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Abstract: The evolutions of uniaxial tension properties and the ratcheting fatigue behavior of AZ31 magnesium alloy sheet pre-corroded in the phosphate buffered solution (PBS) stimulated physiological environment with increasing immersion time were investigated in this study. The corrosion behavior of AZ31 sheet was also studied. It was found that the corrosion rate decreased exponentially with immersion time until stabilized at about 0.05g/m2 h after 28 days immersion. The corrosion behavior was characterized by pitting corrosion and progressive pitting corrosion in the direction of pits depth was gradually inhibited. The Young's modulus and the elongation of AZ31 sheet decreased exponentially with increasing immersion time and became low levels with reductions of around 10% and 20% respectively at 28 days immersion. The ultimate strength, however, decreased no more than 5%. With increasing immersion time, both the ratcheting strain and ratcheting strain rate in the stable stage of ratcheting strain evolution tended to increase. 28 days degradation decreased the fatigue lives by a factor of about 2.5–5. The pre-corroded damage defined as life reduction after degradation on the basis of the Miner's linear damage rule (LDR) was found to increase exponentially with immersion time regardless of the loading conditions. A ratcheting fatigue life prediction model based on the Miner LDR, the Smith–Watson–Topper (SWT) parameter and the Basquin's equation was proposed and yielded good prediction for the pre-corroded AZ31 sheet. [Copyright &y& Elsevier]

• Combined pre-compression significantly enhances the mechanical properties of magnesium alloys. • Combined pre-compression significantly reduces the material's anisotropy. • Combined pre-compression improves fatigue performance and weakens rapid hardening during cyclic loading. The research investigated the microstructure, monotonic mechanical properties, and fatigue behaviors of ZK60 magnesium alloy treated with single-pass pre-compression and combined pre-compression. The study found that combined pre-compression significantly improved mechanical strength in both the transverse and rolling directions compared to the single-pass method. Due to the randomized texture and intricate interwoven grain structures, the combined pre-compression method significantly mitigated the anisotropy observed in samples treated with single-pass pre-compression. Both pre-compression techniques enhanced the fatigue life of the ZK60 magnesium alloy. Samples subjected to combined pre-compression exhibited fatigue performance comparable to those treated with single-pass pre-compression. Additionally, there was a clear negative correlation between the fatigue life of the three samples and the magnitude of the mean stress. The abundance of pre-existing dislocations in the combined pre-compression processed samples helped in reducing the trend towards cyclic hardening. In contrast to single-pass pre-compression, the combined pre-compression method effectively reduced twinning activities and promoted the participation of basal slip during cyclic loading, leading to a more symmetrical hysteresis loop. [ABSTRACT FROM AUTHOR]

Precise monitoring of crack growth and a comprehensive understanding of crack propagation rate are crucial for the evaluation of the structural integrity of magnesium alloys with defects. Different crack deflections caused by the coupling of specimen orientations and crack sizes significantly increase the challenge to magnesium alloy evaluation. In this paper, the systematic finite element analysis was conducted for compact tension (CT) specimens with deflection cracks. A wide range of geometric variations including initial crack length, crack deflection angle and crack propagation length were analyzed. Complete solutions of the stress intensity factor (K I and K II), T -stress and the compliance at the load line were determined. The results showed that the geometric sizes have a significant coupling effect on the fracture mechanics parameters, and the non-deflected cracked formula recommended by the ASTM standard is not applicable to the deflection crack specimens. Then, a prediction method of kinked fatigue crack length of CT specimen based on the compliance multiplier method was proposed. To further verify the importance of the fracture parameters obtained, CT fatigue crack growth (FCG) tests of ZK60 magnesium (Mg) alloy under different orientations and initial crack sizes were carried out. The FCG rate curves of ZK60 Mg alloy under different crack growth driving forces were compared and illustrated. The developed compliance multiplication method can accurately predict the real-time crack propagation length. • The finite element analysis was conducted for CT specimens with deflection cracks. • The K I , K II , T -stress and compliance were determined. • The coupling effects of crack length and kink angle on fracture parameters were analyzed. • Kinked crack length prediction based on compliance multiplier method was proposed. • FCG tests were conducted to apply and validate the obtained fracture parameters. [ABSTRACT FROM AUTHOR]