【作者】 沈佳；

【导师】 杨明波；

【作者基本信息】 重庆理工大学 ， 材料学， 2009， 硕士

【摘要】 镁合金作为轻质的工程结构材料,其在汽车、航空航天和其它领域的应用前景广阔。然而,现有镁合金的高温力学性能等还难以满足工业生产的需要。因此,有必要开发高性能的新型耐热镁合金。含Sc镁基合金作为一种潜在的高温镁合金,其研究正引起国内外的关注和重视。然而,国内外目前对于含Sc镁基合金的研究主要集中在相图的建立及完善上,对其组织和性能控制的研究还相对较少。因此,针对含Sc镁基合金的组织和性能控制展开研究,对于高性能含Sc镁基合金的开发及扩大镁合金的应用具有非常重要的理论指导意义和实际应用价值。本文基于Mg-Ce-Mn-Sc、Mg-Y-Mn-Sc和Mg-Gd-Mn-Sc三种含Sc镁基合金,利用光学显微镜(OM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)、差热分析(DSC)和性能测试等手段,研究了微量Zr、Sr和/或Ca以及T5热处理对含Sc镁合金显微组织和力学性能的影响,并得到了以下研究结果:1)Mg-3Ce-1.2Mn-0.9Sc镁合金主要由α-Mg、Mg12Ce和Mn2Sc三种相组成,在合金中单独和/或复合添加0.5wt%Zr及0.1wt%Sr对合金组织中合金相的类型没有影响,但可使合金的晶粒细化,其中以复合添加0.5wt%Zr+0.1wt%Sr的细化效果最好,其次依次是单独添加0.5wt%Zr和0.1wt%Sr。相应地,经Zr和/或Sr微合金化的Mg-3Ce-1.2Mn-0.9Sc镁合金在室温和高温下的抗拉性能及蠕变性能得到提高。此外,Mg-3Ce-1.2Mn-0.9Sc镁合金在T5处理过程会析出Mn2Sc强化相,也使合金的力学性能得到进一步的改善。2)Mg-4Y-1.2Mn-0.9Sc镁合金主要由α-Mg、Mg12Y和Mn2Sc三种相组成,在合金中单独和/或复合添加0.5wt%Zr及0.1wt%Sr对合金组织中合金相的类型没有影响,但可使合金的晶粒细化,其中以复合添加0.5wt%Zr+0.1wt%Sr的细化效果最好,其次依次是单独添加0.5wt%Zr和0.1wt%Sr。相应地,经Zr和/或Sr微合金化的Mg-4Y-1.2Mn-0.9Sc镁合金在室温和高温下的抗拉性能及蠕变性能得到提高。此外,Mg-4Y-1.2Mn-0.9Sc镁合金在T5处理过程会析出Mn2Sc和Mg12Y强化相,也使合金的力学性能得到进一步的改善。3)Mg-5Gd-1.2Mn-0.4Sc镁合金主要由α-Mg、Mn2Sc、Mg3Gd、Mg5Gd四种相组成,在合金中单独和/或复合添加0.5wt%Zr、0.1wt%Sr及0.3wt%Ca对合金组织中合金相的类型没有影响,但可使合金的晶粒细化,其中以复合添加0.3wt%Ca+0.1wt%Sr细化效果最好,其次依次是添加0.5wt%Zr、0.1wt%Sr的合金。相应地,经Zr、Sr和/或Ca微合金化的Mg-5Gd-1.2Mn-0.4Sc镁合金在室温和高温下的抗拉性能及蠕变性能得到提高。此外,Mg-5Gd-1.2Mn-0.4Sc镁合金在T5处理过程会析出Mn2Sc和Mg5Gd强化相,也使合金的力学性能得到进一步的改善。4)Mg-3Ce-1.2Mn-0.9Sc、Mg-4Y-1.2Mn-0.9Sc和Mg-5Gd-1.2Mn-0.4Sc镁合金的铸态和T5态力学性能存在较大的差异。在铸态和T5态条件下,Mg-4Y-1.2Mn-0.9Sc和Mg-5Gd-1.2Mn-0.4Sc镁合金均具有较高的室温和高温抗拉性能及蠕变性能,而Mg-Ce-Mn-Sc镁合金的力学性能相对较差。更多还原

