The Zr alloying effect on microstructure evolution and mechanical properties of nanostructured Al-Zr alloyed films

Abstract Al-Zr nanocrystalline alloy films with Zr contents range from 0 to 8.3 at.% were prepared by magnetron sputtering. The microstructure evolution, mechanical behaviors and strengthening mechanism of films were studied. All the films formed a supersaturated solid solution structure of Zr in the Al lattice. With the increasing of Zr contents, the grain size of films decreased rapidly. When the Zr content increases to 8.3 at.%, the grain size was reduced to about 20 nm. The added Zr atoms tended to segregate at grain boundaries in the Al-Zr alloy films. The hardness of the film gradually increased from 2.5 GPa of pure Al to 5.4 GPa of Al-8.3 at.% Zr film. The strengthening of Al-Zr alloy film comes from three aspects, grain refinement strengthening, solid solution strengthening and nanocrystalline solution pinning strengthening. Among the three strengthening factors of the Al-Zr alloy films, the contribution of fine grain strengthening is the largest, about 70%, followed by solid solution strengthening, 15–20%. The contribution of nanocrystalline solution pinning strengthening is the weakest, less than 10%.