TY - JOUR

T1 - Microstructural Impact on Fatigue Crack Growth Behavior of Alloy 718

AU - Gruber, Christian

AU - Raninger, Peter

AU - Maierhofer, Jürgen

AU - Gänser, Hans Peter

AU - Stanojevic, Aleksandar

AU - Hohenwarter, Anton

AU - Pippan, Reinhard

N1 - Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2022/4/21

Y1 - 2022/4/21

N2 - 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 ∆Kth 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, ∆K, 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.

AB - 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 ∆Kth 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, ∆K, 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.

KW - alloy 718

KW - fracture surface

KW - microstructure

KW - threshold of stress intensity factor range

KW - threshold value

UR - http://www.scopus.com/inward/record.url?scp=85128746925&partnerID=8YFLogxK

U2 - 10.3390/met12050710

DO - 10.3390/met12050710

M3 - Article

AN - SCOPUS:85128746925

VL - 12.2022

JO - Metals

JF - Metals

SN - 2075-4701

IS - 5

M1 - 710

ER -