基于加工图的7085铝合金热成形性能研究

针对7085铝合金航空构件的热加工工艺问题,对7085铝合金在300～450℃和0.0001～1 s-1条件下进行等温压缩实验,建立了7085铝合金热加工图并且分析了7085铝合金热成形性.结果表明:温度340～450℃、应变速率0.0001～1s-1为加工安全区;失稳区域为温度300～340℃、应变速率0.01～1 s-1,在此区域加工时,形成绝热剪切带且带内组织为剧烈拉长晶粒;潜在危险加工区域为温度300～340℃、应变速率0.0001～0.01 s-1;建议在温度340～410℃、应变速率0.0004～1 s-1选择工艺参数.     

5A90铝锂合金热态下本构关系研究

进行了5A90铝锂合金在200℃~450℃温度范围和0.3×10-3s-1~0.2×10-1s-1应变速率范围内的单向拉伸试验。结果表明,5A90铝锂合金的流动应力随变形温度的升高而减小,随应变速率的增大而增大;而其最大延伸率的变化趋势与流动应力的相反;最佳的成形温度范围在400℃左右。通过试验数据的计算及拟合,得到了任意温度下5A90铝锂合金应力-应变-应变速率关系的本构方程。     

Hot Deformation Behavior and Processing Maps of 2099 Al-Li Alloy

Hot deformation behavior and processing maps of the 2099 Al-Li alloy are investigated by tensile test at the temperature range from 250 to 450 °C and the strain rate range from 0.001 to 5.0 s^?1. The typical true stress-true strain curves show that the flow stress increases with increasing the strain rate and decreasing the deforming temperature. All curves exhibit rapid work hardening at an initial stage of strain followed by remarkable dynamic softening. Based on the flow stress behavior, the processing maps are calculated and analyzed according to the dynamic materials model (DMM). The processing maps exhibit an instability domain in the temperature and strain rate ranges: T = 250-260 °C and \(\dot{\upvarepsilon }\)  = 0.1-0.5 s^?1. The maps also exhibit an optimum hot working condition in the stability domain that occurs in the temperature of 400 °C for a strain rate of 0.001 s^?1 and having a maximum efficiency of 60%. The microstructural examinations exhibit the occurrence of dynamic recovery (DRV) during hot deformation of the 2099 alloy which is the dominant softening mechanism in the alloy. The fracture behavior changes from a brittle fracture to a ductile fracture as strain rate decreases and temperature increases.     

铸态Zn-Al合金高温拉伸变形行为

在SINTECH20/G拉伸试验机上对Zn-Al10-Cu2锌合金进行等温拉伸实验,研究该合金在变形温度为210℃~300℃、应变速率为0.001s-1~0.1s-1条件下的变形行为和拉伸力学性能。结果表明,峰值应力随温度升高而降低,随应变速率的提高而增大。通过线性回归分析,得出流变应力σ解析表达式,其中A、α和n值分别为6.63×1012s-1、0.0108MPa-1和4.81,其热变形激活能Q=150.127kJ/mol。该合金在温度为300℃、应变速率为0.001s-1时,出现超塑性趋势。     

基于应变补偿和修正项的新型铝锂合金温热变形本构模型

采用UTM5000电子万能拉伸试验机,在变形温度573~648K和应变速率0.001~0.1s-1条件下对2060-T8铝锂合金进行等温恒应变速率拉伸试验,得到其在变形过程中的真应力-真应变曲线,建立了基于应变补偿和修正项的温热变形本构方程。通过扫描电子显微镜(SEM)分析拉伸断口,对2060-T8铝锂合金的温热变形行为进行研究。结果表明：2060-T8铝锂合金对变形温度和应变速率具有较高的敏感性,流变应力曲线呈现出应变硬化和流变软化的特征,随着变形温度的升高和应变速率的降低,稳态流变特征逐渐消失,其在温热变形条件下的断裂形式为韧性断裂。修正的本构模型与实验值吻合度较高,可以为2060-T8铝锂合金温热变形的有限元模拟提供前提条件。     

