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首页> 外文期刊>Metallurgical and Materials Transactions A >Localized Recrystallization in Cast Al-Si-Mg Alloy during Solution Heat Treatment: Dilatometric and Calorimetric Studies
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Localized Recrystallization in Cast Al-Si-Mg Alloy during Solution Heat Treatment: Dilatometric and Calorimetric Studies

机译：固溶热处理过程中铸造Al-Si-Mg合金的局部重结晶：膨胀和量热研究

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摘要

During heat treatment, the work piece experiences a range of heating rates depending upon the sizes and types of furnace. When the Al-Si-Mg cast alloy is heated to the solutionizing temperature, recrystallization takes place during the ramp-up stage. The effect of heating rate on recrystallization in the A356 (Al-Si-Mg) alloy was studied using dilatometric and calorimetric methods. Recrystallization in as-cast Al-Si alloys is a localized event and is confined to the elasto-plastic zone surrounding the eutectic Si phase; there is no evidence of recrystallization in the center of the primary Al dendritic region. The size of the elasto-plastic zone is of the same order of magnitude as the Si particles, and recrystallized grains are observed in the elasto-plastic region near the Si particles. The coefficient of thermal expansion of Al is an order of magnitude greater than Si, and thermal stresses are generated due to the thermal mismatch between the Al phase and Si particles providing the driving force for recrystallization. In contrast, recrystallization in Al wrought alloy (7075) occurs uniformly throughout the matrix, stored energy due to cold work being the driving force for recrystallization in wrought alloys. The activation energy for recrystallization in as-cast A356 alloy is 127 KJ/mole. At a slow heating rate of 4.3 K/min, creep occurs during the heating stage of solution heat treatment. However, creep does not occur in samples heated at higher heating rates, namely, 520, 130, and 17.3 K/min.
机译：在热处理过程中，工件的加热速率范围取决于炉子的大小和类型。当将Al-Si-Mg铸造合金加热到固溶温度时，在加速阶段会发生重结晶。使用膨胀法和量热法研究了加热速率对A356（Al-Si-Mg）合金中再结晶的影响。铸态的Al-Si合金中的再结晶是局部事件，并且局限于共晶Si相周围的弹塑性区。没有证据表明在主要Al树枝状区域的中心发生重结晶。弹塑性区的大小与Si颗粒的大小相同，并且在Si颗粒附近的弹塑性区域中观察到重结晶晶粒。 Al的热膨胀系数比Si大一个数量级，并且由于Al相与Si颗粒之间的热失配而产生热应力，从而提供了用于重结晶的驱动力。相反，变形铝合金中的再结晶（7075）在整个基体中均匀地发生，由于冷作而储存的能量是变形合金中再结晶的驱动力。在铸态A356合金中重结晶的活化能为127 KJ /摩尔。以4.3 K / min的缓慢加热速率，在固溶热处理的加热阶段会发生蠕变。但是，以较高的加热速率（即520、130和17.3 K / min）加热的样品不会发生蠕变。

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