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A new mathematical model for predicting flow stress of X70HD under hot deformation

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Journal of Central South University 2015年第6期22卷 2052-2059页

作者：王健王小巩杨海涛余超肖宏 National Engineering Research Center for Equipment and Technology of Cold Rolling Strip (Yanshan University) State Key Laboratory of Rolling and Automation (Northeastern University)

To realize numerical simulation of rolling and obtain the hot forming process parameters for X70 HD steel, the flow stress behaviors of X70 HD steel were investigated under different temperatures（820-1100 ℃ and strain rates（0.01-10 s-1） on a Gleeble-3500 thermo-simulation machine. A new flow stress model was established. The linear and exponential relationship methods were applied to the parameters with respect to temperature and deformation rates. The rise of curve ends under certain conditions was analyzed. The flow stress of X70 HD steel predicted by the proposed model agrees well with the experimental results. So, it greatly improves the precision of the metal thermoplastic processing through finite element method and practical application of engineering.

关键词： flow stress dynamic recovery dynamic reerystallization z parameter

Hot deformation behavior of extruded Az80 magnesium alloy

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Transactions of Nonferrous Metals Society of China 2013年第11期23卷 3180-3185页

作者：李慧中卫晓燕欧阳杰姜俊李轶中南大学材料科学与工程学院长沙410083 中南大学粉末冶金国家重点实验室长沙410083 中南大学有色金属材料科学与工程教育部重点实验室长沙410083

The hot deformation behavior of extruded Az80 magnesium alloy was studied through hot compression tests performed at temperatures ranging from 250 to 450 ~C with strain rates varying from 0.001 to 10 s-1. The flow stress was corrected due to the deformation heating. The zener-Hollomon parameter （z parameter） and processing map were established to describe the hot deformation behavior. The results indicate that the applicable deformation should be conducted at the strain rate of 0.1 s-~ and the temperature range of 350-400 ~C. Besides, the relationship between the microstructure evolution and z parameter was also discussed. High temperature and low strain rate result in a low z parameter, which leads to full dynamic recrystallization （DRX） and large DRX grain size in the microstructure. Considering processing map and microstructure, the hot deformation should be carried out at the temperature of 400 ~C and the strain rate of 0.1 s 1.

关键词： Az80 magnesium alloys hot deformation processing map z parameter

Near net shape casting process for producing high strength 6xxx aluminum alloy automobile suspension parts

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Transactions of Nonferrous Metals Society of China 2014年第7期24卷 2393-2400页

作者：郭世杰徐义韩逸刘金炎薛冠霞长海博文苏州有色金属研究院有限公司苏州215026

The automobile suspension parts of a high strength 6xxx aluminum alloy were produced using a novel technique known as near net shape casting for forging stock preparation. Based on the outline dimension of the forging stock, the shape of the ingot was designed as the near net shape and its casting process was studied by the numerical simulation and experimental investigation. The results show that the shrinkage of the ingot was highly correlated to its shape parameters and could be successfully forecast by the stimulation model. The casting parameters of the near net shape ingot were optimized and the near net shape 6xxx aluminum alloy ingots free of defects were cast in the laboratory. In order to obtain high performance forged suspension parts, the hot compression tests of the ingot were carried out. The results show that the subgrain fraction of the forged ingot was strongly affected by zener-Hollomon parameters （z parameters）. The intermediate z parameters, 1.09×10^16 s^-1, will contribute to the larger number fraction of subgrains inside the forged ingot, which contributes to the high performance of the forged products.

关键词： near-net shape DC casting z parameter subgrains automobile suspension part aluminum alloy

Quantitative analysis of influence of α-Al(MnFeCr)Si dispersoids on hot deformation and microstructural evolution of Al-Mg-Si alloys

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Transactions of Nonferrous Metals Society of China 2022年第6期32卷 1805-1821页

作者： Hiromi NAGAUMI Jian QIN Cheng-bin YU Xiao-guo WANG Lin-sheng WANG High Performance Metal Structural Materials Research Institute Soochow UniversitySuzhou 215021China Shagang School of Iron and Steel Soochow UniversitySuzhou 215021China College of Agricultural Engineering Shanxi Agricultural UniversityTaigu 030801China Press Metal International Ltd. Foshan 528000China

The microstructural evolution of AA6061 and Mn-bearing Al-Mg-Si-Cu alloys was studied by compression tests that were carried out between 300 and 500 °C with a wide range of strain rates. Compared to the AA6061 alloy, the large amount of α-Al(MnFeCr)Si dispersoids in the Mn-bearing alloy yielded a significant increase in the flow stress under all deformation conditions. The effects of the deformation parameters on the evolution of the microstructure were studied using electronic backscatter diffraction measurements. The predominant softening mechanism of both alloys was dynamic recovery. The presence of α dispersoids in Mn-bearing alloys effectively refined the size of substructures with misorientation angles in the range of 2°-5°, which retarded the dynamic recovery. To predict the subgrain size under various deformation conditions, the threshold stresses that were caused by α dispersoids were calculated by the modified Orowan equation and incorporated into a conventional constitutive equation. The subgrain size that was predicted by the modified constitutive equation showed satisfactory agreement with the experimental measurements.

关键词： Al-Mg-Si alloy hot deformation α-Al(MnFeCr)Si dispersoids substructure dynamic softening threshold stress z parameter

Hot workability of high manganese transformation induced plasticity steel

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Baosteel Technical Research 2010年第S1期4卷 32-页

作者： zHANG Weina,LIU zhenyu and WANG Guodong State Key Laboratory of Rolling and Automation,Northeastern University, Shenyang 110004,Liaoning,China

The hot deformation behavior and microstructure evolution of high manganese transformation induced plasticity steel(Fe - 20Mn - 3Si - 3Al) were investigated by using hot compression test in a temperature range from 800℃to 1 050℃and strain rate ranging from 0.01 s^(-1) to 5.0 s^(-1).The effects of temperature,strain rate,and true strain on the flow behavior and microstructures of high manganese transformation induced plasticity steel were *** results show that the dynamic recrystallization occurs only at higher temperature and lower strain *** deformation behaviors of high manganese transformation induced plasticity steel were sensitive to temperature and strain *** apparent stress exponent and the apparent activation energy of the investigated steel were about 4.280 and 463.791 kJ/mol, *** apparent activation energy of the high manganese transformation induced plasticity steel was approached to the austenitic stainless steel(400 -500 kJ/mol).The hot working equation is obtained. Hot deformation peak stress increased with increasing of the value of *** stress and Inz exhibits a linear variation,the linear correlation coefficient was 0.988 *** results show that the dynamic recrystallization was prone to occur when lnz≤43.842 26 and z≤1.098×10^(19),and better hot deformation properties would be obtained under this condition.

关键词： high manganese transformation induced plasticity steel hot deformation microstructure dynamic recrystallization z parameter