The microstructure, mechanical behaviour, and dissolvability of novel Al-Cu-Zn-Mg-based alloys

The use of dissolvable alloys (DAs) in hydraulic fracturing is increasing, particularly in low-permeability reservoirs. However, existing DAs based on Al or Mg alloys have limited mechanical properties despite their desirable dissolvability. This studyaims to explore new Al-based DAs with good dissolvability and mechanical strength. Four Al-Zn-Cu-Mg based alloys with various additional elements (Ag, Ga, In, Sn, Zr, Ti, V, and Cr) were prepared using the melting and casting technique. The microstructures of DAs were analysed using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. Immersion corrosion tests were conducted to evaluate the dissolvability of DAs at 90 degrees C in KCl solutions. Hardness and tensile testing were performed to assess the mechanical properties of the alloys. The resulting phases in the as-cast microstructure included eta-MgZn2, Mg2Sn, theta-Al2Cu, Al3Zr, and Al45Cr7, as predicted using the Calphad method. There was a trade-off observed between dissolvability and mechanical properties, with the alloys containing low melting point intermetallic phases exhibiting greater dissolvability but reduced mechanical strength. DA18 withthe highest Ga, In, and Sn (GIS) content, showed intense corrosion but had the lowest mechanical properties. The presence of In-containing phases was identified as the primary cause of Al degradation, while coarse phases reduced the alloy's strength. Overall, all DAs were reported to be brittle with limited elongation.