s相粗化（組織編號：M1），經(jīng)過兩相區(qū)的790 ℃/0.5 h固溶處理形成粗大的初生αp相（組織編號：M2），經(jīng)過790 ℃/0.5 h固溶處理與650 ℃/6 h時效處理同時存在粗大的初生αp相、細(xì)小的次生αs相（組織編號：M3）。電化學(xué)實(shí)驗(yàn)結(jié)果表明M3的自腐蝕電流密度相對最低為1.10×10-8 A/cm2，極化電阻相對最高為2.30×1010 Ω·cm2，其耐腐蝕性能最好，其次為M2，M1最差。慢應(yīng)變速率拉伸實(shí)驗(yàn)結(jié)果表明M3具有相對最低的應(yīng)力腐蝕敏感性指數(shù)為5.0%，其應(yīng)力腐蝕開裂敏感性相對最低。該合金的應(yīng)力腐蝕開裂機(jī)制為氫吸附促進(jìn)位錯運(yùn)動和氫促進(jìn)局部塑性變形的相互作用。;A metastable β titanium alloy Ti-5.5Cr-5Al-4Mo-3Nb-2Zr was designed. Three types of microstructure with different α phases were obtained by different heat treatment methods. The effects of α phase on stress corrosion behavior of the alloy were investigated by SEM, TEM, electrochemical test, and slow strain rate tensile test. The results show that after aging treatment at 650 ℃ for 6 h, the secondary αs phase is coarsened (microstructure No.: M1). After solution treatment at 790 ℃ for 0.5 h at the two-phase zone, a coarse primary αp phase (microstructure No.: M2) is formed. After solution treatment at 790 ℃ for 0.5 h and aging treatment at 650 ℃ for 6 h, coarse primary αp phase and delicate secondary αs phase (microstructure No.: M3) exist simultaneously. The electrochemical test results show that the self-corrosion current density of M3 is relatively low of 1.10×10-8 A/cm2. The polarization resistance of M3 is the highest at 2.30×1010 Ω·cm2, which indicates the best corrosion resistance of M3, followed by M2, and M1 has the worst corrosion resistance. The results of slow strain rate tensile tests indicate that M3 has the lowest stress corrosion susceptibility index of 5.0%, and its stress corrosion cracking susceptibility is relatively low. The interaction of the hydrogen absorption-induced dislocation emission and the hydrogen-enhanced localized plasticity can explain the stress corrosion cracking mechanism."/>