Effect of Cooling Rate on Superelasticity and Microstructure Evolution in Ti-10V-2Fe-3Al and Ti-10V-2Fe-3Al-0.2N Alloys

Abstract

A Ti-10V-2Fe-3Al alloy with a small amount of nitrogen shows superelasticity. Controlling of the cooling rate from solution treatment temperature improves superelasticity in both Ti-10V-2Fe-3Al and Ti-10V-2Fe3-Al-0.2N alloys. In this study, a wider range of the cooling rate was examined and microstructure change during slow cooling was investigated through examining quenched and aged specimens by means of hardness and resistivity measurement and transmission electron microscopy. Although superelasticity is improved with a decrease in the cooling rate up to 22 K/s for the N-free alloy and up to 50 K/s for the 0.2N alloy, there is no obvious change in microstructure. It is clarified from the observation of specimens quenched and aged at the temperature range where superelasticity is improved that the phase decomposition occurs through isothermal ! phase precipitation. Therefore, microstructure evolution during slow cooling is considered to be precipitation of isothermal ! phase or its precursor phenomena.

A lightweight shape-memory magnesium alloy

“…S4). The maximum superelastic strain is about the same as that of a b-type Ti-based superelastic alloy (22,(24)(25)(26)(27). The XRD pattern of the tensile-fractured specimen tested at -150°C (Fig.…”

“…Metastable b-type Ti alloys that show age hardening commonly have thermal-induced, stress-induced, or both types of martensitic transformation (18)(19)(20)(21)(22). Some b-type Ti alloys exhibit shape-memory effect and superelasticity, which are due to thermoelastic thermaland stress-induced martensitic transformations, respectively, from a bcc to an orthorhombic structure (22)(23)(24)(25)(26)(27). We herein report a metastable b-type Mg alloy including Sc that shows thermoelastic martensitic transformation and exhibits superelasticity with recoverable strain of 4.4% at -150°C and shape recovery upon heating.…”

Thermal stability and phase transformations of martensitic Ti–Nb alloys

“…The SM effect and SE have been reported in Ti–Mo [6], Ti–V [7] and Ti–Nb [8] alloys. However, the Ti–Mo based alloys are susceptible to ω phase embrittlement.…”

The Range of the Occurrence of α Phase in near β Titanium Alloys

“…The occurrence of α phase influences the possibility of thermomechanical processing of such alloys [7][8][9][10][11][12][13][14]31,32]. It should be emphasized, that intermediate or martensitic phases, morphologically and crystallographically different from so called primary α phase, may also occur in these alloys [15][16][17][18][19]. Only the knowledge of the range of the occurrence of two-phase region in such alloys enables proper interpretation of changes in their formability [20][21][22][23][24][25][26]32].…”