Cyclic plasticity and strain localization in cast γ-TiAl based alloy

Abstract

Cyclic strain localization and observation of surface relief in nearly lamellar cast γ-TiAl based alloy Ti–48Al–2Nb–2Cr–0.82B (all in at. %) cycled in strain control were experimentally studied. Hysteresis loop area, the cyclic hardening curves, the cyclic stress-strain curve and VH parameter were measured. Surface relief of cyclically strained specimens was observed using scanning electron microscopy. The variations of the VH parameter indicate the cyclic slip localization. The localization has a pronounced effect on surface relief formation. Persistent slip markings are formed on the surface along interlamellar interfaces γ/α2 and γ/γ. These locations were nuclei for fatigue cracks in the interior of grains. Experimental results concerning the loop shape parameter and surface relief are used to discuss the role of cyclic slip localization on the cyclic stress-strain response and fatigue crack initiation.