Papers by Keyword: Age Hardening

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Authors: Jürgen Hirsch
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Authors: Th. Herding, O. Kessler, Fabian Hoffmann, Peter Mayr
869
Authors: Ying Zhou, Gui Qing Wang
Abstract: The age hardening process for permanent mold samples of Al-7Si-0.3Mg cast alloy has been investigated by hardness measurement, differential scanning calorimetry (DSC), transmission electron microscope (TEM) and electron probe micro analyzer (EPMA). Age hardening results show that the age hardening response of Al-7Si-0.3Mg alloy is independent on cooling rate. There is a hardness value decrease about 10 HV after T4 treatment. Hardness value after as-cast aging at 150 °C for 20 h is just a little smaller than that after T6 treatment for permanent mold samples. The precipitation behaviors during T6 treatment and as cast aging treatment have been analyzed by DSC analyses. The hardness measurement results have been discussed by analyzing the precipitation behaviors and the Mg and Si concentration in α (Al).
3945
Authors: Gui Qing Wang, Yan Liu, Guo Cheng Ren, Zhong Kui Zhao
Abstract: The correlation of age hardening behavior and Si precipitation in α(Al) of Al-8wt%Si-0.35wt%Mg alloy has been investigated by micro hardness measurement, electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) analysis. The EPMA results show that Si concentration in the center of α (Al) dendrites is higher than that in the edge and the main concentration is about 1.5wt% for Al-8wt%Si-0.35wt%Mg alloy in as cast condition. After solution treatment at 530 °C for 8 h followed by water quenching (T4 treatment), hardness value decreases 9 HV, which is accompanied by the decrease of Si concentration in α (Al). Aging the as-cast sample and T4 treatment sample at 150 °C for 20 h, the main concentration of Mg and Si in α (Al) changes little. Hardness value after as-cast aging is only 3 HV lower than that after T6 treatment. Nanometer Si particles and β″ and/or β′ phases are found in aged samples. The higher hardness value for as-cast aging samples should contribute to the nanometer Si particles in α (Al).
1685
Authors: M.A. Abdel-Rahman, Alaa El-Deen, Alaa El-Deen A. El-Nahhas, Yahia A. Lotfy, Emad A. Badawi
Abstract: Many aluminum-based alloys are strengthened by a heat treatment process known as age hardening. The aim of this work was to produce a high-strength 6xxx series aluminum alloy by adjusting the processing conditions, namely solutionizing and artificial aging. It consists of heating the alloy to a temperature at which the soluble constituents will form an homogeneous mass by solid diffusion, holding the mass at that temperature until diffusion takes place, then quenching the alloy rapidly to retain the homogeneous condition. In the quenched condition, heat-treated alloys are supersaturated solid solutions that are comparatively soft and workable, and unstable; depending upon the composition. After solution treatment and quenching, hardening is achieved either at room temperature (natural aging) or by precipitation heat treatment at a suitable temperature (artificial aging). Precipitation heat treatments are generally low-temperature long-term processes. Temperatures range from 115 to 190°C and times vary from 5 to 48 h. Choice of time-temperature cycles for precipitation heat treatment should receive careful consideration. The objective is to select the cycle that produces the optimum precipitate size and distribution pattern. The mechanical characterization of heat-treatable 6xxx (Al-Mg-Si-Cu based) 6063 wrought aluminum alloys was studied. Their effects were investigated in terms of the microstructure, using positron annihilation lifetime techniques and mechanical properties monitoring via Vickers hardness measurements. The hardness is the resistance of a material to plastic deformation, which gives it the ability to resist deformation when a load is applied. The greater the hardness of the material, the greater the resistance it has to deformation. The hardness of 6063 alloy has its maximum value (58) when aged for 8 hours at 175oC after quenching from 520oC; which is the solution temperature of this alloy. The hardness conformed to the literature. We also test the aging ability of the 1xxx aluminum alloy: 1050.
