S.K. Ghosh
材料科学技术（英文）
The present study deals with the effect of cold deformation and subsequent aging on the microstructure and mechanical properties of Al-Cu-Si-Mg alloy. Differential scanning calorimetry indicates that precipitation occurs in the temperature range of 258−272°C for the as quenched wrought alloy. The activation energy value estimated by Kissinger method for the aforesaid precipitation reaction is obtained as 106 kJ/mol. 45% cold deformation prior to aging indicates the first dissolution reaction at about 50°C and the precipitation reaction at a temperature of about 82°C. Microstructural investigations have revealed the formation of fine precipitates within the matrix after aging of the cold deformed sample. As-quenched alloy reveals prominently the aging
response. The increase in hardness, yield and tensile strength with simultaneous decrease in elongation in the deformed alloy is found to be primarily due to the deformation strengthening and not due to the precipitation hardening.
关键词:
Aluminium alloy
S.K. Ghosh
材料科学技术（英文）
The present study deals with the effect of cold deformation and subsequent aging on the microstructure and mechanical properties of Al-Cu-Si-Mg alloy. Differential scanning calorimetry indicates that precipitation occurs in the temperature range of 258−272°C for the as quenched wrought alloy. The activation energy value estimated by Kissinger method for the aforesaid precipitation reaction is obtained as 106 kJ/mol. 45% cold deformation prior to aging indicates the first dissolution reaction at about 50°C and the precipitation reaction at a temperature of about 82°C. Microstructural investigations have revealed the formation of fine precipitates within the matrix after aging of the cold deformed sample. As-quenched alloy reveals prominently the aging
response. The increase in hardness, yield and tensile strength with simultaneous decrease in elongation in the deformed alloy is found to be primarily due to the deformation strengthening and not due to the precipitation hardening.
关键词:
Aluminium alloy
Peilin LI
,
Zhongfeng XU
,
Chun YU
,
Hao LU
,
Junshan YAO
,
Guoyu CHEN
金属学报(英文版)
The 2219 aluminum alloy under refilling friction stir welding (RF-FSW) was investigated. The micrographs showed that the bead could be divided into six zones, and the grain size and shape were greatly different in these zones. According to the microstructure analysis, the weld nugget zone and the shoulder stirring zone consisted of equiaxed grains, while the grains in the heat affected zone were seriously coarsened. It was obvious that bending deformation occurred in the thermo-mechanically affected zone. According to the microhardness analysis, the lowest hardness of the weld was at the thermo-mechanically affected zone, and the microhardness increased with the retraction of the stir-pin. The tensile strength and elongation of the bead were 70% and 80% of the base metal, respectively. The tensile strength was slightly different for the stable stage and the retraction stage, while the elongation decreased in the retraction stage. The mechanical properties and microstructure responded to different retraction speed were analyzed, and it showed that the elongation decreased with increasing retraction speed.
关键词:
Aluminium alloy
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null
,
null
,
null
H.B.Dong
材料科学技术（英文）
A numerical model Alloy/M has been applied to investigate the microsegregation in Al-4.45 wt pct Cu alloy. The calculated data were compared with the experimental measurements for samples solidified at different cooling rates. Discrepancies in solute concentration occur between the experimental observations and calculated results. Reasons for the discrepancies were discussed, and the effect of dendrite joining at a later stage of solidification on the microsegregation was investigated. Calculations that have included this effect showed a better fit with experimental results.
关键词:
Microsegregation
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null
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null
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null
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null
Y.Y.Yang
,
M.Mahfouf
,
D.A.Linkens
材料科学技术（英文）
The accuracy of numerical simulations and many other material design calculations, such as the rolling force, rolling torque, etc., depends on the description of stress-strain relationship of the deformed materials. One common method of describing the stress-strain relationship is using constitutive equations, with the unknown parameters fitted by experimental data obtained via plane strain compression (PSC). Due to the highly nonlinear behaviour of the constitutive equations and the noise included in the PSC data, determination of the model parameters is difficult. In this paper, genetic algorithms were exploited to optimise parameters for the constitutive equations based on the PSC data. The original PSC data were processed to generate the stress-strain data, and data pre-processing was carried out to remove the noise contained in the original PSC data. Several genetic optimisation schemes have been investigated, with different coding schemes and different genetic operators for selection, crossover and mutation. It was found that the real value coded genetic algorithms converged much faster and were more efficient for the parameter optimisation problem.
关键词:
Genetic algorithms
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null
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null
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null
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null
