Abstract
It is high of commercial importance to generate the grain refinement in alloys during solidification by means of electromagnetic fields. Two typical patterns of electromagnetic fields, pulsed electric currents (ECP) and traveling magnetic field (TMF), are frequently employed to produce the finer equiaxed grains in solidifying alloys. Various mechanisms were proposed to understand the grain refinement in alloys caused by ECP and TMF. In this paper, a comparative study is carried out in the same solidification regime to investigate the grain refinement of Al-7 wt. %Si alloy driven by ECP and TMF. Experimental results show that the application of ECP or TMF can cause the same grain refinement occurrence period, during which the refinement of primary Al continuously occurs. In addition, the related grain refinement mechanisms are reviewed and discussed, which shows the most likely one caused by ECP and TMF is the promoted dendrite fragmentation as the result of the ECP-induced or TMF-induced forced flow. It suggests that the same grain refinement process in alloys is provoked when ECP and TMF are applied in the same solidification regime, respectively.
Highlights
IntroductionHigh-performance structural alloys are urgently required in the automobile and aircraft industries
High-performance structural alloys are urgently required in the automobile and aircraft industries.The application of high-performance structural alloys can reduce the weight of vehicles as well as the consumption of energy
ECP was powered off when the recalescence in the sample of Figure 5b was completed, it suggests that the refinement of primary Al mainly generates during the initial solidification period that is composed of the nucleation period and recalescence period
Summary
High-performance structural alloys are urgently required in the automobile and aircraft industries. The application of high-performance structural alloys can reduce the weight of vehicles as well as the consumption of energy. The high-performance structural alloys can be obtained by performing strengthening treatments, such as the solid-solution strengthening, precipitation strengthening, secondary phase strengthening, strain hardening, grain refinement and so on [5,6,7]. All these treatments can dramatically enhance the tensile strength of alloys. The plasticity of alloys can be deteriorated by most of these treatments, and only the grain refinement treatment can guarantee or even improve it [7]
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