AZ31镁合金热变形行为研究及数值模拟
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摘要
本研究利用Gleeble-1500D热/力模拟机对AZ31镁合金进行等温压缩试验,建立该合金的流变应力本构方程,并对不同变形条件镁合金流变应力行为分析。借助XRD衍射和金相组织分析了AZ31镁合金不同热变形条件下的择优取向和组织变化规律,研究了变形温度、变形速率以及变形程度对动态再结晶过程的影响。然后把AZ31镁合金等温压缩试验数据的数学模型输入DEFORM-3D中建立了材料库,来研究等径角挤压过程中不同内圆角半径对热变形过程的影响。得到以下几点结论:
1.AZ31镁合金峰值应力随着变形温度的升高和应变速率的降低而逐渐降低,峰值应变也会逐渐减小。当温度升高到573K以上时,峰值应力明显下降,说明此时AZ31镁合金发生了明显的动态再结晶。通过对AZ31镁合金在高温变形下的流变应力分析,发现AZ31镁合金的流变应力行为用幂指数函数描述最为合适。线性回归分析得到AZ31镁合金的幂指数模型和含Z参数的幂指数函数:
2.试样的XRD分析显示AZ31镁合金在热压缩过程中,没有Mg17Al12相析出,压缩后试样的{101_0}、{112_0}晶面趋向于与试样的截面相平行。温度小于573K时,AZ31镁合金的变形组织主要为孪晶,温度升到623K时,组织才出现大量动态再结晶晶粒,呈现出典型“项链”状组织特征;当应变速率为1 s-1时,合金在变形过程中没动态再结晶的发生,应变速率为0.1 s-1时,动态再结晶晶粒开始大量在组织出现;因此在AZ31镁合金的塑性加工过程中,加工温度应该在573K以上,应变速率应小于0.1 s-1。
3.数值模拟分析结果表明:在等径角挤压过程中,试样在内拐角处的平均应力分布十分集中,这也是试样在此处容易断裂的原因,随着内圆角半径的增大试样的应力变得分散,试样的中部平均等效应变增大,这有利于晶粒的细化,但同时试样头部小应变区域也有所扩大,因此内圆角半径不宜太大,应取5mm比较合适。
In this study, the Gleeble-1500D thermal simulator was used to the isothermal compression tests of AZ31 magnesium alloy. The flow stress curve of magnesium alloy was analyzed, and then established flow stress constitutive equations of AZ31 magnesium alloy. The microstructures under different deformation were examined by XRD and optical microscope. The influences of dynamic recrystallization processes by deformation factors such as temperature, strain rate and strain was analyzed. The stress-strain curve of AZ31 magnesium alloy was gained through Gleeble-1500D simulator. The Equal Channel Angular Extrusion process of AZ31 magnesium alloys was simulated by DEFORM-3D software. The influence on ECAE by internal fillet radius was analyzed. The results are as follows:
1. The flow stress curves of AZ31 magnesium have dynamic recrystallization character under different deformation conditions. The peak stress and strain change with changing the temperature and strain rate. When the temperature rises to 573K, peak stress decreases obviously. So the hot working temperature of AZ31 magnesium alloy should be more than 573K.It is shown that the flow stress behavior of AZ31 magnesium alloy is described more exactly by power exponent model. Through regression ductility enhancement in AZ31 magnesium alloy of power exponent model and parameters of the power exponent function Z:
2. There are no Mg17Al12 precipitates in the hot compress process of AZ31 magnesium alloy by XRD analysis. The {1010} and {1120} crystal face are parallel to cross section of sample in the compression. When the temperature is below 573K, the deformed microstructure basically consists of shear bands and twins. At 623K the microstructure consists of recrystallized grains, the alloy entirely shows the typical characteristics of the necklace-shaped microstructure. When the strain rate is 1 s~(-1), there are no recrystallized grains in alloy. When the strain rate is 0.1s~(-1), the microstructure of alloy is primarily composed of recrystallized grains. So the temperature should be above 573K, the strain rate should be below 0.1s~(-1) in the plastic deforming process of AZ31magnesium alloy.
3. The results of numerical simulation show that there is mean-stress concentration in the fillet. The mean stress becomes smaller and scatter with the internal fillet radius increasing, the average effective strain becomes larger, but the middle steady deformation area becomes smaller. So the internal fillet radius should be 5mm.
