| Summary: | 碩士 === 國立交通大學 === 材料科學與工程研究所 === 86 ===
In this work, through ECAE (Route C) with non-solution-treated specimens, the grain growth, oprecipitation reaction and aging kinetics of 6061 aluminium alloy were studied.
The activation energy of grain growth, for six extrusion passes non-solution-treated specimens, was about 36 KJ/mol as the heat treatment below 523 K and about 139 KJ/mol as the heat treatment about 573 K. The relationship between grain size and hardness could be opresented with a formula, Hv=23+58.9d-2/1.
For the precipitation reaction and kinetics, the curve of DSC of the solution-treated specimens deformed by ECAE (Route C) showed that the β'formation peak shifted to low temperature. The activation energy of β' formation for ECAE deformed specimens was 120 KJ/mol which was higher than the value of specimens without deformation by ECAE. The reason was that the activation energy of b' formation include the activation energy of recovery and recrystallization. For the Kinetics oparameter n, the n value reduced from 2.3 to 0.5 at low temoperature 498 K. The results showed that the b' phase grew from fod shape to column or plate shape before the b' formation peak finished reaction. For the aging treatment subjected to different time at 453 K, the number of ECAE passes increased with decreasing the aging time. The precipitation reaction would be accelerated. For instance, the peak aging of the maximum hardness was 2 hours for N=3, but one was 13 hours for N=0.
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