7055铝合金的非等温时效工艺

结合光学显微镜(OM)、扫描电镜(SEM)以及透射电镜(TEM)等,对非等温时效处理后7055铝合金的组织、硬度、拉伸和抗腐蚀性能进行了研究。结果表明:合金的硬度和强度在60～120℃快速增加,随后缓慢上升并于160℃达到峰值,在时效后期则呈直线下降,伸长率的变化趋势与之相反。非等温时效过程中,起始温度、终止温度及升温速率会对合金的性能有一定影响。升温时效至160℃,合金不仅能够满足T6态的力学性能要求,同时能获得较好的抗腐蚀性能。      

Sc和Zr对7075铝合金再结晶行为的影响

研究通过铸造法制备的含Al3(Sc,Zr)相的7075铝合金静态再结晶行为和再结晶行为与力学性能的关系.Sc和Zr复合添加使Sc?Zr?7075铝合金保留挤压变形过程中形成的大部分纤维组织及高密度位错,导致合金的再结晶转变量由35％降低至22％,相应的亚结构保持量由59％升高至67％.Sc和Zr有效抑制7075铝合金再...     

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。     

7055铝合金中低比例动态再结晶的模拟

研究7055铝合金在温度为390～470℃ 和应变速率为0.01～1 s-1条件下热变形和动态再结晶行为.电子背散射衍射(EBSD)表征结果表明,7055铝合金在热变形下动态再结晶含量较低,动态再结晶含量为1％～13％.为了模拟低比例动态再结晶问题,对JMAK动态再结晶模型进行修正.应用修正的模型,结合商业有限元软件D...     

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。     

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。     

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.     

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.     

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。     

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.     

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.     

Relationship between microstructure and mechanical properties of 5083 aluminum alloy thick plate

The microstructure and mechanical properties of 105 mm thick 5083 aluminum alloy hot rolled plate were investigated by metallurgical microscope, scanning electron microscope and tensile testing machine, and three major characteristic problems in mechanical properties inhomogeneity were explained. The results show that the mechanical properties of the rolled plate are inhomogeneous along the thickness direction. From the surface to the center, the strength shows an inverted “N” shape change and the elongation presents a semi “U” shape change. Several similar structural units composed of long fibrous grains (LFG) and short fibrous grains bands (SFGB) exist in a special layer (Layer 2) adjacent to the surface. This alternating layered distribution of LFG and SFGB is conducive to improving the plasticity by dispersing the plastic deformation concentrated on the boundary line (BL) between them. However, their different deformability will cause the alternation of additional stresses during the hot rolling, leading to the strength reduction. The closer the location to the center of the plate is, the more likely the recovery rather than the recrystallization occurs. This is the possible reason for the unnegligible difference in strength near the central region (Layer 4 and Layer 5).     

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%.     

Tensile behaviour of boron modified Timetal 834 titanium alloy in the intermediate temperature range 400-500 °C

The tensile behaviour of boron modified Timetal 834 titanium alloy was studied in the intermediate temperature range 400-500 °C and compared with that of the base alloy. The yield and ultimate tensile strengths of the B modified alloy were found to be higher than those of the base alloy at all the temperatures investigated. The B modified alloy also exhibited only a marginally lower elongation to failure as compared to the base alloy at all the temperatures investigated. The B modified alloy exhibited dynamic strain aging in the temperature range 400-475 °C which is similar to the observed behaviour in the base alloy.     

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。     

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。     

7055超高强铝合金的时效工艺

通过拉伸试验、TEM观察、EDS分析等手段研究了时效处理对7055超高强铝合金力学性能及微观组织的影响,并最终确定了7055铝合金合理的时效工艺。结果表明,7055铝合金的最佳单级时效工艺为120 ℃×4 h,时效后的抗拉强度达到660 MPa。TEM分析结果表明7055铝合金在120 ℃时效4 h时主要析出相为GPI区,至时效8 h时,基体内开始出现η'相与GPI区并存,随着时效时间的延长,合金中的η'相体积分数不断增加,到时效时间为24 h,合金晶内析出相基本以η'相为主。