铝合金的氢脆和应力腐蚀开裂是受到广泛重视的课题．本文采用正电子湮没（ＰＡ）技术研究了ＬＣ４铝合金在慢拉伸动态充氢时，在３．５％ＮａＣｌ＋２００ｍｇ／１Ａｓ２Ｏ３介质中，多普勒展宽（Ｄｏｐｐｌｅｒｂｒｏａｄｅｎｉｎｇ）Ｓ参数的变化．实验发现在阴极极化下，Ｓ参数下降．这是由于相当部分原来是深阱的正电子陷阱转为为浅阱，或者充氢后产生新的正电子陷阱引起，Ｍｇ与Ｈ互作用形成ＭｇＨ２是形成脆化的可能原因；在阳极极化下也观察到Ｓ参数下降，作者认为这是由于此时ＧＰ区（主要是ＭｇＺｎ２）的优先溶解． Hydrogen embrittlement and stress corrosion cracking of aluminum alloy are topics of great importance. In this paper, the change of S-parameters of Doppler broadening in 3.5% NaCl + 200mg / 1As2O3 medium was studied by using positron annihilation (PA) technique. Experiments found that in the cathode polarization, S parameters decreased. This is due to the fact that a considerable part of the original deep well positrons turn into shallow wells or hydrogen poses new positron traps, Mg and H interact to form MgH2, which is the possible cause of embrittlement. S-parameters were also observed to decline, the authors believe that this is due to GP area (mainly MgZn2) preferential dissolution.