Al-Zn-Mg-Cu-Zr铝合金的高温热压缩变形行为(英文)

在温度为300-450°C和应变速率为0.01-10s-1的变形条件下,对Al-Zn-Mg-Cu-Zr合金(7056和7150铝合金)进行热压缩实验。结果表明:在一定的应变峰值出现后,流动应力随应变增加单调下降,呈现出流动软化。峰值应力取决于温度补偿应变速率Z的大小,可用包含Zener-Hollomon参数的双曲正弦关系来描述合金热流变行为。7056合金的变形激活能为244.64kJ/mol,而7150合金的为229.75kJ/mol;在同样的变形条件下,前者的峰值应力却低于后者。在高Z值条件下,在延长晶粒的亚晶粒中存在大量析出物;而在低Z值条件下,再结晶化的晶粒内出现完整的亚晶。7150合金中存在细小亚晶和大量析出物,由于亚结构强化和析出硬化造成其峰值应力比7056合金高。     

The multiscale modeling of plastic deformation in metallic nanolayered composites

Metallic nanolayered composites exhibit very high flow strength and stable plastic flow to large strains. The explanation of the unusual mechanical behavior of these materials in terms of the atomic structures of the interfaces and layer thickness ranging from nanometers to micrometers requires atomistic simulations, dislocation theory, and crystal plasticity modeling across length scales.     

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…     

7150铝合金高温热压缩变形流变应力行为

在Gleeble-1500热模拟机上对7150铝合金进行高温热压缩实验,研究该合金在变形温度为300~450 ℃和应变速率为0.01～10 s~(-1) 条件下的流变应力行为.结果表明:流变应力在变形初期随着应变的增加而增大,出现峰值后逐渐趋于平稳;峰值应力随着温度的升高而减小,随着应变速率的增大而增大;可用包含Zener-Hollomon参数的Arrhenius双曲正弦关系来描述合金的热流变行为,其变形激活能为226.698 8 kJ/mol;随着温度的升高和应变速率的降低,合金中拉长的晶粒发生粗化,亚晶尺寸增大,再结晶晶粒在晶界交叉处出现并且晶粒数量逐渐增加;合金热压缩变形的主要软化机制由动态回复逐步转变为动态再结晶.     

耐热铝合金(FVS0812)板材温拉伸本构方程

通过在523K~723K的温度范围内和应变速率为0.001s-1~0.1s-1下对耐热铝合金(FVS0812)板进行温拉伸实验,研究耐热铝合金板温拉伸性能,以及该合金在升温条件下流变应力与变形温度、应变速率之间的关系,并使用改进了的Fields and Backofen方程建立FVS0812合金在温拉伸时应力-应变本构模型。     

喷射沉积7075A1／SICp铝基复合材料板材的高温拉伸变形行为

当温度为300-450℃，应变速率为0．001-0.1S^-1时，在WDW-E200拉伸机上采用单向拉伸实验研究喷射沉积7075A1／SIC。复合材料板材的高温变形行为；分析板材的变形激活能以及流变应力、变形温度和应变速率之间的关系。结果表明：随着变形温度升高和应变速率降低，7075AI／SiCp复合材料板材拉伸流变应力减小；其最大拉伸断裂伸长率由5．03％增加到71．07％；7075A1／SICp复合材料板材应变速率敏感系数的最大值仅为0．22，在温度为623、673和723K时其变形激活能分别为380．49、323．42和434．S6kJ／mol，均高于铝的晶格自扩散激活能（142kJ／mol）。     

喷射沉积7075Al/SiCp铝基复合材料板材的高温拉伸变形行为

当温度为300～450℃,应变速率为0.001～0.1 s-1时,在WDW-E200拉伸机上采用单向拉伸实验研究喷射沉积7075Al/SiCp复合材料板材的高温变形行为;分析板材的变形激活能以及流变应力、变形温度和应变速率之间的关系.结果表明:随着变形温度升高和应变速率降低,7075Al/SiCp复合材料板材拉伸流变应力减小;其最大拉伸断裂伸长率由5.03%增加到71.07%;7075Al/SiCp复合材料板材应变速率敏感系数的最大值仅为0.22,在温度为623、673和723 K时其变形激活能分别为380.49、323.42和434.56 kJ/mol,均高于铝的晶格自扩散激活能(142 kJ/mol).     

