Aeroval TI-GR5

Material Description

Ti-GR5 is the most frequently used Ti - Alloy because of its excellent strength-to-weight ratio which makes it particulartly suitable for aerospace applications where a good combination of mechanical properties up to approximately 400°C, formability, weldability and toughness is a mandatory engineering requirement.

The alloying elements influence the temperature at which the cristallograhic transformation (β-Transus) from (α) phase (HCP) to the Beta (β) phase (BCC) occurs.

The nominal 6.0% of Aluminium (an α-phase stabiliser element) contributes to strengthen the low temperature α-phase by solid solution; nominal 4% Vanadium (a β-phase stabiliser element), although exceeding the α-solubility limit at any temperature, confers heat-treatment capability allowing the achievement of consistent strengthening.

Applications

The outstanding set of properties of Ti-GR5 alloy make it the first choice for the manufacturing of structural parts, aeroengine components and fastening ssytems.

Among the variety of possible aerospace applications of Ti-GR5 we find blades and discs for jet engines, landing gears, fasteners, airframe components, space vehicles and structures and missile components.

Ti-GR5 is used where the device is manufactured starting from annealed full section long products as machined wire-rod or bars in different profiles and sizes.  Some among the possible finished products obtainable are pivots, rivets and screws along with a wide range of forged and/or machined components.

Corrosion and Oxidation Resistance

The excellent corrosion resistance of titanium alloys result from the formation of very stable, continuous, highly adherent and protective surface oxide films.  Because titanium metal itself is highly reactive and has an extremely high affinity for oxygen, these beneficial surface oxide films form spontaneously and instantly when fresh metal surfaces are exposed to air and/or moisture.

In fact, a damaged oxide film can generally reheal itself instantaneously if at least traces of oxygen or water are present in the environment.  However, certain anhydrous conditions in the absence of a source of oxygen may result in titanium corrosion because the protective film may not regenerate.

Hot Working

Ti-GR5 can be heated up to forging temperatures by many different types of furnaces as for example: induction heating, resistance heating, electric (radiant), oil and natural gas.  Nevertheless, Ti-Gr5 has a low coefficient of thermal conductivity therefore, heating rate should be equal to 4 to 12 min/cm of thickness to make sure temperature homogeneity throughout the section.  It is preferred to heat Ti-GR5 in oxidising atmospheres in order to avoid hydrogen pickup from furnace products of combustion.  Oxdising atmosphere creates oxide layer (α-case), that can be removed from finished product by pickling with suitable solutions of hydrofluoric and nitric acids.

Weldability

When heated at temperatures above 500°C, titanium is severely contaminated by atmosphereic gases like oxygen, nitrogen and hydrogen.  Therefore, the melting, solidification, and solid-state cooling associated with fusion welding must be conducted in completely inert or vacuum environments.  The fusion welding processes most widely used for joining titanium are gas-tungsten arc welding (GTAW), gas-metal arc welding (GMAW), plasma arc welding (PAW), laser-beam welding (LBW) and electron-beam welding (EBW).  Titanium welding requires also weld joint and weld wire being properly cleaned and free of all foreign material during welding.  Moreover inert gases shall be free of moisture and impurities.

Machinability

Ti-GR5 machinability can be compared to the austenitic stainless steel type 18-8 provided that some precautions are observer.  Sharp tools to reduce heat build-up and galling, rigid set-ups between tooling and component, generous amounts of non-chlorinated cutting fluids, low cutting speeds, high feed rates and safety precautions, no interruption of feedings while tools and component are in contact, are necessary to achieve high machinability performances.

After the solution heat treatment material achieves UTS 680-690 N/mm², in this condition it can be cold-formed by standard processes.

Technical Data Sheets