Development of sustainable novel Mg-Ca-Sc alloys with exceptional corrosion resistance

Abstract

Mg-based alloys have been widely researched for biomaterial and structural applications as they fulfill several prerequisites, such as lightweight, high specific strength, and good biocompatibility, which are highly desirable. However, a long-standing obstacle to the widespread use of magnesium is its low corrosion resistance and increased cost upon increasing alloying content to enhance corrosion resistance. In this study, we report the effect of the simultaneous addition of rare-earth element (Sc) and non-rare earth element (Ca) maintaining low alloying content (∼ 1 wt%) on the mechanical, tribological, and corrosion behavior of Mg. The novel as-cast Mg-0.6Ca-0.5Sc alloy exhibited excellent corrosion resistance with a corrosion rate ∼ 40 % lower than the conventional as-cast WE43 alloy and ∼ 88 % lower than AZ31 alloy. A finer grain size and strong basal texture were achieved through thermomechanical processing, further enhancing the corrosion resistance of the as-cast novel alloys by ∼ 45 %. Stress corrosion cracking and wear testing in physiological saline solution were also conducted to study the combined effect of stress and corrosive electrolyte. The tensile and compression behavior remained practically the same upon adding Sc. However, the addition of 0.5 wt% Sc reduced the yield asymmetry by ∼ 10 % in as-cast and ∼ 5 % in recrystallized conditions. Furthermore, Mg-0.6Ca-0.5Sc alloy exhibited significant strength (∼ 175 %) and ductility (∼ 67 %) improvement under tensile testing in a physiological saline solution environment compared to Mg-0.6Ca alloy. The developed novel Mg-0.6Ca-0.5Sc ternary alloy exhibited enhanced resistance to corrosion, stress corrosion cracking, and wear relative to the Mg-0.6Ca binary alloy.