TC18钛合金棒材和锻件的冲击性能及断口分析

Impact Properties and Fracture Analysis of TC18 Titanium Alloy Bars and Forgings

对TC18钛合金棒材和锻件的L向、 T向冲击性能及断口形貌分别进行研究,分析了合金具有不同微观组织时冲击性能相差较大的原因。结果表明,棒材和锻件的宏观断口虽然相似,但棒材中残存的块状、条状初晶α相在冲击功的作用下与基体β晶不能协调变形且易与基体分离,当硬质初晶α相位于试样内部时,裂纹极易产生和扩展。相比与棒材L, T向的室温冲击韧性值αk,锻件的L向冲击韧性提高幅度较高,其平均比棒材高出15.2 J·cm^-2。通过锻造可破碎棒材中存留的部分铸造初晶α相粒子及偏析物,使其分布均匀,从而促进裂纹在冲击过程中扩展路径的曲折程度,进而提高材料的断裂韧性。为了更深一步了解冲击性能的影响因素,本文在传统预测冲击韧性模型的基础上,考虑了试样预制缺口尺寸和材料的延伸率,重新构建了断裂区面积和冲击韧性的关系模型,并比较了新模型和实验数据的吻合度。

The impact properties of longitudinal and transverse on TC18 titanium alloy bars and forgings and the morphology of the impact fracture surface were studied. The reasons for the difference in impact properties of the alloy with different microstructure were analyzed. The results showed that the macro fracture of the bar and the forging was similar, but the residual initial crystal alpha block and strip in the bar could not coordinate with the matrix under impact work, and could be easily separated from the matrix. When the hard initial crystal was in the sample, the crack was easily produced and expanded. The impact toughness of the forgings was higher in the longitudinal direction than that of the bar in longitudinal and transverse direction at room temperature, and the average was 15.2 J·cm-2 higher than that of the bar. By forging, the partially initial cast crystalline alpha phase particles and segregation in the bar could be broken, the distribution of the particles was uniform, thus promoting the cracks′ zigzag degree of the path in the process and improving the fracture toughness of the material.In order to further understand the impact factors of impact performance, on the basis of traditional prediction of impact toughness model, the relationship model of fracture area and impact toughness was rebuilt by considering the size of specimen prefabricated gap and the elongation of material, and the consistency of the new model and the experimental data was compared.