Effect of Cerium and Magnesium on Surface Microcracks of Al–20Si Alloys Induced by High-Current Pulsed Electron Beam

Liang Hu,Ying Zhang,Yue Sun,Pengfei Xing,Ning Xu,Bo Gao

doi:10.3390/coatings12010061

Liang Hu, Ying Zhang + Show 4 more

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https://doi.org/10.3390/coatings12010061

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Journal: Coatings	Publication Date: Jan 5, 2022
Citations: 4	License type: CC BY 4.0

Affiliation: Northeastern University

Abstract

The effect of Ce and Mg on surface microcracks of Al–20Si alloys induced via high-current pulsed electron beam (HCPEB) was studied. Mg was revealed to refine the primary Si phase in the pristine microstructure by forming a Mg2Si phase, leading to the suppression of microcrack propagation within the brittle phase after HCPEB irradiation. The incorporation of Ce into the Al–Si–Mg alloys further refined the primary Si phase and reduced the local stress concentration in the brittle phase induced by HCPEB irradiation. Ultimately, the surface microcracks were observed to be eliminated by the synergistic effects between the two elements. For Al–20Si–5Mg–0.7Ce alloys, Ce demonstrated a homogeneous distribution in the Al matrix on the HCPEB-irradiated alloy surface, while the Mg and Si exhibited a certain degree of aggregation in the Mg2Si phase. Metastable structures were formed on the HCPEB-irradiated alloy surface, including the nano-primary silicon phase, nano-cellular aluminium structure, and nano-Mg2Si phase. Compared with alloy specimens containing Mg, the Al–20Si–5Mg–0.7Ce alloy specimens exhibited an excellent anticorrosion property after HCPEB irradiation mainly due to the combined effects of the grain refinement and microcrack elimination.

Highlights

In recent decades, the high-current pulsed electron beam (HCPEB) technique has attracted intensive research attention as a novel non-equilibrium technique for surface modification because of its low-cost, ease of operation, short pulse duration, and high efficiency [1,2,3,4]
The present study focuses on the effect of Mg on surface microcracks induced by HCPEB in Al–20Si alloys and on the incorporation of Ce into Al–Si–Mg alloys to further improve the resistance to surface microcrack formation
The microcrack elimination was attributed to grain refinement effect of two elements and reduction of the local stress concentration in the brittle phase induced by rare earth Ce

Summary

Introduction

The high-current pulsed electron beam (HCPEB) technique has attracted intensive research attention as a novel non-equilibrium technique for surface modification because of its low-cost, ease of operation, short pulse duration, and high efficiency [1,2,3,4]. The rapid heating and solidification effects excited by HCPEB can produce metastable structures in the modified surface layer, which exhibits superior properties not obtainable using other conventional methods These structures have been of significant research interest, leading to numerous investigations into HCPEB-treated metals, including steel materials [7,8], Al alloys [9,10], Mg alloys [11,12], Ti alloys [13,14], Zr alloys [15,16], Cu alloys [17], and hard alloys [18,19]. In the microcrack arrest method, the pulsed current concentrates at the tip of the crack in the material during the instantaneous energisation process, thereby inducing a thermal concentration effect and suppressing the propagation of microcracks. The cut specimens were mechanically polished with different sandpapers and polishing pastes, yielding polished alloy specimens for the electron beam modification treatment

HCPEB Processing

Characterisation

Corrosion Analysis

Results and Discussion

Microstructure Analysis under HCPEB Irradiation

Phase Identification

Conclusions