Nanocrystalline Ni3Al-based alloys obtained by recycling of aluminium scraps via mechanical alloying and consolidation

•Bulk nanocrystalline Ni3Al-based alloys were produced by milling and consolidation.•Aluminium scrap alloys were used as starting materials for mechanical alloying.•The microhardness is relatively high (∼950 HV0.1) in comparison to literature data.•A huge increase in material’s hardness is related to nanocrystalline structure.•It was proved that re-use of already existing materials can be done successfully.

Bulk nanocrystalline Ni3Al-based alloys were produced by ball milling of powdered aluminium scrap alloys (two silumines with chemical compositions: Al87.5Si7.8Cu2.1Fe0.7Zn1.4Mn0.4Mg0.1 (R1 scrap) and Al88.4Si5,7Cu3,9Fe0,9Zn0,6Mn0.5 (R2 scrap)) with addition of Ni powder and subsequent hot-pressing consolidation. The final products of mechanical alloying were consolidated at 1000 °C for 180 s under the pressure of 7.7 GPa. The powders and the compacted samples were examined by XRD method. The results obtained show that during the milling supersaturated solid solutions Ni(Al, Si…) are formed and during the consolidation the disordered solid solutions transform into ordered nanocrystalline Ni3Al intermetallic based phases with a mean crystallite size of ∼30 nm. The microhardness of the produced Ni3Al-based alloys is 955 for R1 process and 928 HV0.1 for R2 process respectively. The density of the pellets is nearly 100% of theoretical value for the Ni3Al intermetallic phase and the open porosity of the compacts is negligibly small.

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