Constitutive analysis of compressive deformation behavior of ELI-grade Ti–6Al–4V with different microstructures

• Published in: Journal of materials science 2012-04, Vol.47 (7), p.3115-3124
• Main Authors: Park, Chan Hee, Son, Young Il, Lee, Chong Soo
• Format: Article
• Language: English
• Subjects: Alloys; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Comparative analysis; Compression tests; Crystallography and Scattering Methods; Deformation; Deformation effects; Deformation mechanisms; Heat treating; Heating; Interstitials; Materials Science; Mathematical models; Microstructure; Polymer Sciences; Softening; Solid Mechanics; Stress concentration; Thermal stress; Threshold stress; Titanium; Titanium base alloys; Yield strength
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-011-6145-9

In this study, a constitutive analysis of the flow responses of Ti–6Al–4V under various strain rates was conducted by separately quantifying the hardening and softening effects of microstructure, interstitial solute and deformation heating on the total stress. For this purpose, a series of compression tests on an extra-low interstitial grade alloy with equiaxed, lamellar, or bimodal microstructures was performed at until the metal fractured, and the results were compared to those of the commercial grade alloy. The thermal stress σ * increased with an increasing interstitial solute concentration; the athermal stress increased in the order of equiaxed, lamellar, and bimodal microstructures. Load–unload–reload tests revealed that the flow softening at a relatively high was likely caused by deformation heating rather than by microstructure change; thus flow softening was attributed to a decrease in σ * . Finally, a mechanical threshold stress model was extended to capture those observations; the modified model can provide a reasonable prediction of flow stress in Ti–6Al–4V with different microstructures and interstitial solute concentrations.