考虑几何必需位错非均匀分布的双相钢细观力学行为模拟

铁素体(F)-马氏体(M)双相钢在生产过程中由马氏体相变造成的铁素体内部的几何必需位错(GND)会保留在最终的材料组织中,而由GND非均匀分布导致的材料局部硬化效应使得铁素体晶粒内部的性能分布同样呈现非均匀特性.为了量化GND局部硬化效应对双相钢力学性能的影响,本文通过电子背散射衍射(EBSD)实验测定与数据分析确定了...     

Flow characteristics and constitutive modeling for elevated temperature deformation of a high Nb containing TiAl alloy

The hot deformation behavior of a high Nb containing TiAl alloy with a nominal composition of Ti–42Al–8Nb–(W, B, Y) was investigated at temperatures ranging from 1000 °C to 1150 °C and strain rates from 10⁻³ s⁻¹ to 0.5 s⁻¹ on a Gleeble thermo-simulation machine. The work hardening regime and flow softening behavior of the alloy were analyzed in detail. The results revealed that the onset of dynamic recrystallization (DRX) was quite easy for the present alloy, whereas the dynamic recovery (DRV) was impeded during the hot deformation. The DRX kinetics was studied by Avrami-type equation. The low Avrami exponents of the proposed equation indicate a lower recrystallization rate compared to ordinary metals and alloys. Based on the classical hyperbolic-sine law and the kinematics of DRX, the constitutive equations of the work hardening-recovery period (i.e. flow stress before the peak) and flow softening process (i.e. flow curve after the peak stress) were established for the present alloy, respectively. Comparisons between the experimental and calculated results revealed that except the severely cracked specimens, the stress–strain curves predicted by the established model are in good agreement with experimental results.     

Microstructure-based modeling of the ageing effect on the deformation behavior of the eutectic micro-constituent in SnAgCu lead-free solder

The eutectic micro-constituent in SnAgCu solder governs the deformation behavior of the joint as it shows better deformation resistance than the Sn dendrites and occupies a high volume percentage of the whole solder. The main scope of this study is to develop a three-dimensional (3-D) homogenization model taking into account the microstructural evolution in the eutectic micro-constituent of SnAgCu solder in order to simulate the change in mechanical behavior of the joint caused by isothermal ageing. For this purpose, 3-D configurations of Ag₃Sn and Cu₆Sn₅ intermetallic compounds (IMCs) in near-eutectic SnAgCu solder are visualized in the as-soldered condition and after ageing by focused ion beam/scanning electron microscopy tomography. The tomographic images are used to generate feature-preserving finite element meshes of the actual microstructures. The representative volume element size and constitutive behavior of the eutectic mixture in the two conditions are determined by a numerical homogenization procedure. The results show a considerable reduction in the yield stress level of the eutectic micro-constituent after ageing of the solder joint. It is shown that the increase in the inter-particle spacing and decrease in the aspect ratio of IMCs due to ageing cause a significant change in the strain distribution in the tin matrix, which leads to a lower contribution of IMCs in load-sharing and yield strength of aged solder. The elastic–plastic properties of as-soldered and aged eutectic mixtures are determined by nanoindentation. The results of homogenization are validated through comparison with experimental results and prediction of the dislocation detachment theory.     

Modeling the recrystallization textures of aluminum alloys after hot deformation

The recrystallization textures of aluminum alloys can be explained by a growth selection of grains with an approximate 40° 〈111〉 orientation relationship out of a limited spectrum of preferentially formed nucleus orientations. Accordingly, recrystallization textures can be modeled by the multiplication of a function f(g)^nucl describing the probability of nucleation of the various orientations with a function f(g)^grow representing their growth probability. Whereas the growth probability can be accounted for by a 40° 〈111〉 transformation of the rolling texture, the nucleation probability of the respective grains is given by the distribution of potential nucleus orientations, which is known from local texture analysis of rolled aluminum alloys to be cube bands, grain boundaries, and second-phase particles. The contributions of these nucleation sites are determined according to an approach to calculate the number of nuclei forming at each site, which is based on microstructural investigations of the evolution of the various nucleation sites during deformation. This article describes the model for recrystallization texture simulation in aluminum alloys and gives examples of recrystallization textures of AA3004 deformed in plane-strain compression at different deformation temperatures and strain rates. O. Engler earned his Ph.D. in physical metallurgy at the University of Technology at Aachen, Germany, in 1990. He is currently a long-term visiting staff member at Los Alamos National Laboratory. Dr. Engler is a member of TMS. H.E. Vatne earned his Ph.D. in physical metallurgy at the Norwegian Institute for Science and Technology, Trondheim, in 1995. He is currently a research scientist at Hydro Aluminum.     

