The examination of diffusion welded Cu/alpha-Al2O3 composites in incident light- and scanning electron microscopes

The diffusion welding of poly- and mono-crystalline Cu to mono-crystalline alpha-Al2O3 is carried out under ultra high vacuum. At the start of the wel ding process, pores are formed at the interface between the Cu and the alph a-Al2O3 which gradually heal under the action of the transport processes ta king place. The proportion and size of the of pores present across the enti re surface as a function of the welding time, determined using quantitative image analysis, were compared with similar results obtained from theoretic al models. This showed that the healing process undergone by the pores can be explained in terms of the dislocation creep taking place within the Cu. If Cu containing oxygen is welded to alpha-Al2O3, it is thermodynamically p ossible for a further phase, the copper aluminate CuAlO2, to form. The form ation of this phase during subsequent annealing in an oxygen atmosphere aft er welding was investigated in the scanning electron microscope.