This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy.The results showed that yield strength of the as-extruded Mg-1.2wt.%Ca alloys decrease from∼360...This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy.The results showed that yield strength of the as-extruded Mg-1.2wt.%Ca alloys decrease from∼360MPa to∼258MPa as the ram speed increases from 0.4mm/s to 2.4 mm/s,and the elongation increases from∼3.9%to∼12.2%.The microstructure changes from bimodal grain feature to the complete dynamical recrystallization(DRX)with increase of the extrusion speed.The ultrafine DRXed grains in size of∼0.85μm,the numerous nano-Mg_(2)Ca particles dispersing along the grain boundaries and interiors,as well as the high density of residual dislocations,should account for the high strength.It is believed that the high degree of dynamic recrystallization and the resulting texture randomization play the critical roles in the ductility enhancement of the high-speed extruded Mg alloys.展开更多
At the initial rolling temperature of 250 to 400 ℃, AZ31B magnesium alloy sheets were hot rolled by four different rolling routes. Microstructures and mechanical properties of the hot-rolled magnesium alloy sheets we...At the initial rolling temperature of 250 to 400 ℃, AZ31B magnesium alloy sheets were hot rolled by four different rolling routes. Microstructures and mechanical properties of the hot-rolled magnesium alloy sheets were analyzed by optical microscope and tensile tests respectively. Based on the Hall-Petch relation, considering the average grain size and grain size distribution, the nonlinear fitting analysis between the tensile strength and average grain size was carried on, and then the prediction model of tensile strength of hot-rolled AZ31B magnesium alloy sheet was established. The results indicate that, by rolling with multi-pass cross rolling, uniform, fine and equiaxial grain microstructures can be produced, the anisotropy of hot-rolled magnesium sheet can also be effectively weakened. Strong correlation was observed between the average grain size and tensile property of the hot-rolled magnesium alloy sheet. Grain size distribution coefficient d(CV) was introduced to reflect the dispersion degree about a set of grain size data, and then the Hall-Petch relation was perfected. Ultimately, the prediction accuracy of tensile strength of multi-pass hot-rolled AZ31B magnesium alloy was improved, and the prediction of tensile property can be performed by the model.展开更多
Wear-resistant cladding plates consisting of a substrate(Q345 R) and a clad layer(BTW1) were bonded through hot rolling at the temperature of 1 200 ℃ and a rolling speed of 0.5 m/s. The microhardness of the cladd...Wear-resistant cladding plates consisting of a substrate(Q345 R) and a clad layer(BTW1) were bonded through hot rolling at the temperature of 1 200 ℃ and a rolling speed of 0.5 m/s. The microhardness of the cladding plate was also tested after being heat treated. The microstructure evolution on the interface of BTW1/Q345 R sheets under various reduction rates was investigated with a scanning electron microscope(SEM) and EBSD. It is found that the micro-cracks and oxide films on the interface disappear when the reduction is 80%, whereas the maximum uniform diffusion distance reaches 10 μm. As a result, a wide range of metallurgical bonding layers forms, which indicates an improved combination between the BTW1 and the Q345 R. Additionally, it is discovered that the unbroken oxide films on the interface are composed of Mn, Si or Cr at the reductions of 50% and 65%. The SEM fractography of tensile specimen demonstrates that the BTW1 has significant dimple characteristics and possesses lower-sized dimples with the increment in reduction, suggesting that the toughness and bonding strength of the cladding plates would be improved by the increase of reduction. The results reveal that a high rolling reduction causes the interfacial oxide film broken and further forms a higher-sized composite metallurgical bonding interface. The peak microhardness is achieved near the interface.展开更多
In order to predict flow instability of wear-resistant steel BTW1, the hot compressions of wear-resistant steel BTW1 were firstly performed at the temperature of 900-1150 ℃ and at the strain rate of 0.05-15 s-1. Then...In order to predict flow instability of wear-resistant steel BTW1, the hot compressions of wear-resistant steel BTW1 were firstly performed at the temperature of 900-1150 ℃ and at the strain rate of 0.05-15 s-1. Then, the constitutive relation was established based on Arrhenius-type hyperbolic sine equation. The results demonstrated that the flow stress depended on the deformation temperature and strain rate. When the deformation temperature kept constant, the flow stress increased as the strain rate increased. When the strain rate remained constant, the flow stress decreased as the temperature increased. The flow stresses calculated by constitutive equations were in a good agreement with experimental results. The apparent activation energy for deformation in the above processing region was estimated to be 369 kJ tool-1. A processing map could be obtained by the superimposition of an instability map on a power dissipation map. Based on the analysis of processing map and the microstructures, the theological instability regimes of strain rate and temperature for hot deformation of wear-resistant steel BTWl had been identified.展开更多
