基于高压扭转变形的Al-Zn-Mg-Cu合金微观组织及力学性能研究

发布时间：2018-04-15 04:30

本文选题：Al-Zn-Mg-Cu合金 + 高压扭转　；参考：《合肥工业大学》2017年硕士论文

【摘要】：Al-Zn-Mg-Cu合金作为新一代的优质结构材料具有密度小、比强度高、韧性好、扩散性能好、热加工性能以及焊接性能优异等特点,被认为是最有可能替代钢、铁的有色金属材料。作为一种新型轻量化的优质结构材料,超高强Al-Zn-Mg-Cu合金在汽车工业、船舶工程、航空航天、国防军工以及核工业等领域得到高度重视和广泛应用,尤其在航空工业领域,Al-Zn-Mg-Cu合金的用量已成为衡量现代航空工业先进性的显著标志。本文结合Al-Zn-Mg-Cu合金的变形特点,采用限制型高压扭转模具,在不同工艺参数(变形温度、扭转圈数、加载压力)下对Al-Zn-Mg-Cu合金进行高压扭转实验。采用多种现代材料表征技术(OM、EBSD和XRD)和相关定量计算理论,对不同工艺参数下变形后的试样微观组织、亚结构(晶界特征及取向差)、晶粒取向、织构、微观应变、位错密度等展开了深入研究。结果表明:高压扭转变形对Al-Zn-Mg-Cu合金微观组织影响明显,晶粒尺寸由21.7μm显著细化到0.72μm,大角度晶界比例、位错密度明显增加,织构特征减弱,材料的各向异性减弱,组织均匀性增强。Al-Zn-Mg-Cu系铝合金合金化程度高,微观组织中存在大量的多元合金相,其形态、尺寸和分布对合金的性能具有重要影响。本文采用SEM、EDS和XRD技术对变形后合金中多元合金相的相组成、形貌、数量和分布进行了深入研究,并对多元合金相回溶的微观机制进行了探讨。结果表明:变形温度和扭转圈数是影响多元合金相回溶的两个关键因素,并对合金的相组成产生影响;高压扭转变形过程中随着变形温度和扭转圈数的增加,合金中AlCu相消失,η(MgZn_2)和θ(Al_2Cu)所对应的衍射峰强度降低,合金变形后主要由α(Al)+η(MgZn_2)+θ(Al_2Cu)相组成。此外,对变形试样开展室温下力学性能测试,研究高压扭转变形工艺参数对Al-Zn-Mg-Cu合金抗拉强度和延伸率的影响规律,同时采用扫描电镜对试样断口进行扫描,对变形后合金的断口形貌、微观组织特征和断裂机制进行了深入分析。结果表明:高压扭转变形后Al-Zn-Mg-Cu合金的抗拉强度显著提升,其最高抗拉强度达到了716MPa,提升幅度达到22%,材料的延展性也得到了一定程度提升,延伸率最高达到了14.8%;Al-Zn-Mg-Cu合金高压扭转变形后,试样断口表面出现了大量等轴韧窝,韧窝基底弥散分布着一些第二相粒子,合金的断裂机制主要表现为微孔聚集型韧窝断裂以及粗大第二相开裂断裂。
[Abstract]:As a new generation of high quality structural materials, Al-Zn-Mg-Cu alloy is considered as the most likely non-ferrous metal material to replace steel and iron because of its low density, high specific strength, good toughness, good diffusibility, hot working property and excellent welding properties.As a new lightweight and high quality structural material, ultra-high strength Al-Zn-Mg-Cu alloy has been highly valued and widely used in automotive industry, ship engineering, aerospace, national defense and nuclear industry.Especially in the field of aviation industry, the dosage of Al-Zn-Mg-Cu alloy has become a significant symbol to measure the advanced nature of modern aviation industry.Combined with the deformation characteristics of Al-Zn-Mg-Cu alloy, the high pressure torsion experiment of Al-Zn-Mg-Cu alloy was carried out under different process parameters (deformation temperature, torsion circle number, loading pressure) by using a limited high-pressure torsion die.The microstructure, substructure (grain boundary characteristics and orientation difference), grain orientation, texture, microstrain of the samples deformed under different technological parameters were studied by using modern material characterization techniques such as OMN EBSD and XRD and relevant quantitative calculation theory.The dislocation density has been studied deeply.The results show that the high pressure torsional deformation has an obvious effect on the microstructure of Al-Zn-Mg-Cu alloy, the grain size is refined from 21.7 渭 m to 0.72 渭 m, the large angle grain boundary ratio, the dislocation density, the texture characteristics and the anisotropy of the Al-Zn-Mg-Cu alloy are obviously increased.The alloying degree of Al-Zn-Mg-Cu aluminum alloy is high, and there are a large number of multicomponent alloy phases in the microstructure. The morphology, size and distribution of Al-Zn-Mg-Cu alloy have an important effect on the properties of the alloy.In this paper, the phase composition, morphology, quantity and distribution of the multicomponent alloy phase in the deformed alloy were studied by means of SEM-EDS and XRD techniques, and the microcosmic mechanism of the phase re-dissolution of the multicomponent alloy was discussed.The results show that the deformation temperature and the number of torsion circles are the two key factors affecting the phase remelting of the multicomponent alloy, and the phase composition of the alloy is affected, and the deformation temperature and the number of torsion circles increase with the increase of the deformation temperature and the number of torsion circles during the high-pressure torsional deformation.The AlCu phase in the alloy disappears, and the diffraction peak intensity corresponding to 畏 -MgTiZn2) and 胃 -AlSn2Cu) decreases. After deformation, the alloy is mainly composed of 伪 -Al) 畏 -MgZn2) 胃 / Al2Cu2) phase.In addition, the mechanical properties of the specimens were tested at room temperature, and the influence of the process parameters of high-pressure torsion deformation on the tensile strength and elongation of the Al-Zn-Mg-Cu alloy was studied. At the same time, the fracture surface of the Al-Zn-Mg-Cu alloy was scanned by scanning electron microscope.The fracture morphology, microstructure and fracture mechanism of the deformed alloy were analyzed.The results show that the tensile strength of Al-Zn-Mg-Cu alloy increases remarkably after high pressure torsional deformation, the maximum tensile strength reaches 716 MPA, the lifting range is 22 and the ductility of the material is improved to a certain extent.After high pressure torsion deformation of Al-Zn-Mg-Cu alloy with the highest elongation, a large number of equiaxed dimples appeared on the fracture surface of the specimens, and some second phase particles were dispersed on the dimple substrate.The fracture mechanism of the alloy is mainly characterized by microporous aggregate dimple fracture and coarse second phase fracture.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21

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