1.AZ31镁合金峰值应力随着变形温度的升高和应变速率的降低而逐渐降低,峰值应变也会逐渐减小。当温度升高到573K以上时,峰值应力明显下降,说明此时AZ31镁合金发生了明显的动态再结晶。通过对AZ31镁合金在高温变形下的流变应力分析,发现AZ31镁合金的流变应力行为用幂指数函数描述最为合适。线性回归分析得到AZ31镁合金的幂指数模型和含Z参数的幂指数函数:
2.试样的XRD分析显示AZ31镁合金在热压缩过程中,没有Mg17Al12相析出,压缩后试样的{101_0}、{112_0}晶面趋向于与试样的截面相平行。温度小于573K时,AZ31镁合金的变形组织主要为孪晶,温度升到623K时,组织才出现大量动态再结晶晶粒,呈现出典型“项链”状组织特征;当应变速率为1 s-1时,合金在变形过程中没动态再结晶的发生,应变速率为0.1 s-1时,动态再结晶晶粒开始大量在组织出现;因此在AZ31镁合金的塑性加工过程中,加工温度应该在573K以上,应变速率应小于0.1 s-1。
3.数值模拟分析结果表明:在等径角挤压过程中,试样在内拐角处的平均应力分布十分集中,这也是试样在此处容易断裂的原因,随着内圆角半径的增大试样的应力变得分散,试样的中部平均等效应变增大,这有利于晶粒的细化,但同时试样头部小应变区域也有所扩大,因此内圆角半径不宜太大,应取5mm比较合适。
In this study, the Gleeble-1500D thermal simulator was used to the isothermal compression tests of AZ31 magnesium alloy. The flow stress curve of magnesium alloy was analyzed, and then established flow stress constitutive equations of AZ31 magnesium alloy. The microstructures under different deformation were examined by XRD and optical microscope. The influences of dynamic recrystallization processes by deformation factors such as temperature, strain rate and strain was analyzed. The stress-strain curve of AZ31 magnesium alloy was gained through Gleeble-1500D simulator. The Equal Channel Angular Extrusion process of AZ31 magnesium alloys was simulated by DEFORM-3D software. The influence on ECAE by internal fillet radius was analyzed. The results are as follows:
1. The flow stress curves of AZ31 magnesium have dynamic recrystallization character under different deformation conditions. The peak stress and strain change with changing the temperature and strain rate. When the temperature rises to 573K, peak stress decreases obviously. So the hot working temperature of AZ31 magnesium alloy should be more than 573K.It is shown that the flow stress behavior of AZ31 magnesium alloy is described more exactly by power exponent model. Through regression ductility enhancement in AZ31 magnesium alloy of power exponent model and parameters of the power exponent function Z:
2. There are no Mg17Al12 precipitates in the hot compress process of AZ31 magnesium alloy by XRD analysis. The {1010} and {1120} crystal face are parallel to cross section of sample in the compression. When the temperature is below 573K, the deformed microstructure basically consists of shear bands and twins. At 623K the microstructure consists of recrystallized grains, the alloy entirely shows the typical characteristics of the necklace-shaped microstructure. When the strain rate is 1 s~(-1), there are no recrystallized grains in alloy. When the strain rate is 0.1s~(-1), the microstructure of alloy is primarily composed of recrystallized grains. So the temperature should be above 573K, the strain rate should be below 0.1s~(-1) in the plastic deforming process of AZ31magnesium alloy.
3. The results of numerical simulation show that there is mean-stress concentration in the fillet. The mean stress becomes smaller and scatter with the internal fillet radius increasing, the average effective strain becomes larger, but the middle steady deformation area becomes smaller. So the internal fillet radius should be 5mm.
引文
[1]陈振华.变形镁合金[M].北京:化学工业出版社, 2005.
[2]郭强.镁合金高温单向压缩及多向变形行为研究.[D],长沙:湖南大学,2007.
[3]刘祚时等.镁合金在汽车工业中的应用[J].江西冶金.1998,18(5) :23.
[4]刘正,张奎,曾小勤著.镁基轻质合金理论基础及其应用[M].北京:机械工业出版社, 2002.
[5]丁汉林.AZ91镁合金高温变形行为的实验研究与数值模拟.[D].上海:上海交通大学.
[6]Frost H J,Ashby M F.Deformation Mechanism Maps[M].Oxford:Pergamum Press,1982.
[7]Galiyev A, Sitdikov 0, Kaibyahev R.Correlation of plastic deformation and dynamic recrystallization in magnesium alloy ZK60 [J] .Mater Trans,2003,44 :426.
