The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Jianxun Zhang - One of the best experts on this subject based on the ideXlab platform.

  • high temperature low cycle fatigue behavior of hs80h ferritic Martensitic Steel under dynamic strain aging
    Journal of Materials Engineering and Performance, 2018
    Co-Authors: Wenlan Wei, Yaorong Feng, Lihong Han, Jianxun Zhang, Hang Wang
    Abstract:

    In this work, low-cycle fatigue tests were performed on HS80H ferritic–Martensitic Steel with the strain amplitudes ranging from 0.5 to 2.0% at room temperature and 350 °C. The cyclic stress response at 350 °C was found to be different from that at room temperature due to the effect of dynamic strain aging and showed a significant secondary hardening when the strain values were 0.5 and 0.7%. Furthermore, the dynamic strain aging effect also resulted in an abnormal increase in fatigue life when the strain was 0.7%, which was due to the change in elastic strain. Additionally, the elastic strain and fatigue life were bilinear relations in the double logarithmic coordinates. Finally, the transmission electron microscope observations showed that the dynamic strain aging led to the change in substructure, while the grain was refined.

  • cyclic hardening and dynamic strain aging during low cycle fatigue of cr mo tempered Martensitic Steel at elevated temperatures
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018
    Co-Authors: Wenlan Wei, Yaorong Feng, Lihong Han, Qunbing Zhang, Jianxun Zhang
    Abstract:

    Abstract Dynamic strain aging (DSA) has a noticeable impact on low cycle fatigue behavior of Cr-Mo tempered Martensitic Steel at elevated temperatures. At 350 °C, the stress response presented evidently secondary hardening phenomenon, and the fatigue life is significantly higher than room temperature which is contrary to the usual understanding. The analysis shows that the reason for the secondary hardening is mainly because of DSA which affects the evolution of dislocations. The influence process of the DSA effect on the dislocation evolution in low-cycle fatigue was first observed, which is from lath substructure to a smaller cell substructure at high temperature. Fracture observation indicates that the new dislocation structure promotes the crack propagation resistance of the material. The effect of DSA on the low cycle fatigue properties of high temperature provides a new idea for the study of fatigue resistance of materials.

  • low cycle fatigue behaviors of a new type of 10 cr Martensitic Steel and welded joint with ni based weld metal
    International Journal of Fatigue, 2016
    Co-Authors: Qunbing Zhang, Jianxun Zhang, Pengfei Zhao, Yong Huang, Xiuyang Fang
    Abstract:

    Abstract In the present work, Ni-based filler metal was used to weld a new type of 10% Cr Martensitic Steel. Due to the microstructure and chemical composition difference between Martensitic Steel and the Ni-based weld metal, a clear interface existed in the dissimilar welded joint. At the region of the interface, the microstructure was physically connected and an element transition layer was formed. Low-cycle fatigue (LCF) results showed that the welded joint was not fractured at the interface. Meanwhile, the Martensitic Steel and Ni-based weld metal exhibited cyclic softening and cyclic hardening behaviors, respectively. For Martensitic Steel, the width of the laths increased and the dislocation density decreased after the fatigue test, whereas in the fatigue-tested Ni-based weld metal, the dislocation density increased. The continuous connection and composition transition at the region of interface, combined with the high ductility and cyclic hardening behavior of Ni-based weld metal, is beneficial for the LCF properties of the welded joint.

O'dowd, Noel P. - One of the best experts on this subject based on the ideXlab platform.

  • Strain gradient crystal plasticity modelling of size effects in a hierarchical Martensitic Steel using the Voronoi tessellation method
    'Elsevier BV', 2021
    Co-Authors: Sun Fengwei, Meade, Edward D., O'dowd, Noel P.
    Abstract:

    peer-reviewedInelastic deformation of a high-strength Martensitic Steel (P91) is investigated using a strain gradient crystal plasticity model implemented using the finite element method. Voronoi tessellation is used to model the hierarchical structure, prior austenite grain (PAG)/packet/block, of the Martensitic Steel and the effect of PAG/packet/block size on the macro- and micro-scale mechanical response is analysed numerically. The role of lath interaction and the influence of dislocation type (statistically stored and geometrically necessary dislocations) are investigated. It is found that block size determines the overall mechanical response, consistent with the Hall-Petch relation, while packet and block diameters influence the microplastic strain distribution. A modified Hall-Petch relation is examined which provides a relationship between material flow strength and block diameter (size) which holds for a wide range of initial dislocation densities and block diameterspeer-reviewe

