Influence of Crystallization Conditions on the As-Cast Structure of Fe-Mn-Si Alloy with a Shape Memory Effect

Abstract

Nowadays, smart materials with special functional properties, in particular shape memory alloys, are widely used in more and more units of various equipment. Fe-based alloys of the Fe-Mn-Si-Cr-Ni-X system, due to their relatively low cost and sufficiently high manufacturability, can be widely used in various fields. It is shown that in the studied alloys, alloying elements can be divided into system-forming (10–30 wt.% Mn and 3–10 wt.% Si), and additional (Cr, Ni, V, N, Cu, etc.) elements, which add to improve the shape memory effect. It is shown that the one problem of Fe-SMAs is the evaporation of manganese in the melting. Criteria for the selection of alloys considering the temperature regime of melting with minimal evaporation of manganese and satisfactory overheating above the liquidus temperature have been developed. The Fe-35Mn-8Si alloy were produced at laboratory scale. The effect of the cooling rate during solidification on the structural heterogeneity of the test ingots poured into a cast iron chill mold and into a sand mold is studied. Using pin molds, in which conditions are created that inhibit the shrinkage of the solidifying ingot and provoke cracking, their resistance to hot cracks has been studied. The secondary dendrite arm spacings and the segregation coefficients of manganese and silicon were determined depending on the crystallization conditions. Critical parameters of the technology have been determined, the optimization of which makes it possible to produce Fe-SMAs at industrial scale.