Thermomechanical Studies of Yielding and Strain Localization Phenomena of Gum Metal under Tension

Abstract

This paper presents results of investigation of multifunctional β-Ti alloy Gum Metal subjected to tension at various strain rates. Digital image correlation was used to determine strain distributions and stress-strain curves, while infrared camera allowed for us to obtain the related temperature characteristics of the specimen during deformation. The mechanical curves completed by the temperature changes were applied to analyze the subsequent stages of the alloy loading. Elastic limit, recoverable strain, and development of the strain localization were studied. It was found that the maximal drop in temperature, which corresponds to the yield limit of solid materials, was referred to a significantly lower strain value in the case of Gum Metal in contrast to its large recoverable strain. The temperature increase proves a dissipative character of the process and is related to presence of ω and α″ phases induced during the alloy fabrication and their exothermic phase transformations activated under loading. During plastic deformation, both the strain and temperature distributions demonstrate that strain localization for higher strain rates starts nucleating just after the yield limit leading to specimen necking and rupture. Macroscopically, it is exhibited as softening of the stress-strain curve in contrast to the strain hardening observed at lower strain rates.

Development of Strain Localization in a Beta-Titanium Alloy Gum Metal Analyzed by Infrared Camera and Digital Image Correlation for Various Strain Rates

“…Increase in the specimen temperature after it drops due to thermoelastic effect, started from point A ( Figure 1b) revealed dissipative character of the process. This takes place in the range of reversible deformation [1,2] and is caused by a stress-induced phase transformation of martensite-like orthorhombic α″ nanodomains [3,4]. From the points B and C the slope of ΔT vs. ε dependence increases significantly.…”

Comparative Investigation of the Influence of Ultrafine-Grained State on Deformation and Temperature Behavior and Microstructure Formed during Quasi-Static Tension of Pure Titanium and Ti-45Nb Alloy by Means of Infrared Thermography

“…The infrared (IR) thermography [ 39 ] has been recognized as an attractive method for studying and analyzing the processes of heat generation under deformation. This technique allows for remotely measuring surface temperature of materials under various conditions and studying the heat generation processes caused by energy dissipation during deformation [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ].…”

Quasi-Static and Dynamic Compressive Behavior of Gum Metal: Experiment and Constitutive Model

“…[10,11] This unconventional deformation mechanism was also investigated by analyzing the mean thermal response of Gum Metal under loading using infrared thermography. [12][13][14] In, [13] it was shown that a drop in temperature during loading, related to the thermoelastic effect, is also followed by a temperature rise within the recoverable strain of the alloy. In other words, it was demonstrated that the large nonlinear recoverable deformation of Gum Metal is a dissipative process.…”

“…The findings were confirmed and broadened by a comprehensive investigation realized using infrared thermography in. [14] The peculiarities of the plastic behavior of Gum Metal were initially attributed to the hypothesis of dislocation-free plastic deformation, [1] since the ideal strength of Gum Metal calculated based on density functional theory in [15] was in the order of the alloy tensile strength measured experimentally as shown in. [3] Microstructure characterization of Gum Metal found distinct surface steps called ''giant faults,'' plastic flow localization and ''nanodisturbances''.…”