  • Strain gradient crystal plasticity modelling of size effects in a hierarchical Martensitic Steel using the Voronoi tessellation method
    'Elsevier BV', 2021
    Co-Authors: Sun Fengwei, Meade, Edward D., O'dowd, Noel P.
    Abstract:

    peer-reviewedThe full text of this article will not be available in ULIR until the embargo expires on the 28/03/2021Inelastic deformation of a high-strength Martensitic Steel (P91) is investigated using a strain gradient crystal plasticity model implemented using the finite element method. Voronoi tessellation is used to model the hierarchical structure, prior austenite grain (PAG)/packet/block, of the Martensitic Steel and the effect of PAG/packet/block size on the macro- and micro-scale mechanical response is analysed numerically. The role of lath interaction and the influence of dislocation type (statistically stored and geometrically necessary dislocations) are investigated. It is found that block size determines the overall mechanical response, consistent with the Hall-Petch relation, while packet and block diameters influence the microplastic strain distribution. A modified Hall-Petch relation is examined which provides a relationship between material flow strength and block diameter (size) which holds for a wide range of initial dislocation densities and block diameterspeer-reviewe

  • Prediction of prior austenite grain growth in the heat-affected zone of a Martensitic Steel during welding
    'Elsevier BV', 2020
    Co-Authors: Shi L., Alexandratos S.a., O'dowd, Noel P.
    Abstract:

    peer-reviewedEngineering components operating at high temperature often fail due to the initiation and growth of cracks in the heat-affected zone (HAZ) adjacent to a weld. The size and morphology of the prior austenite grains (PAGs) in the HAZ of a tempered martensite Steel weld can have a strong influence on the final Martensitic microstructure. However, there are few available models to predict PAG size in the HAZ of Martensitic Steel welds. In this work two approaches are examined to predict PAG growth in the HAZ of a Martensitic Steel (P91) weld. Phase field (PF) methods, which explicitly represent the changing morphology of a representative volume of martensite grains, and approximate analytical solutions for grain growth at high temperature are examined. The predicted grain growth kinetics and final grain diameter using a two term analytical solution is shown to agree well with experimental data and with the validated PF simulation. The two term analytical model provides a versatile tool to analyse PAG growth at low computational costs. In addition, a simplified equation for predicting the final PAG diameter in the HAZ of P91 welds is proposed for engineering applications. The methods have been used to estimate the final grain diameter in the HAZ of a single bead-on-plate weld

  • Microscale modelling of the deformation of a Martensitic Steel using the Voronoi Tessellation method
    'Elsevier BV', 2020
    Co-Authors: Sun Fengwei, Meade, Edward D., O'dowd, Noel P.
    Abstract:

    peer-reviewedThe deformation of a Martensitic Steel (P91) at the microscale is investigated using the finite element method. The approach takes into account the hierarchical grain-packet-block microstructure of the Steel as determined experimentally by electron backscatter diffraction (EBSD). The orientation relationship for P91 between the prior austenite grain (PAG) and the Martensitic packet/block is determined and found to be consistent with the Kurdjumow-Sachs (K-S) relationship. This relationship is incorporated within a finite-element model to represent the material microstructure, using a representative volume element (RVE) generated by a modified centroidal Voronoi tesselation (VT) approach. A non-linear, rate dependent, finite strain crystal plasticity model is used to simulate the mechanical response of the material at the micro- and macro-level and the sensitivity of the results to the model assumptions is investigated. It is found that the global (macro) mechanical response predicted by the RVE generated using the modified VT model is in good agreement with that predicted by an RVE taken directly from the measured EBSD microstructure. The influence of block/packet/grain boundaries on the local (micro) deformation is examined and it is found that the microscale prediction obtained using the RVE based on the modified VT microstructure, with an appropriate choice of microstructural parameters, is consistent with that obtained using the measured EBSD map

Wenlan Wei - One of the best experts on this subject based on the ideXlab platform.

