Application of the Theta Projection Technique to the Creep Behaviour of the γ-Titanium Aluminide Ti -45Al-2Mn-2Nb

Gamma titanium aluminides (γ-TiAl) display significantly improved high temperature mechanical properties over conventional titanium alloys. Due to their low densities, these alloys are increasingly becoming strong candidates to replace nickel-base superalloys in future gas turbine aeroengine components. To determine the safe operating life of such components, a good understanding of their creep properties is essential. Of particular importance to gas turbine component design is the … Continue reading Application of the Theta Projection Technique to the Creep Behaviour of the γ-Titanium Aluminide Ti -45Al-2Mn-2Nb

An analysis of modern creep lifing methodologies in the titanium alloy Ti6-4

Traditional creep lifing techniques based on power law equations have shown themselves to be extremely limited, particularly in the prediction of long term data based only on short term experiments. More recently, alternative approaches such as the Wilshire equations and hyperbolic tangent methods have been proposed which offer a new insight into the field, with the Wilshire equations in particular showing promise in predicting long term behaviour based on … Continue reading An analysis of modern creep lifing methodologies in the titanium alloy Ti6-4

A model for time dependent strain accumulation and damage at low temperatures in Ti–6Al–4V

Dwell fatigue effects at low temperatures in a range of titanium alloys have been well documented since the 1970s. However, attempts to model dwell fatigue phenomena are limited. The time dependent effects have been shown to be due to the inherent strain accumulation behaviour at ambient or low temperatures, loosely termed ‘cold creep’ in alloys such as Ti-6Al-4V. Periods of dwell in a fatigue cycle … Continue reading A model for time dependent strain accumulation and damage at low temperatures in Ti–6Al–4V

High temperature creep behaviour in the γ titanium aluminide Ti–45Al–2Mn–2Nb

Gamma titanium aluminides (γ-TiAl) offer strong potential for replacing conventional titanium and nickel-base alloys in future gas turbine engine designs. This is attributed to their lower density compared to the conventional alloys, as well as their high temperature capability and relative resistance to highly oxidising environments. The system Ti-45Al-2Mn-2Nb has been extensively studied under high temperature creep conditions. When compared to an existing, conventional, high … Continue reading High temperature creep behaviour in the γ titanium aluminide Ti–45Al–2Mn–2Nb

“Microstructural characterisation of a functional prototype titanium alloy structure processed via Direct Laser Deposition (DLD)

Processing trials have produced a three-dimensional, thin-walled structure of representative aerospace component geometry, fabricated directly by laser melting of Ti6Al4V powder. This additive-built form has been subjected to metallographic characterization. The fabrication technique is evaluated as an economic, commercial process that can add features such as bosses or flanges as a hybrid-manufacturing route for existing forms of gas turbine components. The samples were extracted from six locations with different wall … Continue reading “Microstructural characterisation of a functional prototype titanium alloy structure processed via Direct Laser Deposition (DLD)

Considerations in fatigue lifing of stress concentrations in textured titanium 6-4

The effect of crystallographic texture has been considered in attempting to derive a total life prediction capability for the titanium alloy Ti6-4. Orientation effects due to texture are shown to be a result of stress relaxation in strain control specimens, and consequently occur in some cases of notched specimens. It is shown that these effects can be predicted using analytical methods such as the Modified Coffin–Manson and Walker strain … Continue reading Considerations in fatigue lifing of stress concentrations in textured titanium 6-4

Modelling the behaviour of titanium alloys at high temperature for gas turbine applications

Increased efficiency within the aero engine can be achieved through higher operating temperatures. In order to meet this requirement designers seek either to implement new alloys or show that existing alloys are capable of operating under more extreme conditions. At higher temperatures fatigue is no longer the sole damage mechanism and contributions from creep and environmental interactions must also be considered. This paper seeks to address some of these … Continue reading Modelling the behaviour of titanium alloys at high temperature for gas turbine applications

The effect of prestrain on low and high temperature creep in Ti834

The low and high temperature creep properties of the α+β titanium alloy Ti834 have been studied for various levels of applied plastic prestrain. Evidence is shown that the prestrain at room temperature causes the formation of quasi-cleavage facets in a manner described by the Evans–Bache model. These facets are also produced when the material is creep tested at room temperature, although larger areas of faceting are found. The applied … Continue reading The effect of prestrain on low and high temperature creep in Ti834