Tensile Behavior of Single-Crystal Nickel Containing Void Defects: Void Growth and Coalescence Mechanisms

S Kun and L Hao and LS Wang and D Jun and JH Yi and SQ Lu and H Xia, RARE METAL MATERIALS AND ENGINEERING, 52, 3767-3777 (2023).

DOI: 10.12442/j.issn.1002-185X.20230187

Molecular dynamics simulations were used to investigate the effect and mechanism of the angle (theta) between the plane of void center formation and the loading direction on void growth and coalescence behavior in single-crystal nickel under uniaxial tension. The results show that the yield stress and average flow stress of single-crystal nickel decrease with increasing theta, and the rate of stress decrease accelerates with increasing theta. When theta=90 degrees(loading direction perpendicular to the plane of void center), the independent growth time of voids in single- crystal nickel is the shortest and void coalescence occurs first, leading to the easiest way to entering the softening stage. This is due to the fastest growth rate of void volume fraction and damage evolution rate in single-crystal nickel when theta=90 degrees. When theta=90 degrees, the significant reduction of 1/6<112> (Shockley) dislocation length and the maximum transformation rate of atomic number from fcc crystal structure to Other and hcp crystal structures in single-crystal nickel lead to the fastest damage evolution rate and the most severe damage level. It is worth noting that voids in single-crystal nickel are most likely to coalesce when theta=90 degrees, due to the larger tensile stress on the void surface under this condition.

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