Characteristics of alloyed iron-aluminide alloys produced by aluminothermy and centrifugal force-assisted crystallization

Abstract

Contemporary industrial manufacturing requires materials with enhanced properties that are crucial for producing modern devices, machinery, and mechanisms featuring higher productivity, reliability, and durability. Intermetallic alloys of the Fe–Al system are among the most promising materials for mechanical engineering because they combine low cost with a range of important physical-mechanical and operational characteristics. Iron aluminides and their alloys have been successfully implemented as functional coatings. These coatings increase product lifespan and reliability, reduce weight, and decrease costly raw material consumption. However, broader adoption of these alloys in general industrial practice, including use as independent structural materials, is hindered by several challenges. These challenges involve improving the overall properties of the alloys, specifically increasing ductility while maintaining strength and hardness and reducing porosity. Additionally, existing production methods are problematic due to their technological complexity, multistage nature, and lengthy processing times. This study presents a potential solution to these challenges: applying centrifugal forces to alloys produced via aluminothermy with tungsten alloying during crystallization. The density of the investigated alloys increased from 5788 to 7271 kg/m³, and porosity decreased from 18.85% to 0.27%. Microhardness decreased from 317–362 HV to 306–323 HV, and compressive strength increased from 1350 to 1598 MPa. This increase in strength was accompanied by a change in strain from 26.76% to 35.27%. There was a slight reduction in grain size, from 105–680 µm to 102–400 µm. Additionally, the maximum mass gain during oxidation testing was 0.39% (0.71 mg/cm²). The thermite mixture compositions used provided an aluminum content within the alloys of 13.66–14.31 wt %, corresponding to the formation of an ordered D0₃ structure, which is known for its favorable service and mechanical properties. This work confirms the fundamental feasibility of producing cylindrical, hollow billets from Fe–Al alloys with satisfactory characteristics.