【Abstract】 Magnesium alloys are the lightest structural alloys commercially available and have great potential for applications in automotive, aerospace and other industries. However, the elevated temperature properties of the current magnesium alloys are relatively poor. Therefore, it is very necessary to develop new elevated magnesium alloys. The Sc-containing magnesium alloys are thought as the potential elevated temperature magnesium alloys, and their research have received much global attention. However, the research about the Sc-containing magnesium alloys presently focuses on the phase diagram, the investigation about the controlling of the microstructure and mechanical properties is very scarce. Therefore, the research about the controlling of the microstructure and mechanical properties for the Sc-containing magnesium alloys has very important theoretical significance and practicable value in developing the Sc-containing magnesium alloys with high properties and widening the application of magnesium alloys.Based on the three Sc-containing magnesium alloys of the Mg-Ce-Mn-Sc, Mg-Y-Mn-Sc and Mg-Gd-Mn-Sc, the effects of minor Sr, Zr and/or Ca, and T5 heat treatment on the microstructure and mechanical properties of the Sc-containing magnesium alloys were investigated by using optical microscope(OM), scanning electron microscope (SEM), transmission electron microscope(TEM), X-Ray diffraction(XRD) and properties testing, and the following research results were obtained:1) The Mg-3Ce-1.2Mn-0.9Sc magnesium alloy is mainly composed ofα-Mg, Mg12Ce and Mn2Sc phases. Adding 0.5wt%Zr and/or 0.1wt%Sr to the alloy does not cause the formation of any new phases but can refines the grains, and adding 0.5wt%Zr+0.1wt%Sr can obtain relatively high refining efficiency, followed by adding 0.5wt%Zr and 0.1wt%Sr, respectively. As a result, the tensile properties at room and high temperatures and creep properties for the Mg-3Ce-1.2Mn-0.9Sc alloy micro-alloyed with Zr and/or Sr are improved. In addition, the mechanical properties of the alloy are further improved by T5 treatment due to the precipitating of the Mn2Sc strengthening phase.2) The Mg-4Y-1.2Mn-0.9Sc magnesium alloy is mainly composed ofα-Mg, Mg12Y and Mn2Sc phases. Adding 0.5wt%Zr and/or 0.1wt%Sr to the alloy does not cause the formation of any new phases but can refines the grains, and adding 0.5wt%Zr+0.1wt%Sr can obtain relatively high refining efficiency, followed by adding 0.5wt%Zr and 0.1wt%Sr, respectively. As a result, the tensile properties at room and high temperatures and creep properties for the Mg-4Y-1.2Mn-0.9Sc alloy micro-alloyed with Zr and/or Sr are improved. In addition, the mechanical properties of the alloy are further improved by T5 treatment due to the precipitating of the Mn2Sc and Mg12Y strengthening phases.3) The Mg-5Gd-1.2Mn-0.4Sc magnesium alloy is mainly composed ofα-Mg, Mn2Sc, Mg3Gd and Mg5Gd phases. Adding 0.5wt%Zr, 0.1wt%Sr and/or 0.3 wt%Ca to the alloy does not cause the formation of any new phases but can refines the grains, and adding 0.3wt%Ca+0.1wt%Sr can obtain best refining efficiency, followed by adding 0.5wt%Zr and 0.1wt%Sr, respectively. As a result, the tensile properties at room and high temperatures and creep properties for the Mg-5Gd-1.2Mn-0.4Sc alloy micro-alloyed with Zr, Sr and/or Ca are improved. In addition, the mechanical properties of the alloy are further improved by T5 treatment due to the precipitating of the Mn2Sc and Mg5Gd strengthening phases.4) The difference in the as-cast and T5 mechanical properties for the Mg-3Ce -1.2Mn-0.9Sc, Mg-4Y-1.2Mn-0.9Sc and Mg-5Gd-1.2Mn-0.4Sc magnesium alloys is very obvious. Under the as-cast state or T5 treatment, the Mg-4Y-1.2Mn-0.9Sc and Mg-5Gd -1.2Mn-0.4Sc alloys have relatively higher tensile properties at room and high temperatures and creep properties than the Mg-3Ce-1.2Mn-0.9Sc alloy.更多还原