Surface-Induced Phase Transformations: Multiple Scale and Mechanics Effects and Morphological Transitions
Strong, surprising, and multifaceted effects of the width of the external surface layer Δξ and internal stresses on surface-induced pretransformation and phase transformations (PTs) are revealed. Using our further developed phase-field approach, we found that above some critical Δξ*, a morphological transition from fully transformed layer to lack of surface pretransformation occurs for any transformation strain εt. It corresponds to a sharp transition to the universal (independent of εt), strongly increasing the master relationship of the critical thermodynamic driving force for PT Xc on Δξ. For large εt, with increasing Δξ, Xcunexpectedly decreases, oscillates, and then becomes independent of εt. Oscillations are caused by morphological transitions of fully transformed surface nanostructure. A similar approach can be developed for internal surfaces (grain boundaries) and for various types of PTs and chemical reactions.
This article is from Physical Review Letters 107 (2011): 175701, doi:10.1103/PhysRevLett.107.175701. Posted with permission.