Liu Gen, Geng Jiwei, Li Yugang, Li Hongping, Wang Mingliang, Chen Dong, Ma Naiheng, Wang Haowei
State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China; School of Materials Science & Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China.
Micron. 2021 Jun;145:103056. doi: 10.1016/j.micron.2021.103056. Epub 2021 Mar 11.
A two-step aging treatment (50 L P, a peak aging following 50 ℃ pre-precipitation) has been investigated for the in-situ TiB/7050Al composite. The 50 L P composite has the comparable mechanical properties to the composite at peak-aged (T6) state, and even better stress corrosion cracking resistance over the composite with the retrogression and re-aging (RRA) treatment. In detail, the different aging conditions lead to different precipitate morphologies and grain boundary microchemistries. According to the microstructure characteristics in the Al matrix, the 50 L P composite has considerably increased grain boundary precipitate interspace in comparison with the T6 composite, since the lower aging temperature should result in the reduced grain boundary precipitate number. Furthermore, the 50 L P composite has more Cu content in the grain boundary precipitate and reduced precipitate free zone width over the RRA composite, indicating the improved stress corrosion cracking resistance. For the reinforcement, the TiB particles should slightly aggravate the stress corrosion cracking susceptibility, since the grain boundary precipitates are still the preferential corrosion sites due to their lower corrosion potentials.
已对原位TiB/7050Al复合材料进行了两步时效处理（50 L P，50℃预析出后的峰值时效）。50 L P复合材料具有与峰值时效（T6）状态下的复合材料相当的力学性能，并且在抗应力腐蚀开裂方面甚至优于采用回归再时效（RRA）处理的复合材料。具体而言，不同的时效条件导致不同的析出相形态和晶界微观化学。根据铝基体中的微观结构特征，与T6复合材料相比，50 L P复合材料的晶界析出相间距显著增加，这是因为较低的时效温度会导致晶界析出相数量减少。此外，与RRA复合材料相比，50 L P复合材料的晶界析出相中铜含量更高，且无析出带宽度减小，这表明其抗应力腐蚀开裂性能得到了改善。对于增强相，TiB颗粒应会略微增加应力腐蚀开裂敏感性，因为晶界析出相由于其较低的腐蚀电位仍是优先腐蚀部位。
