7075铝合金高温力学性能及本构方程研究

在变形温度为440、460和480℃,应变速率为0. 001、0. 01和0. 1 s~(-1)的条件下,依次沿0°、45°和90°的轧制方向,对7075铝合金板材进行热拉伸试验,研究7075铝合金的高温力学性能。结果表明:7075铝合金的力学性能受变形温度、应变速率及轧制方向的影响,7075铝合金的抗拉强度随变形温度的升高而降低,随应变速率的增大而增加,且抗拉强度的增长率比较大;抗拉强度在轧制方向为0°时最高,45°时次之,90°时最低。通过对7075铝合金热拉伸获得的试验数据进行参数拟合,建立了在不同轧制方向上的Arrhenius型本构方程。     

7075铝合金高温流变行为的研究

采用圆柱试样在Gleeble-1500热模拟机上进行高温压缩变形实验，研究了7075铝合金在高温塑性变形过程中流变应力的变化规律。实验在温度为250－500℃、应变速率为0．05－50s^-1的条件下进行。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，流变应力随变形温度升高而降低，随就变速率提高而增大，可用ZenerHollomon参数的双曲正弦形式来描述7075铝合金高温压缩变形时的流变应力行为。     

热压缩7075铝合金流变应力特征

采用Gleeble-1500热模拟高温压缩变形试验,研究了7075铝合金高温塑性变形时的流变应力行为.结果表明,应变速率和变形温度的变化影响合金稳态流变应力的大小,在变形温度为350～500℃、应变速率为0.01～1 s^-1的条件下,随变形温度升高,流变应力降低;而随应变速率提高,流变应力增大;应变速率和流变应力之间满足指数关系,温度和流变应力之间满足Arrhenius关系,可用Zener-Hollomon参数描述7075铝合金高温塑性变形时的流变应力行为.     

LC4铝合金高温变形规律的探讨

研究LC4铝合金的高温变形规律 ,拟合出具有较高精度的高温本构模型。并应用所开发的一套数值模拟软件系统 ,对LC4铝合金的高温压缩规律及压缩过程进行了分析。     

热压缩7075铝合金流变应力特征

采用Gleeble-1500热模拟高温压缩变形试验,研究了7075铝合金高温塑性变形时的流变应力行为。结果表明,应变速率和变形温度的变化影响合金稳态流变应力的大小,在变形温度为350～500℃、应变速率为0.01～1s-1的条件下,随变形温度升高,流变应力降低;而随应变速率提高,流变应力增大;应变速率和流变应力之间满足指数关系,温度和流变应力之间满足Arrhenius关系,可用Zener-Hollomon参数描述7075铝合金高温塑性变形时的流变应力行为。     

7075-T6高强铝合金温热变形本构方程及热加工图北大核心CSCD

为了获得7075高强铝合金的温热成形合理变形的工艺参数,采用Gleeble-3500热模拟试验机测试7075-T6铝合金的应力-应变曲线。研究了该合金在变形温度为150~300℃和应变速率为0.01~10 s^(-1)条件下的流变行为,并基于Arrhenius本构方程建立了0.3~0.6应变下7075-T6铝合金的热加工图,最后结合金相显微组织验证了热加工图的可靠性和实用性。结果表明:7075-T6铝合金对变形温度、应变速率、应变量具有高度敏感性,热形变激活能Q=291.151 kJ·mol^(-1);修正后的Arrhenius本构方程的拟合结果良好,相关系数r值与平均绝对误差AARE分别为99.65%和5.54%,能较好地预测7075-T6铝合金的流变行为;在应变为0.6时,最佳的温热加工安全区域范围为温度为250~300℃、应变速率为0.01~0.05 s^(-1)。     

