Microanalytical characterization of microscopic defects in NiCr-based alloys of low impurity content

Abstract

The quality of thin foil components made from NiCr-based alloys can be reduced by three-dimensional defects formed during alloy preparation and roMng cycles of foil manufacturing. In particular, the appearance of microscopic holes, i.e. defects transparent to light, air or other matter, can completely prevent special applications. Thus for the optimization of foil manufacturing procedure microanalytical investigations were needed to support the decision for either a model of solely vacancy coalescence or a combined model of vacancy coalescence in the presence of second-phase inclusions and direct interaction of inclusion and roll surface. The identification of corundum particles as a major inclusion of almost all investigated transparent defects confirms that thodefects are formed due to both different mechanical behaviour (ofα-Al2O3 inclusions and NiCr-alloy) and vacancy coalescence at the appropriate phase boundary during rolling deformation.