We performed thermal simulation experiments of double-pass deformation of hypereutectoid rails with different microalloying elements at a cooling rate of 1℃/s and deformation of 80%to explore the influence of rare-ea...We performed thermal simulation experiments of double-pass deformation of hypereutectoid rails with different microalloying elements at a cooling rate of 1℃/s and deformation of 80%to explore the influence of rare-earth and microalloying elements on the structure of hypereutectoid rails and optimize the composition design of hypereutectoid rails.Scanning electron microscopy,transmission electron microscopy,X-ray diffraction,and other characterization techniques were employed to quantitatively analyzed the effects of different microalloying elements,including rare-earth elements,on pearlite lamellar spacing,cementite characteristics,and dislocation density.It was found that the lamellar spacing was reduced by adding various microalloying elements.Cementite lamellar thickness decreased with the refinement of pearlite lamellar spacing while the cementite content per unit volume increased.Local cementite spheroidization,dispersed in the ferrite matrix in granular form and thus playing the role of dispersion strengthening,was observed upon adding cerium(Ce).The contributions of dislocation density to the alloy strength of four steel sheet samples with and without the addition of nickel,Ce,and Ce–copper(Cu)composite were 26,27,32,and 37 MPa,respectively,indicating that the Ce–Cu composite had the highest dislocation strengthening effect.The Ce–Cu composite has played a meaningful role in the cementite characteristics and dislocation strengthening,which provides a theoretical basis for optimizing the composition design of hypereutectoid rails in actual production conditions.展开更多
The fatigue crack behavior of U75V rail under different quenching rates was studied using SEM and CLSM.The results show that the pearlite interlayer spacing and fatigue crack growth rate decrease,and the deflection pa...The fatigue crack behavior of U75V rail under different quenching rates was studied using SEM and CLSM.The results show that the pearlite interlayer spacing and fatigue crack growth rate decrease,and the deflection path of cracks and the number of branching cracks of U75V rail increases with an increase of cooling rate.The tearing edge of unstable region transites from pearlite lamellae to dimple.The fatigue crack growth path is closely related to the orientation of lamellae in pearlite microstructure.There are three modes direction of fatigue crack growth path and pearlite lamellar,which are parallel,vertical and 45°angle,and most of the branch cracks occur at an angle of 45°between the lamellar direction and the crack direction.More specifically,the deflection paths of cracks and branching crack have a relaxation effect on the stress intensity at the crack tip,which restrains the fatigue crack growth rate.展开更多
基金the National Natural Science Foundation of China(No.51361021)the Inner Mongolia Science and Technology Major Project(No.ZDZX2018024)。
文摘We performed thermal simulation experiments of double-pass deformation of hypereutectoid rails with different microalloying elements at a cooling rate of 1℃/s and deformation of 80%to explore the influence of rare-earth and microalloying elements on the structure of hypereutectoid rails and optimize the composition design of hypereutectoid rails.Scanning electron microscopy,transmission electron microscopy,X-ray diffraction,and other characterization techniques were employed to quantitatively analyzed the effects of different microalloying elements,including rare-earth elements,on pearlite lamellar spacing,cementite characteristics,and dislocation density.It was found that the lamellar spacing was reduced by adding various microalloying elements.Cementite lamellar thickness decreased with the refinement of pearlite lamellar spacing while the cementite content per unit volume increased.Local cementite spheroidization,dispersed in the ferrite matrix in granular form and thus playing the role of dispersion strengthening,was observed upon adding cerium(Ce).The contributions of dislocation density to the alloy strength of four steel sheet samples with and without the addition of nickel,Ce,and Ce–copper(Cu)composite were 26,27,32,and 37 MPa,respectively,indicating that the Ce–Cu composite had the highest dislocation strengthening effect.The Ce–Cu composite has played a meaningful role in the cementite characteristics and dislocation strengthening,which provides a theoretical basis for optimizing the composition design of hypereutectoid rails in actual production conditions.
基金Inner Mongolia Science and Technology Major Project(No.ZDZX2018024)Natural Science Foundation of Inner Mongolia(No.2019LH05016)+1 种基金Research Program of Science at Universities of Inner Mongolia Autonomous Region of China(No.NJZY20089)Innovation Fund of Inner Mongolia University of Science and Technology(No.2019QDL-B06)。
文摘The fatigue crack behavior of U75V rail under different quenching rates was studied using SEM and CLSM.The results show that the pearlite interlayer spacing and fatigue crack growth rate decrease,and the deflection path of cracks and the number of branching cracks of U75V rail increases with an increase of cooling rate.The tearing edge of unstable region transites from pearlite lamellae to dimple.The fatigue crack growth path is closely related to the orientation of lamellae in pearlite microstructure.There are three modes direction of fatigue crack growth path and pearlite lamellar,which are parallel,vertical and 45°angle,and most of the branch cracks occur at an angle of 45°between the lamellar direction and the crack direction.More specifically,the deflection paths of cracks and branching crack have a relaxation effect on the stress intensity at the crack tip,which restrains the fatigue crack growth rate.
