Liu Kun, Wang Shuai, Hu Peng, Pan Lei, Chen X-Grant
Department of Applied Science, University of Quebec at Chicoutimi, Saguenay, QC G7H 2B1, Canada.
Arvida Research and Development Centre, Rio Tinto Aluminum, Saguenay, QC G7S 4K8, Canada.
Materials (Basel). 2023 May 3;16(9):3515. doi: 10.3390/ma16093515.
Thermo-mechanical fatigue (TMF) is one of the most detrimental failures of critical engine components and greatly limits their service life. In this study, the out-of-phase TMF (OP-TMF) behavior in Al-Si-Cu 319 cast alloys microalloyed with Mo was systematically investigated under various strain amplitudes ranging from 0.1-0.6% and temperature cycling at 60-300 °C and compared with the base 319 alloy free of Mo. Cyclic stress softening occurred in both experimental alloys when applying the TMF loading, resulting from the coarsening of θ'-AlCu precipitates. However, the softening rate of the Mo-containing alloy was lower than that of the base 319 alloy because of its lower θ'-AlCu precipitate coarsening rate per cycle. The Mo-containing alloy exhibited a longer TMF lifetime than the base alloy at the same strain amplitude. Microalloying 319 alloy with Mo enhanced the TMF resistance mainly by slowing the coarsening of θ'-AlCu precipitates and providing supplementary strengthening from thermally stable Mo-containing α-dispersoids distributed in the Al matrix. The energy-based model was successfully applied for predicting the TMF lifetime with a low life predictor factor, which agreed well with the experimentally measured fatigue cycles.
热机械疲劳（TMF）是关键发动机部件最具危害性的失效形式之一，极大地限制了它们的使用寿命。在本研究中，系统研究了含钼微合金化的Al-Si-Cu 319铸造合金在0.1 - 0.6%的各种应变幅值以及60 - 300°C温度循环下的异相热机械疲劳（OP-TMF）行为，并与不含钼的基础319合金进行了比较。施加TMF载荷时，两种实验合金均出现循环应力软化，这是由θ'-AlCu析出相粗化所致。然而，含钼合金的软化速率低于基础319合金，因为其每循环的θ'-AlCu析出相粗化速率较低。在相同应变幅值下，含钼合金的TMF寿命比基础合金更长。用钼对319合金进行微合金化主要通过减缓θ'-AlCu析出相的粗化以及由分布在铝基体中的热稳定含钼α-弥散相提供补充强化来提高TMF抗力。基于能量的模型成功应用于预测TMF寿命，寿命预测因子较低，与实验测量的疲劳循环结果吻合良好。
