Plasticity and Alloy Softening of Nearly Interstitial-Free Alloys of Iron with Chromium, Tungsten and Nickel

摘要

The influence of substituted Cr, W and Ni atoms on the plasticity of polycrystalline iron with very low interstitial content was investigated. Tensile properties of Fe-Cr and Fe-W alloys were determined between -100C and +400C. Both alloy series showed slight indications of alloy softening at about -40C. A series of experiments was performed in order to get additional information on the phenomenon of alloy softening in Fe-Ni alloys. Tensile properties, yield elongation, strain rate sensitivity, activation volumes, dislocation velocity exponents and the Hall-Petch parameter k were determined in the temperature range -196C to 400C. Dislocation structures were observed by transmission electronmicroscopy. At and above room temperature unalloyed iron displays glide not only on the closest packed planes but also on the less close packed ones. Glide on these less closely packed glide planes decreased at the lower temperatures although the number of glide planes on the main system did not increase. This behavior was not observed in the alloy containing Ni. Consequently the alloy softening resulted from an abnormal increase in the strength of unalloyed iron at the lower temperatures. (Author)