Only a few studies have been conducted on the flow behavior of the novel BTW1/Q345R bimetal,which is widely used in coal equipment.In this work,compression tests were conducted on BTW1/Q345R bimetal at a temperature r...Only a few studies have been conducted on the flow behavior of the novel BTW1/Q345R bimetal,which is widely used in coal equipment.In this work,compression tests were conducted on BTW1/Q345R bimetal at a temperature range of 950°C–1200°C and strain rates of 0.05,0.5,5,and 15 s^−1 by using a Gleeble-3800 thermomechanical simulator.A constitutive equation was validated by referring to the Arrhenius equation during the characterization of hot workability.The computed apparent activation energy of the BTW1/Q345R bimetal was 360 kJ/mol,and processing maps under different strain conditions were drawn.Analysis of the stress-strain relationship revealed that work hardening exerted a dominant effect on the thermal deformation of the BTW1/Q345R bimetal.The processing maps predicted that the optimal processing interval will increase with strain.Results showed that thermal deformation of the BTW1/Q345R bimetal should proceed when the temperature range varies from 1182°C to 1200°C and the strain rate interval is from 4.2 to 15 s^−1.展开更多
基金This work is supported by National Natural Science Foundation of China(Nos.51525101,U1610253,51701211,and 51971053)funded by the Project of Promoting Talents in Liaoning province(No.XLYC1808038)+2 种基金H.C.Pan acknowledges the financial assistance from the State Key Laboratory of Solidification Processing in NPU(No.SKLSP201920)the Fundamental Research Funds for the Central Universities(No.N2002011)joint R&D fund of Liaoning-Shenyang National Research Center for Materials Science(No.2019JH3/30100040).
文摘This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy.The results showed that yield strength of the as-extruded Mg-1.2wt.%Ca alloys decrease from∼360MPa to∼258MPa as the ram speed increases from 0.4mm/s to 2.4 mm/s,and the elongation increases from∼3.9%to∼12.2%.The microstructure changes from bimodal grain feature to the complete dynamical recrystallization(DRX)with increase of the extrusion speed.The ultrafine DRXed grains in size of∼0.85μm,the numerous nano-Mg_(2)Ca particles dispersing along the grain boundaries and interiors,as well as the high density of residual dislocations,should account for the high strength.It is believed that the high degree of dynamic recrystallization and the resulting texture randomization play the critical roles in the ductility enhancement of the high-speed extruded Mg alloys.
基金Funded by the National Natural Science Foundation of China(No.U1510131)the Key Research and Development Projects of Shanxi Province(No.201603D121010)+1 种基金the Science and Technology Project of Jincheng City(No.20155010)the Project of Young Scholar of Shanxi Province and the Leading Talent Project of Innovative Entrepreneurial Team of Jiangsu Province and the Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxi(TYAL)
文摘At the initial rolling temperature of 250 to 400 ℃, AZ31B magnesium alloy sheets were hot rolled by four different rolling routes. Microstructures and mechanical properties of the hot-rolled magnesium alloy sheets were analyzed by optical microscope and tensile tests respectively. Based on the Hall-Petch relation, considering the average grain size and grain size distribution, the nonlinear fitting analysis between the tensile strength and average grain size was carried on, and then the prediction model of tensile strength of hot-rolled AZ31B magnesium alloy sheet was established. The results indicate that, by rolling with multi-pass cross rolling, uniform, fine and equiaxial grain microstructures can be produced, the anisotropy of hot-rolled magnesium sheet can also be effectively weakened. Strong correlation was observed between the average grain size and tensile property of the hot-rolled magnesium alloy sheet. Grain size distribution coefficient d(CV) was introduced to reflect the dispersion degree about a set of grain size data, and then the Hall-Petch relation was perfected. Ultimately, the prediction accuracy of tensile strength of multi-pass hot-rolled AZ31B magnesium alloy was improved, and the prediction of tensile property can be performed by the model.
