退火温度对大塑性变形Al-8Mg纳米晶铝合金微观结构与性能的影响  

Effect of Annealing Temperature on Microstructure and Properties of Nanocrystalline Al-8Mg Aluminum Alloy with Severe Plastic Deformation

作　　者：窦开沁 陈昱林 洪海杰 刘满平[1,2] DOU Kai-qin;CHEN Yu-lin;HONG Hai-jie;LIU Man-ping;无(School of Materials Science and Engineering,Jiangsu University,Jiangsu Zhenjiang 212013,China;State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,Hunan University,Changsha 410082,China)

机构地区：[1]江苏大学材料科学与工程学院,江苏镇江212013 [2]湖南大学汽车车身先进制造国家重点实验室,长沙410082

出　　处：《精密成形工程》2023年第8期19-26,共8页Journal of Netshape Forming Engineering

基　　金：国家自然科学基金(U22A20187,U1710124);湖南大学汽车车身先进设计制造国家重点实验室开放基金(32115014)。

摘　　要：目的研究不同退火温度下高压扭转Al-8.0Mg铝合金的微观结构及其对热稳定性的影响。方法利用X射线衍射定量计算了纳米晶Al-8Mg合金在不同退火温度下的微观结构参数。通过透射电子显微镜观察了不同状态的微观结构,讨论了晶粒尺寸和位错密度对热稳定性的影响,并分析了高温下析出相和孪晶的结构演变。结果随着退火温度从125℃上升至280℃,HPT后Al-8.0Mg铝合金的显微硬度由247HV减小至144HV,240℃为硬度转变的临界温度,当退火温度低于240℃时,试样硬度值降低幅度较小。平均晶粒尺寸从125℃下的41.1 nm增大到280℃下的143.6 nm,位错密度由1.32×10^(15)m^(-2)减小到3.54×10^(12)m^(-2)。结论在退火温度低于240℃时,合金表现出较好的热稳定性,在280℃以后析出了大量Al_(3)Mg_(2)相,并观察到了多重退火孪晶。额外的能量在位错结构的回复和非平衡晶界的重排过程中被消耗,导致晶粒尺寸与显微硬度没有发生明显变化。加热过程中产生的结构转变可能是提高材料热稳定性的主要原因。The work aims to study the microstructure and its effects on thermal stability of Al-8.0Mg aluminum alloy with high pressure torsion at different annealing temperature.The microstructure parameters of the nanocrystalline Al-8Mg alloy at different annealing temperature were quantitatively calculated by X-ray diffraction analysis.The microstructure changes were observed through a transmission electron microscopy in different states,and the effects of grain size and dislocation density on thermal stability were discussed.The structural evolution of precipitates and twins at high temperature was analyzed.With the increase of annealing temperature from 125℃to 280℃,the microhardness of the alloy decreased from 247HV to 144HV.Among them,240℃was the critical temperature for hardness transformation.When the annealing temperature was below 240℃,the decrease in hardness of the sample was relatively small.The average grain size increased from 41.1 nm to 143.6 nm and the dislocation density decreased from 1.32×10^(15)m^(-2)to 3.54×10^(12)m^(-2).The alloy shows good thermal stability when the annealing temperature is lower than 240℃.At 280℃,a large number of Al_(3)Mg_(2)phases are precipitated and multiple annealing twins are observed.Owing to the consumption of additional energy in the recovery of dislocation structures and the rearrangement of non-equilibrium grain boundaries,there is no significant change in grain size and micro-hardness.The structural transformation during heating may be the main reason for improving the thermal stability of the material.

关 键 词：高压扭转 纳米晶Al-Mg铝合金 热稳定性 透射电子显微镜 微观结构 

分 类 号：TG113.233[金属学及工艺—物理冶金]