Micro-mechanical properties and associated strengthening mechanism of Be-Al-Ag-Si alloys fabricated by electron beam welding technique

Abstract

Owing to excellent mechanical properties, beryllium‑aluminum (BeAl) alloys have garnered significant attentions as advanced structural materials in the military sector. However, they also suffer from extremely low solubility between Be and Al, and a lack of effective techniques for large-scale BeAl alloy fabrication. In this study, Be-Al-Ag-Si alloys were fabricated with significantly refined microstructures and improved micro-mechanical properties by incorporating additional Ag and Si elements and utilizing electron beam welding (EBW) technique. Micropillar compression results indicate that the yield strength (YS) of the fusion zone (FZ) in the as-welded Be-Al-Ag-Si alloys is approximately 540 MPa, which is around 135% higher than that of the substrate zone (SZ) with YS of approximately 230 MPa. The significant improvement can be mainly attributed to the grain boundary strengthening and dislocation strengthening due to the rapid heating/cooling rate and high thermal residual stress in the FZ, as revealed by microstructural analysis. Additionally, other strengthening mechanisms, such as Orowan and GP zone strengthening, could also make a contribution. These results offer further understanding towards the production of large-scale BeAl alloys with improved flow ability and mechanical properties.