Mg-Li-Zn-Y合金的组织与性能研究

发布时间：2018-07-05 14:42

  本文选题：Mg-Li-Zn-Y合金 + 拉伸　； 参考：《沈阳航空航天大学》2017年硕士论文

【摘要】：本文以Mg-7Li合金、Mg-7Li-3Zn-6Y合金、Mg-3Zn-6Y合金为研究对象,结合金相显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、热分析差示扫描量热法(DSC)等表征手段,利用电子拉伸试验机对铸态和挤压态Mg-Li-Zn-Y合金进行拉伸实验,研究Mg-Li-Zn-Y合金拉伸变形行为及其应变率效应,并探讨了热处理制度对Mg-Li-Zn-Y合金显微组织和性能的影响。结果表明:随着应变速率的提高,铸态Mg-7Li合金拉伸性能表现为应变率强化效应;合金微观断裂机制主要为微孔聚合型断裂与沿晶断裂和解理断裂相结合的混合断裂机制。添加Zn、Y后,铸态Mg-7Li-3Zn-6Y合金除α相和β相外还生成了ZnY相和Mg12YZn相,合金强度升高,但塑性降低明显,合金的微观断裂机制主要为沿晶断裂。与Mg-7Li-3Zn-6Y合金相比,铸态Mg-3Zn-6Y合金屈服强度有所升高,但塑性变化不明显,合金的微观断裂机制主要为解理断裂。400℃固溶处理后,Mg-7Li-3Zn-6Y合金显微组织中并未形成LPSO相,当固溶温度达到450℃和500℃,该合金中生成LPSO相,且450℃×8h固溶处理后,合金的硬度达到最大值;Mg-3Zn-6Y合金固溶处理后显微组织中形成了细长条状的LPSO相,并在固溶制度为470℃×8h时合金的性能达到最佳。与固溶处理相比,时效处理后合金中LPSO相的形成没有进一步的改善合金的硬度,致使合金的硬度有所降低。在热挤压过程中,Mg-7Li合金发生了动态再结晶,与α相相比,β相再结晶较为充分;添加Zn、Y后,Mg-7Li-3Zn-6Y合金的晶粒明显细化,平均晶粒尺寸不足5μm;随着应变速率的升高,两种合金的拉伸性能均表现为应变率强化效应,同时发生了塑性不稳定现象,且添加Zn、Y后,合金塑性不稳定现象受到抑制。
[Abstract]:In this paper, the Mg-7Li-3Zn-6Y alloy, Mg-7Li-3Zn-6Y alloy, was studied by means of metallographic microscope (OM), scanning electron microscope (SEM) X-ray diffraction (XRD), differential scanning calorimetry (DSC), etc. The tensile deformation behavior and strain rate effect of Mg-Li-Zn-Y alloy in as-cast and extruded Mg-Li-Zn-Y alloys were studied by means of electronic tensile testing machine. The effect of heat treatment on microstructure and properties of Mg-Li-Zn-Y alloy was discussed. The results show that the tensile properties of as-cast Mg-7Li alloy show strain rate strengthening effect with the increase of strain rate, and the microfracture mechanism is mainly the mixed fracture mechanism of microporous polymeric fracture and intergranular fracture. In addition to 伪 phase and 尾 phase, ZnY and Mg12YZn phases were formed in as-cast Mg-7Li-3Zn-6Y alloy, the strength of the alloy increased, but the plasticity decreased obviously. The microfracture mechanism of the alloy was mainly intergranular fracture. Compared with Mg-7Li-3Zn-6Y alloy, the yield strength of as-cast Mg-3Zn-6Y alloy increased, but the plastic change was not obvious. The microfracture mechanism of Mg-7Li-3Zn-6Y alloy was mainly cleavage fracture. After solution treatment at 400 鈩，

本文编号：2100549