Mechanical behavior of structurally gradient nickel alloy

Certain structurally gradient metallic materials have shown a combination of high strength and work hardening capability. The fundamental mechanisms behind such a unique mechanical behavior remain less well understood. Here we processed NiCrMo based C-22HS alloys by surface mechanical grinding treatment to achieve a gradient microstructure consisting of surface nanolaminated layer, deformation twinned layer and severely deformed layers. In situ micropillar compression tests performed inside a scanning electron microscope reveal different mechanical behaviors of each layer. This study suggests that the increase of intergranular back stress may have contributed to the high strain hardening behavior of the gradient material.