Creep-Rupture Behavior of Die-Cast Magnesium Alloys (original) (raw)

It is found that the relationship between the time-to-rupture t r and the time to the onset of tertiary creep t οt ( t r / t ot ) in die-cast Mg-9Al alloy is equal to 1.3 and independent of stress, test temperature and diecasting parameters over the range examined. It is shown that the introduction of creep-rupture strain into Monkman-Grant relation modified by Dobes and Milicka demonstrates only the deviation range of the minimum creep rate from the average creep rate. The apparent activation energy E c of creep is below the value of magnesium self-diffusion energy ESD up to 175°C. At higher temperatures, E c > E SD , and creep deformation may be controlled by diffusion processes (dislocation climbing, etc.). The established magnitude of stress exponent n in the power law (the modified Arrhenius rate equation) within the stress range from 20 to 50 MPa is close to the value of n ≅ 3 typical of solid-solution alloys. The increase in n values at higher stresses up to ~ 5 is caused,...