Interfacial structure and mechanical properties of surface iron–nickel alloying layer in pure iron fabricated by surface mechanical attrition alloy treatment

By surface mechanical attrition alloy treatment (SMAAT) and subsequent low temperature anneal treatment, a refined Fe/Ni alloy surface layer, about 50 μm in length, was fabricated on a pure iron plate. Micro-hardness and the friction and wear behavior of alloy surface layers were studied in comparison with those of their SMATed-only nanocrystallization counterpart. The interface microstructure indicated that the nickel powders had been permeated and welded into the pure iron surface in some localized regions by plastic deformation. The SMAAT process includes impacting with high strain velocity, grain refinement and synchronous diffusion. Atomic diffusion has been accelerated by the generation of high density defects through severe plastic deformation. Quick formation of the Fe/Ni intermetallic and solid solution phase alloy layer during SMAAT can be detected. Subsequent annealing treatment further accelerates the diffusion of Ni and Fe elements and leads to the formation of alloy phases. The results of friction and wear tests show that the properties of the alloy layer were remarkably improved. The main reason for this result may originate from its microstructures, i.e. an alloy layer with smaller grains, which reduces the effect of fatigue wear.

► A refined Fe/Ni alloy surface layer about 50 μm was fabricated by SMAAT.
► The SMAAT process includes impacting, grain refinement and synchronous diffusion.
► The reduced diffusion activation energy accelerates short-range diffusion.
► The intermetallic/alloy phases have been formed during SMAAT.
► Refine and alloy reduce fatigue wear effect and improve friction and wear properties.