P. Fernandez G. Gonzalez I. Alfonso I.A. Figueroa
材料科学技术（英）
Two ternary Al-2.2Zn-0.95Mg and Al-5.5Zn-2.1Mg (in wt pct) alloys, with Zn:Mg ratios close to 2.5 were produced by conventional ingot casting metallurgy. The ingots were solution heat treated at 500°C for 0.5 h and aged at 180°C for times between 0.5 and 80 h. The structural characterization was carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and Vickers microhardness measurements (HV). The study was focused on the investigation of the precipitates formation and the relationship between hardness and lattice parameter for α-Al. The results showed that there was an inverse correlation for all the experimental conditions, and the aged peaks coincided with lattice parameter minima. Significant precipitates formation only occurred for the alloy containing 5.5 wt pct Zn and 2.1 wt pct Mg, provoking an important strengthening and variations in the lattice parameter, however, this was not observed for the alloy containing 2.2 wt pct Zn and 0.95 wt pct Mg. A plausible explanation of the increment of hardness values could be the presence of a well distributed μ phase (MgZn2). At initial stages of the precipitation process, μ' was the most abundant precipitate while the phase τ was observed at overaged conditions. These results showed that the aging response of the conventionally cast Al-Zn-Mg alloys could be obtained using the lattice parameter of the α-Al matrix, even for alloy systems with low precipitates formation.
关键词:
Aluminum alloy
,
X-ray diffraction
,
Precipitation
,
Lattice parameter
,
Hardness
Hongzhi Ji
材料科学技术（英）
The relationship between microstructure evolution and coefficient of thermal expansion (CTE) of 7A09 aluinum alloy was investigated in this paper. Differential scanning calorimetry (DSC) was combined with transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) to investigate microstructure evolution taking place in 7A09 aluminum alloy during heating and cooling process. The corresponding CTE curves of the 7A09 alloy were recorded by thermal dilatometer. Results indicated that GPII zones and η' phase were main precipitates in the highest strength tempered (T6) 7A09 alloy. The η phase was the main participate in 7A09 alloy during the cooling process. The nonlinear dependency existed between CTE and temperature in both changing temperature processes. During the heating process, obvious additional contraction of alloy volume was directly caused by phase transition, such as dissolution of ´0 phase, transition from η' to η phase and dissolution of η phase. The additional contraction could slow down the increase of CTE greatly and be expressed in the nonlinearity of CTE curve. Volume and energy changes of alloy system influenced the variation trend of CTE directly, which was caused by the precipitation of ´ phase during the cooling process. These effects were revealed by the corresponding nonlinear change of CTE.
关键词:
Aluminum alloy
Jinsheng ZHANG
,
Xuhui ZHAO
材料科学技术（英）
The lap-shear strength and durability of adhesive bonded Al alloy joints with different pretreatments were studied by the lap-shear test and wedge test. The results indicate that the maximum lap-shear strength and durability of the bonding joints pretreated by different processes are influenced by the grade of abrasive papers and can be obviously improved by phosphoric acid anodizing. Alkali etching can obviously improve the durability of bonding joints although it slightly influences the maximum lap-shear strength. The process which is composed of grit-finishing, acetone degreasing, alkali etching and phosphoric acid anodizing, provides a better adhesive bonding property of Al alloy.
关键词:
Aluminum alloy
,
alloy
,
adhesive
,
bonding
,
abrasive
Hongbin GENG
,
Subbong KANG
,
Shiyu HE
材料科学技术（英）
Experiments were conducted to evaluate the grain refinement and thermal stability of ultra-fine grained Al-4Mg alloy introduced by equal-channel angular pressing (ECAP) at 473 K. The results show that the intensities of X-ray (111/222) and (200/400) peaks for the alloy processed by ECAP decrease significantly and the peak widths of half height become broadening compared with the corresponding value in the annealed alloy. The microstructure of 2 passes ECAPed alloy consists of both elongated and equiaxed subgrains. The residual strain in the alloy increases with increasing passes numbers, that appears as increasing dislocation density and lattice constant of matrix. An equiaxed ultra-fine grained structure of ~0.2μm is obtained in the present alloy after 8 passes. The ultra-fine grains are stable below 523 K, because the alloy retains extremely fine grain size of ~1μm after static annealing at 523 K for 1 h.
