Abstract:

Thermo-mechanical fatigue (TMF) due to the cyclic changes of stress and temperature is considered to be one of the most detrimental failures for the automotive engine parts. To improve the service life of engine components, it is essential to understand their TMF behavior and to improve the TMF resistance. In the present work, the out-of-phase TMF behavior of two Al-Si-Cu and Al-Si-Mg cast alloys (319 and 356) were investigated under various strain amplitudes (0.2–0.6%) and cyclic temperature (60–300 °C). In addition, the influence of Mo microalloying on the TMF behavior of Al-Si-Cu 319 alloy was also studied. During TMF cycling, all three experimental alloys displayed asymmetric hysteresis loops as well as the cyclic softening of maximum tensile/compression stress, which is likely attributed to the coarsening of precipitates. The TMF lifetime of the 319 alloy was generally higher than that of the 356 alloy, and the formation of thermally stable Mo-containing dispersoids in the Mo-added 319 alloy further improved the TMF life than 319. The fatigue life of three experimental alloys was simulated and predicted by the energy-based model, which was in a good agreement with the experimental data.

Keywords: Aluminum cast alloys; thermo-mechanical fatigue; precipitates; Mo addition; fatigue life predication.

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Dr. Lei Pan