High-cycle fatigue strength of ultrafine-grained 5483 Al-Mg alloy at low and elevated temperature in comparison to conventional coarse-grained Al alloys

摘要

This paper presents fatigue behavior of ultrafine-grained (UFG) 5483 Al-Mg alloy processed by hydroextrusion in comparison to its coarse-grained counterpart (CG 5483) and precipitation strengthened CG 7475 alloy. The specimens were tested at low (- 50 ℃), ambient (25 ℃) and elevated (100 ℃) temperature in tension-tension (R = 0.1) fatigue under stress control. It was found that the decrease of temperatures leads to a shift of Wohler curves to higher stress values. Despite of similar YS, UFG 5483 alloy exhibited reduced fatigue strength compared with CG 7475 alloy. The changes in fatigue life were rationalized in terms of lower stability of UFG structure under cyclic loading. UFG 5483 and CG 7475 alloys were susceptible to cyclic softening attributed to fatigue-induced recovery process, whereas CG 5483 exhibited cyclic hardening accompanied by dislocation density increase.