Quantitative assessment of notch fatigue behavior in Mg-RE alloys via zero-point critical distance theory

Notched fatigue tests were conducted at room temperature on three Mg-Y-Zn alloys with varying initial contents of long-period stacking ordered (LPSO) phases. The influence of the notch effect on the fatigue life of these alloys was analyzed. The results indicate that the notch effect significantly reduces the fatigue life of the Mg-Y-Zn alloys, with a higher stress concentration factor correlating to shorter fatigue lives. Under high-stress conditions, the fatigue life of the identical notched specimens decreases as the LPSO phase content increases. Conversely, under low-stress conditions, the fatigue life of the notched specimen tends to increase with rising LPSO phase content. Notably, when compared to parameters such as stress concentration factor, high-stress volume, and relative stress gradient, the relative zero-point parameter provides a more straightforward analytical approach and enables precise notch characterization. A novel zero-point critical distance (ZPCD) model is proposed by incorporating the relative zero-point parameter into the classical TCD framework. Experimental validation demonstrates that the ZPCD model achieves significantly higher prediction accuracy for notch fatigue performance than the traditional TCD method.