7475-T7351铝合金厚板的断裂韧性

Fracture toughness of 7475-T7351 aluminum alloy thick plate

以25 mm厚7475-T7351铝合金板材为对象,研究板材的断裂韧性及其各向异性,借助光学金相显微镜(OM)、扫描电镜(SEM)的观察及分析探讨该板材组织与断裂韧性的关系。研究结果表明:7475-T7351铝合金板材具有良好的断裂韧性,但存在一定的各向异性,L-T向的断裂韧性值KIC=43.80 MPa·m1/2,较T-L向的KIC=36.31 MPa·m1/2高约20%;在L-T向断口上以穿晶韧窝为主,而在T-L向断口上沿晶断裂比例增加;韧窝中大都可以观察到含杂质Fe元素的粗大硬脆第2相粒子;板材中扁平状晶粒及粗大硬脆第2相的分布是造成其断裂韧性各向异性的原因。

The fracture toughness and its anisotropy of 25 mm 7475-T7451 aluminum alloy thick plate were investigated. The relationship between its microstructure and fracture toughness was explored by means of optical microscopy and scanning electron microscopy. The results show that the fracture toughness is high but anisotropic for the plate, for L-T orientation Kic=43.80 MPa·m1/2, about 20% higher than that of T-L orientation Kic=36.31 MPa＇ml/2.The fractography indicates that intragranular dimples are dominant on the fracture surface of L-T orientation, and the ratio of intergranular fracture increases on T-L orientation. Coarse and brittle Fe-containing particles can be observed in most dimples. The pancake-shaped grains and distribution of coarse and brittle particles are supposed to be responsible for the anisotropy of fracture toughness.