Creep and Bolt Load Retention Behavior of Die Cast Magnesium Alloys for High Temperature Applications: Part 2 of 2

The effect of calcium on the creep and bolt load retention (BLR) behavior of AM50 alloy has been investigated. Four AM50 alloys 0, 0.25, 0.56, and 0.88% Ca have been die-cast. BLR-tests have been conducted at 125, 150, and 175°C and preloads of 14, 21, and 28kN. Tensile and compressive creep tests were also conducted at 150°C and initial stresses from 40 to 80 MPa. Both creep and BLR were significantly influenced by calcium content, with increasing calcium content resulting in improved relaxation resistance. The BLR of AM50 with 0.88% Ca was better than that of AE42 at all temperatures although the effect of calcium was temperature dependent. Calcium did not change the sensitivity of BLR to preload, while it increased the relaxation limit (F_r) of AM50 significantly. In addition, calcium improved the creep resistance of AM50 significantly. The relationship between creep strain (ε) of AMC alloys and calcium concentration (C) can be represented by the equation ε = A·e ^{-k3 C}, where A and k₃ are constants depending on applied stress, temperature, and time.