材料期刊网

High purity alpha-titanium bicrystals were prepared using a strain-annealing method after refining twice in a vacuum electric are furnace and then growing crystals three times in a vacuum floating zone melting furnace. Reverse push-pull cycling tests were performed on bicrystals with grain boundaries oriented at about 90 degrees, 70 degrees and 35 degrees to the stress axis. The cyclic stress-strain curves of bicrystals were determined by a multiple-step test method. The position of the cyclic stress-strain curves has no direct dependence on the angle between the grain boundary plane and the stress axis. {<11(2)over bar 1>}, {<11(2)over bar 2>}, {<10(1)over bar 1>} and {<10(1)over bar 2>} types of twinning occurred during cycling. Grain boundaries sliding was observed in the specimen whose grain boundary plane is about 35 degrees inclined to the stress axis. Bunched slip bands in a braid-like pattern were observed. Fatigue cracks initiated along slip bands and grain boundaries owing to grain boundary extrusion or grain boundary sliding.