固溶处理时间对7050铝合金挤压材料力学性能及耐腐蚀性能的影响

Effect of solution treatment time on mechanical properties and corrosion resistance of extruded 7050 aluminum alloy

采用光学显微镜、扫描电镜、透射电镜、室温拉伸实验和晶间腐蚀实验等研究了固溶处理时间对7050铝合金挤压棒材力学性能及耐腐蚀性能的影响。结果表明:挤压后未热处理的7050铝合金的强度和耐腐蚀性能都比较差,其抗拉强度为564.2 MPa,腐蚀最大深度达到50.83μm。经过固溶+T6时效后,7050铝合金在再结晶软化与沉淀强化的共同作用下,其抗拉强度先增加后降低;经470℃固溶处理30 min+T6时效后,7050铝合金抗拉强度达到最高值674 MPa,耐腐蚀性能最好。随着固溶时间从30 min增加至2 h,峰值时效后的合金的晶界类型由弯曲小角度晶界变为平直大角度晶界,晶界处从无第二相析出状态转变为有间断分布的棒状η相状态,η相附近形成无沉淀析出带。在晶界类型转变、η相和无沉淀析出带共同作用下,7050铝合金的耐腐蚀性能变差。

Effect of solution treatment time on mechanical properties and corrosion resistance of 7050 aluminum alloy extruded bar was studied by means of optical microscope, scanning electron microscopy, transmission electron microscopy, tensile test at room temperature and intergranular corrosion test. The results show that the strength and corrosion resistance of the extruded 7050 aluminum alloy without heat treatment are poor, the tensile strength is 564.2 MPa, and the maximum corrosion depth is 50.83 μm. After solution treatment and T6 aging, the tensile strength of the 7050 aluminum alloy increases first and then decreases under the combined action of recrystallization softening and precipitation strengthening. After solution treatment at 470 ℃ for 30 min and T6 aging, the tensile strength of the 7050 aluminum alloy reaches the highest value of 674 MPa, and the corrosion resistance is the best. With the increase of solution time from 30 min to 2 h, the grain boundary type of the alloy after peak aging changes from curved low-angle grain boundary to flat high-angle grain boundary, and the grain boundary changes from no second phase precipitation state to rod-shaped η phase state with discontinuous distribution, and the precipitation-free zone forms near the η phase. The corrosion resistance of the 7050 aluminum alloy decreases under the combined action of grain boundary type transformation, η phase and precipitation-free zone.