Strain rate effects on the mechanical behavior of porous titanium with different pore sizes

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 821; no. C; p. 141593
• Main Authors: Zhao, J.H., Xie, Z.L., Zhong, T., Sun, T., Fezzaa, K., Cai, Y., Huang, J.Y., Luo, S.N.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 21.07.2021; Elsevier BV; Elsevier
• Subjects: Compression tests; Homogeneity; Mechanical properties; Nucleation; Plastic deformation; Pore size; Pore size effect; Porous titanium; Sensitivity; Sintering (powder metallurgy); Strain localization; Strain mapping; Strain rate; Strain-rate sensitivity; Titanium; X ray imagery; X-ray imaging; Yield strength; Yield stress; Strain mapping; Porous titanium; Strain-rate sensitivity; Pore size effect; X-ray imaging
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2021.141593

High strain-rate (up to 6600 s−1) and quasi-static compression tests are conducted on a powder-sintered porous titanium with different pore sizes (mean: 30μm and 120μm). In situ X-ray imaging is implemented to characterize the pores-scale deformation dynamics. The yield strength as a function of strain rate exhibits two stages of rate sensitivity, and the transition occurs at ∼1600 s−1. X-ray images show that pore compaction and strain localizations occur preferentially at pores oriented perpendicular to the loading direction under quasi-static loading, but become more random under high strain-rate loading as a result of higher driving force and plastic deformation nucleation rate. The more homogeneous nucleation of plastic deformation contributes to the increased rate sensitivity beyond ∼1600 s−1. At the same strain rate, the yield strength of porous Ti as well as strain field homogeneity decreases significantly with increasing pore size. The small pore spacing in fine-pored Ti reduces the degree of stress concentrations around pores. Therefore, the higher stress concentrations in coarse-pored Ti lead to an earlier yield of matrix around pores and thus a lower bulk yield strength. •Two stages of rate sensitivity reported firstly for porous Ti.•Yield strength decreases with increasing pore size.•XDIC reveals rate- and pore-size-dependent deformation heterogeneity.•Increasingly homogeneous deformation leads to strain rate effect.•Stress concentration contributes to pore size effect.