双级时效工艺对富铁ADC12铝合金组织和硬度的影响

Influence of duplex aging on the microstructure and hardness of Fe-rich ADC12 aluminum alloy

为了探索双级时效工艺对富铁ADC12铝合金的影响,在不同二级时效温度下对合金进行热处理,探讨合金的显微组织和硬度的变化规律。结果表明:随着二级时效温度的提高,合金中方块状初生硅棱角钝化,树枝状共晶硅细化成球状,长针状富铁相细化且圆滑,硬度逐渐提高。在170℃的二级时效温度下,合金组织分布均匀,布氏硬度比T6工艺的提高了14.1%,但当二级时效温度达到180℃时,合金会出现过时效现象,针状组织再次聚集,硬度急剧降低。

In order to investigate the effect of duplex aging process on ADC12 with rich Fe phase, different second aging heat treatment processes were carried out on these alloys. The variations of microstructures and hardness were discussed. The results indicate that sharp-angled parts in the blocky primary Si were smooth with the increase of second aging temperatures. Meanwhile, the eu-tectic Al-Si with dendritic shapes was refined and turn into the sphere shape. The needle like Fe-rich phase was also refined and smoothed with the hardness promotion. The alloy with homogeneous-ly microstructure was obtained by using the second aging process at 170 ℃, whose hardness （ HB） is 14. 1%, higher than that of the alloy treated by using T6 process. The over aging was observed af-ter the alloy was treated by the second aging at 180 ℃. The needle phase agglomerated again in the microstructure, which led to the reduction of hardness.