Ab Initio Molecular Dynamics Study on the Dissolution of Interfacial Iron Oxides in Hot Compressive Bonding Combined with Experiments

Based on experimental observation, ab initio molecular dynamics was used to investigate the dissolution of interfacial iron oxides in hot compressive bonding (HCB). The surface analysis indicated that there was reoxidation at the unclosed iron surface during the sample heating in HCB. The bonding of pre-oxidized iron was designed to verify the dissolution of iron oxides into matrix. Two models were proposed to understand the dissolution behavior with dynamic simulations. Model I was applied to the case with bonding interface between oxides and matrix,in which periodical interface structure of Fe₃O₄/BCC-Fe was constructed. The dissolution of Fe₃O₄ contained the initial structural dissociation and the diffusion of free oxygen and iron atoms into matrix. It was found that the diffusivity of iron was higher than oxygen. Model II with embedded structure of oxide cluster was proposed to understand the initial dissolution of iron oxide particles in the matrix. The mean square displacement (MSD) results suggested that the local strain may promote the process by increasing the mobility of oxygen. And the Bader charge analysis implied that the electron contribution of iron matrix and its transfer to the dissociated atoms plays a key role in the initial dissolution of interfacial iron oxides.