The Nature of Defects in Quenched α-Brass

The defects such as faulted dislocation loops, perfect dislocation loops and stacking-fault tetrahedra are observed in quenched α-brass. The faulted loops lie on the {111} planes and have various polygonal shapes with edges along the <110> directions. The perfect loops have hexagonal, rhombic and irregular shapes, and the former two are on the {111} planes with their edges along the <110> directions. Analysis of the image contrast reveals that the faulted loops are of the vacancy type having a Burgers vector a/3<111> and the perfect loops are of the vacancy type having a Burgers vector a/2<110>. The perfect loops are favoured when the quenching temperature is high, while the faulted loops are favoured when the temperature is low. The stacking-fault tetrahedra are occasionally observed by high temperature quenching. The formation energy of a vacancy is estimated to be about (1.00±0.05) eV from the density and size of observed loops. The formation of three different defects is discussed by the simple energy comparison.