脉冲电流处理ZK60镁合金的组织演变、机械性能及其细化机理的研究

发布时间：2018-04-22 01:15

本文选题：ZK60镁合金 + 电脉冲处理　；参考：《太原理工大学》2017年硕士论文

【摘要】：随着能源危机的日益严峻,环境恶化的不断加剧,人类社会越来越注重轻量化,绿色化制造。作为一种新型的环保材料,镁合金因其密度低、比强度高、减震性好、机加工性能优良、易回收等优点,广泛应用于航空航天、汽车、3C产品等诸多领域。但由于受材料制备、加工技术、抗腐蚀性能等因素的制约,镁合金的发展潜力与实际应用的现状之间存在巨大差异。在此背景下,对镁合金的研究在为拓宽镁的应用市场,缓解能源危机方面有着重要的战略意义。本文利用高能脉冲电流处理20%和60%两种变形量的ZK60镁合金,通过调节电脉冲频率、脉宽、处理时间等实验参数,使变形镁合金在较低温度下发生静态再结晶,并通过表征结果和理论计算两方面对电脉冲处理过程中产生的热效应和非热效应、再结晶过程中的形核与长大以及再结晶机理进行了分析。结果表明,电脉冲处理能够细化变形镁合金的微观组织从而提高其综合力学性能。ZK60镁合金的晶粒尺寸由铸态的150μm细化到4μm,抗拉强度提高了52.3%,伸长率提高了105%,EBSD分析表明处理后的试样织构强度显著减弱。此外,通过理论计算发现,脉冲电流为镁合金的再结晶提供了额外的吉布斯自由能,降低了再结晶形核的能量势垒,提高了再结晶形核率并显著细化再结晶组织。对比实验数据得知,与传统热处理方法相比,电脉冲处理能够在较低的温度下完成再结晶,再结晶晶粒长大趋势较小,从而得到更加细小均匀的显微组织。探究对比了不同变形量的ZK60镁合金在脉冲处理过程中的再结晶形核机理,不同变形量的ZK60镁合金在脉冲处理过程中的形核方式有很大差异。小变形量试样主要在晶界处形核,而原晶粒内部几乎无新晶核出现,主要发生回复,形成较为粗大不均匀的组织;而大变形量试样由于变形均匀,绝大部分区域在脉冲处理初期就形成了大角度晶界,从而发生形核和长大,形成细小均匀的再结晶组织。
[Abstract]:With the increasingly severe energy crisis and the worsening of environment, human society pays more and more attention to lightweight and green manufacturing. As a new kind of environmental protection material, magnesium alloy is widely used in many fields such as aerospace, automobile and 3C products, because of its low density, high specific strength, good shock absorption, good machinability, easy recovery and so on. However, due to the constraints of material preparation, processing technology, corrosion resistance and other factors, there is a great difference between the development potential of magnesium alloy and the current situation of practical application. In this context, the research on magnesium alloys has important strategic significance in broadening the application market of magnesium and alleviating the energy crisis. In this paper, ZK60 magnesium alloys with 20% and 60% deformations were treated with high energy pulse current. The static recrystallization of wrought magnesium alloys at low temperature was achieved by adjusting the experimental parameters such as frequency, pulse width and treatment time. The thermal and non-thermal effects, nucleation and growth during recrystallization and the mechanism of recrystallization were analyzed by means of both characterization results and theoretical calculations. The results show that Electrical pulse treatment can refine microstructure of wrought magnesium alloy and improve its comprehensive mechanical properties. The grain size of ZK60 magnesium alloy is refined from 150 渭 m to 4 渭 m in as-cast state, tensile strength is increased by 52.3% and elongation is increased by 105% EBSD analysis. The texture strength of the sample decreased significantly. In addition, it is found that pulse current provides additional Gibbs free energy for recrystallization of magnesium alloy, reduces the energy barrier of recrystallization nucleation, increases the rate of recrystallization nucleation and refines the recrystallization structure. Compared with the traditional heat treatment method, compared with the traditional heat treatment method, the electrical pulse treatment can complete recrystallization at lower temperature, and the recrystallization grain length trend is smaller, resulting in more fine and uniform microstructure. The mechanism of recrystallization nucleation of ZK60 magnesium alloys with different deformations during pulse treatment was studied and compared. The nucleation modes of ZK60 magnesium alloys with different deformations were very different during pulse treatment. The small deformation samples nucleate mainly at grain boundaries, but there is almost no new nucleation in the original grains, which mainly restores to form a coarse and uneven structure, while the large deformation samples are homogeneous due to deformation. Large angle grain boundaries were formed in most of the regions at the early stage of pulse processing, which resulted in nucleation and growth, resulting in fine and uniform recrystallization structure.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.22

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