The Influence of Grain Boundary and Hydrogen on the Indetation of Bi-crystal Nickel

Three different types of symmetrical tilt grain boundaries, Ȉ3, Ȉ11, and Ȉ27, were constructed to study the dislocation behavior under the indentation on bi-crystal nickel. After hydrogen charging, the number of hydrogen atoms in the Ȉ3 sample is the smallest and gradually increases in Ȉ11 and Ȉ27 samples. The force-displacement curve of indentation shows that the deformation resistance of the Ȉ3 sample is significantly higher than that of Ȉ11 and Ȉ27 samples. With the presence of grain boundaries, the deformation resistance of Ȉ11 and Ȉ27 samples is significantly improved, while the deformation resistance of the Ȉ3 VDPSOH is weakened. The indentation depth during the formation of dislocations in single  crystals  is  significantly  greater  than  that  of  bi-crystals.  Grain   boundaries  slow  down  the dislocation  propagation speed.  Compared  with  the  bi-crystals   without  hydrogen,  the  presence  of hydrogen reduces the deformation resistance and accelerates the dislocation propagation.