2019 Volume 105 Issue 9 Pages 935-937
In the dislocation characterization by the modified Williamson-Hall method, elastic stiffness ratio c12/c44 and anisotropy parameter Ai (=2c44/(c11–c12)) are important parameters to determine the contrast factor. In order to determine the values of elastic stiffness cij, we need the information of Young’s modulus E*, shear modulus G* in poly crystal, and Young’s modulus of single crystal; E100, E110, E111. The values of E* and G* are experimentally obtained by the resonance method. However, it is not so easy to fabricate single crystal, especially for practically used metals in which many alloying elements are contained. Therefore, we need to estimate the values of E100, E110, E111 in some way. In this paper, the following equations were proposed to estimate these values for the steels with bcc structure.
E100 = 0.647 × E* E110 = 1.079 × E* E111 = 1.387 × E*
The coefficient in each equation was determined by the average value of Ehkl/E* in pure iron. In the steels with bcc structure (E*=206 GPa), it was confirmed that c12/c44 and Ai are given by the following equations as a function of Poisson’s ratio ν.
c12/c44 = –1.466 + 8.887 × ν Ai = 2.885 – 1.602 × ν
As a result, c12/c44≒1.11 and Ai≒2.42 are applicable for the modified Williamson-Hall method under the condition; ν=0.29.
