【作者】 王子田；

【导师】 李保成；

【作者基本信息】 中北大学 ， 武器系统与运用工程， 2013， 博士

【摘要】 镁合金材料在不久的将来,用量将超过铝合金材料,成为武器装备中应用最广的金属结构材料。ZK60镁合金具有最高的强度、良好的塑性及耐蚀性,是目前应用最多的变形镁合金之一。本文系统研究了ZK60合金的塑性变形特性,成形后的一系列力学性能和抗冲击能力,进而评价其在装甲防护方面的价值,以指导镁合金在军事工业上的工程应用。主要研究内容和结论如下：1.ZK60镁合金的热模拟分析表明,ZK60合金的加工性不如AZ80镁合金。通过实验发现,在高于300℃,低于1S-1的应变率条件下ZK60合金的热成形性好。2.对ZK60合金进行了等温平面压缩实验,发现由于难熔化合物的存在,均匀化后ZK60合金不仅消除了铸态的网状组织,且仍保持了晶粒细化效果,这种晶粒细化效果一直延续到后面的热变形、热处理过程中,使ZK60合金在热加工后具有较好的力学性能。3.在平面压缩态、平面压缩+T5态、平面压缩+T6态下,ZK60合金抗拉强度在应变量为2.07时都达到极值点,而延伸率出现极值时对应的应变大小有所不同。4.正挤压变形参数(变形温度、应变量)相同时,正挤压后ZK60合金的抗拉强度平均高于热压缩后ZK60合金抗拉强度78MPa,正挤压后ZK60合金的延伸率平均低于热压缩后ZK60合金延伸率4.2%。同热压缩+T5实验结果一致,正挤压+T5态ZK60合金,具有较好的力学性能。但应变3.40以后,力学性能达到极值。5.对不同热加工态ZK60合金进行了Hopkinson低速冲击(<100m/s)实验研究,发现应变率愈大,ZK60合金的动态真应力——应变曲线上愈出现明显的屈服点和屈服平台阶段；应变率愈大,断裂时对应的应变越大,且σ-ε曲线最后断裂下降部分越长,表明在高应变率下,合金具有好的塑性,且裂纹扩展速度较慢。6.对不同热加工态ZK60合金进行了弹丸高速冲击(500m/s)变形镁合金靶板实验研究,主要结果如下：(1)高速弹击实验后,在靶材弹孔背面,出现了白亮的剪切唇,说明ZK60合金靶材具有较好的塑性,在高速弹击情况下,吸能性较好,具有较好的抗弹性。(2)热变形+T5态ZK60镁合金靶板抗弹性较好,弹坑周围几乎不出现裂纹；热变形+T6态镁合金靶板抗弹性较差,弹坑周围都出现了明显的纵向裂纹；热变形态镁合金弹坑形貌有的出现裂纹,有的不出现裂纹,比较光滑。(3)经过线性回归分析,建立了弹坑深度与靶板材料力学性能之间的关系式：y=13.1-0.03x,其中：y值越小,靶板材料抗弹性越好。关系式说明了只有在Rm、Rp0.2、A都达到最理想状态下,材料就可获得优异的抗弹性。更多还原

【Abstract】 In the near future, the quantities of magnesium alloy material will be much more than aluminum alloy to become the most widely used metal structure material in weapon equipment. Mg alloy has the highest strength, good plasticity and stain resistance to be one of the most used wrought Mg alloys.In this paper, plastic deformation properties, mechanical properties and thermal-shock resistance of ZK60alloy were systematically studied and then its value on armor protective aspect was evaluated in order to lay a theoretical foundation for its use, which could direct its engineering application in the military industry.The main research contents and conclusions are as follows:1. Gleeble thermal simulation analysis shows that the machinability of ZK60alloy is not so well as AZ80Mg alloy. And the thermal formability of ZK60alloy is good when the temperature is above300℃and the strain rates is1s-1.2. The results of hot compression experiment show that with Zr insoluble compounds existing, after homogenization, ZK60alloy not only eliminates its as-cast network structure, but also keeps grain refining effect, which would continue to later thermal deformation and heat treatment and make hot-worked ZK60alloy have good mechanical properties.3. Not only in hot compressed state and hot compressed+T5state but also in hot compressed+T6state, tensile strength of ZK60alloy all reach the peak with the strain rate of2.07. However the strain rate is different when elongation appears extremum.4. The influence of extrusion process parameters on microstructure and properties of ZK60alloy under large deformation is studied in forward extrusion+aging experiments. The results of forward extrusion show that when strain rate is larger (3.40,3.80), the mechanical properties reach a constant level. Later, with strain rate increasing gradually, the waste of die and energy could not be avoided and the properties decrease. 5. When deformation parameters (temperature, strain) are same, the average tensile strength of forward extrusion state ZK60alloy is78MPa more than hot compressed state ZK60alloy, and the average elongation of forward extrusion state ZK60alloy is4.2%less than hot compressed state ZK60alloy. Besides, forward extrusion+T5state ZK60alloy has better mechanical properties as well as the results of hot compressed+T5experiment.6. ZK60alloy is experimented with Hopkinson low velocity impact test (<100m/s). The results show that the larger is strain state, the more obvious is yield point and yield platform of dynamically true stress-strain curve. Besides, the fracture part is longer with the increasing of strain state, especially when the strain state is2600s-1.7. The impact process and failure characteristic of ZK60alloy under high speed impact by steel bullet have been studied. The main results are as follows:(1) Shear ship appears in the shot hole back of target plate. This states that ZK60alloy has better defensible performance.(2) The defensible performance of hot deformed+T5state ZK60alloy is better. The cracks hardly appear around the crater. The defensible performance of hot deformed+T6state ZK60alloy is less. The vertical cracks obviously appear around the crater. Some hot deformed Mg alloy has cracks. But some have not cracks and are smooth.(3) The relation between shear depth and mechanical properties of target plate material is established by linear regression equation:y=13.1-0.03x,(y=h; the less is value of y, the better is defensible performance of target plate material). The relation states that only when Rm, Rp0.2and A all could reach the most ideal state, the material can obtain excellent defensible performance.更多还原