OBSERVATIONS OF CHANGING FINE-STRUCTURE IN NANOSCALE EELS ANALYSIS OFGRAIN-BOUNDARIES IN STAINLESS-STEELS

Increasingly sophisticated demands placed on metals in the modern worl d have stimulated the use of tailor-designed multi-component alloys in many applications, Solute segregation, whether due to thermodynamic o r nonequilibrium processes, can dramatically alter the alloy compositi on near the grain boundary leading to drastic (and often detrimental) change in the properties of the alloy, The solute segregation profile is often a nearly singular function centred at the boundary, leading t o great difficulty in analysis, The traditional method of depth profil ing using Auger electron spectroscopy can only examine fractured surfa ces and, because of limited spatial resolution, yields laterally avera ged information. Recent improvement in the efficiency of electron-micr oscope-based electron energy-loss spectroscopy has allowed a new high- resolution approach in analysing the chemical and electronic propertie s of buried interfaces on a nanometer scale, i.e. we can study the com plicated details of the alloy boundary itself. As an example, we will present the result of a study on stainless-steel alloys used in the U. K. nuclear industry, The effect of irradiation on the structure of the alloy boundary is investigated, The nanoscale change in the chemical state of the alloying element at the grain boundary is observed for th e first time in situ, The result can be potentially utilized to predic t the corrosion-resistance of the stainless steels.