从耐腐蚀性能的角度讨论了地锚拉杆镶嵌锻造的必要性。拉伸试验表明,地锚拉杆镶嵌锻造后,实用强度达不到设计要求的28.8 k N,断裂部位发生在拉杆镶嵌锻造部分,且靠近锁紧扣孔口。对拉杆镶嵌锻造部分的前后组织进行了金相观察,结果显示,...从耐腐蚀性能的角度讨论了地锚拉杆镶嵌锻造的必要性。拉伸试验表明,地锚拉杆镶嵌锻造后,实用强度达不到设计要求的28.8 k N,断裂部位发生在拉杆镶嵌锻造部分,且靠近锁紧扣孔口。对拉杆镶嵌锻造部分的前后组织进行了金相观察,结果显示,拉杆冷变形后的细长晶粒经镶嵌锻造后重新转变成了等轴晶粒,产生了再结晶,冷变形强化效果消失是导致其实用强度下降的根源。进一步研究表明,拉杆产生再结晶是由高温锁紧扣锻坯热传导致其温度升高造成的。故镶嵌锻造前,在拉杆镶嵌锻造部分浸涂一定比例的混合液,使拉杆镶嵌锻造后的温度低至再结晶温度以下。采用此方法后的拉伸实验结果表明,地锚拉杆镶嵌锻造后实用强度未明显下降,金相分析也表明未产生再结晶。展开更多
Single hit compression tests were performed at 1 223-1 473 K and strain rate of 0.1-10 s-1 to study hot deformation behavior and flow stress model of F40MnV steel. The dependence of the peak stress, initial stress, sa...Single hit compression tests were performed at 1 223-1 473 K and strain rate of 0.1-10 s-1 to study hot deformation behavior and flow stress model of F40MnV steel. The dependence of the peak stress, initial stress, saturation stress, steady state stress and peak stain on Zener-Hollomon parameter were obtained. The mathematical models of dynamic recrystallization fraction and grain size were also obtained. Based on the tested data, the flow stress model of F40MnV steel was established in dynamic recovery region and dynamic recrystallization region, respectively. The results show that the activation energy for dynamic recrystallization is 278.6 kJ/mol by regression analysis. The flow stress model of F40MnV steel is proved to approximate the tested data and suitable for numerical simulation of hot forging.展开更多
The drawn copper wires have been analyzed by differential scanning calorimeter(DSC) and a new method, which uses DSC measurements to determine the Johnson-Mehl-Avrami-Kolmogorov(JMAK) exponent via introducing Arrheniu...The drawn copper wires have been analyzed by differential scanning calorimeter(DSC) and a new method, which uses DSC measurements to determine the Johnson-Mehl-Avrami-Kolmogorov(JMAK) exponent via introducing Arrhenius behavior and modifying the baseline of DSC curves, has been proposed. The results show that JMAK exponent and recrystallization activation energy of the drawn copper wires with a strain of 2.77 are about 2.39 and 125 k J/mol, respectively. The line linking the tangency points of DSC curve hypotenuse can be used as the baseline when calculating recrystallization fraction. The JMAK exponent obtained by the DSC method is in a good agreement with that obtained by microhardness measurements. Compared to traditional methods to measure the exponent, the proposed method is faster and less labor intensive.展开更多
Cellular automata (CA) algorithm has become an effective tool to simulate microstructure evolution. This paper presents a review on CA modeling of microstructural evolution, such as grain coarsening, recrystallization...Cellular automata (CA) algorithm has become an effective tool to simulate microstructure evolution. This paper presents a review on CA modeling of microstructural evolution, such as grain coarsening, recrystallization and phase transformation during metal forming process which significantly affects mechanical properties of final products. CA modeling of grain boundary motion is illustrated and several aspects of recrystallization are described, e.g. nucleation and growth, the development of static and dynamic recrystallization. For phase transformation, attention is paid to such key factors as solute element diffusion and change of systemic chemical free energy. In view of the reviewed works, several open questions in the field of further development of CA simulation are put forward and recommendations to them are given.展开更多
