7055铝合金搅拌摩擦焊工艺

利用正交试验法研究搅拌摩擦焊工艺参数对4 mm厚7055-T6铝合金对接接头力学性能和显微组织的影响。结果表明:焊接速度对接头抗拉强度影响最大,旋转速度和压入量依次减小;最优参数焊接的试样的抗拉强度为475.5 MPa,接头强度系数0.788;焊缝的显微硬度低于母材,呈"W型"分布;在正弯角约75.4°和背弯角约62.1°时出现开裂。     

工业态AZ31镁合金的超塑性变形行为

研究了工业态AZ31镁合金在温度 6 2 3～ 72 3K和应变速率 1× 10 -5～ 1× 10 -3 s-1范围内的超塑性变形行为。结果表明 ,工业态AZ31镁合金表现出良好的超塑性 ,其最高断裂延伸率达到 314%,应变速率敏感指数达 0 .4。显微组织观察和断口分析表明 ,工业态AZ31镁合金超塑变形主要由晶界滑动机制所控制 ,同时 ,动态再结晶也是合金超塑变形的一种协同机制。     

Development of a New Hot-cracking Test for Aluminium Alloys

A new hot-cracking test has been developed for aluminium alloys which allows investigations of hot-tearing to be carried out under well-controlled solidification conditions. The stress which develops in the solidifying ingot is perpendicular to the macroscopic growth direction and so columnar structures are tested normal to the growth axis of the columnar grains. A localised hot-spot must be imposed on the system if a macroscopic hot-tear is to form. Temperatures were recorded at various locations in the solidifying ingot so that the build-up of fraction solid could be monitored. The hot-cracking susceptibility of Al-Cu alloys has been investigated as a function of alloy composition and maximum susceptibility occurred in the range 0.5–2.0 wt% Cu. At a fixed composition of 6 wt% Cu, the grain structure/type was found to greatly influence cracking susceptibility as measured by this test. Hot-tears were always intergranular.     

热变形温度对7055铝合金热处理组织和力学性能的影响(英文)

采用Gleeble-1500D热模拟试验机对7055铝合金进行多道次热压缩试验,并对热压缩试样进行T6热处理。采用TEM、OM观察热压缩试样与热处理试样的组织形貌,并对热处理7055-T6试样进行拉伸试验,研究变形温度对7055铝合金多道次热压缩后组织、热处理后的显微组织与力学性能的影响。结果表明:热变形温度不仅影响多道次热压缩后试样的组织,而且显著影响该合金热处理后的组织和力学性能。在本试验条件范围内,随着温度的升高,经多道次热压缩后试样的晶粒长宽比先减小然后增加,位错密度降低,亚晶尺寸增加,热压缩过程中发生再结晶;热处理后合金中再结晶晶粒体积分数先降低后增加。再结晶体积分数越小,合金的强度越高。当温度为400°C时,再结晶体积分数最小,约为45%,并且合金的抗拉强度和伸长率达到最大值。     

Optimization of deformation parameters of dynamic recrystallization for 7055 aluminum alloy by cellular automaton

In order to simulate the microstructure evolution during hot compressive deformation, models of dynamic recrystallization (DRX) by cellular automaton (CA) method for 7055 aluminum alloy were established. The hot compression tests were conducted to obtain material constants, and models of dislocation density, nucleation rate and recrystallized grain growth were fitted by least square method. The effects of strain, strain rate, deformation temperature and initial grain size on microstructure variation were studied. The results show that the DRX plays a vital role in grain refinement in hot deformation. Large strain, high temperature and small strain rate are beneficial to grain refinement. The stable size of recrystallized grain is not concerned with initial grain size, but depends on strain rate and temperature. Kinetic characteristic of DRX process was analyzed. By comparison of simulated and experimental flow stress–strain curves and metallographs, it is found that the established CA models can accurately predict the microstructure evolution of 7055 aluminum alloy during hot compressive deformation.     

双重淬火对7055铝合金组织性能的影响

通过拉伸性能测试、晶间腐蚀和剥落腐蚀性能测试,金相显微镜、透射电子显微镜研究了双重淬火对7055铝合金组织及性能的影响.结果表明:合适的双重淬火可调控晶界和晶内析出状态,使合金时效后晶界上的析出相呈断续分布,晶内沉淀强化相均匀、弥散、细小析出,保证合金高强度的同时,提高晶间和剥落腐蚀性能.     

