Titanium is a metallic element recognized for its unique combination of properties, particularly its exceptional strength and relatively low weight. This metal finds use in demanding environments, such as in aerospace structures and medical devices. Density, a measure of mass per unit volume, is fundamental to understanding why titanium is selected over other materials in these specialized applications.
The Density of Pure Titanium
The density of pure, commercially available titanium is approximately 4.51 grams per cubic centimeter (g/cm\(^3\)). This value can also be expressed as 4,510 kilograms per cubic meter (kg/m\(^3\)). This measurement is standardized at room temperature and atmospheric pressure to ensure consistent reporting. This specific value serves as the baseline for all commercially pure grades, such as Titanium Grade 2.
How Titanium’s Density Compares to Common Metals
Titanium’s density is its defining characteristic when compared against the two most common structural metals: aluminum and steel. Pure aluminum has a density of about 2.7 g/cm\(^3\), meaning titanium is approximately 67% denser. Conversely, the density of common carbon steel is significantly higher, typically ranging around 7.8 g/cm\(^3\) to 8.0 g/cm\(^3\). This comparison highlights that titanium is only about 57% as dense as steel.
Titanium’s low density, combined with its inherent strength, results in a high strength-to-weight ratio. This ratio, also known as specific strength, is a crucial metric for material selection where reducing mass is important. Titanium can match the strength of many common steel alloys while weighing nearly half as much, allowing it to outperform both aluminum and steel in contexts requiring both lightness and strength.
Density Variations in Titanium Alloys and Forms
The density value of 4.51 g/cm\(^3\) applies only to unalloyed, pure titanium. Titanium is most frequently used in alloy form, which slightly alters the final density. The most common alloy is Ti-6Al-4V (Grade 5), composed of 6% aluminum and 4% vanadium. Adding these elements changes the overall mass; aluminum is lighter than titanium, while vanadium is slightly denser. This specific composition results in a density of approximately 4.43 g/cm\(^3\), making the alloy slightly less dense than the pure metal.
The physical form of the material can also lead to apparent density variations, even if the base material remains the same. For instance, metal powders used in additive manufacturing have a lower bulk density due to the spaces and porosity between the individual particles. Once the powder is fully melted and consolidated into a solid, wrought component, the density returns to the theoretical value of the alloy.
Applications Driven by Titanium’s Density
The combination of titanium’s moderate density and high strength is the primary driver for its use in high-performance fields like aerospace. The material’s light weight directly translates to significant reductions in overall aircraft mass, leading to substantial fuel savings. Titanium is used for engine components, airframe structures, and fasteners where the strength-to-weight metric is paramount.
In medical applications, titanium is preferred for implants, such as hip and knee replacements, because its density is closer to that of human bone than denser metals like stainless steel. This density similarity reduces “stress shielding,” where a heavier implant carries too much load, causing the surrounding bone to weaken. High-performance automotive and sporting goods also rely on this property to enhance speed and efficiency. Components like connecting rods and bicycle frames are made from titanium to reduce mass, thereby improving engine response or athlete performance.