Enhanced frictional performance in gradient nanostructures by strain delocalization

•A computational model is established to investigate the scratch test of gradient nanostructures.•The coefficient of friction can be significantly lowered by gradient nanostructures.•The friction coefficient can be minimized by tuning gradient microstructures.•The enhanced friction performance originates from strain delocalization by gradient nanostructures.•A combination of high strength and low friction coefficient can be achieved in gradient nanostructures.