不同厚度7050铝合金板材的组织与性能

Microstructure and properties of 7050 aluminum alloy plates with different thickness

利用光学显微镜、扫描电镜、室温拉伸和紧凑拉伸试验对4种不同厚度的7050铝合金板材的显微组织、拉伸性能和断裂韧性进行分析。结果表明:7050合金板材中粗大第二相主要为Al_7Cu_2Fe相和Al_2CuMg相,晶粒组织为不完全再结晶组织;从表层到心部第二相粒子数量增加,尺寸增大,分布变集中,再结晶比例逐渐降低;板材厚度增加,第二相粒子数量增加,尺寸增大,再结晶比例降低,但再结晶晶粒和亚晶尺寸逐渐增大。因此,厚度方向表层到心部,板材的强度和断裂韧性逐渐降低。此外,强度和断裂韧性具有一定的各向异性,同一厚度处L向的强度高于LT向和ST向,L-T向的断裂韧性大于T-L和S-L向。板材厚度增加,强度和断裂韧性降低,并且不同方向的性能差异增大。因此,板材厚度越大,越不利于获得均匀的组织和性能。

Microstructure,tensile property and fracture toughness of 7050 aluminum alloy plates with different thickness were investigated by means of optical microscopy,scanning electron microscopy,tensile and compact tension tests. The results show that,the coarse second phase particles are mainly Al_7Cu_2Fe and Al_2CuMg and the microstructure is partially recrystallized. From the surface to the center along thickness direction,the amount of second phase particles and size increase,the distribution becomes more densely,but the recrystallization fraction reduces. With the plate thickness increases,the amount and size of second phase rise,recrystallization fraction decreases,but the size of recrystallized grains and sub-grains increase. So,the strength and fracture toughness of the plate decrease along the thickness direction from the surface to the center. Besides,the strength and fracture toughness of the plate show a certain anisotropy,the strength in rolling（ L） direction is higher than that in the long transverse（ LT） direction and the short transverse（ ST） direction,and the fracture toughness in the L-T orientation is higher than that in the T-L and S-L orientations at the same thickness. With the thickness rises,the strength and fracture toughness decrease and the property anisotropy increases in different directions. So the higher the thickness of the plate,the more difficult to obtain homogeneous microstructure and properties.