[8]McQueen H J.Constitutive analysis in hot working[J].Metal Mater Trans.2002,33A:345.
[9]Takuda H,Fujimoto H,Hatta N.Modeling on flow stress of Mg-A1一Zn alloys at elevated temperature. Mater Process Technol,1998,513 :80-8l:.
[10]Takuda H,Morishita T,Kinoshita T,Shirakawa N.Effect of temperature and grain size on the dominant diffusion process for supper plastic flow in an AZ61 magnesium alloy [J]. Mater Process Technol,2005,164-165:1258.
[11] Takuda H, Finite-element analysis of the formability of a magnesium-based alloy AZ31 sheet, Journal of Materials Processing Technology, 1999, 80:135-140.
[12] Takuda H, The formability of a thin sheet of Mg-8.5Li-1Zn alloy, Journal of Materials Processing Technology, 2000 (101):281-286.
[13]赵国丹.AZ31镁合金热变形力学行为和动态再结晶的研究[D].重庆:重庆大学,2005.
[14]F Chen,Huang: J. Hot Working Characteristics of Steels in Austenitic State [J]. Mater Process Technol. 2003, 142:643-647.
[15]单智伟,刘路,钟伟珍,吴昕,柯伟等.大晶粒AZ31镁合金的超塑性行为及其演化机制[J].材料热处理学报, 2001, 9:17-20.
[16]Galiyev A,Kaibyshev R ,Sakai T. Continuous dynamic recrystallization in magnesium alloy.Materials Science Forum,2003,419-422:509-514.
[17]胡庚祥,蔡殉,戎咏华.材料科学基础[M].上海:上海交通大学出版社,2006.
[18]D Ponge, G Gottstenin.Necklace formation during dynamic recrystallization: mechanisms and impact on flow behavior [J]. Acta mater, 1998, 46(1):69-80.
[19]J.C.Tan,M.J.Tan. Dynamic continuous recrystallization characteristics in two stage deformation of Mg-3Al-1Zn alloy sheet [J]. Materials Science and Engineering, 2002, A00: 1-9.
[20]郭会光,刘建生.金属塑性加工模拟与控制[J].太原重型机械学报,1997,18:195-200.
[21]乔端,钱银根.非线性有限元及其在塑性加工中的应用[M].北京:冶金工业出版社, 1990.
[22]金子純一,菅又信,沼政弘,西川泰久,高田秀男.合金展伸材机械的性质成形性及組织影响[J].日本金属学会,2002,64: 141-147.
[23] Takuda H,Fujimoto H,Hatta N. Deformation mechanism in a coarse-grained Mg-Al-Zn alloy at elevated temperatures [J]. International Journal of Plasticity, 2001, 17:387-397.
[24]王忠堂等.镁合金管材挤压工艺及力能参数实验研究[J].沈阳工业学院学报,2001,20: 66-69.
[25]刘满平,马春江,王渠东,朱燕萍,丁文江.工业态AZ31镁合金的超塑性变形行为[J].中国有色金属学报,2002,17: 797.
[26]牛济泰.材料和热加工领域的物理模拟技术[M].北京:国防工业出版社,1999.
[27]潘崇超,凌刚,李佃国.Inconel751合金热压缩变形条件下的流变应力模型[J].塑性工程学报2005,12(2) :7-10.
[28]Segal V M. Materials processing by simple shear [J].Materials Science and Engineering 1995, A197 (2):157-164.
[29]Wang G,WU S D,Zuo L,et al. Microstructure texture grain boundaries in recrystallization region in pure Cu ECAE sample [J]. Materials Science and Engineering,2003, A346 (1-2):83-90.
[30]Sun P L,Yu C Y,Kao P W. Microstructure characteristics of ultrafine-grained aluminum produced by equal channel angular extrusion [J]. Scripta Materialia,2002,47(6) :377-381.
[31]曹剑.AZ31镁合金的超塑性研究[D].湖南大学,2005.
[32]靳丽.等通道角挤压变形镁合金微观组织与力学性能研究[D].上海交通大学,2006.
[33]Yoshinori Iwahashi,Jing tao Wang,Zenji Horita,et al. Principle of equal channel angular pressing for the processing of ultra-fine grained materials [J].Scripta Materialia, 1996,35(2):143-146.
[34]Raghavan Srinivasan R.Computer simulation of the equal channel angular extrusion (ECAE) process [J]. Script Mater, 2001, 44(1):91-96.
