TMS Titanium Resource Hub: The Ultimate Titanium Glossary

Definition: Annealing is a heat-treatment process where titanium is heated to a specific temperature and then slowly cooled. This process softens the metal, relieves internal stresses, and improves ductility. For example, after titanium sheet metal is cold-worked (bent or stamped), it can be annealed to make it less brittle and easier to machine.

How it Works: In practice, a titanium part (say a formed titanium sheet or drawn titanium wire) is heated to an elevated temperature (often around 600–700 °C for CP titanium) and then cooled at a controlled rate. This alters the microstructure, reducing hardness. Different titanium alloys have prescribed annealing temperatures and times to achieve desired properties.

Real-World Applications: Annealing is commonly used after forging or cold forming operations. For instance, titanium tubing used in aerospace hydraulic systems may be annealed after bending, ensuring it has uniform properties and won't crack under pressure. It's also used to relieve stress in welded titanium assemblies (like frames or tanks) to prevent brittleness.

Internal Links: The annealing process is relevant to many products – e.g., annealed titanium bar stock is easier to machine, and most alpha-beta alloys like Ti-6Al-4V are supplied in an annealed condition for improved workability.

Fun Fact: Titanium actually gains ductility at cryogenic temperatures after annealing – unlike most metals that become brittle in the cold. That's why annealed titanium alloys have been used in super-cold applications (like spacecraft fuel systems) without losing toughness!

Definition: “Alpha alloys" are titanium alloys that are stable in the alpha phase at room temperature. The alpha phase of titanium has a hexagonal close-packed (HCP) crystal structure. Alpha alloys are generally non-heat-treatable (their strength comes from composition and processing, not from heat treatment) and often include elements called alpha stabilizers (like aluminum or oxygen) to keep the alloy in the alpha phase.

Characteristics: Alpha alloys (and commercially pure titanium, which is basically all-alpha) typically have excellent corrosion resistance and good weldability. They retain toughness at very low temperatures (down to cryogenic ranges), which makes them useful for sub-zero applications. However, they are of lower to moderate strength compared to other titanium alloy types. They cannot be significantly strengthened by heat treatment (since they don't have a beta phase to transform), so they rely on mechanical working for strengthening.

Examples: Commercially pure grades like Grade 2 titanium are essentially alpha alloys (with slight impurity element variations). There are also alloyed alpha materials, e.g. Ti-5Al-2.5Sn (5% Al, 2.5% Sn) which is used in aerospace for its creep resistance at high temperatures. These alloys stay in the alpha phase unless heated very high.

Real-World Uses: Alpha alloys and CP titanium are often used in chemical processing equipment, marine hardware, and airframe components that need reliability and corrosion resistance over outright strength. For instance, the skin of deep-diving submersibles and some aircraft parts use Grade 2 or Grade 4 CP titanium (alpha materials) because they can handle seawater or cryogenic fuels without corroding or becoming brittle.

Internal Links: Alpha alloys contrast with beta alloys and alpha-beta alloys which have different structures. In the grade guide, the CP grades (1–4) are alpha, while alloys like Grade 5 are alpha-beta. If you need raw material, alpha alloys are available in all mill product forms (for example, CP Grade 2 plates or blocks for machining).

Fun Fact: Alpha alloys can actually strengthen a bit during low-temperature service – an effect called “cryogenic strengthening." The Apollo lunar lander's legs were made of a titanium-aluminum alloy (mostly alpha phase) that had to perform in the freezing vacuum of the Moon – and it did so without issues!

Definition: Alpha-beta alloys are the most common titanium alloys, containing a mixture of both alpha and beta phases at room temperature. They usually include a blend of alpha stabilizers (like Al, O) and beta stabilizers (like V, Mo, Fe) to achieve a two-phase microstructure. This mix can be manipulated with heat treatments. Ti-6Al-4V (Grade 5) is the iconic alpha-beta alloy – it's about 90% of titanium used in the world!

