Structures of Grain Boundaries and Aspects of Deformation Behavior in Ni3Al Alloys
Final rept. 1 Sep 1983-1 Aug 1988
WRIGHT LAB WRIGHT-PATTERSON AFB OH MATERIALS DIRECTORATE
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The structures of two grain boundaries in Ni3Al were determined using transmission electron microscopy TEM. The line directions and spacings of secondary grain boundary dislocation gbds were calculated for coincidence site lattice CSL relationships near the experimentally determined misorientations. The structures of the boundaries were found to be in good agreement with 9 and 31b relationships of the ordered lattice. The grain boundary dislocations were found to be characteristic of the ordered structure. No grouping of partial gbds was observed. Lattice dislocations consisting of pairs of 13 112 superpartials bounding extended superlattice intrinsic stacking faults SISFs were observed by TEN. They were found to independently react to APB coupled 112 110 pairs in the commonly observed pure screw orientation. Implications with regard to Kear-Wilsdorf type locking mechanisms and deformation behavior are discussed. Boron was observed to have strong effects upon the population of boundary types, grain size, and grain growth. In addition, small amounts of B completely eliminate widely extended stacking faults. It is concluded that effects of B other than influencing boundary cohesion are important.
- Properties of Metals and Alloys