[35]Hu Hong-Jun,Zhang Ding Fei,Yang Ming Bo. The die structure design of equal channel angular extrusion for AZ31 magnesium alloy based on three-dimensional finite element method [J]. Materials and Design, 2009, 30:2831–2840.
[36]刘咏,唐志宏,周科朝等.纯铝等径角挤技术(Ⅱ)--变形行为模拟[J].中国有色金属学报,2003,13(1):21-26.
[37]王裕.等通道转角挤压的有限元模拟及应用[D].太原理工大学,2006.
[39] Preface to viewpoint set on: phase transformations and deformation in magnesium alloys [J].Scripta Materialia, 2003, 48: 981-984.
[40] S R Agnew, C N Tom, D W Brown,T M Holden, S C Vogel. Study of slip mechanisms in a magnesium alloy by neutron diraction and modeling [J]. Scripta Materialia , 2003, 48:1003–1008.
[41] K Máthis, Z Trojanová, P Lukác. Hardening and softening in deformed magnesium alloys [J]. Materials Science and Engineering, 2005,A324: 141-144.
[42] M H Yoo, S R Agnew, J R Morris, K M Ho. Non-basal slip systems in HCP metals andalloys: source mechanisms [J]. Materials Science and Engineering, 2001, A319–321: 87–92.
[43] Michio Kiritani. Similarity and difference between fcc, bcc and hcp metals from the viewpoint of point defect cluster formation [J]. Journal of Nuclear Materials, 2000, 276: 41-49.
[44] Hung-Kuk. Physics of plasticity [J]. Journal of Materials Processing Technology ,2000,97:19-29.
[45] Hee Y, Kim, Soon H Hong. High temperature deformation behavior and micro structural evolution of Ti-47Al-2Cr-4Nb intermetallic alloys [J]. Scripta Materialia, 1998, 38(10):1517–1523.
[2]郭强.镁合金高温单向压缩及多向变形行为研究.[D],长沙:湖南大学,2007.
[3]刘祚时等.镁合金在汽车工业中的应用[J].江西冶金.1998,18(5) :23.
[4]刘正,张奎,曾小勤著.镁基轻质合金理论基础及其应用[M].北京:机械工业出版社, 2002.
[5]丁汉林.AZ91镁合金高温变形行为的实验研究与数值模拟.[D].上海:上海交通大学.
[6]Frost H J,Ashby M F.Deformation Mechanism Maps[M].Oxford:Pergamum Press,1982.
[7]Galiyev A, Sitdikov 0, Kaibyahev R.Correlation of plastic deformation and dynamic recrystallization in magnesium alloy ZK60 [J] .Mater Trans,2003,44 :426.
[8]McQueen H J.Constitutive analysis in hot working[J].Metal Mater Trans.2002,33A:345.
[9]Takuda H,Fujimoto H,Hatta N.Modeling on flow stress of Mg-A1一Zn alloys at elevated temperature. Mater Process Technol,1998,513 :80-8l:.
[10]Takuda H,Morishita T,Kinoshita T,Shirakawa N.Effect of temperature and grain size on the dominant diffusion process for supper plastic flow in an AZ61 magnesium alloy [J]. Mater Process Technol,2005,164-165:1258.
[11] Takuda H, Finite-element analysis of the formability of a magnesium-based alloy AZ31 sheet, Journal of Materials Processing Technology, 1999, 80:135-140.
[12] Takuda H, The formability of a thin sheet of Mg-8.5Li-1Zn alloy, Journal of Materials Processing Technology, 2000 (101):281-286.
[13]赵国丹.AZ31镁合金热变形力学行为和动态再结晶的研究[D].重庆:重庆大学,2005.
[14]F Chen,Huang: J. Hot Working Characteristics of Steels in Austenitic State [J]. Mater Process Technol. 2003, 142:643-647.
[15]单智伟,刘路,钟伟珍,吴昕,柯伟等.大晶粒AZ31镁合金的超塑性行为及其演化机制[J].材料热处理学报, 2001, 9:17-20.
[16]Galiyev A,Kaibyshev R ,Sakai T. Continuous dynamic recrystallization in magnesium alloy.Materials Science Forum,2003,419-422:509-514.
[17]胡庚祥,蔡殉,戎咏华.材料科学基础[M].上海:上海交通大学出版社,2006.
[18]D Ponge, G Gottstenin.Necklace formation during dynamic recrystallization: mechanisms and impact on flow behavior [J]. Acta mater, 1998, 46(1):69-80.