  • high temperature low cycle fatigue behavior of hs80h ferritic Martensitic Steel under dynamic strain aging
    Journal of Materials Engineering and Performance, 2018
    Co-Authors: Wenlan Wei, Yaorong Feng, Lihong Han, Jianxun Zhang, Hang Wang
    Abstract:

    In this work, low-cycle fatigue tests were performed on HS80H ferritic–Martensitic Steel with the strain amplitudes ranging from 0.5 to 2.0% at room temperature and 350 °C. The cyclic stress response at 350 °C was found to be different from that at room temperature due to the effect of dynamic strain aging and showed a significant secondary hardening when the strain values were 0.5 and 0.7%. Furthermore, the dynamic strain aging effect also resulted in an abnormal increase in fatigue life when the strain was 0.7%, which was due to the change in elastic strain. Additionally, the elastic strain and fatigue life were bilinear relations in the double logarithmic coordinates. Finally, the transmission electron microscope observations showed that the dynamic strain aging led to the change in substructure, while the grain was refined.

  • cyclic hardening and dynamic strain aging during low cycle fatigue of cr mo tempered Martensitic Steel at elevated temperatures
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018
    Co-Authors: Wenlan Wei, Yaorong Feng, Lihong Han, Qunbing Zhang, Jianxun Zhang
    Abstract:

    Abstract Dynamic strain aging (DSA) has a noticeable impact on low cycle fatigue behavior of Cr-Mo tempered Martensitic Steel at elevated temperatures. At 350 °C, the stress response presented evidently secondary hardening phenomenon, and the fatigue life is significantly higher than room temperature which is contrary to the usual understanding. The analysis shows that the reason for the secondary hardening is mainly because of DSA which affects the evolution of dislocations. The influence process of the DSA effect on the dislocation evolution in low-cycle fatigue was first observed, which is from lath substructure to a smaller cell substructure at high temperature. Fracture observation indicates that the new dislocation structure promotes the crack propagation resistance of the material. The effect of DSA on the low cycle fatigue properties of high temperature provides a new idea for the study of fatigue resistance of materials.

Han Dong - One of the best experts on this subject based on the ideXlab platform.

  • effect of hot rolling temperature on grain size and precipitation hardening in a ti microalloyed low carbon Martensitic Steel
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012
    Co-Authors: Lisheng Xu, Han Dong
    Abstract:

    Abstract The grain refinement and strength improvement resulted from hot rolling temperature in Ti microalloyed low carbon Martensitic Steel was investigated in this study. Two different started hot rolling temperatures (950 °C and 1100 °C) but with the same reheating quenching process were applied to the Steel. The microstructures and second precipitated particles were examined by scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-rays diffraction and phase analysis method. It was found that hot rolling could induce the precipitation of TiC. Moreover, the amount of the TiC in Steel rolled at 950 °C is higher and the size of the precipitates is much finer than that in Steel rolled at 1100 °C. Both the large deformation without recrystallization and the precipitates in Steel rolled at 950 °C are more effective on the grain refinement after the reheating process, in which the effective grain size (EGS) can be refined to 1.4 μm. In addition, the Steel rolled at 950 °C exhibits a much higher strength than that rolled at 1100 °C due to the additional dislocation strengthening and more precipitation strengthening

  • effects of ti addition and reheating quenching on grain refinement and mechanical properties in low carbon medium manganese Martensitic Steel
    Materials & Design, 2012
    Co-Authors: Y Han, J Shi, W Q Cao, Han Dong
    Abstract:

    Abstract The grain refinement and mechanical properties improvement resulted from Ti addition and reheating quenching were demonstrated in this study. The direct quenched medium manganese Steel with low carbon content (0.05C) was treated by reheating quenching process. The yield strength and Charpy impact energy were measured. The microstructures and the second precipitated particles were examined by optical microscopy (OM), scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), X-rays diffraction and phase analysis method. It was found that reheating quenching at 900–1000 °C resulted in significant grain refinement, especially the refinement of effective grain size (EGS), which was attributed to the large amount nano-sized precipitation of TiC. In addition, high elastic modulus was also obtained from the large amount TiC precipitated from the matrix. It is concluded that reheating quenching process is a useful method to refine the grain size and improve the combined mechanical properties of the Martensitic Steel through Ti addition.