基金the National Natural Science Foundation of China(No.U151013)the Key Research and Development Program of Shanxi Province(Nos.201603D111004 and 201603D121010)+1 种基金the Natural Science Foundation of Shanxi Province of Chinathe Provincial Special Fund for Coordinative Innovation Center of Taiyuan Heavy Machinery Equipmen(No.20171003)
文摘Wear-resistant cladding plates consisting of a substrate(Q345 R) and a clad layer(BTW1) were bonded through hot rolling at the temperature of 1 200 ℃ and a rolling speed of 0.5 m/s. The microhardness of the cladding plate was also tested after being heat treated. The microstructure evolution on the interface of BTW1/Q345 R sheets under various reduction rates was investigated with a scanning electron microscope(SEM) and EBSD. It is found that the micro-cracks and oxide films on the interface disappear when the reduction is 80%, whereas the maximum uniform diffusion distance reaches 10 μm. As a result, a wide range of metallurgical bonding layers forms, which indicates an improved combination between the BTW1 and the Q345 R. Additionally, it is discovered that the unbroken oxide films on the interface are composed of Mn, Si or Cr at the reductions of 50% and 65%. The SEM fractography of tensile specimen demonstrates that the BTW1 has significant dimple characteristics and possesses lower-sized dimples with the increment in reduction, suggesting that the toughness and bonding strength of the cladding plates would be improved by the increase of reduction. The results reveal that a high rolling reduction causes the interfacial oxide film broken and further forms a higher-sized composite metallurgical bonding interface. The peak microhardness is achieved near the interface.
基金This work was supported by the National Natural Science Foundation of China (No. U1510131) and the Applied Basic Research Project of Shanxi Province (Nos. 201701D121078 and 201701D221143).
文摘In order to predict flow instability of wear-resistant steel BTW1, the hot compressions of wear-resistant steel BTW1 were firstly performed at the temperature of 900-1150 ℃ and at the strain rate of 0.05-15 s-1. Then, the constitutive relation was established based on Arrhenius-type hyperbolic sine equation. The results demonstrated that the flow stress depended on the deformation temperature and strain rate. When the deformation temperature kept constant, the flow stress increased as the strain rate increased. When the strain rate remained constant, the flow stress decreased as the temperature increased. The flow stresses calculated by constitutive equations were in a good agreement with experimental results. The apparent activation energy for deformation in the above processing region was estimated to be 369 kJ tool-1. A processing map could be obtained by the superimposition of an instability map on a power dissipation map. Based on the analysis of processing map and the microstructures, the theological instability regimes of strain rate and temperature for hot deformation of wear-resistant steel BTWl had been identified.
基金This work was supported by the Applied Basic Research Project of Shanxi Province,China(Grant Nos.201701D121078 and 201701D221143)the National Natural Science Foundation of China(Grant No.U1510131).
文摘Only a few studies have been conducted on the flow behavior of the novel BTW1/Q345R bimetal,which is widely used in coal equipment.In this work,compression tests were conducted on BTW1/Q345R bimetal at a temperature range of 950°C–1200°C and strain rates of 0.05,0.5,5,and 15 s^−1 by using a Gleeble-3800 thermomechanical simulator.A constitutive equation was validated by referring to the Arrhenius equation during the characterization of hot workability.The computed apparent activation energy of the BTW1/Q345R bimetal was 360 kJ/mol,and processing maps under different strain conditions were drawn.Analysis of the stress-strain relationship revealed that work hardening exerted a dominant effect on the thermal deformation of the BTW1/Q345R bimetal.The processing maps predicted that the optimal processing interval will increase with strain.Results showed that thermal deformation of the BTW1/Q345R bimetal should proceed when the temperature range varies from 1182°C to 1200°C and the strain rate interval is from 4.2 to 15 s^−1.