Abstract
Fatigue tests were performed on the AZ91 cast alloy to identify the mechanisms of the fatigue crack initiation. In different fatigue regions, different mechanisms were observed. In the low and high cycle fatigue regions, slip markings formation accompanied with Mg17Al12 particles cracking were observed. Slip markings act as the fatigue crack initiation sites. The size and number of slip markings decreased with decreased stress amplitude applied. When slip markings formation was suppressed due to low stress amplitude, particle cracking became more important and the cracks continued to grow through the particle/solid solution interface. The change of the fatigue crack initiation mechanisms led the S-N curve to shift to the higher number of cycles to the fracture, demonstrated by its stepwise character. A lower fatigue limit of 60 MPa was determined at 20 kHz for 2 × 109 cycles compared to the 80 MPa determined at 60 Hz for 1 × 107 cycles.
Highlights
Due to the high specific strength, low density, and good castability, Mg alloys are still widely used materials in many engineering applications in the automotive industry, aerospace, biomedicine, electrical engineering, etc. [1,2,3,4,5,6,7]
Fatigue tests of AZ91 magnesium alloy from low to very high cycle fatigue regions were performed to describe the fatigue crack initiation mechanism and revealed its change
Low and high cycle fatigue regions were characteristic by the fatigue crack initiation on the slip markings (SMs) created in the solid solution areas of the cast microstructure of AZ91 magnesium alloy
Summary
Due to the high specific strength, low density, and good castability, Mg alloys are still widely used materials in many engineering applications in the automotive industry, aerospace, biomedicine, electrical engineering, etc. [1,2,3,4,5,6,7]. When no defects are present in the cast microstructure, the slip markings (SMs), manifesting the localization of the cyclic plastic deformation formed in the solid solution areas, act as the stress concentrators for the fatigue crack initiation [3,17] Their size and amount were shown to be determined by the applied stress amplitude and a reached number of cycles to the fracture. Very high‐frequency (20 kHz) loading was performed at almost identical stress amplitudes as the fatigue tests in the HCF region (tested at 10 + 60 Hz), when the specimens of 11 exceeded 1 × 107 cycles and were considered as run‐outs. All thVMeeufralyttiihpgliuegehfar-tfeirggeuiqoeuncsernaaccnkydi(n2ail0tliaktthHieozna)wplopaalsidecdihnasgrtarwcetsaessriaspmteicrpfflooitrrumAdZeesd9.1aTcthaaesltmfmraoacsgttuniredeseiusnumtricfaaalclleosytwrfeoassrs ampecinxhliicatteuiraeadtcdietoeesndraiss1tpitch×laeoc1effas0tt7higewcuyetecrrleateenssstlacosrncyidansltitawzhleleeidnrHee CocfnoaFtnirgsetiuhgdeeieorcnersda(ptceeakcssitmgerrdueonnaw-tot1hsu0utmrs+f.ae6ccA0ehsnaH.nzeis)Nx,mpow.erhFicemahntaiegtrnhuatecetpseceprrireasfctcoiikcrmmeends Aa2imntZ×iiatc9ira11sot0tscir9otaerncssutyspcactlaullaelmcrosaeypalss.nlfifedtouarttdhu1eer0e8sospf,cey6lcic0kilmeeMsecwnPasawatsiwanesgasctsiodmtneefsareitmdcetedsirn, eaawdstee4adr9se.a8worMbhusenPen-arov,tuwehtde.hIissnleper[et3vhc2iine]mgtcheaaensstfilanfitafgietgitdguimeuefeesectcretersxanpccgekrteehsdefeondrt in the microstructure were the most responsible factor for the fatigue crack initiation Like casting defects, were observed serving as fatigue crack initiation places
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