挤压态7075铝合金高温流变行为及神经网络本构模型

采用Gleeble1500D热模拟实验机研究挤压态7075铝合金在变形温度为250～450℃、应变速率为0.01～10s-1下单道次压缩过程的高温流变行为。结果表明:材料在350℃及以下变形时,流变应力曲线呈动态回复型;在温度为350℃以上、应变速率为0.1s-1时,流变曲线局部陡降明显;当应变速率为10s-1时,流变曲线发生波动,呈动态再结晶型;挤压态7075铝合金的流变应力曲线峰值应力及稳态应力均高于铸态合金的,且在变形温度较高时,挤压态材料更易于发生动态软化。基于BP神经网络建立挤压态7075铝合金的本构关系模型,预测值与实验值对比表明:所建立的本构模型整体误差在5.35%以内,拟合度为2.48%,该模型可以用于描述7075铝合金的高温变形流变行为,为该合金热变形过程分析和有限元模拟提供基础。     

4032铝合金的高温压缩变形行为及本构方程

采用Gleeble-1500热模拟试验机对4032铝合金在变形温度370～490℃、应变速率0.02～5 s-1的条件下的流变应力进行了研究.分析了变形温度和应变速率对4032铝合金高温塑性变形应力的影响,计算出了激活能和应力指数值.建立了4032铝合金的本构方程.     

7075铝合金热压缩过程中最大损伤值的数值模拟

通过热压缩物理模拟试验得到7075铝合金的真应力-真应变数据,将其输入到Deform-2D软件中,作为材料模型,选择Cockroft&Latham模型及剪切摩擦模型,设置温度300℃,压下量60%,应变速率为0.01、0.1、1、10 s-1,摩擦系数为0.1、0.2、0.3、0.5、0.7,对试样压缩过程中的最大损伤值进行模拟。模拟分析得到了在一定条件下,7075铝合金热压缩过程中最大损伤值随压下量、摩擦系数及应变速率的变化规律。     

7075铝合金高温热变形性能的研究

采用Gleeble-3800热模拟机,沿与原材料轴线呈0°、45°、90°方向切割试样,在320、400和480℃,变形速率0.01、0.1和1/s时对7075铝合金进行试验。研究了温度、应变速率对7075铝合金热变形过程中力学性能及显微组织的影响。结果表明:在同一应变速率下,7075铝合金的流变应力和进入稳态流动时所需的应变随温度的升高而降低;在低温成形时,晶粒的形状连续而均匀;随着变形温度升高,晶粒逐渐变得粗大;在较高温度变形时,大晶粒周围有细小的等轴晶出现,发生了动态再结晶。在同一变形温度下,7075铝合金的流变应力随应变速率的增大而提高;应变速率越大,越易出现动态再结晶。     

Superplastic deformation behavior of 7075 aluminum alloy

A study has been made to investigate the effect of a prior amount of warm rolling on the superplastic forming behavior of a standard grade 7075 aluminum alloy. The thermomechanical treatment process presented for grain refinement includes furnace cooling from the solution treatment temperature to the overaging temperature, warm rolling from 65–85% deformation, recrystallization, and artificial aging treatment. Increasing the amount of warm rolling beyond 80% deformation does not produce material with higher elongation to failure when the thermomechanical treatment process presented is used. The largest value of elongation to failure was 700%, which was obtained for a specimen having a grain size of 8 μm at a strain rate of 6×10⁻³S⁻¹. The fracture surface exhibits a granular appearance indicative of an intergranular fracture mode. Dislocation activities within grains were observed, indicating the occurrence of dislocation slip during grain boundary sliding.     

7075-T6铝合金的高温成形性能和微观组织

采用等温拉伸试验,研究了温度对7075-T6铝合金板材力学性能的影响规律.通过金相观察和断口形貌分析,讨论了7075-T6铝合金板材高温拉伸变形的微观组织变化和断裂失效机制.结果表明,随温度升高,材料强度和硬度逐渐降低,断后伸长率总体上呈上升趋势,但在250℃时出现低值.温度低于200℃,应力随应变先快速增加后缓慢增加...     

