High-temperature creep behavior and creep mechanism of in situ (ZrB2+Al2O3)np/7055 Al nanocomposites
Tao Wang, Xizhou Kai, Luyao Huang, Qiang Peng, Kelun Sun, Yutao Zhao
Abstract
In the present research, (ZrB 2 +Al 2 O 3 ) np /7055 Al nanocomposites were synthesized via Al-Zr-B-O in-situ reaction. Subsequently, the high-temperature creep behavior was tested at different temperatures (473 K, 523 K and 573 K) under various applied stresses (60 MPa, 70 MPa and 80 MPa). It was found that the steady-state creep rates of the composites with a volume fraction of 3 % were 9.7 to 22.9 times lower than those of 7055 Al alloys , indicating the significant improvement in creep resistance with the addition of (ZrB 2 +Al 2 O 3 ) nanoparticles . The enhanced creep resistance can be attributed to the high-temperature thermal stability of nanoparticles , which effectively impede dislocation motion and prevent grain boundaries from migrating during high-temperature creep. Furthermore, precipitates in the composites exhibited a smaller size compared with those in the matrix. Notably, these nanoparticles delayed crack initiation and increased the length of the crack extension path due to crack deflection and crack branching. Additionally, the true stress exponents in the matrix and composites were 5, suggesting that the dominant creep mechanism was dislocation climbing. Moreover, the creep resistance mechanisms were discussed.