TY - JOUR AU - Gryguc, Andrew AU - Behravesh, S.B. AU - Jahed, H. AU - Wells, M. AU - Williams, B. AU - Gruber, R. AU - Duquett, A. AU - Sparrow, T. AU - Lambrou, M. AU - Su, X. PY - 2020/12/28 Y2 - 2024/03/28 TI - Effect of thermomechanical processing defects on fatigue and fracture behaviour of forged magnesium JF - Frattura ed Integrità Strutturale JA - Fra&IntStrut VL - 15 IS - 55 SE - Fatigue DO - 10.3221/IGF-ESIS.55.16 UR - https://www.fracturae.com/index.php/fis/article/view/2967 SP - 213-227 AB - <p>The microstructural origins of premature fatigue failures were investigated on a variety of forged components manufactured from AZ80 and ZK60 magnesium, both at the test specimen level and the full-scale component level. Both stress and strain-controlled approaches were used to characterize the macroscopically defect-free forged material behaviour as well as with varying levels of defect intensities. The effect of thermomechanical processing defects due to forging of a industrially relevant full-scale component were characterized and quantified using a variety of techniques. The fracture initiation and early crack growth behaviour was deterministically traced back to a combination of various effects having both geometric and microstructural origins, including poor fusion during forging, entrainment of contaminants sub-surface, as well as other inhomogeneities in the thermomechanical processing history.</p><p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; At the test specimen level, the fracture behaviour under both stress and strain controlled uniaxial loading was characterized for forged AZ80 Mg and a structure-property relationship was developed. The fracture surface morphology was quantitatively assessed revealing key features which characterize the presence and severity of intrinsic forging defects.&nbsp; A significant degradation in fatigue performance was observed as a result of forging defects accelerating fracture initiation and early crack growth, up to 6 times reduction in life (relative to the defect free material) under constant amplitude fully reversed fatigue loading.</p><p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; At the full-scale component level, the fatigue and fracture behaviour under combined structural loading was also characterized for a number of ZK60 forged components with varying levels of intrinsic thermomechanical processing defects. A novel in-situ non-contact approach (utilizing Digital-Image Correlation) was used as a screening test to establish the presence of these intrinsic defects and reliably predict their effect on the final fracture behaviour in an accelerated manner compared to conventional methods.</p> ER -