Fabrication and mechanical properties of high-performance aluminum alloy

High-performance Al–Cu–Mg alloy was fabricated by high-energy ball milling, sintering, and hot extrusion. The microstructure and mechanical properties of the material were preliminarily investigated. Results show that the formation of liquid phase during sintering promotes the densification of the aluminum powders. A97.1 % theoretical density is achieved in this alloy after sintering. The material shows excellent mechanical properties after extrusion and heat treatment. The ultimate tensile strength and yield strength of the extruded samples with heat treatment are 613 and 465 MPa, respectively.     

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.     

分级均匀化对7055铝合金组织和力学性能的影响

采用差热分析、X射线衍射分析、光学显微镜、扫描电镜、透射电镜和常温拉伸等方法研究分级均匀化工艺对7055铝合金显微组织、枝晶偏析、Al3Zr粒子析出行为和力学性能的影响。结果表明:合金经(468℃、24h)+(473℃、4 h)的分级均匀化处理后,消除了铸锭晶界上的非平衡凝固共晶组织;铸锭先于264℃保温最有利于获得尺寸细小、均匀弥散分布的Al3Zr粒子;在单级均匀化基础上增加473℃的短时高温均匀化,能够提高合金基体中溶质原子的固溶度,增强时效强化效果,提高综合性能。     

Effects of cerium on the microstructure and mechanical properties of AZ31 alloy

AZ31 alloy with Ce addition was studied. The influence of Ce contents on the microstructure and tensile properties of the alloy was analyzed. Ce addition results in the formation of AlzCe and the annealed microstructure is improved by the addition. There was no recrystallization of the alloy after rolling, however, it did occur after annealing. The alloy can be strengthened by adding Ce and the alloy with 1.05 wt.% Ce possessed the best synthetical properties of all the tested alloys. As rolled, σb and δof this alloy are 321 MPa and 6.9%, and as annealed, they are 259 MPa and 21.8%.     

固溶处理对高纯7055铝合金组织的影响

采用光学显微镜(OM)、扫描电镜(SEM)和X射线衍射谱仪研究了固溶处理对高纯7055铝合金组织的影响。结果表明:合金固溶时,粗大的初生AlZnMgCu相溶解缓慢,并逐渐球化;而初生AlZnMgCuFeTi相几乎不溶解。固溶温度越高(460-480℃),时间越长(0-240min),初生AlZnMgCu相溶解越多,再结晶越多,晶粒尺寸越大。再结晶主要于初始晶界上的粗大初生相上形核(PSN机制),并向弥散Al3Zr粒子少的变形晶粒内部长大。490℃固溶时,出现过烧组织,晶粒粗大。分级固溶较单级固溶可更好的控制合金组织,如460℃×120min 480℃×60min与480℃×180min相比,再结晶和晶粒尺寸小得多,但初生AlZnMgCu相溶解程度相差不大。     

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。     

含Al量对锌基合金力学性能的影响

研究了五种不同铝含量的锌基合金在100℃和200℃时的高温力学性能,并与室温力学性能进行了比较.结果表明:在室温下ZA45具有较高的力学性能; 而ZA50则具有较高的高温力学性能.     

Rheological characterization of A201 aluminum alloy

The thermodynamic characterization as well as the rheological characterization of the A201 alloy were conducted. Thermodynamic simulations (CALPHAD method) and calorimetric experiments were performed to determine the solidus and liquidus temperatures, the melting range and the sensitivity of the solid fraction at the thixoforming temperatures. The rheology of aluminium alloy A201 was examined using a high temperature Searle rheometer. The flow behaviour was analyzed with concentric cylinders of graphite to avoid chemical interactions with the liquid or semi-solid aluminium. The rotational body was grooved to prevent a phenomenon called wall slippage. Continuous cooling experiment was used to observe the shear rate effects on the flow behaviour. It can be seen that the viscosity level decreases at higher shear rates. Shear rate jump experiment was carried out to evaluate the steady state flow curve within the analyzed shear rate range from 60 s^?1 to 260 s^?1. It is found that the power law indexes are ?1.35 and ?1.49 for 35% and 45% solid fraction, respectively. Finally, some mechanical property data of as-cast and as-thixoformed A201 alloy are included indicating the potential for high strength applications.     

