Effect of Texture on Strain Localization and Crack Initiation in Polycrystalline Beryllium Under Static Tension: Experimental Study and Micromechanical Simulations

The mechanisms of deformation and crack initiation in polycrystalline beryllium during static tension were studied in this work using EBSD analysis and crystal plasticity simulations. Results showed that cold deformation of beryllium was accompanied by an extremely inhomogeneous distribution of accumulated strain associated with different activities of slip systems and grain interactions. The fracture of beryllium occurs by two mechanisms strongly related to its crystallographic texture. Impossibility of slip along the basal and prismatic systems leads to brittle transgranular fracture at small strains. Localization of strain at the conjugation of grains with favorable and unfavorable conditions for prismatic slip produces intergranular cracks due to the exhaustion of beryllium plasticity. Moreover, activation of basal or prismatic slip is not only controlled by the grain orientation but also by the stress concentration raised by grain interactions. The modified Cockcroft-Latham criterion and the stress triaxiality parameter showed a reasonable agreement between the predicted and observed regions of intergranular crack formation. For accurate estimation of the fracture probability, the strong dependence of fracture strain or of the criterion limiting value on the grain orientation should be taken into consideration.