Characterization and hydrolysis mechanism of soluble Al-Mg-Ga-Sn alloys in hydraulic fracturing applications

Abstract

To engineer a dissolvable Al-Mg-Ga-Sn aluminum alloy material suitable for multi-stage hydraulic fracturing and sealing tools, an array of alloys was fabricated using high-temperature casting with varying concentrations of Ga and Sn. The compositions were designed such that the ratio of Ga to Sn remained constant at 1. The objective was to examine the influence of Ga and Sn content on the mechanical properties of the alloys and their reactivity with water. Results indicated that with 1.0 wt% of both Ga and Sn, the alloy displayed a ultimate tensile strength (σb) of 182±1 MPa, elongation (δ) of 33.8±0.8 %, reduction of area (φ) of 11.6±0.9 %, yield strength (σSc) of 161±1 MPa, relative compressibility (δ) of 63.0±1.0 %, and relative expansion of the cross-section (φ) of 170.8±0.9 %. Additionally, when subjected to water at 90℃, the alloy achieved a maximum dissolution rate of 3.0±1 g·h-1·cm-2. Upon contact with an aqueous environment, an electrochemical reaction ensues where aluminum atoms in the matrix lose electrons, transforming into Al3+ ions within the solution. Concurrently, Sn2+ and Ga2+ ions migrate to the surface oxide film, substituting Al3+ ions at the grain boundaries, which induces vacancies in the oxide film, reducing its resistance to further ionic penetration and densification loss. This study elucidates the macroscopic process mechanism of the interaction between water-soluble alloys and aqueous media, and proposes a corresponding microscopic mechanism.