2099合金热变形加工图研究

采用Gleeble-1500热模拟试验机对2099合金进行等温热压缩试验,研究了基于动态材料模型的加工图,分析了该合金在变形温度为300~500℃,应变速率为0.001~10 s-1范围内安全区和失稳区的组织特征,并对其热加工工艺进行优化。结果表明,2099合金的加工失稳区主要位于300~420℃,0.001~0.02 s-1和300~500℃,0.562~10 s-1范围内。失稳区组织出现了局部流变、局部剪切、局部流变+局部剪切等特征;安全区组织以动态回复、动态回复+动态再结晶为主要特征。合金热加工工艺优化为:真应变<1.1时,工艺参数为380~420℃,0.025~1 s-1;真应变>3.4时,工艺参数为420~500℃,0.001~0.562 s-1。     

考虑应变因素的2099合金高温流变行为模型

采用等温热压缩试验研究2099合金在变形温度300～500℃、应变速率0．001～10s-1条件下的热变形行为。为了准确地表征流变行为,采用摩擦与温度修正后的实验数据构建本构模型。结果表明,温度和应变速率对合金热变形行为的影响可用包含Arrhenius关系的z参数来表征。此外,通过计算不同应变量下的材料常数（a、n、Q和A）考虑了应变对本构模型的影响。利用统计分析对比了由本构模型获得的预测曲线与试验修正曲线,二者显示了很好的吻合,这表明所构建的本构模型能够很好地预测2099合金的热变形流变行为。     

2024A铝合金高温流变行为及本构关系研究

采用Gleeble-3500热模拟试验机对2024A铝合金进行等温热轧,对其高温流变行为进行了研究。通过试验获得2024A铝合金在温度为300~450℃、应变速率为0.01~10s-1时的真应力-真应变曲线。结果表明,2024A铝合金的流变应力与温度、应变速率和变形量之间呈非线性关系,流变应力随着应变速率增大而升高,随着变形温度的升高而降低。基于试验数据,分别建立考虑应变补偿的Arrhenius和修正的Johnson-Cook(M-JC)本构模型,引入统计学方法对模型精度进行量化评估:Arrhenius模型的平均相对误差和均方根误差分别为5.02%和5.88MPa,M-JC模型的平均相对误差和均方根误差分别为3.72%和5.27MPa,可见M-JC模型预测精度优于Arrhenius模型,说明M-JC模型能更为准确地描述2024A铝合金的高温轧制过程中的流变行为。     

Modeling Constitutive Relationship of Ti-555211 Alloy by Artificial Neural Network during High-Temperature Deformation

利用Gleeble-3800热模拟实验机,在应变速率0.001~1 s-1以及变形温度750~950 ℃范围内对Ti-555211合金进行等温恒应变速率压缩实验。基于人工神经网络的方法建立了Ti-555211合金热变形本构模型。模型的可靠性用平均相对误差和相关系数来确定。结果表明,所建立的本构模型与实验值的平均相对误差为1.60%,相关系数为0.99938,表明该模型能很好地预测该合金的本构关系。用神经网络来确定本构关系比传统的数学方程更加具有优势。热模拟实验结果表明,随着变形温度的升高和应变速率的减小,该材料的峰值应力有所减小,不连续屈服现象随着变形温度升高和应变速率的增大变得更加明显。流变曲线在不同的变形参数条件下表现形式也不同。     

AZ80镁合金热变形流变应力研究

在应变速率为0.001s-1～10s-1,变形温度为200℃～400℃条件下,在Gleeble-3800热模拟机上对AZ80合金的流变应力进行了研究。结果表明,AZ80合金的流变应力强烈地受变形温度的影响,当变形温度低于300℃时,其峰值流变应力呈现幂指数关系;当变形温度高于300℃时,其峰值流变应力呈现指数关系。在该文实验条件下,AZ80合金热变形应力指数n=8.43,热变形激活能Q=165.83kJ/mol。     

5A90铝锂合金Nd:YAG激光焊缝组织的晶粒形态与晶粒取向

采用Gleeble-1500D热模拟试验机进行热压缩实验,研究了TC4-DT钛合金在温度850～980℃、应变速率为0.001～10 s-1、变形量为50％条件下的热变形行为.根据应力-应变曲线分析了该合金的流变应力变化特点,建立了该合金的Arrhenius型本构方程及加工图.结果表明:流变应力随变形温度降低及应变速率增大而升高;变形温度与应变速率对TC4-DT合金应力影响显著;本实验测得的平均激活能为587.2 kJ/mol;该合金合适的加工条件为ε＜0.6 s-1,温度大于850℃.     

