Misorientation induced by withdrawal rate transition and its effect on intermediate temperature stress rupture properties of a Ni3Al based single crystal superalloy

The dendritic Ni3Al based single crystal superalloy of [0 0 1] crystal orientation was prepared at constant (50, 100 and 200 μm/s) and changing withdrawal rates (from 100 μm/s to 50 μm/s, and from 200 μm/s to 50 μm/s). It was found that the growth history plays significant role in the primary dendrite arm spacing in the 'as cast' state, while its influence on the dendrite orientation was little. It is stated that the spatial orientation was the basic factor of intermediate temperature stress rupture properties of complete solution treated alloys, i.e. the samples with orientation close to the [0 0 1]-[0 1 1] boundary exhibit higher stress rupture lives and lower elongations in comparison to the alloys with orientation closer to the [0 0 1]-[1 1 1] boundary. Furthermore, withdrawal rate change during solidification resulted in the misorientation, which led to the decrease of intermediate temperature stress rupture lives and elongations.