The experimental phase equilibria studies of the Fe-Sn-As system

Metals commonly found in electronic components, mine waste, natural minerals, slag, and soil are often related to the iron-tin-arsenic system. Understanding its phase equilibria is essential for advancing pyrometallurgical processing and the recycling from these complex feedstocks. The iron-tin-arsenic system was investigated to improve thermodynamic description of the Cu-Fe-Sb-Sn-Ni-S-As matte/speiss/liquid metal system and enhance the predictive accuracy of the FactSage-based 20-component system. Vacuum-sealed samples were equilibrated at specified temperatures, quenched to preserve microstructures, and subsequently analyzed using an electron probe microanalyzer. Liquidus and solidus projections from 500 to 1500℃ revealed a miscibility gap extending from the Fe-Sn binary to the centre of the diagram. Identified phases include liquid metals, BCC-Fe (Sn- and As-containing), Fe 5 (Sn,As) 3 -Me 5 X 3 , “Fe 3 (As,Sn) 2 ”, FeSn-MeX, FeSn 2 , Fe 2 As, Fe 3 Sn, FeAs, and FeAs 2 , along with their primary phase fields. Incongruently melting Fe 5 (Sn,As) 3 at 904 ℃ and “Fe 3 (As,Sn) 2 ” are newly identified ternary phases. Sub-solidus experiments performed in equilibrium with liquid Pb flux in the Fe-Sn system confirm Fe 3 Sn stability. Three saddle points and seventeen invariant reactions were identified. Monotectic and syntectic reactions were observed at two sets of invariant points within the miscibility gap. • First time the phase equilibria of the Fe-Sn-As system have been studied. • The liquid metals, BCC-Fe, Fe 5 (Sn, As) 3 -Me 5 X 3 , FeSn, FeSn 2 , Fe 2 As, “Fe 3 (As,Sn) 2 ”, FeAs, and FeAs 2 solution phases were determined. • Incongruently melting Fe 5 (Sn, As) 3 related to Me 5 X 3 and Sn-containing “Fe 3 As 2 ” were identified as new phases in this system. • Fe 3 Sn stability was confirmed. • The results confirmed a miscibility gap, extending from the Fe-Sn binary to the centre of the Fe-Sn-As compositional triangle.