U-Nb合金中夹杂物的纳米压痕表征

Nanoindentation Characterization of Inclusions in U-Nb Alloy

采用纳米压痕技术对铸态U-5.5Nb合金中Nb_2C、U(C,N)以及基体力学性能进行了表征,根据获得的硬度值计算了屈服强度和塑性指数。实验结果表明Nb_2C夹杂物的弹性模量和硬度最大,而U(C,N)夹杂物的弹性模量和硬度远小于Nb_2C但明显高于基体;计算结果显示Nb_2C夹杂物屈服强度最高而塑性指数值最小,倾向于发生弹性变形,U(C,N)夹杂物强度低但塑性指数值最大,更容易发生塑性变形并发生破裂。基体多步循环加载获得的弹性模量和硬度值与单次加载基本一致,并且弹性模量值和文献中报道的单向拉伸实验测得的值相符。

Mechanical properties of the Nb2C and U(N,C)inclusions and matrix in the U-5.5Nb alloy were characterized by nanoindentation and the yield strength and plasticity index were calculated from the obtained hardness.The result from experiment shows that the Nb2C inclusion has the highest elastic modulus and hardness,while the corresponding values of the U(N,C)inclusion are far less than those in the Nb2C inclusion but higher than those of matrix.Moreover,the result calculated from hardness shows that the yield strength of the Nb2C inclusion is the highest,but the plasticity index is the lowest,which reveals that the Nb2C inclusion inclines to elastic deformation.However,the yield strength of the U(N,C)inclusion is low and the plasticity index of the U(N,C)is the highest,which reveals that the U(N,C)inclusion prefers to plastic deformation and also can break easily.Elastic modulus and hardness from multi-cycle load/unload test are close to those obtained by single load/unload test.In addition,the elastic modulus obtained from nanoindentation accord with the value obtained by tensile test in the literature.