S34MnV钢的高温压缩变形行为实验

针对大型船用曲轴曲拐所用材料S34Mn V合金钢,利用Gleeble-3800热模拟实验机对其进行高温压缩实验,研究了S34Mn V合金钢在变形温度为950~1250℃、应变速率为0.001~10 s-1和压缩变形量为70%条件下的高温变形行为,得到了其真实应力-应变曲线。分析了变形温度、应变速率对S34Mn V合金钢高温流变行为的影响。结果表明,变形温度和应变速率对流动应力影响显著,流动应力随变形温度升高而下降,随应变速率增大而上升;低的应变速率、高的变形温度,更易于动态再结晶的发生,有利于降低流动应力。     

AM80-xSr-yCa镁合金高温压缩变形行为

采用Gleeble-1500热模拟实验机对一种新型AM80-xSr-yCa镁合金进行高温压缩变形实验,研究其在温度300℃~450℃、应变速率0.01s-1~10s-1条件下的流变行为。高应变速率下,试样的变形热带来的温升不可忽略,对真应力-真应变的测量值进行相应修正后,求得了本构方程中的系列常量。结果表明,应变速率和变形温度的变化,强烈影响着合金流变应力的大小,流变应力值随变形温度的降低和应变速率的提高而增大;金相组织观察表明,动态再结晶是该实验条件下晶粒细化和材料软化的主要机制,再结晶的程度主要受变形参数影响。变形温度越高,变形量越大,动态再结晶进行的越充分;应变速率越大,再结晶平均晶粒尺寸就越小。     

Mg-5Y-0.5Ce-0.5Zr合金的热压缩行为

在变形温度为300～450 oC、应变速率为0.01～1 s-1的条件下进行热压缩试验,对Mg-5Y-0.5Ce-0.5Zr镁合金的热变形行为进行了研究。结果表明,在热压缩变形过程中,该合金的流变应力随着变形温度和应变速率的变化而变化。在同一应变速率下,流变应力随着变形温度的增高而降低;在同一变形温度下,流变应力随着应变速率的减小而减小。该合金热压缩流变应力的本构方程可采用双曲正弦形式构建,热变形激活能Q为253 kJ/mol。     

Hot deformation behaviors of Fe-microalloyed Ti-6Al-4V based on experiments and calculations

Our previous results have shown that comprehensive mechanical properties of titanium alloys can be effectively improved by addition of Fe[1]. We systematically investigate hot deformation behaviors of Ti-6Al-4V-0.35Fe in this study, which is significant to improve plastic deformation ability of titanium alloys. In experiment, we use a Gleeble 3800 thermo-mechanical simulator to obtain the relationship between thermomechanical parameters and flow stress in a range of temperatures (800-950 &amp;amp;#176;C) and strain rates (0.001-10 s-1). The single-peak profiles of the flow curves indicate that dynamic recrystallization (DRX) mechanism dominates the deformation. TEM analysis indicate that the grain size in DRX changes under different deformation temperatures, and finer grains are formed at relatively lower temperature due to the dynamic globularization. The dislocation walls are formed in subgrain boundaries due to dislocation slipping-climbing. The Avrami-type DRX model and the strain compensated multivariable regression model have been applied to fit the experimental stress-strain data during hot deformation. A comparative study between these two types of constitutive models is conducted to represent the flow behavior. It is found that both models have good accuracy in predicting the flow stress of Ti-6Al-4V-0.35Fe alloy. A processing map based on dynamic material model (DMM) at the strain of 0.8 (steady-state flow stage) has been established to identify the flow instability regions and stability regions. The strain rate range of stability region is 0.001-0.6s-1 which has been expanded compared to the range of 0.0003-0.1s-1 of Ti-6Al-4V. Optimal hot working parameters are confirmed to be 920-950 &amp;amp;#176;C and 0.001-0.005 s-1, and nearly complete DRX has taken place. Our results indicate that hot working property of Fe-microalloyed Ti-6Al-4V is better than that of Ti-6Al-4V alloy in 800-950 &amp;amp;#176;C temperature scale, and processing cost has been decreased.     

