Mechanisms of fatigue crack propagation in a Q&amp;P-processed steel

Hockauf, Kristin; Wagner, Martin F.‐X.; Mašek, Bohuslav; Lampke, Thomas

doi:10.1016/j.msea.2019.03.056

Cited by 16 publications

(10 citation statements)

References 31 publications

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“…Fatigue striations have a significant effect on retarding crack growth due to it will lead to a relatively long fracture path and side faces, 39 which is not beneficial to crack growth. As shown in Figure 11C,D, a cleavage facet was observed in CT‐QP980BM, which may be related to the expansion of fatigue crack along the boundary of the brittle martensite package 25 . The fatigue fracture of CT‐DP980HAZ was similar to that of CT‐DP980BM, as shown in Figure 11E.…”

Section: Resultsmentioning

confidence: 73%

“…However, the FCG rate of CT‐QP980BM gradually became higher than that of CT‐DP980BM with the increase of Δ K , as shown in Figure 8. The higher FCG rate of CT‐QP980BM at high Δ K attributed to the increasing number of phase transformation products (martensite), which would provide more brittle pathways for rapid crack propagation 25 . Previous studies 26 concluded that the strain hardening effect brought by martensite transformation phase could accelerate the FCG rate and offset the contribution of residual compressive stress caused by RA to martensite transformation.…”

Section: Resultsmentioning

confidence: 97%

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Effects of notch position on the fatigue crack growth behavior of dissimilar laser welded DP980/QP980 joint

Huang

Zhong

et al. 2022

Fatigue Fract Eng Mat Struct

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Laser welding of heterogeneous high‐strength steels (AHSSs) is increasingly used in the automotive industry, while the inhomogeneous microstructure of the joint could affect its fatigue crack growth (FCG) behavior. Therefore, fiber laser welding experiments were performed in this study to evaluate the microstructure, mechanical properties, and effects of notch position on FCG behavior of dissimilar laser welded DP980/QP980 joint. Results show that the hardness of fusion zone (FZ) near the QP980 side was higher and softening zones were observed in the heat affect zone (HAZ) on both sides of the joint. The stress–strain curves of all the samples show continuous yield and follow the two‐stage work hardening mechanism. The weld overmatch effect induced by laser welding could hinder the propagation of fatigue crack. The microstructural inhomogeneity, weld mismatch effect, and crack closure contribute to the variety of FCG rates. Ductile fracture mechanism became more dominant with the increase of ΔK.

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Section: Resultsmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 97%

Effects of notch position on the fatigue crack growth behavior of dissimilar laser welded DP980/QP980 joint

Huang

Zhong

et al. 2022

Fatigue Fract Eng Mat Struct

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“…[9][10][11][12][13] In recent years, researchers have gradually studied fatigue life and macroscale FCG characteristics under constant amplitude loading (CAL) and the transformation of RA under cyclic loading. [14][15][16][17] Diego et al 14 studied the high cycle fatigue behaviors of Q&P steels, the effects of fatigue testing parameters on fatigue behaviors, and mechanisms of fatigue crack initiation and propagation during cycling loading. They explored the role of RA in Q&P steel by the electron backscatter diffraction (EBSD) characterization technique, which revealed that the phase transformation of RA is related to its grain size and crystal orientation.…”

Section: Introductionmentioning

confidence: 99%

“…They explored the role of RA in Q&P steel by the electron backscatter diffraction (EBSD) characterization technique, which revealed that the phase transformation of RA is related to its grain size and crystal orientation. Kristin et al 15 first studied the mechanisms of FCG near the threshold value of Q&P steel and the effect of RA content on the propagation law in the Paris steady-state crack propagation stage. Song et al 16 studied the fatigue life, constant amplitude FCG characteristics, and fatigue crack microstructure characteristics of Q&P steel and investigated the effects of sub-stable austenite content and stability.…”

Section: Introductionmentioning

confidence: 99%

Study on the multi‐scale online fatigue crack deformation and growth behaviors under overload in Q&P steel

Gao,

Zhan,

et al. 2024

Fatigue Fract Eng Mat Struct

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The multi‐scale online fatigue crack deformation and growth behaviors under single overload (SOL) and periodic overload (POL) case in Quenching and Partitioning (Q&P) steel were studied using two micro cameras and sub‐image stitching and matching digital image correlation (DIC) method. Firstly, the microscopic crack tip speckle images and crack images on both sides of the compact tension (CT) specimen during the fatigue crack growth (FCG) process were collected under different overload parameters. Then, the FCG overload retardation, crack tip closing and blunting behaviors, and the crack tip strain distribution and evolution, overload retardation mechanism were analyzed. In addition, the corresponding multi‐scale FCG morphological characteristics and material microstructure under overload case were observed. The results indicate that the overload ratio and interval affect the overload retardation effect of Q&P steel seriously; the overload crack tip blunting and plastic zone are the major factors inducing the overload retardation effect in Q&P steel.

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“…[ 1 ] Generally, the automotive steels own a specific characteristic of either microstructure such as dual phase steel, twinning induced plasticity steel, or phase transformation such as transformation induced plasticity steel, medium Mn steel, and quenching and partitioning treatment steel. [ 2,3 ] Therefore, the third‐generation automobile steels were summarized with the 3 M characteristics of multiphase, metastable, and multiscale. [ 4 ] To achieve this target, high contents of alloying elements like Mn and Al must be added which brings vast diffculty in industrial production simultaneously accompanied by high preparation cost.…”

Section: Introductionmentioning

confidence: 99%

Approaching to High Elongation of Automotive Steel by Controlled Cooling Strategy

Xue

Yin

Tian

et al. 2020

steel research int.

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Automobile steel with moderate tensile strength demands for higher total elongation, whereas present production cannot satisfy such requirement. To cope with the challenge for desired ductility, Ti, Nb, and V microalloyed steel is applied to a late‐stage ultrafast cooling (LUC) method as well as an interrupted ultrafast cooling (IUC) strategy to explore the effect of cooling process on the total elongation. It is found that an IUC can increase the total elongation and the lűders strain to about 45% and 60% higher in comparison with the LUC counterpart, respectively. Metallographic microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and orientation distribution function (ODF) are used to characterize the microstructure and texture components. It is revealed that the multiscale grain distribution and the multiphase constituent, especially the existence of ultrafine pearlite microstructure with several atomic layers of grain boundaries, are greatly important for the ductility enhancement. It is inferred that larger undercooling caused by ultrafast cooling strategy makes the dislocation density much higher, whereas Nb precipitation tends to induce the formation of lamellar pearlite structure.

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Mechanisms of fatigue crack propagation in a Q&P-processed steel

Cited by 16 publications

References 31 publications

Effects of notch position on the fatigue crack growth behavior of dissimilar laser welded DP980/QP980 joint

Effects of notch position on the fatigue crack growth behavior of dissimilar laser welded DP980/QP980 joint

Study on the multi‐scale online fatigue crack deformation and growth behaviors under overload in Q&P steel

Approaching to High Elongation of Automotive Steel by Controlled Cooling Strategy

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