Effect of prior fatigue exposure on the creep behaviour of an aluminium alloy (Al-12Si-CuMgNi)

The creep-fatigue interaction (CFI) behaviour, in terms of the effects of p rior fatigue exposure on the subsequent creep behaviour, is evaluated and r eported for an aluminium alloy (Al-12Si-CuMgNi) at an elevated temperature of 623 K. The prior fatigue is imparted in the form of low cycle fatigue (L CF) loading in fully-reversed, total-strain controlled testing up to a quar ter of fatigue life at a total strain amplitude of 4.45 x 10(-3) (correspon ding to a plastic strain amplitude of 3.35 x 10(-3) at half-life). Subseque ntly, isothermal tensile creep tests were conducted at 623 K to evaluate th e minimum creep rate, rupture time and strain to failure, as a function of applied stress. Results show that the material exhibits enhanced creep resi stance due to prior fatigue exposure. We attribute this to residual back st ress arising from the prior low cycle fatigue exposure. The creep rupture t ime follows the Monkman-Grant power-law relationship for both virgin and th e prior LCF exposed alloy.