On fatigue lives of diecast and extruded Mg alloys

Ishihara, Sotomi; Namito, Tomonori; Yoshifuji, S.; Goshima, Takahito

doi:10.1016/j.ijfatigue.2010.11.023

Cited by 8 publications

(1 citation statement)

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“…Oxide films were present at each initiation site, but absent elsewhere on the fracture surface. In the high cycle fatigue regime, observed crack initiation mechanisms include cyclic slip deformation active near grain boundaries and in grain interiors [5,19], and at twin boundaries [20], as well as stress concentration around inclusions in many cases [21][22][23][24][25]. In low cycle fatigue, researchers have found crack initiation modes to be dependent on the magnitude of cyclic loading, with cracks initiating both along grain boundaries and at twin tips [26].…”

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The effects of heat treatment on very high cycle fatigue behavior in hot-rolled WE43 magnesium

Adams

Allison

Jones

2016

International Journal of Fatigue

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The role of crack initiation and short crack growth on fatigue life in the very high cycle fatigue regime (VHCF) is investigated for three heat treatments of the wrought magnesium alloy WE43. As-received (T5) WE43 with a relatively fine grain size was solution treated and aged to produce precipitation strengthened coarse-grained microstructures in the underaged and peak-aged (T6) conditions. Ultrasonic axial fatigue tests with a cyclic frequency of 20kHz were conducted using smooth specimens. Heat treatment was shown to have a strong effect on fatigue strength, with the fine-grained, strain-hardened T5 condition exhibiting much higher values than the coarse-grained conditions. No significant difference in fatigue strength was observed between the underaged and peak-aged microstructures of equivalent grain size. Crack initiation and short crack growth behaviors in each condition were investigated to determine if one of these behaviors dominated the VHCF lives. It was found that average short crack growth rates for the three conditions were similar and had no clear dependence on microstructural condition. Crack initiation was shown to occur through cyclic slip deformation in particularly large and favorably oriented grains in each condition. Subsurface crack initiation was observed at low stresses and high lifetimes in the coarse-grained conditions, but not in the fine grained T5 condition. Crack growth rates in vacuum were investigated using a unique combination of ultrasonic fatigue instrumentation and scanning electron microscopy (UFSEM) in order to simulate subsurface crack propagation. Environment was shown to have a significant effect on crack growth rate, with rates in vacuum nearly two orders of magnitude lower than in laboratory air.

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