Effect of heat treatment on the properties of rapidly quenched Al – Ge – Si alloys

Abstract

This paper examines Al – Ge – Si alloys containing up to 40 wt.% germanium that can potentially be used for brazing corrosion resistant steels to highstrength aluminium alloys. Using ultrarapid quenching, ingots of the abovealloys were converted into 55±5 μm thick bands. Properties of both ingots and bands were methodically studied, and effect of heat treatment on the properties of ingots and bands – determined. Optimal regimes of heat treatment for bands were tested that help achieve the required plasticity. Homogenous and heterogenous materials were brazed together. X-ray phase analysis and electron microscopy showed that rapidly quenched bands have a homogenous structure and contain a eutectic comprised of solid solutions (Al, Ge) and (Si, Ge) and a metastable compound Al6Ge5. The ingots of the alloys consist of two eutectics. The first one consists of solid solutions (Al, Ge) and (Si, Ge), while the second one comprises a solid solution (Al, Ge) and a Ge-based solid solution. The bands have a nanocrystalline structure. Having measured microhardness and plasticity of the bands, the authors identified the best regime of heat treatment, which is 300 oC/10 min. A series of pilot tests was conducted to analyze the applicability of the studied alloys as filler metals. For this, aluminium alloy AA6082 was brazed to corrosion resistant steel AISI 304 and a heterogenous joint was made. A metallographic study revealed no compromized integrity or defects in any of the brazed joints.«Funding: The reported study was funded by RFBR and DFG, project number 21-52-12026».