6061(Al-Mg-Si)鋁合金經ECAE(Equal Channel Angular Extrusion)後晶粒成長與時效動力之研究

Abstract

本實驗係以6061（Al-Mg-Si）鋁合金未固溶及固溶試片經ECAE（Route C）後，分別作晶粒成長及析出反應與動力之分析與研究。 實驗結果顯示，在晶粒成長方面：未固溶試片經ECAE擠壓次數N=6，試片在不同溫度退火，得知在＜523 K時，其晶粒成長活化能□36 KJ/mol，而＞573K時則為139 KJ/mol。晶粒大小與硬度之關係為Hv=23+58.9d-2/1。於析出反應動力方面：固溶試片經ECAE（Route C）製程後，會使DSC曲線之β’相生成峰向低溫移動，其生成活化能約為120 KJ/mol，較原固試片之生成活化能為大，乃因其包含了因復、再結晶的活化能在內。在反應級數n值方面，低溫（498 K）時n值從2.3左右降至高溫（553 K°）時的0.5左右，表示在β'相生成反應終了前，β'相從棒狀轉成為圓柱狀或板狀。以453K作不同時間之時效，發現隨ECAE擠壓次數N值之增加，其達到時效峰值之時間會縮短，即可加速析出之反應，如N=3時，其到達尖峰硬度的時效時間為2小時，而原固溶試片N=O，則需13小時。

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.