挤压态Mg-1Zn-2Y镁合金高应变率变形行为

发布时间：2018-01-09 00:14

本文关键词：挤压态Mg-1Zn-2Y镁合金高应变率变形行为　出处：《沈阳工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：镁合金在地面交通、航空、航天等工程领域有着广泛的应用,但目前针对镁合金在高温高应变率下动态压缩力学行为的研究还不是很多,大多数的研究主要是针对高温低应变速率条件。可是,在一些诸如厂房爆炸、爆恐袭击、突发性火灾等场合,金属材料有可能受到高温高应变率条件下的冲击载荷,所以不同温度下高应变率动态力学性能的研究极为重要。为此,本文采用分离式霍普金森压杆对Mg-1Zn-2Y镁合金的室温及高温高应变率力学行为,及其变形与失效机制进行了深入的研究。本文分别对温度为室温、100℃、150℃、200℃加载方向为ED和ERD的挤压态Mg-1Zn-2Y镁合金进行了高速冲击压缩试验,应变率范围为1290-3047s~（-1）;分别使用光学显微镜(OM)和扫描电镜(SEM)对材料在变形前和变形后的金相组织进行了分析;使用χ-ray对合金的织构进行分析;使用扫描电镜(SEM)对冲击试验后的断口进行分析。据此,探讨了Mg-1Zn-2Y镁合金的变形及断裂机制。本文实验结果表明:室温时,Mg-1Zn-2Y镁合金挤压态试样在ED及ERD方向都发生了屈服(ERD方向屈服点不明显)。室温时,ED方向试样体现出正的应变率强化效应,ERD方向试样只在1290-1552s~（-1）范围内为正的应变率强化效应,在1552-2602s~（-1）应力对应变速率的变化不敏感,沿ERD方向压缩的应变率敏感性低于ED方向。相比而言,ED方向的屈服强度较ERD方向低,应变率强化效应比ERD方向更为显著,断裂强度较ERD试样高,但其断裂应变较ERD方向低。此外,ED方向真应力应变-曲线先下凹再上凸,ERD方向则没有拐点,曲线上凸。高温下Mg-1Zn-2Y镁合金挤压态试样的屈服强度对应变速率的变化不敏感。相比而言,ED方向的塑性会更好一些,ED方向的冲击吸收功大于ERD,表现出较为稳定的应变率强化效应,但ERD方向的应变率强化效应和绝热剪切敏感性大于ED方向。无论在室温还是高温下,Mg-1Zn-2Y镁合金挤压态试样沿ED方向进行压缩时的流变应力要高一些,这与织构有关,室温及100℃时高应变率冲击下的Mg-1Zn-2Y镁合金的断裂为韧脆共存的断裂特征,为解理断裂,不同加载方向解理断裂程度不同。
[Abstract]:Aviation magnesium alloy on the ground, transportation, aerospace and other engineering fields are widely used, but for the magnesium alloy in high temperature and high strain rate on dynamic compressive mechanical behaviors are not much, most of the research is mainly aimed at high temperature and low strain rate conditions. However, in some areas such as plant explosion, explosion of terrorist attacks. The sudden fire and other occasions, metal materials are likely to be in high temperature and high strain rate impact load condition, so different temperature under high strain rate on the dynamic mechanical properties is very important. Therefore, this paper adopts the split Hopkinson pressure bar of Mg-1Zn-2Y magnesium alloy at room temperature and high temperature and high strain rate mechanical behavior and deformation mechanism. The failure is studied. Based on the temperature at room temperature, 100 degrees, 150 degrees, 200 degrees of high speed impact loading direction compression test for the extruded Mg-1Zn-2Y magnesium alloy ED and ERD, The strain rate range of 1290-3047s~ (-1) respectively; using optical microscope (OM) and scanning electron microscopy (SEM) on the microstructure of materials in deformation before and after deformation were analyzed using X -ray alloys; texture analysis; using scanning electron microscopy (SEM) on fracture impact test was analyzed. Accordingly, to investigate the deformation and fracture mechanism of Mg-1Zn-2Y magnesium alloy. The experimental results showed that at room temperature, the Mg-1Zn-2Y magnesium alloy extruded samples in ED and ERD direction (ERD direction happens to yield the yield point is not obvious). At room temperature, the ED sample shows the positive strain strengthening effect of ERD in the direction of the specimen only 1290-1552s~ (-1) in the range of positive strain strengthening effect in 1552-2602s~ (-1) is not sensitive to the change of stress and strain rate, compression along the ERD direction of the strain rate sensitivity is lower than that of ED direction. In contrast, the ED direction ERD direction is low yield strength, Strain rate than ERD direction is more significant strengthening effect, fracture strength is ERD samples of high, but its fracture strain is ERD direction ED direction is low. In addition, the stress-strain curve under the first concave to convex, ERD direction is no inflection point, convex curve is not sensitive. Mg-1Zn-2Y magnesium alloy extruded samples under high temperature the yield strength and strain rate changes. In contrast, the plastic will be better in the ED direction, ED direction of the impact absorbing energy is greater than ERD, showed a relatively stable strain rate strengthening effect, but the direction of the ERD strain rate strengthening effect and adiabatic shearing sensitivity of greater than ED. No matter at room temperature or high temperature state the sample along ED direction compression stress rheology to the high number of extruded Mg-1Zn-2Y magnesium alloy, and the texture of the high strain rate of fracture of Mg-1Zn-2Y magnesium alloy under the impact of room temperature and 100 DEG C for fracture characteristics of ductile brittle cleavage fracture for coexistence, The fracture degree of cleavage in different loading directions is different.

【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.22

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