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通过对γ-TiAl基合金压缩断裂及压缩卸载试验和试样断口与表面的扫描电镜(SEM)观察,分析压缩应力对裂纹产生、扩展及裂纹形态的影响,进而对该材料的压缩损伤与断裂行为进行较为深入的研究。压缩试验是室温下在Instron 1341试验机上进行的。结果表明,损伤起始于材料的塑性区载荷下降阶段,材料在断裂前发生很大的塑性变形,其压缩时有较大的塑性缓冲;随着压缩卸载应力的增大,观察到的试样表面裂纹依次增多或扩展增长,材料损伤的程度与压缩应力成正比。在压缩试样断口的中部发现存在的一个纵向韧带,当外加载荷增加,两个由压缩接触端面起裂的倾斜剪切裂纹扩展到试样中部,然后通过剪切穿过纵向韧带而连接,并诱发试样的完全脆性断裂。两个端面的切应力是裂纹形成的主要控制因素。该材料的压缩性能比拉伸性能更佳的主要原因是由于压缩时材料的损伤起始于塑性阶段,产生沿45°方向剪应力最大方向的剪切断裂和沿着压缩轴方向的准解理断裂的混合形式,而普通拉伸时材料损伤起始于弹性阶段,发生完全脆性解理断裂,在低应力下试样就会断裂。
The effect of compressive stress on the crack growth, propagation and crack morphology was analyzed by compressive fracture and unloading test of γ-TiAl alloy and scanning electron microscope (SEM) observation of fracture surface and surface of the sample. The compressive damage and fracture Conduct a more in-depth study. Compression tests were carried out on an Instron 1341 testing machine at room temperature. The results show that the damage begins at the stage of decreasing the plastic zone load, and the material undergoes great plastic deformation before fracture, and has a large plastic buffer during compression. As the compressive unloading stress increases, the observed specimen Surface cracks in turn increase or expansion of growth, the extent of material damage and compressive stress is proportional to. A longitudinal ligament was found in the middle of the fracture of the compression specimen. As the applied load increased, two oblique shear cracks, beginning from the compression contact end face, extended to the middle of the specimen and were then connected by shearing through the longitudinal ligaments Induced complete brittle fracture of the specimen. Shear stress at both ends is the main control factor for crack formation. The main reason why the compressibility of the material is better than the tensile property is that the material damage during compression starts from the plastic phase, resulting in shear fracture along the direction of 45 ° maximum shear stress and quasi-cleavage along the compression axis Fracture, while the material damage in normal stretching begins in the elastic phase, complete brittle cleavage fracture occurs, and the sample breaks at low stress.