The results of untiring efforts by the research community over the past few decades have led to the successful development and processing of a number of advanced titanium alloys with widely varying properties that can cater to niche applications. Advanced titanium alloys on one hand challenge structural steels with their higher specific strength coupled with their low temperature capability down to 4 K and pose serious threat on the other hand to superalloys for long-term applications up to 773 K. An improved understanding of the processing-microstructure-mechanical property correlation led to the realization of large scale as well as performance critical titanium alloy products in space arena. Recent advances in additive manufacturing, wherein the desired components are directly 3D printed from pre-alloyed powders/wires have given a definite advantage for cost-prohibitive titanium alloys. This review article discusses challenges in the processing, mechanical properties and microstructure evolution of various grades of titanium alloys. It also provides useful information for researchers working on titanium alloys with a glimpse in to the recent advances in Ti alloys and transformation of scientific knowledge to technological advancements in products for space applications.

Recent advances in processing of titanium alloys and titanium aluminides for space applications: A review

Study on hot deformation behavior and processing map of a Ti-47.5Al-2.5V-1.0Cr-0.2Zr alloy with a fully lamellar microstructure

Effects of β-stabilizer elements on microstructure formation and mechanical properties of titanium alloys

Cross rolling (CR) process was successfully applied to solve the grain refinement of the equiaxed microstructure. In this work, microstructural evolution, textural discrepancy, mechanical properties and twin-accommodated mechanisms were studied in the equiaxed near β titanium alloy for different modes of rolling i.e. unidirectional rolling (UR) and cross rolling (CR). The results showed that CR can effectively promote the grain refinement of both the α and β phases as compared to UR, which leads to weaker texture intensities of the CR sample, and results in an elevated ductility. The { 10 1 ‾ 1 } twinning is the major twin-accommodated mechanisms observed in near β-Ti alloys. The { 10 1 ‾ 1 } twinning accommodated the rotation of subgrains and tailored subgrains orientation during the UR process. In comparison, during the CR process, accumulated stress increases the volune fraction of residual activated twins. Furthermore, with the increasing deformation, the α phase was progressively fragmented into fine grains by the thickening and extension of { 10 1 ‾ 1 } twins. The results in the present study can be applided to optimize deformation processes to achieve ultra-fine grained microstructures, and to figure out the refinement of massive-grained microstructures.

On the {101‾1} twin-accommodated mechanisms in equiaxed near β-Ti alloys operating by unidirectional and cross rolling

Microstructure globularization of high oxygen concentration dual-phase extruded Ti alloys via powder metallurgy route

Role of microstructure on the tension/compression asymmetry in a two-phase Ti-5Al-3Mo-1.5V titanium alloy

A β-solidified nearly lamellar γ-TiAl ( α 2 + γ ) based alloy was investigated to understand the evolution of microstructure during hot isothermal compression test at 1050 °C (below eutectoid). Cylindrical samples were compressed to different true strains up to 60%. The deformed samples were then characterized using scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) to understand the active deformation mechanisms. Dynamic flow softening behavior, i.e., dynamic recrystallization (DRX) type flow was observed. While no new strain induced phases were observed, there were minor changes in the phase fractions as a function of strain. Kinking and bending of lamellae at certain areas in the microstructure of compressed samples were predominant. Preliminary analysis by TEM indicated the presence of twinning in both γ and β phases.

Evolution of microstructure in niobium rich (α2+γ) based titanium aluminide alloy during hot compression

A detailed investigation was conducted to study the concurrent effect of temperature and strain rate on the microstructure evolution in Ti–5Al–3Mo–1.5V dual-phase Titanium alloy. By applying varying strain rates from $$10^{-3} $$
 to 10 $$\hbox {s}^{-1}$$
 between 1098 and 1298 K at an interval of 50 K, isothermal compression characteristics and microstructural changes were recorded. The sizes of globules, concentrated predominantly at the lamellar kinks, were found to be inversely proportional to the strain rate. Further, a dynamic material model was employed to assess and plot the processing map displaying the safe hot working regime. The apparent hot-working activation energy in the $$\alpha +\beta $$
 and $$\beta $$
 phase field was 636 kJ/mol and 379 kJ/mol, respectively. A higher activation energy than the self-diffusion threshold of the $$\alpha +\beta $$
 and $$\beta $$
 field was attributed to lamellae breakup and dynamic recrystallization in the respective phase fields. The microstructure analysis and identified softening mechanisms further helped in concluding the safe hot working regime to be 1248 K and 10
 $$^{-3}$$
 $$\hbox {s}^{-1}$$
 .

Rohit Kumar Gupta

Papers

Role of microstructure on the tension/compression asymmetry in a two-phase Ti-5Al-3Mo-1.5V titanium alloy

Evolution of microstructure in niobium rich (α2+γ) based titanium aluminide alloy during hot compression

Hot deformation characteristics and microstructure evolution of Ti-5Al-3Mo-1.5V alloy