The fatigue crack initiation and early propagation behavior of 2A97 Al-Li alloy was studied. The smooth specimens were fatigued at room temperature under constant maximum stress control when stress ratio （R） is 0.1 ...The fatigue crack initiation and early propagation behavior of 2A97 Al-Li alloy was studied. The smooth specimens were fatigued at room temperature under constant maximum stress control when stress ratio （R） is 0.1 and frequency （f） is 40 Hz. Microstructure observations were examined by optical microscopy, transmission electron microscopy, scanning electron microscopy and electron back scattered diffusion, in order to investigate the relationship between microstructure and fatigue crack initiation and early propagation behavior of 2A97 alloy. The results show that the fatigue cracks are predominantly initiated at inclusions and coarsen secondary phases on the surface of 2A97 alloy. The fatigue crack early propagation behavior of 2A97 alloy is predominantly influenced by the interactions between grain structure and dislocations or persistent slip bands （PSBs）. When the misorientation of two neighbouring grains is close to the orientations of the favorable slip plane within these two grains, high-angle grain boundary severely hinders the PSBs passing through, and thus leads to crack bifurcation and deflection.展开更多
2A97 Al-Li alloy was processed by thermo-mechanical treatment at different pre-stretch deformations of 0, 3% and 6%. The microstrucatre observation results reveal that some δ＇ and T1 precipitates are found in a（Al...2A97 Al-Li alloy was processed by thermo-mechanical treatment at different pre-stretch deformations of 0, 3% and 6%. The microstrucatre observation results reveal that some δ＇ and T1 precipitates are found in a（Al） matrix of 2A97 alloy processed by the heat treatment with no pre-stretch deformation. When the pre-stretch deformation is 3% and 6%, respectively, amounts of tiny T1 and a few of S＇ precipitates precipitates are observed in the microstructures of 2A97 alloy. The tensile test results show that the tensile properties of 2A97 alloys are improved via thermo-mechanical treatment. When the pre-stretch deformation is from 0, 3% to 6%, the ultimate tensile strength values of the 2A97 alloys increase gradually from 447.7, 516.5 to 534.3 MPa, and the elongations decrease from 17.6%, 12.8% to 10.2%, respectively. Moreover, with increasing pre-stretch deformation amount from 0 to 6%, the in-plane anisotropy value of 2A97 alloys becomes more obvious.展开更多
在不同焊速下进行了厚度1.4 mm 2A97铝锂合金的光纤激光焊接。通过光学显微镜观察、扫描电镜观察、拉伸试验、显微硬度试验对比了不同焊接速度下2A97激光焊接头宏观形貌、显微组织、热裂纹倾向及力学性能。结果表明:随着焊接速度的增加...在不同焊速下进行了厚度1.4 mm 2A97铝锂合金的光纤激光焊接。通过光学显微镜观察、扫描电镜观察、拉伸试验、显微硬度试验对比了不同焊接速度下2A97激光焊接头宏观形貌、显微组织、热裂纹倾向及力学性能。结果表明:随着焊接速度的增加熔宽先减小,当速度超过一定临界值后熔宽随焊速的进一步增大而略微增大;焊缝晶粒尺寸随焊速的增大而单调减少。焊接速度过小、过大都会使接头成形质量变差。焊接速度小时,咬边严重,焊缝中易形成纵向热裂纹;焊接速度过高时,焊缝中出现横向热裂纹;本文实验条件下,在焊接速度为10m/min时获得了焊缝成形较好的接头,并对其力学性能做了测试。展开更多
文摘The fatigue crack initiation and early propagation behavior of 2A97 Al-Li alloy was studied. The smooth specimens were fatigued at room temperature under constant maximum stress control when stress ratio （R） is 0.1 and frequency （f） is 40 Hz. Microstructure observations were examined by optical microscopy, transmission electron microscopy, scanning electron microscopy and electron back scattered diffusion, in order to investigate the relationship between microstructure and fatigue crack initiation and early propagation behavior of 2A97 alloy. The results show that the fatigue cracks are predominantly initiated at inclusions and coarsen secondary phases on the surface of 2A97 alloy. The fatigue crack early propagation behavior of 2A97 alloy is predominantly influenced by the interactions between grain structure and dislocations or persistent slip bands （PSBs）. When the misorientation of two neighbouring grains is close to the orientations of the favorable slip plane within these two grains, high-angle grain boundary severely hinders the PSBs passing through, and thus leads to crack bifurcation and deflection.
文摘2A97 Al-Li alloy was processed by thermo-mechanical treatment at different pre-stretch deformations of 0, 3% and 6%. The microstrucatre observation results reveal that some δ＇ and T1 precipitates are found in a（Al） matrix of 2A97 alloy processed by the heat treatment with no pre-stretch deformation. When the pre-stretch deformation is 3% and 6%, respectively, amounts of tiny T1 and a few of S＇ precipitates precipitates are observed in the microstructures of 2A97 alloy. The tensile test results show that the tensile properties of 2A97 alloys are improved via thermo-mechanical treatment. When the pre-stretch deformation is from 0, 3% to 6%, the ultimate tensile strength values of the 2A97 alloys increase gradually from 447.7, 516.5 to 534.3 MPa, and the elongations decrease from 17.6%, 12.8% to 10.2%, respectively. Moreover, with increasing pre-stretch deformation amount from 0 to 6%, the in-plane anisotropy value of 2A97 alloys becomes more obvious.
文摘在不同焊速下进行了厚度1.4 mm 2A97铝锂合金的光纤激光焊接。通过光学显微镜观察、扫描电镜观察、拉伸试验、显微硬度试验对比了不同焊接速度下2A97激光焊接头宏观形貌、显微组织、热裂纹倾向及力学性能。结果表明:随着焊接速度的增加熔宽先减小,当速度超过一定临界值后熔宽随焊速的进一步增大而略微增大;焊缝晶粒尺寸随焊速的增大而单调减少。焊接速度过小、过大都会使接头成形质量变差。焊接速度小时,咬边严重,焊缝中易形成纵向热裂纹;焊接速度过高时,焊缝中出现横向热裂纹;本文实验条件下,在焊接速度为10m/min时获得了焊缝成形较好的接头,并对其力学性能做了测试。
