Research on Grain Refinement in Hypoeutectic Al-Si Alloy during Solidification under an Alternating Electric Current Pulse
Research on Grain Refinement in Hypoeutectic Al-Si Alloy during Solidification under an Alternating Electric Current Pulse
复制标题
交变电流脉冲下亚共晶铝硅合金凝固过程晶粒细化研究
DOI：
10.3390/met9050571
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发表时间：
2019-05-01
期刊：
影响因子：
2.9
通讯作者：
Wu, Hongjing
中科院分区：
文献类型：
--
作者：
Li, Ning;Zhang, Limin;Wu, Hongjing
通过无脉冲和有脉冲电流作用下的瞬态定向凝固实验，研究了Al-7Si合金的柱状晶向等轴晶的转变。在没有AECP的情况下，宏观组织由典型的柱状和等轴区组成，由近水平面分隔。当在凝固过程中施加AECP时，在铸态宏观组织中出现额外的细等轴区（FEZ）。从测量的温度曲线，确定冷却速率和温度梯度。结果表明，在冷却速率为0.14 K·s-1时，CET发生。此外，用模具包埋网板的宏观组织观察表明，负责形成细等轴晶的主要因素是晶核从上接触表面和侧壁的脱离。这种分离又归因于驱动力F引起的电流相关自由能变化（ΔGe）。
Experiments on transient directional solidification were carried out to study the columnar to equiaxed transition (CET) in Al-7Si alloy without and with an alternating electric current pulse (AECP). Without AECP, the macrostructure consists of typical columnar and equiaxed zones, separated by a near horizontal plane. As the AECP is applied during solidification, an additional fine equiaxed zone (FEZ) occurs in the as-cast macrostructure. From measured temperature profiles, cooling rate and temperature gradient are determined. It is found that CET occurs for a critical value of the cooling rate, which is observed to be about 0.14 K·s−1 in the present investigation. Furthermore, the macrostructural observation with mold for embedding the mesh plate demonstrates that the major factor responsible for the formation of fine equiaxed grains is the detachment of crystal nuclei from the upper contact surface and the lateral wall. The detachment is in turn ascribed to electric current-associated free energy change (ΔGe)-induced the driving force F.