Cold gas dynamic spraying of a high temperature Al alloy

The present paper describes a study of the influence of cold spraying on the microstructure, heat treatment response and mechanical behavior of a high temperature 2618 aluminum alloy (Al-Cu-Mg-Fe-Ni) modified with 0.16 wt.% Sc. The microstructure of the starting powder consisted of a network of Al₂CuMg phase on the grain boundaries of the Al matrix, along with Al₉FeNi precipitates for atomized powder particles larger than 20 μm, and a cellular solidification structure for particles smaller than 20 μm. The coating after deposition was composed of the same microstructure features as observed in the feedstock powder but highly deformed. The observed overall deformation suggests the occurrence of localized adiabatic shear instability at the particle/particle boundary and adiabatic deformation softening at the powder interior during splat formation. The coating hardness was similar to the one obtained at the peak aged condition (T6). The coating aging response was influenced by the presence of Al₇FeCu₂ particles that depleted the matrix from Cu, reducing the overall hardness and overcoming the benefits of Sc addition.     

Single-aging characteristics of 7055 aluminum alloy

The microstructures and properties of 7055 aluminum alloy were studied at different single-aging for up to 48 h using hardness test, tensile test, electrical conductivity measurement, XRD and TEM microstructure analysis. The results show that at the early stage of aging, the hardness and strength of the alloy increase rapidly, the peak hardness and strength are approached after 120 ℃ aging for 4 h, then maintained at a high level for a long time. The suitable single-aging treatment of 7055 alloy is 480 ℃, 1 h solution treatment and water quenching, then aging at 120 ℃ for 24 h. Under those condition, the tensile strength, yield strength, elongation and electrical conductivity of the studied alloy are 513 MPa, 462 MPa, 9.5% and 29%（IACS）, respectively. During aging, the solid solution decomposes and precipitation occurs. At the early aging stage of 120 ℃, GP zones form and then grow up gradually with increasing ageing time. η′ phase forms after ageing for 4 h and η phase starts to occur after 24 h aging.     

Effect of chemical composition variation on microstructure and mechanical properties of a 6060 aluminum alloy

The 6XXX series aluminum alloys (Al-Mg-Si) are widely used in many different engineering and architectural applications. These alloys usually undergo a thermal treatment, which consists of a heat treatment solution and artificial aging, since the desirable mechanical properties depend on the microstructural state of the material. The recycling of materials has been increasing recently for economic and ecologic reasons. By using scrap was raw material, important reductions in energy and total costs can be achieved, and, at the same time, negative environmental impacts can be greatly reduced. In the present work, the possibility of using a larger amount of scrap as raw material in the production of an AA 6060 alloy is evaluated by analyzing the difference in microstructure and mechanical properties between a commercial 6060 alloy and a variation with higher Fe and lower Si contents that was specially produced for this study. Both materials were placed into a heat treatment solution at 560 °C for 1 h, and then underwent water quenching followed by artificial aging at 180 °C for different periods of time. Hardness and tension tests were used to evaluate the mechanical properties. Light and transmission electron microscopy have been used to determine important features such as grain size before and after being placed into the heat treatment solution, and the characteristics of the second-phase particles in the two materials. This study leads to the conclusion that a higher amount of scrap material can be used in the production of 6060 Al alloy without significant changes in mechanical properties compared with the more usual compositions.     

低温环境下2519A铝合金动态力学性能及组织演化

为研究低温下动态冲击对2519A铝合金流变应力和组织演化的影响,在低温下利用霍普金森压杆对2519A-T87态铝合金进行应变速率为1000~4200 s-1的动态冲击压缩实验,同时运用光学显微镜与透射电镜,对低温下的冲击微观组织进行观察和分析。结果表明:在低温环境下,绝热剪切带中心区域为亚晶组织,再结晶程度较低;同时,在形变带内出现长度较短、连续性较差的微裂纹,裂纹末端向基体扩展。随着冲击温度的降低,材料的屈服抗力迅速增加,出现绝热剪切带的临界应变速率随之降低。在中高应变速率下,长条状弥散相粒子发生不同程度的脆性断裂,从而引起流变应力的迅速提高。