Microstructural Evolution of Cast Hyper-Eutectic Al-18% Si Alloy during Cyclic Semi-Solid Heat Treatment
Microstructural Evolution of Cast Hyper-Eutectic Al-18% Si Alloy during Cyclic Semi-Solid Heat Treatment
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显微组织%20演化%20of%20铸造%20过共晶%20Al-18%%20Si%20合金%20during%20循环%20半固态%20热%20处理
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发表时间：
2015
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通讯作者：
M. Ramadan
中科院分区：
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作者：
M. Ramadan
循环半固态热处理代表了一种改善各种金属合金的微观结构和机械性能的有前景的技术。本研究主要研究了循环半固态热处理对含0.8%Fe的Al-18%Si合金显微组织的影响。所有样品均在电加热电阻炉中加热，加热速率为 10°C∙min -1 至 585°C。对于完整的一个循环热处理（5 分钟加热时间），样品在 585°C 下保持 5 分钟后，在静止空气冷却中冷却至 550°C，并立即取出样品进行水淬。研究发现，热处理周期应限制在 3 个周期或更少，以保持细晶粒尺寸和球状结构，而不发生团聚和聚结。循环半固态热处理将富铁金属间化合物相的形态改变为板状和细板状富铁金属间化合物相，而不是铸态样品中观察到的针状富铁金属间化合物相。由于其更细的球状结构，与铸态相比，循环加热在所有加热循环中都显示出相对较高的硬度。由于粗化不连续效应，循环半固态热处理技术比等温热处理技术具有更低的粗化速率常数。
The cyclic semi-solid heat treatment represents a promising technique for improving microstructure and mechanical properties of a wide range of metallic alloys. In the current research the influence of cyclic semi-solid heat treatment on microstructure of Al-18% Si alloy containing 0.8% Fe has been studied. All specimens were heated in an electrically heated resistance furnace with heating rate of 10˚C∙min −1 to 585˚C. For a complete one cycle heat treatment (5 min heating time), samples after 5 min holding at 585˚C were cooled to a temperature of 550˚C in still air cooling and the samples were taken out immediately for water quenching. It was found that heat treatment cycles should be limited to 3 cycles or less in order to maintain fine grain size and globular structure without agglomeration and coalescence. Cyclic semi-solid heat treatment changes morphology of iron-rich intermetallics phases to be plate-like and fine plate iron-rich intermetallics phases, in stead of needle-like iron-rich intermetallics phases that are observed in as-cast samples. Cyclic heating shows a relatively higher hardness for all heating cycles compared with as-cast one due to its finer and globular structure. Cyclic semi-solid heat treatment technique results in lower coarsening rate constant compared with isothermal heat treatment one due to coarsening discontinuous effect.