Morphologies of alumina nano-and microparticles at the Fe/Al ₂O₃ interface and the effects of reaction time and substrate roughness on size distribution

Non-metallic inclusions are formed from a variety of sources such as deoxidations, chemical interactions between the steel and slag, slag entrapment, breakdown of refractory materials and reoxidation by air. In particular, hard alumina inclusions are known to be detrimental to the mechanical properties of steel welds as well as to the steel materials themselves. Under the conditions of high supersaturation degree, dendritic alumina inclusions are formed not by a nucleation and growth mechanism of each alumina nucleus but by the sintering of several tens of nanometer particles. In contrast to this, coral-shaped or globular alumina particles are formed by a diffusional process under low supersaturation conditions. The number of particles decreased as their size increased and as the surface roughness decreased.