A high-strength Mg-15.3Gd-l.8Ag-0.3Zr （GQ152K, mass fraction） alloy was prepared by conventional ingot metallurgy process. The solution and aging （denoted as T6） treated alloy exhibits remarkable mechanical properties with ultimate tensile strength of 421 MPa and tensile yield strength of 309 MPa. It has higher igniting temperature of 1 208 K. Moreover, it can stand against flame at 1 203 K for over 6 min in vertical burning tests, and its flammability behavior is very similar to that of 6101A1 alloy. Vertical burning tests appear to be able to directly study the flammability behavior of Mg alloys and it appears to be a good approach to study the flammability behavior of Mg alloys in an aircraft fire accident.
The microstructures of Mg-2Nd-4Zn-1Zr alloy in the as-cast state and after heat treatment were investigated. Several kinds of secondary phases were found and characterized by transmission electron microscopy （TEM）, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. In the as-cast alloy, the existing eutectic compounds are Mg-Nd-Zn ternary phases： T phases and W phases. After the heat treatment, with increasing the temperature or time, it was found that T phase almost dissolved into the α-Mg matrix, while a large amount of W phase remained in the matrix. On the other hand, with prolonging the time, the morphology of the phase changed from continuous network to the spherical shape along the grain boundary. The density of the W phase gradually decreased and finally it was coarsened and stabilized in the treatment process.
An as-solution treated Mg-6Gd-1Y-0.4Zr alloy was processed by low temperature thermo-mechanical treatments （LT-TMT）, including cold tension with various strains followed by aging at 200 °C to peak hardness. The results show that the precipitation kinetics of the alloy experienced LT-TMT is greatly accelerated and the aging time to peak hardness is greatly decreased with increasing tensile strain. The tensile yield strength, ultimate tensile strength and elongation at room temperature of the alloy after cold tension with strain of 10% and peak aging at 200 °C are 251 MPa, 296 MPa and 8%, respectively, which are superior to the commercial heat-resistant WE54 alloy, although the latter has a higher rare earth element content.
介绍了含长周期堆垛有序结构(Long period stacking order,简称LPSO结构)的Mg-RE-Zn(-Zr)合金的研究现状,重点分析了Mg-Gd-Zn(-Zr)合金中14H-LPSO结构的最新研究进展,综述了等通道角挤压和搅拌摩擦加工工艺在镁合金强韧化中的应用现状,提出了当前Mg-Gd-Zn(-Zr)合金研究需解决的主要问题和未来研究方向,展望了等通道角挤压和搅拌摩擦加工工艺在Mg-Gd-Zn(-Zr)合金强韧化方面的应用前景。
A Mg-14.28Gd-2.44Zn-0.54Zr （mass fraction, %） alloy was prepared by conventional ingot metallurgy （I/M）. The microstructure differences in as-cast and solution-treated alloys were investigated. Sliding tribological behaviors of the as-cast and solution-treated alloys were investigated under oil lubricant condition by pin-on-disc configuration. The wear loss and friction coefficients were measured at a load of 40 N and sliding speeds of 30-300 mm/s with a sliding distance of 5000 m at room temperature. The results show that the as-cast alloy is mainly composed ofα-Mg solid solution, the lamellar 14H-type long period stacking ordered （LPSO） structure within matrix, andβ-[（Mg,Zn）3Gd] phase. However, most of theβ-phase transforms to X-phase with 14H-type LPSO structure after solution heat treatment at 773 K for 35 h （T4）. The solution-treated alloy presents low wear-resistance, because the hard β-phase is converted into thermally-stable, ductile and soft X-Mg12GdZn phase with LPSO structure in the alloy.
随着近年来汽车等工业节能减排对更高性能轻质镁合金的迫切需求,镁合金在工业应用中展现出了很大的发展前途。稀土镁合金系由于具有高温强度高、优良抗蠕变性能及耐热性能以及良好的塑性和耐腐蚀性等高性能,已经成为越来越受到重视的镁合金系之一,并在航空航天、电子、汽车、通讯等领域得到了广泛应用。目前,国内外已开发了Mg-Gd、Mg-Y、Mg-Gd-Y、Mg-Y-Gd等一系列稀土镁合金。综述了高性能稀土镁合金的研究进展和应用现状,主要介绍了Mg-Y和Mg-Gd二元和多元合金系的研究开发及应用的新进展,以及含长周期堆垛有序结构(Long Period Stacking Ordered Structure,简称LPSO结构)的Mg-Y-Zn、Mg-Gd-Zn、Mg-Gd-Y-Zn、Mg-Y-Gd-Zn合金系的研究现状。最后,展望了高性能稀土镁合金的发展趋势。
