Determination of the mechanical properties of inclusions and matrices in α-U and aged U-5.5Nb alloy by nanoindentation measurements

Abstract

The mechanical properties of the inclusions and matrices in as-cast α-U and aged U-5.5(wt%)Nb alloy are investigated by nanoindentation measurements. The experimental results show that the primary inclusion in α-U is U(N,C), and the hardness and elastic modulus of this inclusion are close to those of the matrix. For the aged U-5.5Nb alloy, the primary inclusions consist of both U(N,C) and Nb2C, but the hardness and elastic modulus of the Nb2C inclusions are much higher than those of both the matrix and U(N,C) inclusions. The calculated results show that the U(N,C) inclusions in α-U have a low strength and a high plasticity index, and these values are close to those of the matrix. Additionally, the Nb2C inclusions in the U-5.5Nb alloy have much higher strength than those of the matrix and U(N,C) inclusions. The low plasticity index of the Nb2C inclusions indicates that they have good elasticity. The experimental results confirm that the low strength and hardnesss of the U(N,C) inclusions result in the generation of voids by cracking during the fracture process, while the incompatibility of the high strength and hardness of the Nb2C inclusions with those of the matrix promotes the nucleation of voids by debonding at the inclusion-matrix interface.