Zhongwen Ou's research while affiliated with 307 Hospital of the Chinese People's Liberation Army and other places

In this work, a hot extrusion forming process for magnesium (Mg) alloy square tubes, namely, tube-extrusion-continuous expending shear (TECES), was proposed. The thin-walled hollow square tube of Mg alloy with a thickness of 3 mm was successfully prepared by hot extrusion experiment. The evolution rules of effective stress, effective strain, and flow velocity in the process of tube forming were analyzed by numerical simulation, and the influence of different expanding ratios on tube forming was compared. The results show that the effective stress distribution of the tube is not uniform during the forming process, and the maximum stress appears at the first shear corner. In the shear deformation (SD) zone, there is a high strain zone at the corner of the square tube and outside the tube wall. As the tube is extruded, the uniformity of strain distribution in the deformation zone is improved. In the whole forming process, the flow rate of the tube increases first and then decreases, and the whole remains stable. As the expansion ratio increases when the expansion ratio is greater than 1.6, the resistance of plastic deformation increases, the fluidity of the metal becomes worse, and the formed tube cracks at the corner or is difficult to fill. When the expansion ratio is less than 1.6, the damage value area appears on the inner side of the tube wall, and the distribution uniformity is poor, which may lead to cracks or uneven thickness of the tube wall. The microstructure characterization of different deformation zones of the tube was carried out, and the results show that the TECES process can effectively refine the grain, and the average grain size of the formed tube is 10.1 μm.

This study proposed the direct extrusion and continuous-shear deformation (DECS) process for the co-extrusion of Mg-AZ31B/Al 6063, aiming to prepare high-plasticity Mg/Al composite sheets. The effect of extrusion temperature on the microstructure and mechanical properties of the Mg/Al composite sheet was systematically studied. The results show that Mg/Al composite sheets with no voids or cracks at the interface were successfully prepared by the DECS process. The microstructure of the Mg layer at different extrusion temperatures primarily consists of equiaxed fine grains, with grain sizes of 7.29 μm, 8.98 μm, and 9.88 μm at 330℃, 360℃, and 390℃, respectively. The Mg layer exhibits a typical extrusion texture, with the c-axis of most grains parallel to the transverse direction (TD). With the increase in extrusion temperature, the c-axis of some grains deviates from the TD toward the normal direction (ND). The Al layer mainly consists of elongated deformed grains and fine dynamically recrystallized (DRXed) grains distributed along the extrusion direction (ED). The AZ31 Mg alloy with refined grains maintains the ultimate tensile strength of the Mg/Al composite sheet, while the Al matrix enhances its plasticity. At 330℃, the Mg/Al composite sheet shows an ultimate tensile strength of 244.48 MPa ± 4.35 and an elongation of 39.42% ± 0.06. The influence of the bonding layer thickness on the shear and tensile properties of the composite sheet was studied, revealing that increasing the bonding layer thickness reduces the shear strength of the Mg/Al composite sheet but positively affects its tensile strength.

This paper studied the microstructure, mechanical properties, and corrosion resistance of AZ61 magnesium (Mg) alloy with and without homogenization treatment before extrusion. After homogenization treatment, the size of the second phase decreases, resulting in a more uniform microstructure of the extruded sample. Compared to the as-extruded sample, the yield strength (176.04 MPa) and tensile strength (266.3 MPa) of the homogenization-extruded samples were higher than those of the as-extruded samples, and the elongation after pre-homogenization treatment is 16.1%. The homogenization-extruded samples showed higher corrosion resistance in the potential dynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests. The mechanical properties and corrosion resistance of the homogenization-extruded samples were improved due to the microstructure improvement.