Characteristics: Because they have both phases, alpha-beta alloys are heat-treatable. By solution treating and aging (a heat treatment process), these alloys can be significantly strengthened. They offer a balance of properties: higher strength than pure alpha alloys, while still retaining decent ductility and toughness. They are generally weldable (with proper technique) and have good corrosion resistance, though not quite as superb as CP titanium in extremely aggressive environments.

Examples: Aside from Ti-6Al-4V (Grade 5) and its variants (like Grade 23, the ELI version), other alpha-beta alloys include Ti-6Al-6V-2Sn and Ti-6Al-2Sn-4Zr-2Mo, used in aerospace. Grade 9 (Ti-3Al-2.5V) is another alpha-beta alloy often called a “half-6-4" because it's basically a lower aluminum/vanadium version – giving it a bit lower strength but excellent cold formability (used in titanium bicycle frames and aircraft tubing).

Real-World Uses: Alpha-beta alloys are found in aircraft structures, jet engine components, automotive racing parts, prosthetics, and high-performance sporting equipment. If you have a titanium part in hand, odds are it's an alpha-beta alloy. For example, the titanium bolts holding together a race car's suspension or the hip joint implant in an orthopedic patient are likely made of Ti-6Al-4V. These alloys can also be forged into critical shapes like turbine blades or forged rings for aerospace.

Internal Links: Many products sold by TMS are alpha-beta alloys. Notably, Grade 5 titanium (6Al-4V) is sold in forms like bars, sheets, etc. When machining or heat-treating these, you might employ annealing or aging processes to optimize properties. Compare also to beta alloys, which push strength even higher at some cost to ductility.

Definition:Beta alloys are titanium alloys engineered to retain the beta phase (a body-centered cubic crystal structure) at room temperature, usually by adding significant amounts of beta stabilizing elements (like Mo, V, Nb, Fe, Cr). These alloys stay mostly beta after quenching from high temperature, and can then be aged to precipitate alpha phase in controlled ways.

Characteristics: Beta alloys are typically very high strength – higher than alpha-beta alloys – and heat-treatable to an even greater degree. They also tend to have good formability in the solution-treated condition (soft beta phase), making them easier to cold-work or forge into complex shapes before aging to harden. However, they can be less ductile and slightly less tough in certain conditions than alpha-beta alloys. Weldability varies (some are not weld-friendly due to segregation of alloying elements). Beta alloys often have slightly lower thermal resistance, so they may lose strength at elevated temperatures more than alpha or alpha-beta alloys.

Examples: Common beta alloys include Ti-3Al-8V-6Cr-4Zr-4Mo (often called Beta-C) and Ti-10V-2Fe-3Al (used in aerospace fasteners and landing gear). These alloys might not have common grade numbers like CP or 6-4, but they are specified in aerospace standards. Another example is Ti-15V-3Cr-3Sn-3Al, used for springs and sheet applications requiring extreme strength and strip thickness.

Real-World Uses: Beta titanium shines in spring applications, high-strength fasteners, and structural parts needing ultra-high strength. For instance, certain titanium landing gear components on fighter jets are made from beta alloys to handle enormous loads. High-performance titanium springs (in automotive racing or aerospace) often use beta alloys like Beta-C. Beta alloys are also used to make some eyeglass frames and orthodontic wires – exploiting their combination of flexibility (when annealed) and strength (when aged).

Internal Links: Beta alloys are less common in commercial retail forms, but TMS Titanium can supply them on request. For most customers, the highest strength readily available material is Grade 5 or sometimes Grade 23 ELI (an alpha-beta alloy). If you truly need beyond that strength, beta alloys are the next frontier. They will still start as mill products (like bar or sheet) that can be forged or machined, often followed by special heat treatment rather than simple annealing.

Fun Fact: Some beta titanium alloys are so strong that titanium golf club heads were made from them to maximize driving distance. One beta alloy (Ti-10-2-3) proved perfect for thin-yet-strong driver faces, giving golfers an edge with titanium's “springy" effect. It was even said that early beta-titanium clubs made balls fly so far, they got temporarily banned until rules caught up!