[19]J.C.Tan,M.J.Tan. Dynamic continuous recrystallization characteristics in two stage deformation of Mg-3Al-1Zn alloy sheet [J]. Materials Science and Engineering, 2002, A00: 1-9.
[20]郭会光,刘建生.金属塑性加工模拟与控制[J].太原重型机械学报,1997,18:195-200.
[21]乔端,钱银根.非线性有限元及其在塑性加工中的应用[M].北京:冶金工业出版社, 1990.
[22]金子純一,菅又信,沼政弘,西川泰久,高田秀男.合金展伸材机械的性质成形性及組织影响[J].日本金属学会,2002,64: 141-147.
[23] Takuda H,Fujimoto H,Hatta N. Deformation mechanism in a coarse-grained Mg-Al-Zn alloy at elevated temperatures [J]. International Journal of Plasticity, 2001, 17:387-397.
[24]王忠堂等.镁合金管材挤压工艺及力能参数实验研究[J].沈阳工业学院学报,2001,20: 66-69.
[25]刘满平,马春江,王渠东,朱燕萍,丁文江.工业态AZ31镁合金的超塑性变形行为[J].中国有色金属学报,2002,17: 797.
[26]牛济泰.材料和热加工领域的物理模拟技术[M].北京:国防工业出版社,1999.
[27]潘崇超,凌刚,李佃国.Inconel751合金热压缩变形条件下的流变应力模型[J].塑性工程学报2005,12(2) :7-10.
[28]Segal V M. Materials processing by simple shear [J].Materials Science and Engineering 1995, A197 (2):157-164.
[29]Wang G,WU S D,Zuo L,et al. Microstructure texture grain boundaries in recrystallization region in pure Cu ECAE sample [J]. Materials Science and Engineering,2003, A346 (1-2):83-90.
[30]Sun P L,Yu C Y,Kao P W. Microstructure characteristics of ultrafine-grained aluminum produced by equal channel angular extrusion [J]. Scripta Materialia,2002,47(6) :377-381.
[31]曹剑.AZ31镁合金的超塑性研究[D].湖南大学,2005.
[32]靳丽.等通道角挤压变形镁合金微观组织与力学性能研究[D].上海交通大学,2006.
[33]Yoshinori Iwahashi,Jing tao Wang,Zenji Horita,et al. Principle of equal channel angular pressing for the processing of ultra-fine grained materials [J].Scripta Materialia, 1996,35(2):143-146.
[34]Raghavan Srinivasan R.Computer simulation of the equal channel angular extrusion (ECAE) process [J]. Script Mater, 2001, 44(1):91-96.
[35]Hu Hong-Jun,Zhang Ding Fei,Yang Ming Bo. The die structure design of equal channel angular extrusion for AZ31 magnesium alloy based on three-dimensional finite element method [J]. Materials and Design, 2009, 30:2831–2840.
[36]刘咏,唐志宏,周科朝等.纯铝等径角挤技术(Ⅱ)--变形行为模拟[J].中国有色金属学报,2003,13(1):21-26.
[37]王裕.等通道转角挤压的有限元模拟及应用[D].太原理工大学,2006.
[39] Preface to viewpoint set on: phase transformations and deformation in magnesium alloys [J].Scripta Materialia, 2003, 48: 981-984.
[40] S R Agnew, C N Tom, D W Brown,T M Holden, S C Vogel. Study of slip mechanisms in a magnesium alloy by neutron diraction and modeling [J]. Scripta Materialia , 2003, 48:1003–1008.
[41] K Máthis, Z Trojanová, P Lukác. Hardening and softening in deformed magnesium alloys [J]. Materials Science and Engineering, 2005,A324: 141-144.
[42] M H Yoo, S R Agnew, J R Morris, K M Ho. Non-basal slip systems in HCP metals andalloys: source mechanisms [J]. Materials Science and Engineering, 2001, A319–321: 87–92.
[43] Michio Kiritani. Similarity and difference between fcc, bcc and hcp metals from the viewpoint of point defect cluster formation [J]. Journal of Nuclear Materials, 2000, 276: 41-49.
[44] Hung-Kuk. Physics of plasticity [J]. Journal of Materials Processing Technology ,2000,97:19-29.
[45] Hee Y, Kim, Soon H Hong. High temperature deformation behavior and micro structural evolution of Ti-47Al-2Cr-4Nb intermetallic alloys [J]. Scripta Materialia, 1998, 38(10):1517–1523.
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