2A97-T84铝锂合金切削力及切削温度仿真研究

为了研究2A97-T84铝锂合金切削加工时切削参数对切削力和切削温度的影响规律,使用Abaqus有限元仿真软件在100~300 m/min切削速度、0.5~2.5 mm背吃刀量工况条件下建立起二维切削模型。仿真结果表明,切削力受切削速度影响不大,随切削深度的增加而增加;刀尖切削温度随切削深度增加呈现先减小后增大的趋势,随切削速度的增加迅速增大。

Effect of thermo-mechanical treatment process on microstructure and mechanical properties of 2A97 Al-Li alloy

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.

Fatigue crack initiation and early propagation behavior of 2A97 Al-Li alloy

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.

Texture evolution behavior and anisotropy of 2A97 Al-Li alloy during recrystallization at elevated temperature

2A97 Al-Li alloy was cold-rolled to 2 mm and then thermally exposed at different temperatures for 1 h and at 723 K for different time,respectively.The texture evolution behavior and the anisotropy of 2A97 Al-Li alloy were investigated.The result shows that the{001}<120>and{011}<233>textures are the dominant recrystallization texture.The{124}<211>texture is the final recrystallization texture.In case of low-temperature thermal exposure(473,573 K),the{011}<211>texture is aggregated to the{112}<111>and{123}<634>textures.During the recrystallization at 723 K,the{001}<110>,{111}<112>and{011}<100>textures are the intermediate transition grain orientations.The concurrent precipitation of Al_(20)Cu_(2)Mn_(3)and Al_(3)Zr results in the occurrence of unusually sharp{011}<233>and{001}<120>texture components during recrystallization.The alloy with both recrystallization and deformation texture possesses the smallest anisotropic,and the texture is the direct reason that results in the anisotropy.

孔挤压强化对2A97铝锂合金耳片疲劳性能的影响

对2A97-T84铝锂合金不同尺寸的直耳片进行了孔挤压强化,研究孔挤压前后耳片的疲劳性能。结果表明:孔挤压强化工艺能有效提高2A97-T84耳片的疲劳性能,且小尺寸耳片的强化效果优于大尺寸耳片,其小、大尺寸耳片疲劳寿命提高幅度最大可达80.6%和62.5%;当峰值应力相同时,孔挤压强化后小尺寸耳片的疲劳寿命最高为大尺寸耳片的7.6倍。对比断口形貌可知,孔挤压强化后耳片的疲劳裂纹源位置、数量等均发生了变化:其位置由耳孔内表面转移至耳孔内壁近表面处且数量明显减少,疲劳辉纹宽度变窄,这说明经孔挤压强化后,孔内壁表层金属发生了强烈的塑性变形,耳孔周围产生了残余压应力,组织发生了位错塞积和缠结,形成了位错胞状结构,这些均降低了孔壁边缘的应力集中系数,减缓了疲劳裂纹源的萌生,使得疲劳裂纹的扩展速率降低,从而提高了耳片的疲劳性能。