Nanoindentation and microbending analyses of glassy and crystalline Zr([sbnd]Hf)[sbnd]Cu thin-film alloys

Nanoindentation and microbending testing were used to investigate the mechanical properties of Zr([sbnd]Hf)[sbnd]Cu thin-film alloys prepared by nonreactive magnetron co-sputtering. A detailed analysis of nanoindentation data and microscopic images of indents allowed a more precise determination of the effective Young's modulus of the films thanks to taking the pile-up effect into account. Microbending testing in a scanning electron microscope was performed with microcantilevers fabricated by focused ion beam and the data were evaluated using a finite element method model. As outputs of this elasto-plastic model, Young's modulus, yield strength, elastic strain, apparent yield point and approximate ultimate strength and strain of the films were determined. From material point of view, the effect of elemental composition (Cu content and Hf substitution) and the structure (glassy and crystalline) was investigated and discussed. It was shown that the substitution of Hf for Zr has less pronounced effect on the mechanical properties than the increase in the Cu content in the films that leads to a pronounced increase in the hardness, Young's modulus, elastic strain, yield strength, apparent yield point and ultimate strength but also to a decrease in the plastic parameter k and ultimate strain. Furthermore, a different atomic ordering in the crystalline and glassy Zr[sbnd]Cu films of the identical elemental composition results in differences in their mechanical properties and deformation behavior. The crystalline film was observed to be harder and stiffer with approximately the same elastic strain but higher yield strength and its plastic deformation was free of shear band events.