Definition: A billet is a solid block of titanium, typically cylindrical or rectangular, that has been formed by casting, forging, or rolling, and is used as a starting form for further processing. Think of it as a big “chunk" of titanium metal with a uniform cross-section. Billets are semi-finished products – they aren't the final part but will be turned into something useful by machining or forging.

Billet vs. Ingot: Billets are usually smaller than ingots and have undergone some working. For example, an ingot might be a huge 5-ton cast block of titanium straight out of the vacuum furnace. That ingot can then be forged or rolled into smaller sections – those sections are called billets. A billet might be a 6-inch diameter rod several feet long, ready to be extruded into titanium bar or used to machine parts. In steel terminology, billets are often square in cross-section (while “blooms" are larger squares and “slabs" are rectangular). In titanium, we mostly refer to round or rectangular billets.

Real-World Applications: Titanium billets are the starting stock for aerospace components, medical implants, and industrial parts. For instance, to make a titanium aircraft forging like a wheel or a structural node, one might start with a billet of Grade 5. The billet gets heated and pressed into a near-final shape (see Forging below). Similarly, big titanium fasteners (bolts for aircraft) might be lathe-turned from a smaller beta alloy billet. Titanium blocks sold by TMS are essentially cut billet sections, useful for machining custom parts.

Internal Links: If you're browsing TMS products, a titanium block is a form of billet that you can buy and directly machine. Large round bar stock can also be considered a billet form (for example, a 8" diameter bar of Ti-6Al-4V could be called a billet). To get a billet, we start from an ingot, break it down by forging/rolling (primary fabrication) into billet, then further process into mill products like smaller bars or plates as needed.

Fun Fact: The world's largest titanium billet (actually a forged cylinder) weighed over 15 tons! Such a mega-billet might be used to carve out critical aerospace parts. In one instance, a single forged Ti-6Al-4V billet weighing ~16,000 kg was produced for a rocket program – enough titanium in one piece to machine an entire airplane wing spar or dozens of engine rings.

Definition: Forging is a process of shaping titanium by applying compressive forces, usually between hammer dies or a hydraulic press, while the titanium is heated. In other words, it's pounding or pressing hot titanium into a desired shape. This is a primary way to make strong, tough components because the process refines the metal's internal grain structure.

How Titanium Forging Works: Titanium forging typically occurs at high temperatures (but below the melting point). For alpha-beta alloys like Ti-6Al-4V, forging is often done in the alpha-beta phase range (for example, around 900–950 °C) to get a mix of phases in the final piece. A titanium billet or ingot is heated in a furnace, then placed on a die and smashed into shape by a forge press or hammer. The result could be anything from a simple disc or ring forging to a complex near-net shape. Because titanium can react with air at forging temps, sometimes forging is done in vacuum or with protective coatings on the billet to avoid contamination.

Types of Forged Products: Common titanium forgings include rings, discs, flanges, shafts, and airframe shapes. For example, jet engine compressor rings and fan blades are often made from forged titanium – the material's grain flow after forging follows the part's shape, giving it extra strength where needed. Another example: large structural bulkheads for military aircraft have been forged from Ti-6Al-4V to get maximum toughness. Even titanium surgical implants like hip stems can be forged to enhance their strength before final machining.

Advantages: Forging improves mechanical properties – titanium that's been forged has a more uniform, refined microstructure than a cast piece. It eliminates internal voids and aligns the grain with the part geometry, resulting in higher fatigue strength. Forged titanium parts are therefore stronger and more reliable than cast or machined-from-ingot parts. They also waste less material than machining a shape entirely from a larger block (important since titanium is pricey).

Internal Links: If you buy a titanium block from TMS you can later forge it into a custom shape if you have the capability. Many of TMS's aerospace customers purchase billets specifically for forging operations. Even if you're just a hobbyist, smaller-scale forging is possible: e.g., heating a small Grade 5 rod to red heat and hammering out a titanium knife blank. (Just be mindful of titanium's need for an inert atmosphere at high heat to avoid oxidation!)

Fun Fact: Did you know titanium forgings helped land humans on the Moon? The Apollo Lunar Module's crucial load-bearing parts (like the engine mount and strut attachments) were made from forged titanium alloys. They delivered high strength with minimum weight – essential for getting astronauts safely to the lunar surface and back.