  • characterization of microstructure obtained by quenching and partitioning process in low alloy Martensitic Steel
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010
    Co-Authors: Chang Wang, Han Dong
    Abstract:

    Abstract Microstructure of low alloy Martensitic Steel treated by quenching and partitioning (QP the fresh martensite is formed at the final quenching step and looks like ‘blocky’ type phase with size about 0.2–3 μm, and the retained austenite is mainly located on the packet boundary and initial austenite grain boundary. The measured volume fractions and carbon contents of these phases were slightly different from those predicted by the constrained paraequilibrium (CPE) model proposed by Speer, which was interpreted by the effects of the different grain sizes of the untransformed austenite after first quenching. Mechanical properties of Steels processed by Q&P assume much higher strength and ductility than those processed by Q&T. It is concluded that Q&P process is a promising approach to control the multiphase structure with hard matrix and a ductile retained austenite, which gives an excellent combination of strength and ductility.

  • effect of microstructural refinement on the toughness of low carbon Martensitic Steel
    Scripta Materialia, 2008
    Co-Authors: Chunfang Wang, Maoqiu Wang, Jie Shi, Weijun Hui, Han Dong
    Abstract:

    The ductile to brittle transition temperature of a commercial Martensitic Steel decreases with the refinement of its microstructure. Electron backscattered diffraction analysis of the cleavage crack path shows that the packet boundaries can strongly hinder fracture propagation, and thus Martensitic packets can act as the effective microstructure unit for cleavage.

Sun Fengwei - One of the best experts on this subject based on the ideXlab platform.

  • Strain gradient crystal plasticity modelling of size effects in a hierarchical Martensitic Steel using the Voronoi tessellation method
    'Elsevier BV', 2021
    Co-Authors: Sun Fengwei, Meade, Edward D., O'dowd, Noel P.
    Abstract:

    peer-reviewedInelastic deformation of a high-strength Martensitic Steel (P91) is investigated using a strain gradient crystal plasticity model implemented using the finite element method. Voronoi tessellation is used to model the hierarchical structure, prior austenite grain (PAG)/packet/block, of the Martensitic Steel and the effect of PAG/packet/block size on the macro- and micro-scale mechanical response is analysed numerically. The role of lath interaction and the influence of dislocation type (statistically stored and geometrically necessary dislocations) are investigated. It is found that block size determines the overall mechanical response, consistent with the Hall-Petch relation, while packet and block diameters influence the microplastic strain distribution. A modified Hall-Petch relation is examined which provides a relationship between material flow strength and block diameter (size) which holds for a wide range of initial dislocation densities and block diameterspeer-reviewe

  • Strain gradient crystal plasticity modelling of size effects in a hierarchical Martensitic Steel using the Voronoi tessellation method
    'Elsevier BV', 2021
    Co-Authors: Sun Fengwei, Meade, Edward D., O'dowd, Noel P.
    Abstract:

    peer-reviewedThe full text of this article will not be available in ULIR until the embargo expires on the 28/03/2021Inelastic deformation of a high-strength Martensitic Steel (P91) is investigated using a strain gradient crystal plasticity model implemented using the finite element method. Voronoi tessellation is used to model the hierarchical structure, prior austenite grain (PAG)/packet/block, of the Martensitic Steel and the effect of PAG/packet/block size on the macro- and micro-scale mechanical response is analysed numerically. The role of lath interaction and the influence of dislocation type (statistically stored and geometrically necessary dislocations) are investigated. It is found that block size determines the overall mechanical response, consistent with the Hall-Petch relation, while packet and block diameters influence the microplastic strain distribution. A modified Hall-Petch relation is examined which provides a relationship between material flow strength and block diameter (size) which holds for a wide range of initial dislocation densities and block diameterspeer-reviewe