Limit of structure refinement for 7075 aluminum alloy at elevated temperature by hot deformation

1　INTRODUCTIONThedeformationrefinementofmetalmicrostruc tureincludesmeaningsintwoaspects :firstly ,refinetheinitialcoarsegrainstructure ,fromscoresofmi crometertoahundredmicrometer,tofinesubgrain ;thentrytomaintainthefinedeformedsubgrainstruc tureinthefollowinghotworkingorheattreatmentprocessing .Experimentsprovethattheperformanceofcommercialalloyscanbeimprovedgreatlybyse vereplasticdeformation ,whichrefinesgrainofmet alstoseveralmicrometerorsub micrometerrange[18] .For 70 75aluminumalloy…     

7075铝合金热压缩变形流变应力

在Gleeble-1500热模拟试验机上,采用高温等温压缩试验,对7075铝合金在高温压缩变形中的流变应力行为进行了研究。结果表明,应变速率和变形温度的变化强烈地影响合金流变应力的大小,流变应力随变形温度升高而降低,随应变速率提高而增大;可用Zener-Hollomon参数的指数形式来描述7075铝合金高温压缩变莆时的流变应力行为。     

Particle cracking and rotation during plastic deformation of 7075 aluminum alloy

The utility of a novel digital image processing technique for automatic detection and separation of cracked constituent particles was applied to quantitatively characterize the microstructural damage on Fe-rich intermetallic particles that were cracked in a 7075 Al-alloy. This cracking of the Fe-rich intermetallic particles was due to a function of strain under uniaxial tension, compression, and torsion. The comparison of the data on the strained samples revealed that at tensile strain, the number fraction of the cracked Fe-rich particles was significantly higher than those at torsion while the compression strains and the average volume of the cracked Fe-rich particles increased when the strain increased. The percentage-cracked particles had a linear relationship with all of the strains for all of the loading conditions. Significant rotations of Fe-rich intermetallic particles occurred during the deformation of this alloy under torsion. These rotations tended to align themselves along the direction of applied/induced tensile stretch, which in turn affected the progression of damage due to particle cracking.     

Hot deformation behaviour of 7075 alloy

The hot deformation behaviour of Stir cast 7075 alloy was studied using processing map technique. The map has been interpreted in terms of the microstructural processes occurring in situ with deformation, based on the values of a dimensionless parameter η which is an efficiency index of energy dissipation through microstructural processes. An instability criterion has also been applied to demarcate the flow instability regions in the processing map using another parameter (ξ). Both the parameters (η and ξ) were computed from the experimental data generated by compression tests conducted at various temperatures and strain rate combinations over the hot working range (300-500 °C and 0.001-1.0 s⁻¹) of the present material. The processing map exhibits one distinct η domains without any unstable flow conditions under the investigated temperature and strain rate conditions. The dynamic recrystallization zone and instable zones, i.e. adiabatic shear band formation, interface crack, and wedge cracking, were identified in the processing map. Microstructural examination was performed for validation. The processing maps can be used to select optimum strain rates and temperatures for effective hot deformation of 7075 alloy.     

Effect of deformation temperature on microstructures and properties of 7075/6009 alloy

The 7075/6009 aluminum composite ingot with the diameter of 65 mm was prepared by double-stream-pouring continuous casting. The deformation behavior and the mechanical properties of the composite ingot compressed at 543, 573, 623, 673 and 723 K were analyzed. The results show that the gradient distributions of composition and hardness in the transition layer of the composite plates still exist after plastic deformation of the ingots. Meanwhile, the thickness of the transition layer reduces from millimeter order to micrometer order. The mechanical properties of the composite plate increase with the increase in deformation temperature from 543 K to 673 K. The best mechanical properties of the 7075/6009 aluminum composite are: σ_b=381 MPa, σ_0.2=322 MPa and δ=16.6%. The appropriate deformation temperature range is (0.75–0.85)T_M, where T_M is the melting point of 7075 alloy.