What Is Titanium Alloys And Their Properties?

Titanium and its alloys are widely recognized for their exceptional combination of properties. This makes them highly useful in various industries such as aerospace, automotive, medical, and marine applications. 

It's very important to understand how these titanium alloys manage to perform well at conditions where no other material can perform. This article is dedicated to the titanium alloys and how different properties of titanium alloys make them so useful.

Titanium occurrence in nature

Titanium is a metal and most of its alloys are paramagnetic. Titanium exists in its oxide form in nature and needs to be refined and processed to obtain the useful titanium.

Titanium can be found in rock, sand, clay and with minerals in the form of titanium oxide. It always occurs in oxide form due to its highly reactive nature toward oxygen.

The conversion of titanium oxide into useful titanium metal is a long, time consuming, complex, and costly process. This is the reason that titanium and all its alloys are very costly. 

Titanium color is silver white or silver gray depending on how and where its naturally occurring oxide was found and what minerals were or are attached with it.  

It’s possible to give titanium color from the full spectrum of color throughout the process called anodizing. 

By regulating the voltage provided during the anodizing process, the natural occurring titanium color can be changed.

What are titanium alloys

Like any other alloy, all titanium alloys are primarily composed of titanium with other elements like aluminum, vanadium, nickel, and molybdenum added to it. 

The addition of materials to make alloys is done with proper research and material is added in a fixed predetermined quantity. The addition of the alloying element enhances some specific properties of titanium. 

This allows engineers to tailor titanium for superior mechanical, physical, and chemical characteristics.

Classification of titanium alloys

There are many different ways in which titanium alloys can be classified. These alloys can be classified based on properties of titanium and their internal material structures. This includes Alpha Alloys where titanium is only alloy with oxygen. Oxygen increases titanium strength while reducing its ductility. 

Near-Alpha Alloys have high temperature resistance and these alloys are considered as the most common high temperature alloys of titanium and can resist up to 550C.

Beta and Near-Beta alloys are developed by adding beta stabilizer in titanium. This increase is strength and corrosion resistance. These alloys are heat treatable and their strength, hardness and ductility can be controlled through this.

Alpha and Beta Alloys are medium to high strength titanium alloys and can deliver tensile strength up to 1250 MPa. Talking about physical properties of titanium alloy, these have excellent fatigue and fracture toughness characteristics.

Grades of Titanium and Titanium Alloys

The American Society of Testing Materials ASTM has divided titanium and its alloys in 36 different grades. This grading divides the hundreds of thousands of different titanium alloys into groups. 

This grading makes it easy for the manufacturers and material handling companies to manage materials and recommend specific processes to all materials that fall under a specific grade. 

An example of this, for titanium alloy seamless pipes there are different heat treatment conditions for different grades of titanium. Titanium alloy grades 9, 18, 28, and 38 need to be cold worked. After performing the primary manufacturing process the material needs to be either stress relieved or the heat treatment process of annealing should be performed.

Following are the titanium and its alloys grades

Grade 1 to 4

Titanium from grade 1 to grade from is considered as pure titanium and here pure means no other elements have been intentionally added to make an alloy. So all these grades have pure unalloyed titanium.

Difference in these grades lies in the physical properties of titanium that change as oxygen reacts with titanium to make oxide. Grade 1 is considered most pure with grade 2 titanium has standard oxygen reacted to make titanium oxide. Similarly titanium grade 3 and 4 has medium to high oxygen attached to titanium. All these grades contain titanium that is softer and ductile than any other form of titanium alloy.

Grade 5

Grade 5 is the first grade in the titanium grading series that contains a titanium alloy. And it does not contain any ordinary alloy, grade 5 is all about titanium alloyed with 6% aluminum and 4% vanadium (Ti-6Al-4V). 

This alloy is also called Ti 6-4 and it’s the most versatile and most commonly used titanium alloy in the world. It has high temperature resistance, high tensile strength, high corrosion resistance, high fatigue resistance and excellent other mechanical, physical and chemical properties. 

Properties of Titanium Alloys 

To fully understand the titanium alloy its important to understand both the physical properties of the titanium alloy and chemical properties of titanium alloy.

Strength of Titanium Alloy

Titanium alloys can also be classified based on their strength and their relative American Society of Testing Material ASTM grades. This physical property of titanium alloy differs a lot and it highly depends on the alloying element.

All those titanium alloys that have yield strength of 500 MPa or less are classified as low strength alloy and they include ASTM grade 1, 2, 3, 7, and grade 11. 

Any titanium alloy whose strength is between 500 to 900 MPa is considered moderate strength titanium alloy. Some specific examples are titanium alloy with 2.5% copper (Ti-2.5%Cu) or titanium with 8% aluminum, 1% molybdenum and 0.1% vanadium (Ti-8%Al-1%Mo-0.1%V).  These alloys are assigned ASTM grade 4.5 and 9.

Medium strength titanium alloys have yield strength ranging from 900 to 1200 MPa. These alloys have good fatigue strength, high corrosion resistance, and excellent toughness. Some examples include Ti - 6%Al - 2%Sn - 4%Zr - 2%Mo and Ti - 5.5%Al - 3.5%Sn - 3%Zr - 1%Nb - 0.3%Mo - 0.3%Si.

