Microstructural Impact on Fatigue Crack Growth Behavior of Alloy 718

Metals

Reinhard Pippan¹  Christian Gruber²  Jürgen Maierhofer²  Hans-Peter Gänser²  Peter Raninger²  Anton Hohenwarter³  Aleksandar Stanojevic⁴ 

[1] Erich Schmid Institute of Materials Science, 8700 Leoben, Austria;Materials Center Leoben Forschung GmbH, 8700 Leoben, Austria;Montanuniversität Leoben—Chair of Materials Physics, 8700 Leoben, Austria;Voestalpine BÖHLER Aerospace GmbH & Co KG, 8605 Kapfenberg, Austria;

关键词: alloy 718;    threshold value;    threshold of stress intensity factor range;    fracture surface;    microstructure;   

DOI  :  10.3390/met12050710

来源: DOAJ

【 摘 要 】

Alloy 718 for forged parts can form a wide range of microstructures through a variety of thermo-mechanical processes, depending on the number of remelting processes, temperature and holding time of homogenization annealing, cogging and the number of forging steps depending on the forming characteristics. In industrial practice, these processing steps are tailored to achieve specific mechanical and microstructural properties in the final product. In the present work, we investigate the dependence of the threshold of stress intensity factor range ΔK_th on associated microstructural elements, namely grain size and distribution. For this purpose, a series of tests with different starting microstructures were performed at the falling stress intensity factor range, ΔK, and a load ratio of R = 0.1 to evaluate the different threshold values. Fracture initiation and crack propagation were analyzed afterward using scanning electron microscopy of the resulting fracture surfaces. In order to obtain comparable initial conditions, all specimens were brought to the same strength level by means of a two-stage aging heat treatment. In the future, this knowledge shall be used in the context of simulation-aided product development for estimating local fatigue crack propagation properties of simulated microstructures obtained from forging and heat treatment modeling.

【 授权许可】

Unknown