Definition: An ingot is a large, cast block of titanium metal that results from the primary melting process. It's the first solid form of titanium after it's extracted from its raw state. Ingots are typically massive – imagine a cylindrical or rectangular chunk of titanium weighing anywhere from a few hundred pounds to several tons. They serve as the starting material for all downstream titanium mill products.

How Ingots are Made: Titanium ingots are produced by melting titanium sponge (see Titanium Sponge) together with alloying elements (if making an alloy) in a vacuum furnace, because titanium has to be melted in an inert environment (it reacts with air when liquid). A common method is vacuum arc remelting (VAR): titanium sponge and alloy bits are packed into a cylindrical electrode, which is melted by an electric arc in a vacuum chamber, dripping into a mold and solidifying as a huge ingot. Some ingots are made by electron-beam melting or plasma melting as well. These initial ingots might be remelted multiple times to improve homogeneity (aerospace-grade Ti-6Al-4V is often triple-melted to ensure purity and uniform structure).

Size and Form: Ingots can be very large. For example, a standard aerospace titanium ingot might be 30 inches in diameter and 6 feet long, weighing around 8,000–12,000 lbs (4–6 tons). There are also slab ingots (rectangular cross-section) for rolling into plates. Once you have an ingot, it usually goes to a forge or rolling mill to be broken down into billets, blooms, slabs, or other mill forms.

Real-World Journey: After an ingot is made, it's not useful in that form due to its size and cast structure. It will be hot forged and rolled in successive steps. For instance, an ingot of Ti-6Al-4V might be forged into a 10-inch square billet, then further rolled into round bars or flat plates. Every piece of titanium sheet, bar, tube, or wire originally came from an ingot that has been worked down. If you have a small 1" titanium rod in your shop, picture a giant glowing ingot as its great-great-grandparent!

Internal Links: While you can't buy an ingot directly from TMS's store (they're supplied to mills and large forges), understanding ingots helps you understand product availability. For example, certain size limitations on titanium plate exist because only so large an ingot can be rolled out. If you need a super thick block, it may have to come from the center of an ingot or big billet. Also, ingot metallurgy influences things like inclusion content and quality grades (e.g., aerospace grade material comes from carefully processed ingots).

Fun Fact: Titanium ingots are so dense and large that they cool slowly – it can take days for a massive ingot to fully cool in the mold after vacuum melting! During World War II, titanium production was so secret and novel that early ingots were nicknamed “Titanium Babies" because they'd “gestate" in furnaces and come out weighing as much as an elephant calf.

Titanium Sheet / Plate - Stacks of titanium plate – an example of mill products ready for fabrication. Mill products refer to the basic wrought forms of titanium that come out of mills after rolling, forging, or extruding processes. These are the standard shapes that manufacturers purchase to make final products. The common titanium mill product forms include: plate, sheet, bar, rod, wire, tubing, pipe, and billet/block. Essentially, if it's a straightforward shape made in bulk and sold by size, it's a mill product.

Key Mill Forms:

• Sheet & Plate: Flat titanium stock. Sheet is typically thin (under ~5mm/0.187″) while plate is thicker. These are produced by hot-rolling slabs or billets. For example, TMS offers titanium sheet/plate in various thicknesses (from foil-like 0.016″ sheets up to hefty 4″ plates). Sheets and plates are used for enclosures, armor, aerospace skins, etc.

• Bar & Rod: Solid long pieces with circular or rectangular cross-section. Titanium round bar (a.k.a. rod) is commonly available in diameters from a few millimeters up to several inches. Square and rectangular bars (sometimes called blocks or flats) are also available. These are usually hot-rolled or forged from billets, then peeled or ground to size. They're the starting point for many machined parts or fasteners.

• Wire: Thin, flexible strands of titanium, made by drawing down rod through dies. Titanium wire can be as small as fractions of a millimeter. It's used for springs, medical devices, jewelry, and welding filler metal.