Yield strength of above 1200 MPa classified titanium alloy as high strength alloys. These high end titanium alloys are used in very high temperature and high stress applications. Some Examples include Ti - 10%V - 2%Fe - 3%Al and Ti - 4%A l -4%Mo - 4%Sn - 0.5%Si.

Biocompatible of Titanium Alloys

To be considered biocompatible, some specific physical properties of titanium alloy and some specific chemical properties of titanium alloy is very important. 

Physical properties like titanium color, and density, mechanical properties like yield strength, wear resistance, fatigue resistance, and ductility, and chemical properties of titanium alloy like corrosion resistance and inertness toward living cells are very important.

Biocompatible titanium alloys like 

1. Ti-6Al-4V (Titanium - 6% Aluminum - 4% Vanadium)

2. Ti-15Mo (Titanium - 15% Molybdenum)

3. Ti-6Al-7Nb (Titanium - 6% Aluminum - 7% Niobium)

4. Ti-35Nb-7Zr-5Ta (Titanium - 35% Niobium - 7% Zirconium - 5% Tantalum)

Are extensively utilized in medical and dental applications. They are used due to their ability to seamlessly integrate with the human body while maintaining excellent mechanical properties. 

These titanium alloys are commonly used in orthopedic implants such as artificial joints, hip and knee replacements, and dental implants.

High Corrosion Resistance Titanium Alloys

Titanium alloys are well known for their high corrosion resistance. These chemical properties of titanium alloys make them most favorable for all those applications that involve seawater and harsh environments. 

The high corrosion resistance of titanium deep drawing is due to their ability to develop a protective layer of oxide. Oxide layers develop when the titanium outer surface comes in direct contact with oxygen. This protective layer of oxide prevents penetration of moisture and thus prevents corrosion and rusting of titanium made parts.

Components such as ship hulls, propeller shafts, and offshore structures made from titanium alloys exhibit prolonged service life and reliability in marine conditions, contributing to the efficiency and sustainability of maritime operations.

Some common high corrosion resistance titanium alloys includes

1. Ti-6Al-7Nb (Titanium - 6% Aluminum - 7% Niobium)

2. Ti-3Al-2.5V (Titanium - 3% Aluminum - 2.5% Vanadium)

3. Ti-6Al-2Sn-4Zr-2Mo (Titanium - 6% Aluminum - 2% Tin - 4% Zirconium - 2% Molybdenum)

4. Ti-0.15Pd (Titanium - 0.15% Palladium)

High Temperature Resistance Titanium Alloys

Best thing about titanium alloys is that all physical properties of titanium alloy, chemical properties of titanium alloy and material properties of titanium alloys are maintained at elevated temperature. 

This makes them suitable for high temperature applications in industries such as aerospace, automotive, and power generation. 

Several titanium alloys exhibit exceptional high temperature resistance due to their unique composition and microstructure. Some examples of such titanium alloys are

• Ti-6242 (Titanium - 6% Aluminum - 2% Tin - 4% Zirconium - 2% Molybdenum)

• Ti-5553 (Titanium - 5% Aluminum - 5% Vanadium - 5% Molybdenum - 3% Zirconium)

Manufacturing of Titanium and Titanium Alloys

Titanium and all its alloys are non-reactive at room temperature but their reactiveness increases at elevated temperature. Titanium became highly reactive at temperatures above 700 degree centigrade. 

Due to reactiveness at elevated temperature, titanium parts production needs to be performed in a controlled environment.

Titanium alloys are extremely difficult to machine. This is due to their excellent strength, high hardness, and wear resistance. High quality diamond tip tools are used to machine titanium alloys with special setup.

To machine titanium alloys, titanium is heated above 300 degree centigrade and tools are cooled using liquid nitrogen. This helps machine titanium easily and increase tool life.

Titanium alloys can be processed with a variety of manufacturing and sheet metal fabrication services like sheet metal welding services, sheet metals stamping process, sheet metal cutting services, and custom sheet metal bending. Titanium alloys also support all types of surface finish process.

Facts about Titanium and its alloys

• Titanium is also called wonder material or aerospace material due to its unique process and extensive use in the aerospace industry.

• Titanium and its alloys have low creep strength at elevated temperature. At a temperature about 300 C, the creep strength of titanium alloys decreases dramatically.

• Titanium and most of its alloys are non magnetic metals but they can be made magnetic that is why they are called paramagnetic.

• Titanium is considered inert and non-reactive at room temperature due to an oxide layer developing at the top. This oxide layer protects further reaction of titanium with any other element.

• As there are no iron elements attached with titanium or its alloys. So titanium and all its alloys are basically rust proof. 

• Titanium alloys have a very high strength to weight ratio with its strength to weight ratio much higher than steel.

• Titanium alloys are considered bullet proof and due to their high strength to weight ratio, they are used in most bullet proof applications. 

  
  

Conclusion

Whether in aerospace, automotive, medical, marine, or power generation, titanium alloys play an important and crucial role in ensuring reliable performance and durability under any extreme conditions. There is a wide variety of titanium alloys available in the market and each alloys can be process with a different heat treatment process to get the desire properties.