Abstract
High-frequency (10–1700 c/s) push/pull fatigue tests on a magnesium alloy at 0.75 of the melting point show that the rate of fatigue-hardening generally increases with increasing frequency and stress level. The time to onset of major crack propagation is virtually independent of frequency, though decreasing slightly at the higher frequencies. Beyond this point, the rate of crack propagation may be either time- or cycle-dependent, according to stress level. Fatigue specimens show marked grain growth at a rate that increases with increasing stress level. High-frequency tests are associated with less growth and enhanced boundary cavitation. Smaller grains give rise to less overall plastic strain than large grains and evidence is presented of grain-boundary sliding during fatigue.
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