• Tubing & Pipe: Hollow sections. Titanium tubing is usually defined by outer diameter and wall thickness – often seamless for high-performance uses. Tubes are drawn from hollows or extruded. They're critical in chemical industry piping, aircraft hydraulic lines, bicycle frames, etc. (Titanium pipe is similar to tube but often refers to standard nominal sizes for industrial plumbing).

• Blocks & Billets: As discussed, these are larger chunks – e.g., a titanium block might be a cube or slab cut from plate or forged billet, sold for machining a custom part.

Quality and Specs: Mill products come with certifications to certain specifications (AMS, ASTM, MIL spec, etc.) indicating their grade and condition. For example, a plate might be certified to AMS 4911 (the spec for Ti-6Al-4V annealed plate). Mill products can be supplied annealed (most common), cold-worked, or pickled (acid cleaned) depending on customer need.

Real-World Connection: If you're building something out of titanium – say a custom car part or a piece of equipment – you'll buy a mill product first. You might get a 12″ x 12″ Grade 5 plate and machine out your part, or buy some Grade 2 tubing to weld into an exhaust. Mill products are essentially the raw stock for all titanium fabrication.

Internal Links: All the items in our store's product section are mill products. The Glossary terms like billet and ingot describe how these mill forms originate. Different grades of titanium (see the Grade Guide) are available in different mill product forms – e.g., Grade 5 is commonly found as bar and plate, while Grade 9 is often sold as seamless tube for aerospace. Our product pages (Sheet, Bar, Block, etc.) list which grades are available in those forms.

Fun Fact: Titanium mill products have some quirks – for instance, titanium sheet and plate can't be easily produced by cold rolling like steel or aluminum because titanium's strength and low ductility at room temp. Instead, titanium sheets are often hot-rolled and then chemically milled (etched) to achieve final gauge and smoothness. Also, ever wondered why titanium chips are curly? Mill products like bar are often rotary forged or cross-rolled, imparting a subtle spiral grain flow – when you machine them, the chips tend to come off as tight curls!

Definition: Titanium sponge is the primary form of pure titanium obtained after processing titanium ore. It's called "sponge" because of its porous, spongy appearance – it looks like a gray metallic sponge. This sponge is later melted to produce titanium ingots. Essentially, titanium sponge is raw, purified titanium metal with a foamy texture.

How it's Made (Kroll Process): Most titanium sponge is made via the Kroll process. In this process, titanium dioxide ore (from minerals like ilmenite or rutile) is reacted with chlorine gas to form titanium tetrachloride (TiCl₄). Then, TiCl₄ is reduced with magnesium in a high-temperature reactor. The magnesium strips away the chlorine, leaving behind titanium metal which deposits as a spongey mass, and MgCl₂ as a byproduct. The chemical equation in simple form: TiCl4 + 2 Mg → Ti (sponge) + 2 MgCl2. After the reaction, the MgCl₂ is removed, and you're left with lumps of titanium sponge.

Properties: Sponge is about 99.5% to 99.9% pure titanium (if making CP grade sponge). It's brittle and can be crushed. It's not useful as a structural material itself due to its porosity and brittleness, but it's perfect for remelting. Sponge is typically broken into chunks and inspected for quality (good sponge will be free of contaminants like oxygen or chlorine residues).

Next Steps: Chunks of titanium sponge, often together with scrap titanium and alloy additives, get melted in a vacuum furnace to produce an ingot. The quality of the sponge largely determines the quality of the final metal. Aerospace-grade titanium sponge undergoes extra refining steps to reduce impurities.

Real-World Insight: When you hold a shiny titanium bolt or a Grade 5 bar in your hand, it all started as a dull gray sponge chunk! Titanium sponge production is a big industry – major producers are in the US, Japan, China, and Russia. The sponge itself is highly porous, so it has a huge surface area and can burn if ignited (it's pyrophoric). Sponge fires are an occasional hazard in titanium plants.

