Microstructure, microtexture and grain boundary character evolution in microwave sintered copper

Abstract

Abstract In the present investigation, the evolution of microstructure and microtexture of commercially available copper powder during solid state sintering using microwave furnace has been studied. The powder was compacted using 300\u202fMPa uniaxial die pressure and the green compacts were sintered at 610\u202f°C, 880\u202f°C and 1020\u202f°C in argon atmosphere at 20\u202fmin and 45\u202fmin isothermal holding times using multi-mode microwave furnace which has output power of 3\u202fkW and operated at 2.45\u202fGHz frequency. The temperatures were selected to obtain different dominant densification processes. For sintered samples comparative analysis has been made based on densification behavior, microstructural and microtexture evolution and mechanical properties. Electron backscatter diffraction (EBSD) study indicated that there is a distinct evolution of microtexture and microstructure in terms of evolution of grain boundary character distribution, misorientation, size, shape and morphology of grains and pores. Attributed to high temperature driven volume diffusion process, 1020\u202f°C sintered samples showed better sintering between copper particles, grain growth, grain coalescence, reduction in porosity area fraction and increased pore rounding. For all microwave sintered samples, the highest fraction of CSL boundary fraction found to be Σ3 boundary with a common (111) grain boundary plane which indicated coherent twin boundaries with low energy. More Σ3 twin population is found on intermediate sintering temperature range whereas significant reduction is observed higher temperature sintering which might be the result of grain coalescence and volume diffusion at higher sintering temperature that reduced high angle grain boundaries. Microwave sintered copper samples brought random microtexture evolution with variation of sintering temperature and holding time. This might indicate the presence of non-conventional sintering mechanisms during microwave sintering.