ZK31-1.5Y镁合金热变形行为及加工图

研究了ZK31-1.5Y镁合金在变形温度为250~450℃、应变速率为0.001~1 s-1条件下的热压缩变形特性,基于动态材料模型建立了热加工图,并结合真应力-真应变曲线确定了该合金在实验条件下的热变形机制及最佳工艺参数。结果表明:ZK31-1.5Y合金的真应力-真应变曲线主要以动态再结晶和动态回复软化机制为特征,峰值应力和稳态应力随变形温度的降低或应变速率的升高显著增加。合金功率耗散图和失稳图中分别包含了3个效率峰值区和1个马鞍形流变失稳区,峰区效率范围为38%~65%,叠加后形成的加工图给出了实验参数范围内热变形时的最优工艺参数,其热变形温度为350~450℃、应变速率为0.1~1 s-1。当应变量由0.1~0.6逐渐增大时对加工图分布规律影响不大。     

高温变形条件下5A02铝合金的塑性成形性能

随着工业技术的发展和能源问题的突出,铝合金以其质量轻、耐腐蚀性能好、成形性能和加工性能良好等优势成为轻型化首选的材料类型之一。以5A02铝合金冷轧板材为研究对象,通过单向拉伸试验和金相试验对不同变形温度、应变速率条件下5A02铝合金的塑性性能进行分析,并且借助试验数据和Zener-Hollomo参数模型,对高温条件下5A02铝合金的本构模型进行研究。研究结果表明：5A02铝合金在高温条件下变形时,应变速率和变形温度对延伸率的影响很大。在应变速率为0.01s-1、0.001 s-1、0.0005 s-1和0.0001 s-1条件下,当变形温度大于250℃时,5A02铝合金的延伸率大于100%。当变形温度为150℃~250℃时,5A02铝合金的真实应力-应变曲线属于动态回复型,而当变形温度大于250℃时,流变应力曲线存在明显的软化现象。     

基于本构方程和热加工图的Al-xMg-2.8Zn合金的热变形行为研究

通过热压缩模拟试验研究了Al-xMg-2.8Zn合金在变形温度为300~490 ℃、应变速率为0.001~5 s^-1条件下的热变形行为。修正了应变-应力曲线中由于变形热引起的流动软化现象后,利用Arrhenius本构方程和热加工图预测并分析了Al-xMg-8Zn合金的热变形行为。结果表明,随着Mg含量的增加,应变速率的升高,或者变形温度的降低,流变应力随之增大。结合热加工图和微观组织观察,确定了合金的最佳热加工参数范围。通过对比发现,随着Mg含量的增加,最佳热变形温度和应变速率范围均变大,变形失稳区域向高温和低应变速率区域扩展。     

Flow curve correction and processing map of 2050 Al–Li alloy

Hot compression tests of 2050 Al–Li alloy were performed in the deformation temperature range of 340–500 °C and strain rate range of 0.001–10 s^–1 to investigate the hot deformation behavior of the alloy. The effects of friction and temperature difference on flow stress were analyzed and the flow curves were corrected. Based on the dynamic material model, processing map at a strain of 0.5 was established. The grain structure of the compressed samples was observed using optical microscopy. The results show that friction and temperature variation during the hot compression have significant influences on flow stress. The optimum processing domains are in the temperature range from 370 to 430 °C with the strain rate range from 0.01 to 0.001 s^–1, and in the temperature range from 440 to 500 °C with the strain rate range from 0.3 to 0.01 s^–1; the flow instable region is located at high strain rates (3–10 s^–1) in the entire temperature range. Dynamic recovery (DRV) and dynamic recrystallization (DRX) are the main deformation mechanisms of the 2050 alloy in the stable domains, whereas the alloy exhibits flow localization in the instable region.     

晶粒度对690合金热变形特性的影响

利用物理模拟实验方法对具有不同晶粒尺寸的690合金试样进行热压缩变形实验,变形温度范围为1100～1200℃,应变速率分别为0.1,1,10s-1,获得了合金的流变应力数据,并对合金变形后的组织特征进行了分析,建立了包含初始晶粒度参数的本构关系模型。结果表明:晶粒尺寸增大使690合金高温变形时的流变应力增加,发生动态再结晶的临界应变增大,动态再结晶体积分数减小,根据所建立的流变应力本构模型计算出的流变应力值与实验值相近,从而完善了690合金的热变形本构方程。