Upper bound analysis of deformation and dynamic ageing behavior in elevated temperature equal channel angular pressing of Al-Mg-Si alloys

In the present study, the plastic deformation and dynamic strain ageing behavior of Al-6082 (Al-Mg-Si) alloy treated with elevated temperature equal channel angular pressing (ECAP) were investigated using upper bound analyses. Tensile tests were carried out over wide ranges of temperature and strain rate in order to evaluate the dynamic ageing conditions. ECAP processing was then experimentally performed at temperatures from room temperature up to 200 °C under various strain rates ranging between 10⁻⁴s⁻¹ and 10⁻¹s⁻¹. The upper bound analysis solutions and the experimental results are comparable. A theoretical dynamic ageing region was found to be in the temperature range of 90 °C to 260 °C, which is in agreement with the experimental observations in the temperature range of 75 °C to 175 °C.     

奥氏体不锈钢高温拉伸过程中的不均匀变形

材料高温变形过程中会发生不均匀变形,甚至产生缺陷。通过高温拉伸卸载实验,分析304奥氏体不锈钢在变形温度为1150℃时不同卸载应变量下试样的表面形态。实验表明,随着应变量的增大,表面粗糙度逐渐增大。从试样宏观上看,当应变量较小时,尽管试样局部有明显的不均匀性,但仍保持着几何上的均匀性;当应变量较大时,演变为竹节形。在此基础上,提出高温拉伸过程的不均匀变形机制,即在拉伸变形初期形成一个变形集中区域,且不断的转移,从而形成试样轮廓上的凹陷,当应变较大时,变形会集中在某个区域内引起断裂。分析认为,奥氏体不锈钢在高温变形条件下,一旦出现应变集中区域,由于较高的应变速率强化性能,使应变集中区域变形抗力增大,阻止了该区域截面积的进一步减小,使应变集中区域发生转移。     

Corrosion resistance of dilute CuMg alloys at elevated temperature

In comparison with CuAl (Al: 0.2 and 0.5 wt.%) alloys, corrosion resistance (CR) of CuMg (Mg: 0.12 and 0.34 wt.%) alloys was studied at 673-1173 K in atmospheric O₂. All the samples were pre-annealed at 873 K in atmospheric H₂. The CR of CuMg alloys at 673-973 K is improved in contrast to a pure Cu but much poorer than that of CuAl alloys, while the improvement can hardly be observed for CuMg alloys at and above 1073 K, which is similar to CuAl alloys. The poorer CR of CuMg alloys compared with that of CuAl alloys at 673-973 K is largely attributed to the incorporation of Cu in the MgO surface layer and the low Pilling-Bedworth ratio of CuMg-O system smaller than unity, and the vanishing of CR for CuMg alloys at and above 1073 K is ascribed to the instability of the MgO layer at the Cu₂O/CuMg interface.     

Healing behavior of preexisting hydrogen micropores in aluminum alloys during plastic deformation

Synchrotron X-ray microtomography was used to observe the shrinkage and annihilation behaviors of hydrogen micropores in three dimensions during hot and cold plastic deformation of an Al–Mg alloy. Whether complete healing of micropores is achieved after plastic deformation was examined by exposing the material to a high temperature after plastic deformation. Although micropores generally show a pattern of shrinking and closing, closer inspection of a single specimen revealed a variety of geometrically variable behaviors. It is noteworthy that some of the micropores are reinitiated in positions identical to those before their annihilation, even after an 8–22% macroscopic strain has been further applied after annihilation. We attribute local variations such as these to significant local strain variation, which we measured in a series of tomographic volumes by tracking the microstructural features.     

一种新型水平连铸Al-Mn-Si-X合金热压缩变形流变应力

采用圆柱体在Gleeble-1500热模拟机上进行热压缩实验,对一种新型水平连铸Al-Mn-Si-X合金热变形流变应力行为进行研究,变形温度为350℃~500℃,应变速率为0.01s-1~10s-1。结果表明,流变应力先随应变的增大而增大,达到峰值后则逐渐减小并趋于平稳,表现出流变软化特征;而应力峰值是随着温度的升高而减小,随应变速率的增大而增大。应用包含Zener-Hollomon参数的Arrhenius双曲正弦关系描述合金热压缩变形流变应力,其变形激活能Q=159.2kJ/mol。