum strain of 0.8. The microstructure of the experimental alloy in the hot-compression procedure at elevated temperatures was observed by OM (optical microscope) and TEM (transmission electron microscope). The results provide the experimental basis for selecting hot wrought conditions of the alloy. The peak flow stress becomes larger with the increasing strain rate at constant temperature, and gets smaller with the increasing deformation temperature at constant strain rate. The deformation activation energy increases greatly in the range of higher than 420°C, and no more change in the range of 340-380°C. The alloy can be extruded successfully at 360°C with of δb 310 Mpa, δ2 of 290Mpa, and δof 16%。
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