Synchronous improvement in mechanical properties and corrosion resistance of Mg-Gd-Ag-Zr alloy through nanoprecipitates

Abstract

It is still challenging to synchronously improve mechanical properties and corrosion resistance through one strategy during developing Mg alloys. Introducing high-density precipitates is an effective and popular approach to strengthen Mg alloys, while these precipitates generally degrade the corrosion resistance. In this paper, the nanoprecipitates are developed in Mg-13.4Gd-2.2Ag-0.4Zr wt.% cast alloy through the solution and aging treatment for evading this dilemma. Compared with its as-cast counterpart, the peak-aged alloy with high-density nanoprecipitates exhibits enhanced strength, comparable ductility, and improved corrosion resistance. The nanoprecipitates in the peak-aged alloy are composed of β nanoparticles at grain boundaries, and intragranular γ′′ and β′ nanoplates. These nanoprecipitates are contributed to the improved strength through the Orowan mechanism. The β nanoparticles induce weak galvanic corrosion, and the γ′′ nanoplates have not induced visible galvanic corrosion, thus contributing to the enhanced corrosion resistance of the peak-aged alloy. This result suggests that developing nanoprecipitate is a feasible route to collaboratively optimize the mechanical and corrosion properties of the Mg alloys.