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通过力学性能测试、扫描电镜观察以及有限元模拟计算的方法,研究了全层组织γ-TiA l基合金在压缩状态下的变形及损伤机制。结果表明:较小的加载卸载应力作用下,材料的压缩性能没有受到影响,直至卸载应力超过最大压缩应力之后,由于材料内部损伤的积累程度增大,在材料内部形成主裂纹,使得有效承载面积下降,后续再加载过程中材料的断裂应力整体下降。压缩状态下:首先,随着变形程度的增加,晶粒周围出现大量的滑移线及挤出脊,滑移线和挤出脊处出现较大的裂纹,试样表面产生平行于压缩轴方向的裂纹并迅速扩展,表面裂纹面密度明显增加,45°方向上的沿层裂纹扩展程度较大,但裂纹长度仅限于晶粒尺寸的大小(100~300μm)。其次在压缩加载过程中,材料在较小的正应力作用下,观察得到表面萌生以下4种裂纹:平行于压缩轴方向的纵向沿层裂纹;与压缩轴方向成较小角度的纵向沿层裂纹;与压缩轴方向成较小角度的纵向穿层裂纹;纵向的穿晶裂纹。
The deformation and damage mechanisms of the γ-TiAl-based alloy in the fully compressed state were studied by means of mechanical tests, scanning electron microscopy and finite element method. The results show that the compressive property of the material is not affected by the smaller loading-unloading stress. After the unloading stress exceeds the maximum compressive stress, the main crack is formed in the material due to the accumulation of the internal damage, so that the effective bearing area Decline, the subsequent reload process material fracture stress overall decline. In the compressed state, firstly, with the increase of the deformation, a large number of slip lines and extrusion ridges appeared around the grains, and larger cracks appeared at the slip lines and extrusion ridges. The sample surface had a parallelism with the compression axis The surface crack density increases obviously, and the crack propagation along the layer in 45 ° direction is larger. However, the crack length is only limited to the grain size (100-300 μm). Secondly, during the compressive loading process, the material under the action of the small normal stress observed the following four types of surface initiation: crack along the longitudinal direction parallel to the compression axis; longitudinal crack along the layer at a smaller angle to the compression axis ; Longitudinal cracks at a small angle to the direction of the compression axis; longitudinal transgranular cracks.