Which microstructural defect risks accelerated crack propagation in directionally solidified turbine blades where grains solidify via a modified Bridgman casting method?

💡 Explanation

Concentration changes from species diffusing at different rates result in Kirkendall voids; these weaken grain boundaries because of void coalescence and act as crack initiation sites. Therefore, accelerated propagation occurs at grain boundaries, rather than homogenous matrix failure or alternative deformation mechanisms.

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