关键词:
Aluminum alloy
,
null
,
null
,
null
Yi FENG
,
Zhengang ZHU
,
Shisheng HU
,
Yi PAN
材料科学技术（英）
The dynamic mechanical properties of open-cell aluminum alloy foams with different relative densities and cell sizes have been investigated by compressive tests. The strain rates varied from 700 s-1 to 2600 s-1. The experimental results showed that the dynamic compressive stress-strain curves exhibited a typical three-stage behavior: elastic, plateau and densification. The dynamic compressive strength of foams is affected not only by the relative density but also by the strain rate and cell size. Aluminum alloy foams with higher relative density or smaller cell size are more sensitive to the strain rate than foams with lower relative density or larger cell size.
关键词:
Aluminum alloy
,
null
,
null
,
null
Hongzhi Ji
材料科学技术（英）
The relationship between microstructure evolution and coefficient of thermal expansion (CTE) of 7A09 aluinum alloy was investigated in this paper. Differential scanning calorimetry (DSC) was combined with transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) to investigate microstructure evolution taking place in 7A09 aluminum alloy during heating and cooling process. The corresponding CTE curves of the 7A09 alloy were recorded by thermal dilatometer. Results indicated that GPII zones and η' phase were main precipitates in the highest strength tempered (T6) 7A09 alloy. The η phase was the main participate in 7A09 alloy during the cooling process. The nonlinear dependency existed between CTE and temperature in both changing temperature processes. During the heating process, obvious additional contraction of alloy volume was directly caused by phase transition, such as dissolution of ´0 phase, transition from η' to η phase and dissolution of η phase. The additional contraction could slow down the increase of CTE greatly and be expressed in the nonlinearity of CTE curve. Volume and energy changes of alloy system influenced the variation trend of CTE directly, which was caused by the precipitation of ´ phase during the cooling process. These effects were revealed by the corresponding nonlinear change of CTE.
关键词:
Aluminum alloy
张金涛
,
杨春勇
,
潘亮
,
李春东
金属学报
采用溶胶-凝胶法, 以γ-环氧丙氧丙基三甲氧基硅烷(γ-GPTMS)和正硅酸乙酯 (TEOS)为前驱体, 在2A12铝合金表面制备了稀土铈盐(Ce(NO3)3)掺杂的有机－无机杂化膜, 研究了铈盐掺杂浓度和涂层固化温度等工艺条件. 通过极化曲线和电化学阻抗谱(EIS), 比较了掺杂与未掺杂有机－无机硅烷杂化膜、铬酸盐转化膜和RE转化膜在3.5%NaCl (质量分数)溶液中的耐腐蚀性能. 测试结果均表明, 铈盐掺杂硅烷杂化膜的极化电阻比掺杂前增大了约13倍,并显著高于铬酸盐转化膜和RE转化膜.
关键词:
铈盐
,
Organic-inorganic hybrid films
,
Aluminum alloy
Lihui LANG
,
Joachim DANCKERT
,
Karl Brian NIELSEN
材料科学技术（英）
The hydrodynamic deep drawing process enables net shape or near net shape forming of complicated sheet metal parts made from difficultly forming materials, such as aluminium or high strength steels. Based on the conventional hydrodynamic deep drawing process, a new process, hydrodynamic deep drawing process, in which radial pressure is applied to the rim of the blank, is proposed. This new process has been analysed using FEM simulations and the obtained results have been compared with the experimental results. The material used in the experiments was Al-Mg-Si alloy, and in the FEM-simulations the elastic-plastic behaviour of Al-Mg-Si alloy was modelled using Barlat's 89 yield criteria.
关键词:
Hydroforming
,
null
,
null
,
null
