微量稀土元素Gd对7056铝合金组织与腐蚀性能的影响

Effect of Trace Rare Earth Element Gd on Microstructure and Corrosion Resistance of 7056 Aluminum Alloy

采用晶间腐蚀、应力腐蚀和电化学腐蚀试验,结合光学显微镜、扫描电镜和透射电镜,研究微量稀土元素Gd对7056铝合金微观组织与腐蚀性能的影响.实验结果表明:在7056铝合金中添加质量分数为0.11%Gd,形成L12-Al3(Gd,Zr)弥散相,强烈阻碍位错与晶界运动,提高合金再结晶抗力,使基体保留更多的细小亚晶组织;相比于大角度晶界,亚晶界与晶内的腐蚀电位差更小,腐蚀驱动力减弱;相比于7056铝合金,7056-Gd铝合金具有更大的应力腐蚀抗力,其临界应力强度因子KI由5.45 MPa·m^1/2增加至10.59 MPa·m^1/2;两种合金的开路电位、电化学阻抗谱和循环极化曲线的监测结果具有一致性,均表明7056-Gd铝合金具有较好的耐腐蚀性能.

The effects of trace rare earth element Gd on the microstructures and corrosion resistance of 7056 aluminum alloy were investigated by intergranular corrosion(IGC),stress corrosion crack(SCC)and electrochemical corrosion tests,combined with optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The experimental results showed that the addition of 0.11%Gd to 7056 aluminum alloy forms L12-Al3(Gd,Zr)dispersion phase,which improved the recrystallization resistance of the alloy by strongly hindering the movement of dislocation and grain-boundary,and allowed the matrix to retain more fine subgrain structure.Compared with the large-angle grain boundary,the corrosion potential difference between the subgrain boundary and the crystal was smaller,and the corrosion driving force was reduced.Compared with 7056 aluminum alloy,7056-Gd aluminum alloy had greater resistance to stress corrosion crack.Its critical stress intensity factor is increased from 5.45 MPa·m^1/2 to 10.59 MPa·m^1/2.The results of open circuit potential(OCP),electrochemical impedance spectroscopy(EIS)and cyclic polarization curves of the two alloys are consistent,indicating that 7056-Gd aluminum alloy has higher corrosion resistance.