Ramachandra Canumalla

• (C. Ramachandra) Ph.D.
• Vice President and Chief Technology Officer at Weldaloy Specialty Forgings

Orientation relationships between the silicide S2 and the matrix of alpha-prime platelets are established for the titanium alloy 685 (Ti-6Al-5Zr-0.5Mo-0.25Si), a near-alpha alloy designed for the high-temperature components of jet engines. A stereogram showing the parallel planes of alpha-prime and S2 is presented for the alloy in the water-quenche...

Titanium alloys, with their low density, exceptional mechanical properties, and outstanding corrosion resistance, play a vital role in various aerospace applications. Our decision science-driven assessment focused on metastable β, near-β, α + β, and near-α Ti alloys for landing gear applications, integrating multiple-attribute decision-making (MADM...

We compiled, assessed, and ranked refractory high-entropy alloys (RHEAs) from the existing literature to identify promising coating materials for hot-forging dies. The selection methodology was rigorously guided by decision science principles, seamlessly integrating multiple attribute decision making (MADM), principal component analysis (PCA), and...

Haynes 230 alloy, which combines excellent oxidation resistance, up to ~1150°C, high-temperature strength, and good forming capabilities, is ubiquitous in aeroengine applications. The relatively lightweight Ti-containing high-entropy alloys (Ti-HEAs), having distinctly high elevated- and ambient-temperature properties, are potential competitors to...

Alpha (α) /beta (β) and near-α high-temperature titanium alloys are used in compressor parts in jet engines. Some of these alloys show very low ductility at room temperature. Efforts have been made to understand this aspect. It is attempted to comprehensively put together the findings in the literature on this aspect of low ductility at room temper...

Superalloy 718 and its derivatives are ubiquitous to aeroengine applications owing to their excellent formability, ultra-high strength, good thermal stability, adequate weldability, and so forth. However, currently, the relatively lighter Ti-comprising refractory high entropy alloys (Ti-comprising RHEAs), having a unique combination of ambient and...

Near-α Ti alloys find themselves in advanced aeroengines for applications of up to 600 °C, mainly as compressor components owing to their superior combination of ambient- and elevated-temperature mechanical properties and oxidation resistance. We evaluated, ranked, and selected near-α Ti alloys in the current literature for high-temperature applica...

There is rapidly growing interest in Ti-containing multi-principal element alloysTi-containing multi-principal element alloys (MPEA), due to their distinct combination of the room- and elevated-temperature mechanical properties and corrosion resistance for a wide range of potential applications. This has motivated us to analyze the literature data...

Solidification paths were established in a two-phase (α2+γ) alloy of nominal composition Ti–48Al–2V (at.%). The alloy buttons were prepared by vacuum arc melting. The phases present in the alloy were characterized by X-ray diffraction, optical microscopy and scanning electron microscopy. Room temperature microstructure of the alloy consisted of col...

Environmental barrier coatings (EBCs) are external ceramic coatings on silicon-based ceramic components to protect them from water vapor attack in combustion environments. A spectroscopic nondestructive technique to monitor the degradation of environmental barrier coatings was investigated. Lithium oxide was selected as a spectroscopic marker mater...

Different regions namely anterior, posterior, medial and lateral, of the cortical bone in six sections in the diaphysis from proximal to the distal end of a Turkey tibia were evaluated for structural differences. The predominant feature, Haversian canals showed high area fraction (can be viewed as high porosity) in the posterior region as compared...

In order to protect the thermal barrier coatings (TBCs) fromoxidation and hot corrosion attack, several barrier coatings on top of the yittria-stabilized zirconia (YSZ) TBC have been evaluated. Thermal cycling tests in air and hot corrosion resistance tests in molten Na SO were used to determine the durability of these coatings. Barrier layers inve...

Mathematical modeling of supersonic gas atomization for spray forming has been investigated. Influence of the droplet dynamic and thermal behaviour on the resultant microstructure has been studied. Analytical models have been constructed taking into account the higher Reynolds number owing to supersonic gas flow. The impact velocity profiles of the...