  • Microscale modelling of the deformation of a Martensitic Steel using the Voronoi Tessellation method
    'Elsevier BV', 2020
    Co-Authors: Sun Fengwei, Meade, Edward D., O'dowd, Noel P.
    Abstract:

    peer-reviewedThe deformation of a Martensitic Steel (P91) at the microscale is investigated using the finite element method. The approach takes into account the hierarchical grain-packet-block microstructure of the Steel as determined experimentally by electron backscatter diffraction (EBSD). The orientation relationship for P91 between the prior austenite grain (PAG) and the Martensitic packet/block is determined and found to be consistent with the Kurdjumow-Sachs (K-S) relationship. This relationship is incorporated within a finite-element model to represent the material microstructure, using a representative volume element (RVE) generated by a modified centroidal Voronoi tesselation (VT) approach. A non-linear, rate dependent, finite strain crystal plasticity model is used to simulate the mechanical response of the material at the micro- and macro-level and the sensitivity of the results to the model assumptions is investigated. It is found that the global (macro) mechanical response predicted by the RVE generated using the modified VT model is in good agreement with that predicted by an RVE taken directly from the measured EBSD microstructure. The influence of block/packet/grain boundaries on the local (micro) deformation is examined and it is found that the microscale prediction obtained using the RVE based on the modified VT microstructure, with an appropriate choice of microstructural parameters, is consistent with that obtained using the measured EBSD map

  • Strain gradient crystal plasticity modelling of size effects in a hierarchical Martensitic Steel using the Voronoi tessellation method
    Elsevier, 2019
    Co-Authors: Sun Fengwei, Meade, Edward D., O\u27dowd, Noel P.
    Abstract:

    The full text of this article will not be available in ULIR until the embargo expires on the 28/03/2021Inelastic deformation of a high-strength Martensitic Steel (P91) is investigated using a strain gradient crystal plasticity model implemented using the finite element method. Voronoi tessellation is used to model the hierarchical structure, prior austenite grain (PAG)/packet/block, of the Martensitic Steel and the effect of PAG/packet/block size on the macro- and micro-scale mechanical response is analysed numerically. The role of lath interaction and the influence of dislocation type (statistically stored and geometrically necessary dislocations) are investigated. It is found that block size determines the overall mechanical response, consistent with the Hall-Petch relation, while packet and block diameters influence the microplastic strain distribution. A modified Hall-Petch relation is examined which provides a relationship between material flow strength and block diameter (size) which holds for a wide range of initial dislocation densities and block diameterspeer-reviewe

  • Microscale modelling of the deformation of a Martensitic Steel using the Voronoi Tessellation method
    Elsevier, 2018
    Co-Authors: Sun Fengwei, Meade, Edward D., O\u27dowd, Noel P.
    Abstract:

    The deformation of a Martensitic Steel (P91) at the microscale is investigated using the finite element method. The approach takes into account the hierarchical grain-packet-block microstructure of the Steel as determined experimentally by electron backscatter diffraction (EBSD). The orientation relationship for P91 between the prior austenite grain (PAG) and the Martensitic packet/block is determined and found to be consistent with the Kurdjumow-Sachs (K-S) relationship. This relationship is incorporated within a finite-element model to represent the material microstructure, using a representative volume element (RVE) generated by a modified centroidal Voronoi tesselation (VT) approach. A non-linear, rate dependent, finite strain crystal plasticity model is used to simulate the mechanical response of the material at the micro- and macro-level and the sensitivity of the results to the model assumptions is investigated. It is found that the global (macro) mechanical response predicted by the RVE generated using the modified VT model is in good agreement with that predicted by an RVE taken directly from the measured EBSD microstructure. The influence of block/packet/grain boundaries on the local (micro) deformation is examined and it is found that the microscale prediction obtained using the RVE based on the modified VT microstructure, with an appropriate choice of microstructural parameters, is consistent with that obtained using the measured EBSD map