Al-Si合金熔体热处理的结构转变

用示差扫描量热分析了Al-Si合金温度处理的熔体结构变化规律及结构变化温度。结果表明,在升温阶段的Al-7%Si亚共晶、Al-12%Si共晶及Al-20%Si过共晶合金的熔体中均存在额外的热效应,范围均在798～850℃之间,额外热效应温度范围与含硅量无关,结构转变焓值随合金的硅含量增加而增加,氢含量不影响结构转变的温度;而在降温过程中仅在Al-20%Si过共晶合金中发现了额外热效应,额外热效应的出现及温度范围取决于降温速度。分析认为,升温阶段的额外热效应体现了Al的熔体结构变化,降温阶段的额外热效应与熔体中的Si-Si原子团簇的行为有关。

Structure evolution of Al-Si alloys during melt thermal treatment

The melt structure evloution and transformation temperature of three typical Al-Si alloys with different content of silicon were investigated by differential scanning calorimetry(DSC).The results show that Al-7%Si hypoeutectic alloy,Al-12% Si eutectic alloy and Al-20% Si hypereutectic alloy exhibit the extra heat effect of structure transformation at 800-850℃ during heating process while the enthalpy values of extra heat effect are found to be increased with the increase of silicon content and structure transformation temperature is not affected by hydrogen content,and the extra heat effect of structure transformation during the cooling stage is detected only in the Al-20% Si hypereutectic alloy.The occurance and temperature range of extra heat effect depends on cooling rates.It is argued that the extra heat effect of melt structure transformation is closely related to aluminum melt structure during the heating process and mainly ascribed to the behavior of Si-Si atom clusters during cooling stage.