FeNiMnAl high entropy alloys

The aim of this project is to understand the fundamental mechanisms involved in the deformation of carbon-doped Fe40.4Ni11.3Mn34.8Al7.5Cr6. To that end, we will grow single-slip, [123]-oriented single crystals of undoped and carbon-doped Fe40.4Ni11.3Mn34.8Al7.5Cr6 using either a Bridgman furnace or an optical floating zone furnace in the author’s lab. Using these single crystals, we will:

  1. Determine the stress-strain behavior under tension as a function of temperature (to 700oC in ~150oC increments) and strain rate (5 x 10-6 s-1 to 1 s-1). In particular, we will examine whether the HEAs show the usual 3-stage work-hardening behavior exhibited by single-slip f.c.c. single crystals and determine how the carbon affects both the onset and the work-hardening rate of each stage. At higher temperatures, we will look for evidence of dynamic strain ageing, including the Portevin-Le Chatelier effect. Compression tests will be performed to determine whether there is any tension/compression asymmetry.
  2. Determine the deformation mechanisms using a combination of post-mortem transmission electron microscope dislocation analysis of primary slip-plane-sectioned specimens, and post-mortem analysis of slip lines on crystal’s surfaces after deformation to various strains.
  3. Determine the stacking fault energy as a function of carbon content based on weak-beam imaging of a/6<211> dislocation partials viewed perpendicular to their slip plane.
  4. Determine the extent of cross-slip using in-situ straining studies in a transmission electron microscope at a variety of temperatures.
  5. Utilize atom probe tomography to look for nanoprecipitates and segregation. Model the effects of the interstitials on the deformation behavior of Fe40.4Ni11.3Mn34.8Al7.5Cr6 based on the experimentally-observed deformation mechanisms

Faculty contact: Ian Baker