Internal Links: We don't sell titanium sponge as a product since it's a refinery intermediate, but understanding sponge helps explain why titanium is relatively expensive. The multi-step Kroll process and limited sponge production capacity globally influence the cost and availability of all titanium mill products. In the context of materials, when someone says “commercially pure titanium," they often mean the metal melted from straight sponge with minimal alloys.

Fun Fact: The term “titanium sponge" is quite literal – early titanium pioneers described it as looking like burnt charcoal or a kitchen sponge. One unusual use of titanium sponge (besides melting it) is as a getter in high-vacuum systems: because sponge titanium avidly reacts with oxygen and nitrogen at heat, small bits are used to “soak up" residual gases in vacuum tubes. Titanium truly started from sponge and now it's in everything from golf clubs to spaceships!

Definition: “Commercially Pure" titanium refers to unalloyed titanium metal, primarily the ASTM Grade 1 through Grade 4 series. CP titanium is essentially pure titanium (≈99+%) with trace elements (like O, Fe, C) as impurities that differentiate the grades. Unlike alloyed grades (which have intentional additions like aluminum or vanadium), CP titanium's composition is not meant to impart high strength via alloying – instead, it maximizes properties like corrosion resistance and ductility. Grades 1–4: These four grades are all CP but with slightly increasing amounts of oxygen and iron (which are impurities in titanium).

• Grade 1: The softest, most ductile, highest purity (lowest oxygen) titanium. Very formable, but lowest strength.

• Grade 2: The most popular CP grade – it has a bit more oxygen than Grade 1, giving it moderate strength while remaining quite ductile. It's a great all-purpose titanium for industrial use.

• Grade 3: Higher oxygen yet, so stronger than Grade 2 but a little less ductile. Less commonly used, but available for when you need a bit more strength than Grade 2.

• Grade 4: The strongest CP grade (highest allowed oxygen and iron content). It approaches the strength of some lower-end alloys, while still being just titanium. It's somewhat less formable but still has excellent corrosion resistance.

Key Properties: CP titanium is known for outstanding corrosion resistance (especially in oxidizing environments like seawater, chlorine, and certain acids) because it forms a protective oxide film. It's also biocompatible – Grades 1–4 are often used in medical implants and devices because pure titanium is not rejected by the body (and contains no allergenic elements). CP titanium is non-magnetic and has high impact toughness, especially at cold temperatures (it doesn't undergo a ductile-to-brittle transition like steels do).

Uses:

• Grade 1 (very soft) is used when extreme formability is required – for example, it can be deep drawn into complex shapes or used as explosive cladding on steel.

• Grade 2 is widely used in chemical processing plants (valves, heat exchangers, pipes) due to its corrosion resistance. It's also used for marine hardware, general industrial parts, and surgical implants like dental screws.

• Grade 4 (strongest CP) finds use in aerospace for parts that need good corrosion resistance and fair strength (it's used for airframe components and sometimes in biomedical implants that need extra strength).

• Medical: All CP grades are common for implantable devices (bone plates, screws, mesh) because of biocompatibility. Grade 4 is often favored for load-bearing implants due to its higher strength.

• Electronics: CP titanium is used in cases where magnetism must be avoided (it's non-magnetic), e.g., MRI machines or submarines.

Internal Links: In the TMS store, you can select CP titanium in many product forms: sheet/plate, bar, tubing, etc., often by specifying Grade 2 or Grade 4. The Grade 2 Titanium page in our Grade Guide gives more detailed properties. Also, CP vs alloyed titanium is a fundamental choice: CP (Grades 1–4) gives you supreme corrosion resistance and ductility, whereas alloys (like Grade 5) give you higher strength. Many projects start by deciding “Do I need CP or an alloy?" based on these traits.

Fun Fact: Pure titanium is one of the most hypoallergenic metals. Some people who can't wear jewelry made of nickel-containing gold or steel find that CP titanium jewelry (like Grade 1 or 2 earrings) never irritate their skin. It's the metal of choice for body piercings and implants – your body actually integrates with it (osseointegration), which is why titanium implants in bones can last decades. Pure titanium is so biocompatible that even the International Space Station uses CP titanium for critical life-support hardware, knowing it won't corrode or poison the crew.