Papers by Author: Xiu Rong Zhu

Abstract: Fe-Cr-Ni preform reinforcing aluminum composite was produced by squeeze casting. And then, T6 heat treatment was conducted to enhance the composite’s performance. After which, isothermal compression tests in temperature range of 298 - 473 K at an strain rate range from 0.001 to 10 s^-1 were carried out on Gleeble 3500 thermo-mechanical simulation machine. It is found that, for a specific strain rate, the flow stress decreases markedly with temperature increases. And for a fixed temperature, the flow stress generally increases as the strain rate increases. Based on the experimental true stress-true strain data, the Arrhenius type model was established.

Abstract: In this paper, squeeze casting process was adopted to produce the Fe-Cr-Ni preform reinforced Al-Si-Cu-Ni-Mg aluminum composite. And then, T6 heat treatment was conducted to enhance the composite’s performance. After which, isothermal compression tests in temperature range of 473-773 K at an interval of 150 K and strain rate range from 0.001 to 10 s^-1 were carried out on Gleeble 3500 thermo-mechanical simulation machine. It is found that, for a specific strain rate, the flow stress decreases markedly with temperature increases. And for a fixed temperature, the flow stress generally increases as the strain rate increases. Based on the experimental true stress-true strain data, the Arrhenius type model was established.

Abstract: Microstructures and mechanical properties of Mg-10Gd-3Y-2Zn-0.5Zr alloy were investigated. Three kinds of phases including Mg, Mg₃(GdYZn) and Mg₁₂(GdY)Zn were found in the as-cast alloy. Two different patterns of the long-period stacking order (LPSO) phases including lamellar structure and block-like structure were observed in the homogenized alloy and both of them were identified as the phase of Mg₁₂(GdY)Zn. After extrusion with ratio of 10:1 under 420°C, fine dynamic recrystallized grains were obtained and its average size was only about 4μm. The alloy exhibited excellent mechanical properties by hot extrusion and heat treatment. The ultimate tensile strengths of the as-extruded and peak-aged alloys were 415MPa and 480MPa, the tensile yield strength were 335MPa and 410MPa, the elongations were 16% and 13.5%, respectively. The high mechanical properties were mainly attributed to the combined effects of fine grains, LPSO phases and the dispersed precipitates.

Abstract: Al-12Si-3.2Cu-1Mg-2.4Ni-χTi (χ=0, 0.2) alloys were prepared by squeeze casting process, and then heat-treated. The mechanical properties were tested at 350°C, the microstructure and phases in them were investigated by optical microscope, SEM, EDS and XRD. It is found that the grain size has an obvious increment after 0.2 wt. % Ti additions to Al-12Si-3.2Cu-1Mg-2.4Ni, and the ultimate tensile strength at elevated-temperature increased accordingly. Intermetallic compounds, such as γ-Al₇Cu₄Ni, M-Mg₂Si, Q-Al₅Cu₂Mg₈Si₆ and δ-Al₃CuNi existing in alloys with and without Ti addition. Needle-like Ti containing phase with the elements of Al, Si and Ti created in Al-12Si-3.2Cu-1Mg-2.4Ni-0.2Ti alloy, and the eutectic Si is found to distribute by the side of Ti containing phase.

Abstract: The effect of different hydrostatic extrusion ratios on the microstructure and mechanical properties of the ZK60 magnesium alloys were investigated. The results showed that, the major deformation mechanism of the alloy is twinning at room temperature, which resulted in that the tensile strengthen and hardness of the extruded alloy improved greatly. With deformation ratio increasing, the ultimate tensile strengthen and hardness are linearly increased, with the functions of Y= 4.2X+358.3 and Y=2.3X +73.69, respectively. And the maximum tensile strength and hardness of the extruded alloy are 383 MPa and 87HB, respectively. But the elongation decreases obviously, the minimum decreasing degree is 50%. With the deformation ratio increasing, the tendency of elongation rate increased as an “M” model.

Abstract: The extruded microstructure and properties of Mg-2.7Nd-1.2Gd-0.4Zn-0.3Zr alloy by squeeze casting were investigated. After aging process (T5), the dislocation density was enhanced and the dislocation interaction was increased; the factors of grain refinement, RE phases redistribution, the increment of dislocations and the interaction between dislocations and precipitate phases were contributed to the strength increase after hot extrusion and aging treatment, the fracture mode of the hot-extruded alloy was the fracture of the secondary phases and the trans-grain fracture.