The Effect of Crystallographic Texture on the Constant-Stress, Constant-Heating-Rate Mechanical Test

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2024-02, Vol.55 (2), p.375-388
• Main Authors: Semiatin, S. L., Levkulich, N. C., Butler, T. M.
• Format: Article
• Language: English
• Subjects: Alpha particles; Alpha rays; Axial stress; Cavitation; Characterization and Evaluation of Materials; Chemistry and Materials Science; Constitutive relationships; Crystallography; Ductility; Heating; Holes; Low temperature; Materials Science; Mechanical tests; Metallic Materials; Nanotechnology; Original Research Article; Plastic flow; Rolling direction; Sheet material; Strain rate; Structural Materials; Surfaces and Interfaces; Temperature; Temperature dependence; Texture; Thin Films; True stress
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-023-07270-y

The effect of texture on plastic flow during the constant-stress, constant-heating-rate (CSCHR) mechanical test was established using Ti–6Al–4V sheet material with a strong basal-transverse starting texture. For this purpose, test samples were cut parallel to either the rolling direction (RD) or the long transverse direction (TD) of the sheet. CSCHR testing comprised preheating/soaking at 538 °C followed by heating at a constant rate of 75 °C/min while applying a constant true stress of 103, 172, or 276 MPa. The resulting plastic-strain- vs -time/temperature curves all exhibited a very low rate of straining at low temperatures followed by increasing strain rates at higher temperatures. For each applied stress level, the onset of high-strain-rate deformation occurred at a higher temperature for the TD sample than for the corresponding RD sample. The difference in RD and TD observations was successfully interpreted in terms of a constitutive relation incorporating a strength coefficient dependent on texture as quantified by measured Taylor Factors. A moderate effect of texture on cavitation and fracture was also noted. Specifically, cavities initiated along the boundaries between (hard) alpha particles and the (soft) beta matrix, leading to higher cavity growth rates and lower ductility in TD samples for a given applied stress. Such observations were ascribed to the texture dependence of local stress triaxiality and hence the cavity-growth rate. In addition, an observed effect of peak temperature on ductility was ascribed to the temperature dependence of the cavity growth rate.