In commercial practice, two-step ageing is commonly used in Al–Zn–Mg alloys to produce a fine dispersion of h¢ precipitates to accentuate the mechanical properties and resistance to stress corrosion cracking. While this is true in Al–Zn–Mg alloys, two-step ageing leads to inferior properties in Al–Mg–Si alloys. This controversial behaviour in diffe...

Discontinuous precipitation (DP) occurs in many alloy systems under certain conditions. Although solute supersaturation is the chemical driving force for DP, this has to be coupled with another driving force for grain boundary migration. This was identified to be diffusional coherency strain ahead of the moving boundary in the case of diffusion ind...

A commercial (α+β) titanium alloy Ti-6Al-1.6Zr-3Mo-0.3Si (designated as VT9) of Russian origin is used for compressor discs and blades in jet engines up to temperatures of 773K. The β transus for this alloy is ∼1233K. The alloy blanks were subjected to β solution treatment at ∼1293K for 0.5 hours and cooled at different rates namely water quenching...

Ti-6Al-1.6Zr-3.3Mo-0.3Si (VT 9) is an (α+β) titanium alloy of Russian origin designed for applications as compressor disc and blade in jet engines for use upto the temperatures of 773K. These alloys are known to exhibit an appreciable amount of creep even at ambient temperatures. Thus creep and low cycle fatigue (LCF) interaction at room temperatur...

The effect of delayed aging on mechanical properties is characteristically found in Al-Mg-Si alloys. “Delayed aging” refers to the time elapsed between solutionizing and artificial aging. Delayed aging leads to inferior properties. This effect was investigated in an Al-Cu-Mg alloy (AU2GN) of nominal composition Al-2Cu-1.5Mg-1Fe-1Ni as a function of...

Discontinuous precipitation (DP) occurs in many alloy systems under certain conditions. It is called discontinuous precipitation because precipitation occurs on prior matrix grain boundaries followed by grain boundary movement. The DP nodule consists of alternate lamellae of the precipitate and the matrix respectively. The chemical driving force fo...

ABSTRACT: The strengthening of particulate reinforced metal-matrix composites is associated with a high dislocation density in the matrix due to the difference in coefficient of thermal expansion between the reinforcement and the matrix. While this is valid, the role of work hardening characteristics of the matrix alloys in strengthening of these c...

Systematic investigations of tensile properties of alpha + beeta type high temperature Ti alloy VT9 (Ti-6 Al-3.3 Mo-1.65 Zr-0.3 Si wt. per cent) developed on ageing at 803, 823 and 853 K for 2, 6 and 121 hr, respectively following the solution treatment in alpha + beeta phase field at 1233 K for 1 hr and air cooling, show that the highest tensile s...

This paper discusses the effect of CO2 laser alloying of pre-placed BN coating with Ti–6Al–4V alloy. The formation of titanium boride and titanium nitride investigated using energy dispersive X-ray diffraction (EDXRD) result were related to the microhardness and microstructure. The nitrogen and boron diffusion during the laser boronising process id...

The spray deposition of a commercial hypereutectic Al-Si allloy under various processing conditions has been investigated. The microstructure and wear properties of the alloy produced by spray deposition process are compared with those produced by conventional casting method. The microstructure of the spray deposited material showed considerable re...

The laser surface alloying of prcplaced SiCp coating with AA 2014, AA 2219 and Russian 1441 alloys was carried out using high power CW CO2 laser. The Al-SiCp composite layer was created at the aluminium alloy surface. The surface composite layer formed on AA 2014 was better than that obtained in AA 2219 and Russian 1441 alloys. The thickness of the...

Different types of silicides precipitate in high-temperature titanium alloys depending upon the composition and heat treatment of the alloys. However, there are inconsistencies and lacunae with respect to the chemical and crystallographic characteristics of the silicides and these are pointed out here. Hexagonal silicides s1 (a=0.7804 nm; c=0.5447...

