Experimental Investigation And Computer Simulation Of Diffusion Kinetic In Several Diffusion Welding Materials

Abstract:In modern engineering applications, the technical requirements for high-performance components are getting increasingly higher. Some components with significantly different properties, such as metals and ceramics, need to be tightly connected together. That is actually difficult to achieve via the traditional welding. As an novel solid-state welding technique, diffusion welding enables two interfaces of the welded parts to be tightly bonded under pressure at elevated temperatures. It is capable of joining similar or dissimilar metals directly or by adding an interlayer between parts and the advantage of this method is that it will not cause the macroscopic deformation and melting of the parts and it can get good quality of welded joints. In recent years, the diffusion welding method as one of special welding technology has aroused people’s attention and become a hot research field of welding.In this work, three type of alloys were selected, which are used widely in diffusion welding field, Ni-X (X=Ge, Ti and V), Cu-Mn-Al and Fe-Si-Al alloys.A series of diffusion couples were prepared, the concentration profiles were derived from the Electron Probe Micro-Analysis (EPMA). By using the Boltzmann-Matano and Kirkaldy method, the concentration profiles were analyzed, and the inter-diffusion coefficients in these systems were calculated on the basis of critical review of the diffusion kinetics data on these systems in the literature. The atomic mobility parameters for these systems were accurately assessed by DICTRA (Diffusion Controlled TRAsformations) software. By combining the corresponding thermodynamic database, the obtained atomic mobilities were applied to predict various diffusion phenomena.The main innovations of this paper are obtained as follows:(1) The inter-diffusion coefficient of the fcc_Al Ni-X (X=Ge, Ti and V) alloys were experimental determined by diffusion couple method, the self-diffusion coefficient of the target system were calculated by first-principles, semi-empirical formulas and CALPHAD methods. The diffusion kinetic database was established by DICTRA software.(2) The mutual diffusion coefficients in bcc_A2phase of Cu-Mn-Al system were measured by diffusion couple method. The mobilities of Cu%Mn and A1in the bcc_A2phase of the Cu-Mn-A1alloys were accurately assessed by DICTRA software.(3) Single-phase/two-phase diffusion couples were used to investigate the inter-diffusion in bcc_A2and bcc_B2phase of Fe-Si and Fe-Si-A1system. The atomic mobilities in the disordered phase of Fe-Si and Fe-Si-A1system were assessed by DICTRA software laying the foundation for the investigation of the ordered phase.