Nanostructured Al–Fe alloys produced by e-beam deposition: static and dynamic tensile properties

Three different aluminum–iron alloys were produced by electron-beam deposition with the iron content in the range 1.15–1.71 at.%. These alloys did not contain any identifiable iron-bearing particles, and exhibited full density with high-angle grain boundaries in the micrometer range, and a sub-grain size typically smaller than 100 nm. The tensile deformation characteristics of the alloys were examined at a dynamic strain rate of 1.1×103 s−1 and a quasi-static strain rate of 1×10−3 s−1 at room temperature. The alloy containing 1.7% Fe exhibited an abnormally high tensile strength of about 950 MPa with a ductility of up to 6%. Detailed atomic resolution imaging of the structure of the alloys has been performed along with an examination of their fracture surface features. The fracture surfaces of the alloys showed ductile dimples which typically spanned five to 10 times the sub-grain diameter. It is postulated that the nano-scale sub-grains of the alloy impart high strength, while the structure associated with high-angle boundaries provides reasonable ductility. Possible mechanisms responsible for the high strength in the present Al–Fe alloys are explored. The present results are also examined in conjunction with a comprehensive survey of available results on the strain-rate sensitivity of tensile yield strength and ductility in microcrystalline, sub-microcrystalline and nanocrystalline metals and alloys, and on the solid-solution strengthening of aluminum alloys.