H.S. Liu B. Zhang G.P. Zhang
材料科学技术（英文）
Al/Mg alloy multilayered composites were produced successfully at the lower temperature (280°C) by accumulative roll bonding (ARB) processing technique. The microstructures of Al and Mg alloy layers were characterized by scanning electron microscopy and transmission electron microscopy. Vickers hardness and three-point bending tests were conducted to investigate mechanical properties of the composites. It is found that Vickers hardness, bending strength and stiffness modulus of the Al/Mg alloy multilayered composite increase with increasing the ARB pass. Delamination and crack propagation along the interface are the two main failure modes of the multilayered composite subjected to bending load. Strengthening and fracture mechanisms of the composite are analyzed.
关键词:
Accumulative roll bonding (ARB)
,
Al/Mg alloy multilayered composite
,
Ultra-fine grains
,
Hardness
,
Bending properties
H.S. Liu B. Zhang G.P. Zhang
材料科学技术（英文）
Al/Mg alloy multilayered composites were produced successfully at the lower temperature (280°C) by accumulative roll bonding (ARB) processing technique. The microstructures of Al and Mg alloy layers were characterized by scanning electron microscopy and transmission electron microscopy. Vickers hardness and three-point bending tests were conducted to investigate mechanical properties of the composites. It is found that Vickers hardness, bending strength and stiffness modulus of the Al/Mg alloy multilayered composite increase with increasing the ARB pass. Delamination and crack propagation along the interface are the two main failure modes of the multilayered composite subjected to bending load. Strengthening and fracture mechanisms of the composite are analyzed.
关键词:
Accumulative roll bonding (ARB)
,
Al/Mg alloy multilayered composite
,
Ultra-fine grains
,
Hardness
,
Bending properties
陈光华
,
吴现成
,
贺德衍
无机材料学报
采用射频等离子体增强化学气相沉积（ＣＶＤ）＋负偏压热丝辅助方法直接在Ｓｉ（１００）衬底上制备了多晶Ｃ３Ｎ４薄膜．Ｘ射线衍射测试表明，薄膜同时含有α－和β-Ｃ３Ｎ４晶相以及未知结构，没有观测到石墨衍射峰．利用扫描电子显微镜观测到线度约２μｍ、横截面为六边形的β－Ｃ３Ｎ４晶粒．纳米压痕法测得薄膜的硬度达７２．６６ ＧＰａ．
关键词:
化学气相沉积
,
C3N4
,
XRD
,
SEM
,
Hardness
P. Fernandez G. Gonzalez I. Alfonso I.A. Figueroa
材料科学技术（英文）
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
F. Huang N.R. Tao K. Lu
材料科学技术（英文）
The microstructures and hardness of pure Al samples subjected to plastic deformation with different temperatures and strain rates were investigated. The results showed that the strain-induced grain refinement is significantly benefited by increasing strain rate and reducing deformation temperature. The saturated size of refined subgrains in Al can be as small as about 240 nm in cryogenic dynamic plastic deformation (DPD). Grain boundaries of the DPD Al samples are low-angle boundaries due to suppression of dynamic recovery during deformation. Agreement of the measured hardness with the empirical Hall-Petch relation extrapolated from the coarse-grained Al implies that the low-angle boundaries can contribute to strengthening as effective as the conventional grain boundaries.
关键词:
Dynamic plastic deformation
,
Microstructure
,
Hardness
,
Strain rate
,
Temperature
F. Huang N.R. Tao K. Lu
材料科学技术（英文）
The microstructures and hardness of pure Al samples subjected to plastic deformation with different temperatures and strain rates were investigated. The results showed that the strain-induced grain refinement is significantly benefited by increasing strain rate and reducing deformation temperature. The saturated size of refined subgrains in Al can be as small as about 240 nm in cryogenic dynamic plastic deformation (DPD). Grain boundaries of the DPD Al samples are low-angle boundaries due to suppression of dynamic recovery during deformation. Agreement of the measured hardness with the empirical Hall-Petch relation extrapolated from the coarse-grained Al implies that the low-angle boundaries can contribute to strengthening as effective as the conventional grain boundaries.
关键词:
Dynamic plastic deformation
,
Microstructure
,
Hardness
,
Strain rate
,
Temperature
Lizeng Ling Shiguo Long Zengsheng Ma Xu Liang
材料科学技术（英文）
In this paper, mechanical properties of Nickel film under residual stress have been systematically examined by finite element method in nanoindentation. It was found that load-displacement curves shifted under elastic residual stress and residual stress exceeded the yield stress for fixed indentation depth. Indentation profiles changed monotonously with compressive and tensile stresses at peak force which determinates contact area observed directly by finite element modeling (FEM). The elastic residual stress has an effect slightly on the hardness but residual stress exceeded the yield stress shows a remarkable effect in nickel film. The hardness increased when residual stress exceeded the yield stress increased under tensile and compressive stress applied to specimen. The relationship between residual stress and hardness was linear. It was found that residual stresses didn0t affect elastic modulus whether elastic residual stress or plastic stress was applied to specimen.
关键词:
Residual stress
,
Hardness
,
Elastic Modulus
,
Indentation profile
,
Finite element method
