Demonstration of elemental partitioning during austenite formation in low-carbon aluminium alloyed steel

Excerpt

Austenite formation is an important and much studied process in steel research, being intensively investigated in low and medium carbon steels. In ferritic-pearlitic steels this process can be split into two: nucleation of austenite in pearlitic colonies with rapid growth of austenite consuming pearlite followed by the slower growth of austenite consuming ferrite [1‐6]. Studies of the effect of substitutional elements such as manganese and chromium on austenite formation have shown that they slow down the transformation when partitioning of the elements occurs during austenitization [2, 3]. There has been little research concerning the effect of aluminium as a substitutional element in steel in amounts higher than 0.1 wt% despite a general awareness that Al is a ferrite stabilizer and tends to expand the ferrite + austenite phase field of the equilibrium phase diagram. This could be due to technological concerns over the production of high Al-content steels. Commercial interest has emerged recently with studies on Al additions, of the order of 0.5–2 wt%, to low carbon high strength strip steels to produce a multi-phase microstructure containing retained austenite for cold forming applications [7‐10]. There is still limited knowledge regarding the role of Al as a solute in such steels; work is required to understand its influence on phase transformations and microstructures. This study investigates the influence of Al in solid solution on austenite formation during continuous heating. …