Titanium aluminides, based on the compositions TiAl and TiâAl, are considered promising structural material for aerospace, in particular, for engine components to replace the heavy superalloys. However, these intermetallics are plagued by poor ductility at room temperature. Intense research efforts, over the last one decade, directed to address the...

The development of the microstructure on aging of an (α + β) type titanium alloy containing 6A1-1.6Zr-3.3Mo-0.3Si (VT9) (in weight percent) has been studied. The β-transus temperature of this alloy is approximately 1243 K. Solution treatment in the β-phase field of the alloy followed by quenching in water at room temperature resulted in the formati...

The development of the microstructure on aging of an ({alpha} + {beta}) type titanium alloy containing 6Al-1.6Zr-3.3Mo-0.3Si (VT9) (in weight percent) has been studied. The {beta}-transus temperature of this alloy is approximately 1243 K. Solution treatment in the {beta}-phase field of the alloy followed by quenching in water at room temperature re...

The development of the microstructure on aging of an (α + β) type titanium alloy containing 6A1-1.6Zr-3.3Mo-0.3Si (VT9) (in weight percent) has been studied. The β-transus temperature of this alloy is approximately 1243 K. Solution treatment in the β-phase field of the alloy followed by quenching in water at room temperature resulted in the formati...

It can be stated that the lower the solution-treatment temperature (in the range studied) in the ({alpha} + {beta}) phase field followed by oil quenching, the lower is the stability of the resulting microstructure when subjected to aging at 973 K even for a very short time for 2 hours. The term stability is understood in terms of increasing size of...

Low-cycle fatigue (LCF) behaviour of the alloy Ti-27Al-15Nb, in (α 2+B2) heat-treated condition was studied in total axial strain control mode at different total strain amplitudes (Δɛ 1/2) from ±0·65 to ±1·0% and room temperature. While there was little hardening of the material at the lowest strain amplitude (Δɛ t/2: ±0·65%), pronounced hardening...

The solidification structure of undercooled melt of Ag-Cu alloy, entrained in its primary Cu-rich phase, has been investigated. The undercooling procedure consisted of equilibration of a Cu-13 pct Ag alloy in the two-phase liquid-solid region, followed by repeated thermal cycling of the liquid. Slow cooling of the sample in the present work establi...

Microstructural stability in the near-α titanium alloy (alloy 834) containing Ti-6Al-4Sn-4Zr-0.70Nb-0.50Mo-0.40Si (in weight percent), in the β and(α + β) solution-treated and quenched conditions, has been investigated. The β transus for this alloy is approximately 1333 K. Solution treatment in the β phase field at 1353 K followed by quenching in w...

Several near-[alpha] and ([alpha] + [beta]) titanium alloys have been developed for high-temperature applications in jet engines. The important feature in these alloys is the addition of a small amount of silicon to enhance creep resistance at elevated temperatures up to about 873 K. The near-[alpha] alloy of nominal composition Ti-6Al-5Zr-0.5Mo-0....

Composites of commercial purity aluminium containing up to 8 wt-% mica have been prepared by a PM route. Aluminium and mica powders were mechanically mixed and compacted at a pressure of 472 MPa. Three sets of identical green compacts were sintered at 883 K for 1 h under pure nitrogen and hydrogen atmospheres and in vacuo (10 mPa). Sintered density...

Alloys of Fe-Cr-Ni and Fe-Cr-Mn were plasma arc-melted and chill cast in the form of ingots. Exposure of liquid melts to a nitrogen plasma for the purpose of adding nitrogen to the above alloys was used to dissolve varying amounts (up to 0.32 wt pct) of nitrogen. Carbon and sulfur were varied up to 0.5 and 0.056 wt pct, respectively. The alloys wer...

Cu-1.15at%Cr-0.03at%Zr-0.14at%Si was irradiated with 300 keV Cu+ ions to damage levels between 0.01 and 20 dpa at displacement rates of 2.3 × 10−5 to 2.3 × 10−2 dpa/s and temperatures of 80 to 883 K. The effect of heavy ion irradiation on the stability of the coherent chromium phase in this alloy was examined using transmission electron microscopy...

