CHARACTERIZATION OF THE STRUCTURE AND THE DEFECTS OF ODS SUPERALLOYS
Abstract
THE MICROSTRUCTURAL FEATURES AND THE DEFECTS OF OXIDE DISPERSION STRENGTHENED (ODS) SUPERALLOYS HAVE BEEN STUDIED BY MEANS OF TRANSMISSION ELECTRON MICROSCOPY(TEM). A PREFERENTIAL GRAIN ORIENTATION IS ESTABLISHED FOR THE ODS ALLOY MA6000: THE COARSE GRAMS SHARE A <110>+5 AXIS PARALLEL TO THE EXTRUSION DIRECTION. OXIDE DEPLETED ZONER AND ROWS OF SMALL GRAINS ARE OBSERVED IN MA6000. THEIR PRESENCE COULD BE ATTRIBUTED TO AN INCOMPLETE MANUFACTURING PROCESS OF THE ALLOY. THE GRAIN BOUNDARY (GB) STRUCTURE OF THIS ALLOYS IS HIGHLY PETURBED. PRACTICALLYALL THE GBS BETWEEN THE COARSE GRAINS ARE OF THE LOW-ANGLE TYPE, CONSISTING OFFAMILIES OF MIXED DISLOCATIONS WITH BURGENS RECTORS B=1/2<110> . AFTER HIGH TEMPERATURE CREEP THE PARTICLE OF THE ORDERED PHASE (LI2) FORM A LAMELLAR STRUCTURE ALONG A DIRECTION NORMAL TO THE DIRECTION OF THE APPLIED STRESS. ADDITIONALLY DISLOCATION NETWORKS ARE FORMED AROUND THE ORDERED PARTICLES IN THE OXIDE DEPLETED ZONES. CREEP DOES NOT SEEM TO INFLUENCE SEVERELY ...
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