7055铝合金零件开裂原因与预防
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摘要
通过体视显微镜、光学显微镜、扫描电镜、能谱仪、显微硬度测试仪等手段,对2件喷射成形、在热处理过程中发生开裂的7055铝合金零件的宏观开裂特征、微观断口形貌、金相组织和显微硬度进行对比分析,结果表明:2件铝合金零件成分、组织、状态均未见异常;裂纹断面主要呈冰糖状沿晶界断裂特征,而人工断面则主要呈韧窝型穿晶断裂特征。综合零件制备工艺分析认为,零件裂纹应为淬火裂纹,产生原因与7055铝合金淬火敏感性及零件热处理工艺控制有关。建议采取淬火前充分均匀化处理、淬火时减小淬火速率、合理控制零件截面形状、应力集中部位采用圆角过渡等措施预防淬火裂纹产生。
The cause for cracks in 7055 aluminum alloy parts during heat treatment process was analyzed,and prevention measures for the cracks were discussed and summarized based on the analysis results. The macro morphology of cracks,fracture morphology,metallurgical structure and micro-hardness of 7055 aluminum alloy parts manufactured by spray forming were analyzed by means of stereoscopic microscopy,optical microscopy,scanning electron microscopy( SEM),energy dispersive spectroscopy( EDS) and micro-hardness testing. The analysis results indicate that the composition,microstructure and microhardness show no abnormal evidence. The crack fracture is intergranular while the man-made fracture is mostly covered with dimples. Considering the preparation process of the material,it is supposed that the cracks in 7055 alloy parts are quenching cracks,which is related to the quenching sensitivity of the alloy and the heat treatment process. Measures were put forward to prevent quenching cracks,such as thorough homogenizing before quenching,lowering the quenching rate,controlling the shape of the part section and rounding for stress concentration regions.
The cause for cracks in 7055 aluminum alloy parts during heat treatment process was analyzed,and prevention measures for the cracks were discussed and summarized based on the analysis results. The macro morphology of cracks,fracture morphology,metallurgical structure and micro-hardness of 7055 aluminum alloy parts manufactured by spray forming were analyzed by means of stereoscopic microscopy,optical microscopy,scanning electron microscopy( SEM),energy dispersive spectroscopy( EDS) and micro-hardness testing. The analysis results indicate that the composition,microstructure and microhardness show no abnormal evidence. The crack fracture is intergranular while the man-made fracture is mostly covered with dimples. Considering the preparation process of the material,it is supposed that the cracks in 7055 alloy parts are quenching cracks,which is related to the quenching sensitivity of the alloy and the heat treatment process. Measures were put forward to prevent quenching cracks,such as thorough homogenizing before quenching,lowering the quenching rate,controlling the shape of the part section and rounding for stress concentration regions.
引文
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[2]陈增奎,周卫卫,范新中,等.7055高强铝合金大型环件轧制技术研究[J].精密成形工程,2016,8(2):16-20.
[3]侯小虎,张秀云,郭强,等.喷射成形7055铝合金热处理工艺与力学性能的研究[J].材料热处理技术,2008,37(12):5-7.
[4]陈康华,刘红卫,刘允中,等.强化固溶对7055铝合金力学性能和断裂行为的影响[J].中南工业大学学报,2000,31(6):528-531.
[5]刘胜胆,张新明,黄振宝,等.7055铝合金的淬火敏感性研究[J].中南大学学报:自然科学版,2006,37(5):846-849.
[6]Xu D K,Rometsch P A,Li L,et al.Critical conditions for the occurrence of quench cracking in an Al-Zn-Mg-Cu alloy[J].Journal of Materials Science,2014,49(14):4687-4697.
[7]王国军,吕新宇.7055铝合金的化学成分、物相组成及其性能特点[J].上海有色金属,2008,29(3):118-122.
[8]张新明,刘胜胆,游江海,等.时效对7055铝合金淬火敏感效应的影响[J].中国有色金属学报,2007,17(2):260-264.
[9]赵新星.工件淬火裂纹的原因分析与对策[J].纺织机械,2006(2):46-48.
[10]刘宗昌.淬火裂纹形态及影响因素[J].包头钢铁学院学报,1991,10(1):44-49.
[11]王家芳.淬火裂纹缺陷的预防[J].现代制造工程,2003(12):67-70.
[12]李海,郑子樵,王芝秀.7055铝合金二次失效特征研究—(II)显微组织与断口形貌特征[J].稀有金属材料与工程,2005,34(8):1230-1234.
[13]Srivatsan T S,Sriram S,Veeraraghavan D,et al.Microstructure,tensile deformation and fracture behaviour of aluminium alloy 7055[J].Journal of Materials Science,1997,32(11):2883-2894.
[14]Liu S D,Zhang X M,Chen M A,et al.Influence of aging on quench sensitivity effect of 7055 aluminum alloy[J].Materials Characterization,2008,59(1):53-60.
[15]刘胜胆,张新明,游江海,等.7055铝合金的TTP曲线及其应用[J].中国有色金属学报,2006,16(12):2034-2039.