Papers by Author: Zhong Yi Niu

Abstract: Extrusion Mg-6Li-6.5Gd-1Dy-2Zn alloy was prepared successfully by vacuum melting. The microstructures and mechanical properties of as-cast and as-extruded Mg-6Li-6.5Gd-1Dy-2Zn alloys were investigated. Extruding process refines the α (Mg) phase and β (Li) phase, and makes the Mg3X phase crushed and dispersed well. After heat treatment, Mg3X phase particles became finer and much more RE enriched phase particles formed in the matrix. These effects result in the improvement of mechanical properties of the alloys. In this study, after solution treated at 510°C for 3h and aged at 215°C for 99h, the as-extruded alloy exhibits the best mechanical properties, and the microhardness, ultimate tensile and elongation reach 103.0, 249 MPa and 34.8%, respectively.

Abstract: The as-cast Mg-14Li-3Al-(0-0.9)RE alloys were prepared with vacuum melting method, then processed by hot extrusion. The microstructure and tensile properties were investigated. The results show that both addition of RE and extrusion deformation can refine the grain size. Al₃La compounds are formed with addition of La-rich misch metal. The as-extruded Mg-14Li-3Al-0.6RE alloy obtains the finest grain size (4.28 μm) and the highest mechanical properties (σ_b =222.75 MPa, δ=23.8%), which is related to the grain refinement and the formation of Al₃La.

Abstract: A series of alloys were designed and prepared using vacuum melting furnace. The as-cast microstructure and phase compositions of these alloys were characterized by optical microscope, X-ray diffraction (XRD) and scanning electronic microscope (SEM). The hardness and mechanical properties of alloys at room temperature were measured as well. The results show that the addition of RE leads to the formation of intermetallic Al3La distributed within grain boundaries. The intermetallic compound with oriented structure impedes grain growth, and refines the grain. The strength and the hardness of the alloys increase with the increase of the RE content in the range of 0.2-0.8 wt %.