Compressive Mechanical Properties of Nanostructured Intermetallic Alloys Al3Ti-X (X = Mn or Fe)

Abstract

The mechanical behavior of the sintered nanostructured intermetallic alloys, Al67Ti25Mn8 and Al67Ti25Fe8 has been investigated by means of compression tests as a function of temperature. These intermetallic materials are produced by mechanical alloying and spark plasma sintering. The sintered alloys have been characterized by X-Ray Diffraction and Transmission Electron Microscopy. Their nanostructure consists of a single-phase with an L12 (cubic) structure and an average grain size in the nanoscale (lower than 30 nm). These nanostructured intermetallics show considerably high ductility in compression at high temperature but are brittle at temperatures below 400 °C. In such cases the compressive fracture strength can reach values as high as 1.8 GPa (Al67Ti25Fe8). At 500 °C, some ductility is found together with a relatively high flow stress (around 1 GPa), the corresponding deformation curve shows strain hardening and in some cases stress serrations (strain aging). At 600 °C, a low flow stress is measured (~300 MPa) with high ductility. At 700 and 800 °C, a quasi-superplastic behavior is found with a total deformation of around 45 and very low flow stresses. No evidence of dislocation motion is found at temperatures above 700 °C suggesting a deformation mechanism based on grain boundary sliding.