Silicide precipitation in the (α+β)-type titanium alloy containing (in weight per cent) 6Al-2Zr-3.30Mo-0.30Si (alloy VT9) has been investigated. The β transus temperature for this alloy is approximately 1243 K. Solution treatment in the β phase field at 1323 K followed by quenching in water at room temperature resulted in the formation of a single-...

Epoxy resin graphite composites were prepared by adding a hardener Hy (951) to epoxy resin Cy (205) in the ratio of 1:10 by weight while varying the graphite content from 3 to 12 wt %. Bushings (OD 44 mm, ID 20 mm, length 40 mm) were directly cast from the liquid slurry of the composite mixture. Wear characteristics of epoxy-graphite composites wer...

Al–4Cu–20Pb alloy was spray deposited at a gas pressure of 1.4 MPa and melt flow rate of 1.6 kg min−1. The microstructure of the preform exhibited equiaxed morphology with grain size varying from 20–25 μm. Uniform distribution of submicron size lead particles were observed in the Al-matrix. Wear testing, employing a pin-on-disc type set-up, reveale...

The stability of precipitate phases in aCu-base alloy under irradiation with 300 KeV Cu+ions has been investigated. The irradiations were carried out in the temperature range of 200°C to 530°C at displacement rates of 2.3 × 10−2 and 2.3 × 10−5 dpa/s, respectively. Of the two types of precipitates which form in this alloyunder thermal ageing, the me...

The effect of solution treatment temperature, cooling rate and aging temperature on tensile properties and fracture behaviour of high temperature titanium alloys VT9 (Ti-6Al-1.6Zr-3.3Mo-0.3Si) and IMI685 (Ti-6Al-5Zr-0.5Mo-0.25Si) has been studied at room temperature. The strength of these alloys invariably increases due to aging treatment, however,...

The tensile properties and fracture behaviour of alloy Ti-6AI-5Zr-0.5Mo-0.25Si (wt%) have been investigated over a wide range of temperature from 300 to 823 K, in the as-water-quenched (WQ) and different aged (473 to 1073 K for 24 h)conditions followingß-solution-treatment (1323 K for 0.5 h). There is only a limited increase in strength but a drast...

The lowcyclefatiguebehaviour of a near α titanium alloy, IMI 685, has been studied in its single phase microstructural state with martensitic platelets of α′, at room temperature and at 500°C. There is excellent cyclic stability at low strain amplitude (Δϵp/2<1.12%) both at room temperature and at 500°C. However, there are marked differences in the...

Abstract. High temperature titanium alloys like IMI 685 contain small amounts of silicon (z 0.25 wt. per cent) to improve creep resistance. Different types of silicides, namely Ti5Si3,, (TlZr)5Si3 (S1) and (TiZr)6 Si3 (S2), have been observed to precipitate in various silicon-bearing titanium alloys depending upon their composition and heat treatme...

The titanium alloy with the nominal composition by wt pct 6A1-5Zr-0.5Mo-0.25Si (alloy 685) is an important near a alloy designed for high temperature components in jet engines. The importance of silicon in titanium alloys in improving their creep resistance has been well documented; ~-7 however, the precise mechanism of creep strengthening is still...

The influence of small silicon additions, in the form of silicides or solid solution, on the tensile properties and fracture behavior of titanium alloys is studied using samples of alloy Ti-6Al-5Zr-0.5Mo-0.25Si (alloy 685). The heat treatment of the solid-solution specimen consisted of silicon-solutionizing at 1323 K for 0.5 hr in vacuum, followed...

The effect of silicon in solid solution and in the form of suicides has been studied on the tensile properties and fracture behavior of alloy Ti-6Al-5Zr-0.5Mo-0.25Si (alloy 685). The heat treatment to hold silicon in solid solution consists of solutionizing at 1323 K for 0.5 hour under vacuum (∼10-5 MPa), followed by water quenching, and the treatm...