Fracture mechanisms of Glidcop Cu-Al2O3 composite before and after ECAP observed by "in-situ tensile test in SEM"

The method of "in-situ tensile testing in SEM" is suitable for investigations of fracture mechanisms because it enables to observe and document deformation processes directly, thanks to which the initiation and development of plastic deformation and fracture can be reliably described. The deformation and fracture mechanisms of Glidcop AL-60 grade with 1.1 wt.% of Al2O3 phase (1.62 vol.% of Al2O3) were analyzed before and after ECAP (Equal Channel Angular Pressing) using technique of the "in-situ tensile testing in SEM". Before ECAP it was showed that the deformation process caused increasing of pores and formation of cracks. Decohesion of small Al2O3 particles and clusters occurred and the final fracture path was influenced by coalescence of originated cracks. The principal crack propagated towards the sample exterior surface. After ECAP initial cracks were formed in the middle of the specimen first of all in triple junctions of nanograins and together with decohesion of Al2O3 particles and clusters at small strains led to the failure. Based on the experimental observations a model of damage and/or fracture mechanisms has been proposed.