文摘从耐腐蚀性能的角度讨论了地锚拉杆镶嵌锻造的必要性。拉伸试验表明,地锚拉杆镶嵌锻造后,实用强度达不到设计要求的28.8 k N,断裂部位发生在拉杆镶嵌锻造部分,且靠近锁紧扣孔口。对拉杆镶嵌锻造部分的前后组织进行了金相观察,结果显示,拉杆冷变形后的细长晶粒经镶嵌锻造后重新转变成了等轴晶粒,产生了再结晶,冷变形强化效果消失是导致其实用强度下降的根源。进一步研究表明,拉杆产生再结晶是由高温锁紧扣锻坯热传导致其温度升高造成的。故镶嵌锻造前,在拉杆镶嵌锻造部分浸涂一定比例的混合液,使拉杆镶嵌锻造后的温度低至再结晶温度以下。采用此方法后的拉伸实验结果表明,地锚拉杆镶嵌锻造后实用强度未明显下降,金相分析也表明未产生再结晶。
基金Project (50275094) supported by the National Natural Science Foundation of China
文摘Single hit compression tests were performed at 1 223-1 473 K and strain rate of 0.1-10 s-1 to study hot deformation behavior and flow stress model of F40MnV steel. The dependence of the peak stress, initial stress, saturation stress, steady state stress and peak stain on Zener-Hollomon parameter were obtained. The mathematical models of dynamic recrystallization fraction and grain size were also obtained. Based on the tested data, the flow stress model of F40MnV steel was established in dynamic recovery region and dynamic recrystallization region, respectively. The results show that the activation energy for dynamic recrystallization is 278.6 kJ/mol by regression analysis. The flow stress model of F40MnV steel is proved to approximate the tested data and suitable for numerical simulation of hot forging.
基金Projects(51171135,51371132,51471123) supported by the National Natural Science Foundation of ChinaProjects(2012K07-08,2013KJXX-61) supported by Key Science and Technology Program of Shaanxi Province,ChinaProject(2013JC14) supported by the Education Department Foundation of Shaanxi Province,China
文摘The drawn copper wires have been analyzed by differential scanning calorimeter(DSC) and a new method, which uses DSC measurements to determine the Johnson-Mehl-Avrami-Kolmogorov(JMAK) exponent via introducing Arrhenius behavior and modifying the baseline of DSC curves, has been proposed. The results show that JMAK exponent and recrystallization activation energy of the drawn copper wires with a strain of 2.77 are about 2.39 and 125 k J/mol, respectively. The line linking the tangency points of DSC curve hypotenuse can be used as the baseline when calculating recrystallization fraction. The JMAK exponent obtained by the DSC method is in a good agreement with that obtained by microhardness measurements. Compared to traditional methods to measure the exponent, the proposed method is faster and less labor intensive.
基金supported by the Natural Science Foundation for Key Program of China (Grant No. 50935007)National Basic Research Program of China (Grant No. 2010CB731701)+2 种基金Foundation for Fundamental Research of Northwestern Polytechnical University in China (Grant No. NPU-FFR-JC20100229)Research Fund of the State Key Laboratory of Solidification Processing of Northwestern Polytechnical University in China (Grant No. 27-TZ-2010)111 Project (Grant No. B08040)
文摘Cellular automata (CA) algorithm has become an effective tool to simulate microstructure evolution. This paper presents a review on CA modeling of microstructural evolution, such as grain coarsening, recrystallization and phase transformation during metal forming process which significantly affects mechanical properties of final products. CA modeling of grain boundary motion is illustrated and several aspects of recrystallization are described, e.g. nucleation and growth, the development of static and dynamic recrystallization. For phase transformation, attention is paid to such key factors as solute element diffusion and change of systemic chemical free energy. In view of the reviewed works, several open questions in the field of further development of CA simulation are put forward and recommendations to them are given.
