Effect of thermomechanical processing on evolution of various phases in Ti-Nb alloys

Abstract

This paper deals with the effect of thermomechanical processing on microstructural evolution of three alloys, viz. Ti-8Nb, Ti-12Nb and Ti-16Nb. The alloys were hot rolled at 800°C and then subjected to various heat treatments. Samples from hot-rolled alloys were given solution-treatment in β and α + β phase fields, respectively followed by water quenching and furnace cooling. The solution-treated alloys were subsequently aged at different temperatures for 24 h. Phases evolved after various heat treatments were studied using X-ray diffractometer, optical, scanning and transmission electron microscopes. The alloy Ti-8Nb exhibits α and β phases while the alloys Ti-12Nb and Ti-16Nb show the presence of α ″, β and ω phases in the as-cast and hot-rolled conditions. The β solution treated and water quenched specimen of the alloy Ti-8Nb displays α″ phase while the alloys Ti-12Nb and Ti-16Nb exhibit α″, β and ω phases. The alloy Ti-8Nb shows the presence of α, β and ω phases while those of Ti-12Nb and Ti-16Nb display the presence of α, α ″, β and ω in α + β solution treated and water quenched condition. The observation of ω phase in solution treated condition depends on the cooling rate and the Nb content while in the aged specimens, it is governed by aging temperature as well as the Nb content.

Influence of thermomechanical processing on biomechanical compatibility and electrochemical behavior of new near beta alloy, Ti-20.6Nb-13.6Zr-0.5V

“…In line with the findings of others, 34,41 the microstructure of FC or AC samples consisted of Widmanstätten α-laths (in a basket-weave arrangement) that were composed of different variations of α plates within pre-existing β-grains. The volume fraction of the α phase in the FC samples was high due to the lower cooling rate.…”

“…A large number of papers have reported the presence of a martensite structure in Ti materials if the solution is treated at a high temperature (above β phase field) with a sufficiently high cooling rate. 20,34,[41][42][43][44][45][46] Thus, rapid cooling from the above temperature resulted in a martensite phase in the microstructure of the WQ samples. Two types of metastable martensites, α′ and α″, which are hexagonal and orthorhombic structures, respectively, are found in Ti alloys quenched from the β phase based on the concentration of the beta alloying elements.…”

Niobium carbide as a technology demonstrator of ultra‐high temperature ceramics for fully ceramic microencapsulated fuels

“…Ta is refractory as either oxide or metal, and was never found in the ejected sampling or XRD. Both Ti and Ta have full miscibility with Nb, which explains why both were only detected and quantified when vaporized by plasma (Table and Figure ). The lattice constant of TaC 1‐x is lower than NbC 1‐x at the same stoichiometry despite their identical atomic radii …”

Micro-hardness and Young's modulus of a thermo-mechanically processed biomedical titanium alloy

“…A non-equilibrium metastable phase called martensite can be created in Ti alloys if the cooling rate from the β phase field is sufficiently high (Banerjee and Krishnan 1981, Boyer et al 1994, Majumdar 2012). Considerable literature is available (Boyer et al 1994, Majumdar 2012, Collings 1984, Ahmed and Rack 1996, Hao et al 2002, Mantani and Tajima 2006, Banumathy et al 2011, Lee et al 2013 which reports the presence of martensitic structure in Ti materials if the solution treatment has been done at high temperature (above β phase field) with sufficiently high cooling rate. It is expected that the formation of soft β and α′′ martensite phases in the microstructure of water quenching plays an important role in producing lower hardness.…”