【作者】 徐伟；

【导师】 张密林；

【作者基本信息】 哈尔滨工程大学 ， 应用化学， 2007， 硕士

【摘要】 镁锂合金具有低密度、高比强度、高比刚度、阻尼性能好以及抗高能粒子穿透能力强等一系列优点，在宇航领域、电子工业及通讯行业有着广泛的应用。然而商业镁锂合金由于强度较低、抗腐蚀力能力差在应用上受到很大的限制。本论文以超轻Mg-14Li-1Al（LA141）镁锂合金为研究对象，以均匀化处理、添加稀土Y对其显微组织和性能的影响为主要研究内容，讨论了Y的含量与合金微观组织及力学性能的关系。论文的主要内容为，用真空感应熔炼炉配制成份为Mg-14Li-1AI-xY试验合金，利用光学金相显微镜、扫描电子显微镜、X射线衍射仪等检测设备分析了不同Y含量对Mg-14Li-1Al的显微组织和力学性能的影响。同时，也研究了Y含量对Mg-14Li-1Al挤压、变形的微观组织和力学性能的影响。本文还研究了Mg-14Li-1Al-xY挤压、轧制变形后晶粒细化的机理。研究结果表明：使用真空感应熔炼炉，在氩气保护的氛围下，成功的制备了高质量的Mg-14Li-1Al-xY合金。稀土元素Y的加入改变了β相晶粒的形态并导致了新相Al₂Y的出现，当Y的含量为0．5wt％时，Mg-14Li-1Al的强度最高、延伸率较高，综合力学性能最佳。抗拉强度为77MPa，延伸率为11％。挤压后轧制的板材抗拉强度有较大的提高，达到142MPa，其延伸率为19％。挤压、轧制过程发生的动态再结晶细化了晶粒，从而提高合金的力学性能。Y的加入有助于合金力学性能的提高。原因如下：细化的晶粒提高了合金的力学性能，少量的Al₂Y在β相的弥散分布也有助于合金力学性能的提高。Al₂Y的数量及分布对合金的力学性能影响很大，Y含量高会导致Al₂Y的聚集，进而降低合金的力学性能，而少量的Y会提升合金的常温和高温性能。更多还原

【Abstract】 The application of Mg-Li alloys in the aircraft, electronics and communication industries has been expanding at a high rate due to their low density, high strength-to-weigh and rigidity-to-weigh ratio, good damping capacity and good electromagnetic shielding properties. Research works of this thesis aim at the super light magnesium lithium alloy- Mg-14Li-lAl（LA141） and mainly focuses on the effects of the homogenizing treatment, the addition of rare earth Y, the extrusion and rolling on microstructure and mechanical properties of alloys. And the effects of Y addition on the microstructure and mechanical properties were studied.The typical test alloys of Mg-14Li-lAl-xY were prepared in vacuum inductance furnace. The influence of Y on the as-cast microstructure of a Mg-14Li-lAl alloy was investigated by optical microscope（OM）、scanning electron microscope（SEM）、and X-ray diffraction（XRD）, et al. The mechanical properties and microstructure of Mg-14Li-lAl alloy with Y addition processed by rolling and extrusion were investigated as well. The mechanism of grain refine of minor rare earth in Mg-14Li-1Al-xY system alloy after rolling and extrusion were investigated.The results showed that the high quality Mg-14Li-1Al-xY magnesium alloys can be prepared in vacuum inductance. Mechanical properties of the Mg-14Li-lAl alloys were improved by the addition of Y. Rare earth changed the morphology ofβphase grain and the new phase Al₂Y was found. In addition, the as-cast alloy with 0.5wt% Y shows the best mechanical properties with the highest strength and a relative good elongation. The proof strength of extrusion is 77 MPa and the elongation is 11%. The proof strength of rolling after extrusion increased greatly and reached 142MPa and its elongation is 19% The mechanism of grain refine of minor rare earth in Mg-14Li-lAl system alloy after rolling and extrusion are investigated. The mechanism of grain refinement of rare earth on Mg-14Li-lAl alloy after extrusion and rolling is the dynamic recrystallization effect which makes the tensile strength of Mg-14Li-lAl alloy increase greatly. This could be attributed to grain refinement and the homogeneous distribution of Al₂Y phase. The amount and distribution of the Al₂Y phase has great effect on mechanical properties. The addition of Y could decrease the amount of the Al element inβphase and might cause the agglomeration of Al₂Y, which reduce the mechanical properties of Mg-14Li-1Al. On the contrary, minor content of Y can both improve mechanical properties at room and high temperature.更多还原