Novel technique for evaluating grain boundary fracture strength in metallic materials

A technique to evaluate grain boundary fracture strength of metallic materials was developed. Coincident site lattice (CSL) boundaries were prepared by diffusion-bonding of oriented two single-crystal Ni–20Cr pieces. Microtensile specimens were fabricated across the CSL boundaries by femtosecond laser machining. Due to the highly ductile character of Ni–20Cr, notches were machined along the grain boundaries to initiate grain boundary fracture. The microtensile tests at room temperature demonstrated that Σ3(1 1 1) boundary was the strongest of all the CSL boundaries examined.

► Microtensile test technique to evaluate grain boundary fracture strength was developed.
► Notched microtensile specimens were fabricated by femto-second laser.
► Σ3(1 1 1) boundary was the strongest CSL boundary at room temperature.