高强铝合金高温拉伸性能及断裂行为研究

发布时间：2018-01-16 22:08

本文关键词：高强铝合金高温拉伸性能及断裂行为研究　出处：《太原科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着航空航天工业的不断发展,铝合金作为飞机结构件用中厚板、挤压件、自由锻件与模锻件的需求量越来越大,性能要求也越来越严格。在保证铝合金构件性能要求的同时也要保证其使用寿命,那么就要求生产铝合金构件的每一步都不存在断裂隐患。在热锻过程中,温度及应变速率对铝合金的高温拉伸性能及断裂行为都会产生严重的影响。目前,国内外对新型Al-Zn-Mg-Cu高强铝合金的高温拉伸性能及断裂行为研究还很少,因此本文通过实验数据与数值模拟相结合的方法,研究了新型Al-Zn-Mg-Cu高强铝合金的高温拉伸性能及断裂行为,以期为新型Al-Zn-Mg-Cu高强铝合金热锻过程中合金的性能及断裂行为的控制提供一定的指导。本文针对铸态和锻态高强铝合金,采用热模拟高温拉伸实验并借助金相显微镜(OM)、扫描电子显微镜(SEM)以及能谱(EDS)等检测手段,研究了不同温度及应变速率对锻态和铸态铝合金高温拉伸性能及断裂行为的影响规律。通过高温拉伸实验得到了温度及应变速率对抗拉强度、屈服强度、缩颈开始的真应变、断裂真应变的影响规律。通过IBM软件对实验数据进行回归分析,建立了抗拉强度和屈服强度随温度及应变速率变化的关系模型,为在制定锻造工艺时确保设备对材料施加的应力小于抗拉强度,防止锻造裂纹的产生提供了理论依据。对拉断后试样断口附近微观组织及断口形貌进行了观察分析,得出了温度及应变速率对断口附近微观组织及断口形貌的影响规律,发现随着温度的升高和应变速率的降低,断口附近再结晶程度升高。再结晶晶粒的晶界为大角度晶界,析出相容易在晶界处聚集,可能造成沿晶断裂。因此在制定锻造工艺时,要选择合理的锻造工艺参数,防止断裂行为的发生。本文通过高温拉伸实验与有限元模拟相结合的方法,采用Normalized CockcroftLatham准则对拉伸过程进行模拟仿真,得到了温度和应变速率对裂纹萌生临界损伤值和断裂损伤值的影响规律,这对制定该合金的锻造工艺具有指导意义。
[Abstract]:With the development of aerospace industry, the demand of aluminum alloy as the medium and thick plate, extrusion parts, free forgings and die forgings for aircraft structure parts is increasing. Performance requirements are becoming more and more stringent. In order to ensure the performance requirements of aluminum alloy components and also to ensure its service life, it is required that every step of the production of aluminum alloy components does not have a potential fracture. In the process of hot forging. Temperature and strain rate have a serious effect on the tensile properties and fracture behavior of aluminum alloy at high temperature. At home and abroad, there is little research on the high temperature tensile properties and fracture behavior of the new Al-Zn-Mg-Cu high strength aluminum alloy, so this paper combines the experimental data with the numerical simulation method. The high temperature tensile properties and fracture behavior of a new type of high strength Al-Zn-Mg-Cu aluminum alloy were studied. In order to provide some guidance for the control of the properties and fracture behavior of the new Al-Zn-Mg-Cu high strength aluminum alloy during hot forging. Thermal simulated high temperature tensile test, optical microscope, scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) were used. The effects of different temperature and strain rate on the tensile properties and fracture behavior of forged and as-cast aluminum alloys were studied. The tensile strength and yield strength were obtained by high temperature tensile test. The relationship between tensile strength and yield strength with temperature and strain rate was established by regression analysis of experimental data by IBM software. To ensure that the stress applied by the equipment to the material is less than the tensile strength when the forging process is made. It provides a theoretical basis for the prevention of forging cracks. The microstructure and fracture morphology near the fracture surface of the specimen after tensile fracture are observed and analyzed. The effect of temperature and strain rate on the microstructure and fracture morphology near the fracture surface is obtained. It is found that with the increase of temperature and the decrease of strain rate. The recrystallization degree is increased near the fracture surface. The grain boundary of recrystallized grain is large angle grain boundary, the precipitated phase is easy to gather at the grain boundary, which may cause intergranular fracture. In order to select reasonable forging parameters and prevent fracture behavior, this paper combines the high temperature tensile test with finite element simulation. The drawing process is simulated by Normalized CockcroftLatham criterion. The influence of temperature and strain rate on the critical damage value and fracture damage value of crack initiation is obtained, which is of guiding significance to the forging process of the alloy.
【学位授予单位】：太原科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.21

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