Abstract
In this paper, the effect of high-current pulsed electron beam (HCPEB) on the microstructure refinement of an Al–20Si–5Mg alloy in the cross-section modified zone was studied, and a double-layer ultrafine crystal structure of the Al–20Si–5Mg alloy was formed. It was found that the cross-section modified zone was divided into three zones, namely, the remelted layer, the heat-affected zone, and the thermal stress wave-affected zone after HCPEB treatment. For the remelted layer, metastable structures were formed due to the rapid heating and cooling rates. For the heat-affected zone, the grain of the aluminum phase was refined due to the cooperative effects of shock wave (formed during an eruption event of the brittle phase), thermal-stress wave (formed during thermal expansion of the alloy surface), and quasi-static thermal stress (formed as a result of an unevenly distributed temperature gradient in the inner material) at high temperatures. For the thermal stress wave-affected zone, the grain refinement was not obvious due to the decreasing energy of the shock wave and the thermal-stress wave at low temperatures. In addition, firm evidence for the tracing of shock waves in the heat-affected zone was demonstrated for the first time and verified for the founding of the broken acicular eutectic silicon. Through this experiment, the mechanical properties of Al–20Si–5Mg alloy materials in both the remelted layer and heat-affected zone were significantly improved after HCPEB treatment.
Highlights
As an advanced surface modification technique, high-current pulsed electron beam (HCPEB)technology has attracted scholarly attention in the field of material surface modification owing to the advantages of this technique, including slight deformation of the workpiece, energy conservation, high efficiency, flexible processing method, and good repeatability [1,2,3,4].Proskurovsky et al [5] proposed the concept of “deep modification” for the first time, in whichHCPEB modified the surface layer and the deep structures of materials
Some researchers proposed that the cross-section of the material after HCPEB treatment be divided into three zones: the remelted layer, the heat-affected zone, and the thermal stress wave-affected zone [5,6,7,8]
The morphology of the hypereutectic Al–20Si–5Mg alloy in terms of the surface and cross-section before and after HCPEB treatment was examined by means of field emission scanning electron microscopy (FESEM Hitachi S-4800, Tokyo, Japan) with energy-dispersive X-ray spectroscopy (EDS) and electron backscattering diffraction (EBSD) attachments
Summary
As an advanced surface modification technique, high-current pulsed electron beam (HCPEB). Qin et al [9] studied the effect of HCPEB treatment on the microstructure of 45# steel and found two corrugated lines parallel to the boundary of one grain located close to 0.5 mm below the surface. They considered that these phenomena were ascribed to the effect of a stress wave. A shock stress wave, is an atypical nonlinear wave, several hundreds of MPa in amplitude and much stronger than a thermal stress wave It has a strong impact on material structure and properties far beyond the heat-affected zone [9]. The tracing of the refinement was further studied, and the deep modification effect of HCPEB in the heat-affected zone was studied in detail and verified
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