Readily superplastic forging at high strain rates in an aluminium-based alloy produced from nanocrystalline powders

Abstract

A high-strain-rate superplasticity at strain rates from 10⁻¹ to 1 s⁻¹ (which was many orders of magnitude higher than the strain rates in typical commercial superplastic alloys) was found in a new aluminium-based crystalline alloy, as-extruded Al-Ni-Mm crystalline and Al-Ni-Mm-Zr crystalline alloys (Mm = misch metal) fabricated by warm consolidation of their amorphous or nanocrystalline powders. The alloys were developed with very fine grained structures less than 100 nm in size, with a uniform distribution of both the Al₃Mm and the Al₃Ni particulates which were 70 nm in diameter. As a result of these specific microstructures, these alloys have superior mechanical properties at room temperature; for example the tensile strength is greater than 800 MPa and the Young's modulus is equal to 96 GPa. As-extruded workpieces of the alloys could be forged superplastically at a commercial production speed (less than 1 s) into complicated components with a con-rod shape, which exhibited good postdeformation mechanical properties.