α+β titanium alloys have a wide application prospect in aero engine blisk manufacturing, owing to their high specific strength and good high-temperature performance. Whereas there are few studies on mechanical properties and plastic deformation modes of large-size blisk specimens at variable strain rate conditions. In this work, the effects of different strain rates on the mechanical properties of forged TC17 and TC4 alloys were examined by tensile testing machine, and Vickers hardness tester, OM, SEM, and EBSD were used to study the Vickers hardness, deformation microstructures and fracture morphologies. As increasing strain rate, the strengths of both alloys increase and the elongation decrease, showing positive strain rate sensitivities of flow stress, and the strain rate sensitivity coefficients decrease with true strain. Besides the solid solution strengthening of alloying elements, lath α-phases and residual β-phases in TC17 alloy with basket-weave microstructure are interweaved with each other, resulting in more phase interfaces. Phase interfaces are effective in blocking dislocations motion and lead to pile-up of dislocations, improving the strength of TC17 alloy. In addition, the voids are easier to nucleate at the phase interfaces and form dimples. Therefore, a lot of small dimples are observed on the fracture surface, which make the poorer ductility of TC17 alloy. Fewer phase interfaces exist in TC4 alloy with bimodal microstructure, which is related to the better plastic deformation capacity of equiaxed primary α-phases and the regular arrangement of secondary α-phases in transformed β-phases. The fewer phase interfaces increase the mean free path of dislocations and form fewer large dimples, which lead to a decrease in strength but an increase in ductility of TC4 alloy.
Effect of strain rate on mechanical properties of TC17 and TC4 alloy forgings
2023
Aufsatz (Zeitschrift)
Elektronische Ressource
Unbekannt
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