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Authors: Emad A. Badawi, M.A. Abdel-Rahman, Alaa El-Deen A. El-Nahhas, M. Abdel-Rahman
Abstract: Many Aluminum-based alloys are strengthened by using a heat-treatment process known as age-hardening. The aim of this work was to produce a high-strength 6xxx-series Aluminum alloy by adjusting the processing conditions, namely solutionizing and artificial aging. It consists of heating the alloy to a temperature at which the soluble constituents will form an homogeneous mass via solid diffusion, holding the mass at that temperature until diffusion takes place, then quenching the alloy rapidly to retain the homogeneous condition. In the quenched condition, heat-treated alloys are supersaturated solid solutions that are comparatively soft and workable, and unstable, depending upon the composition. After solution treatment and quenching, hardening is achieved either at room temperature (natural aging) or via a precipitation heat treatment at a suitable temperature (artificial aging). Precipitation heat treatments are generally low-temperature, long-term processes. Temperatures range from 115 to 190C; times vary from 5 to 48 h. The choice of time-temperature cycles for precipitation heat treatment should receive careful consideration. The objective is to select the cycle that produces an optimum precipitate size and distribution pattern. The mechanical characterization of heat-treatable 6xxx (Al-Mg-Si-Cu based) 6066 wrought aluminum alloys was studied. Their effects were investigated in terms of microstructure using positron annihilation lifetime techniques and monitoring the mechanical properties by mean of Vickers hardness measurements. The hardness is the resistance of a material to plastic deformation, and gives it the ability to resist deformation when a load is applied. The greater the hardness of the material, the greater resistance it has to deformation. The Vickers hardness of 6066 alloy has its maximum value (98) when aged for (10) hours at (175C) after quenching at 530C; so this temperature is the solution temperature of this alloy .The hardness conformed to reference values.
15
Authors: Roger N. Lumley, Robert G. O'Donnell, Dayalan R. Gunasegaram, Michel Givord
Abstract: Conventionally produced high pressure die-cast (HPDC) components are not considered to be heat treatable because gases entrapped during the die-casting process expand during solution treatment causing unacceptable surface blistering. Components may also become dimensionally unstable. Both these effects prevent the heat treatment of die-castings as these phenomena are detrimental to the visual appearance, mechanical properties and utilisation of the component. Recent work has revealed a process window in which HPDC aluminium alloys that are capable of responding to age hardening may be successfully heat treated without encountering these problems. As a result, improvements of greater than 100% in the tensile properties are possible, when compared with the as-cast condition. The new heat treatment schedules are described for HPDC parts of different size and shape, the role of chemistry on ageing is discussed and microstructural development during heat treatment examined†.
351
Authors: Aluru Praveen Sekhar, Supriya Nandy, Kalyan Kumar Ray, Debdulal Das
Abstract: This report presents a comparative assessment of the suitability of two existing physical models for predicting yield strength of artificially aged AA6063 Al-alloy. One model is based on the modified Orowan mechanism of dislocation by-pass for non-shearable rod shaped precipitates rejuvenated by Zhu and Stark, and the other model is based on classical dislocation-particle interaction that incorporates both cutting and by-pass mechanisms for spherical shaped precipitates developed by Deschamps and Brechet. Using these models, simulation of yield strength values have been performed considering nucleation-growth as well as nucleation-growth-coarsening of precipitates during the entire period of ageing. Comparison of experimental and simulated results reveals that the model by Deschamps and Brechet predicts yield strength more accurately when nucleation-growth-coarsening of precipitates are incorporated.
83
Authors: Gui Qing Wang, Yan Liu, Guo Cheng Ren, Zhong Kui Zhao
Abstract: The aging hardening behaviors of Al-8Si-3%Cu (wt%) and Al-3Cu (wt%) alloys have been investigated. Samples were solution treated at 500 for 24 h followed by water quenching before aging. Hardness has been measured for quenched samples aging at 150°C. Strong age hardening occurs for Al-3Cu alloy and hardness increases by about 60% after peak aging. There is a hardness decrease in the early aging stage of Al-8Si-3Cu alloy and hardness increases by about 15% after peak aging. The age precipitation behaviors have been analyzed using DSC and TEM. Effects of microstructure characteristics on age precipitation and age hardening response of Al-8Si-3Cu alloy have been discussed.
1667
Authors: Emad A. Badawi, M.A. Abdel-Rahman, Alaa El-Deen A. El-Nahhas
Abstract: The aim of this work is to establish a correlation coefficient between the positron annihilation lifetime technique (PALS) and the Vickers hardness for the heat treatable aluminum alloys (6066, 6063).The potential of positron annihilation spectroscopy in the study of light alloys is illustrated with special regards to age hardening, severe plastic deformation, annealing and quenching in aluminum alloys. Vickers hardness is the standard method for measuring the hardness of metals, particularly those with extremely hard surfaces. Accordingly, a correlation coefficient of 90 % between τ and Hv is obtained. This correlation can help us to explain many behaviors of these alloys under deferent conditions.
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