Special Metallic Materials Systems

Copper Alloy

A metallic alloy based primarily on copper; many copper alloys are used when high electrical or thermal conductivity is important.

Major Functional Advantage of Copper Alloys

High electrical conductivity, high thermal conductivity, or a useful combination of the two.

Why are copper alloys important beyond structural applications?

Their high electrical and thermal conductivity makes them useful where transport of electrical current or heat is a primary material requirement.

Electrical Conductivity of Copper Alloys

The ability of copper-based material to conduct electric current, making appropriate copper alloys useful for electrically functional components.

Thermal Conductivity of Copper Alloys

The ability of copper-based material to transfer heat, making appropriate copper alloys useful in thermally demanding components.

Cu-Ni Alloy

A copper-nickel alloy system used where its combination of metallic properties and corrosion resistance is desirable.

Precipitation-Hardened Copper Alloy

A copper alloy capable of developing greater mechanical properties through precipitation-hardening heat treatment.

Quenching of Precipitation-Hardened Copper Alloys

The precipitation-hardened copper alloys described in the source generally require liquid quenching.

Copper Conductivity–Strength Trade-Off

Copper-alloy selection can involve balancing conductivity requirements with the mechanical properties obtained through alloying and thermal processing.

Copper Alloy Processing–Property Relationship

Copper-alloy composition and heat-treatment response determine the balance of conductivity and mechanical behavior available for an application.

Refractory Metal

A metal such as tungsten, molybdenum, tantalum, or niobium investigated for applications involving extremely high temperatures.

Examples of Refractory Metals

Tungsten (W), molybdenum (Mo), tantalum (Ta), and niobium (Nb).

Primary Attraction of Refractory Metals

Their suitability for very-high-temperature applications.

Room-Temperature Behavior of Refractory Metals

The source states that refractory metals are often brittle at room temperature.

Oxygen Sensitivity of Refractory Metals

Refractory metals can be highly sensitive to oxygen, requiring careful processing consideration.

Why can refractory metals be challenging for fusion AM?

Their room-temperature brittleness and high oxygen sensitivity can create significant difficulties during fusion-based processing.

Refractory-Metal Processing Challenge

Very-high-temperature capability does not automatically imply easy manufacturability; brittleness and oxygen sensitivity must also be considered.

Magnesium (Mg)

A very-low-density metallic material whose use in AM is limited by challenges including adherent oxide and flammability.

Primary Attraction of Magnesium

Low density.

Major AM Challenges of Magnesium

Low density, adherent surface oxide, and flammability have limited its potential in additive manufacturing.

Magnesium Flammability Challenge

Magnesium's flammability creates an important processing and safety concern during additive manufacturing.

Magnesium Oxide Challenge

An adherent oxide on magnesium contributes to difficulties in processing the material.

Future Direction for Magnesium AM

Newer magnesium alloys with reduced flammability are being investigated to improve their suitability for additive manufacturing.

Magnesium Property–Process Trade-Off

Magnesium offers attractive low density, but this benefit must be balanced against oxide and flammability-related processing challenges.

Metal-Matrix Composite (MMC)

A composite material consisting of a metallic matrix containing reinforcing material.

Metal Matrix

The continuous metallic phase surrounding and supporting the reinforcement in a metal-matrix composite.

Reinforcement in a Metal-Matrix Composite

A secondary material incorporated into a metallic matrix to modify the resulting material properties.

Reinforcements Identified for AM Metal-Matrix Composites

The source identifies oxide, carbide, and boride reinforcements.

Oxide-Reinforced Metal-Matrix Composite

A metal-matrix composite containing oxide material as reinforcement.

Carbide-Reinforced Metal-Matrix Composite

A metal-matrix composite containing carbide material as reinforcement.

Boride-Reinforced Metal-Matrix Composite

A metal-matrix composite containing boride material as reinforcement.

Reinforcement Agglomeration

The undesirable clustering of reinforcing particles rather than their remaining suitably distributed through the metal matrix.

Why can reinforcement agglomeration be harmful?

Clustering of reinforcement can be detrimental to the mechanical properties of a metal-matrix composite.

Potential AM Advantage for Metal-Matrix Composites

The high cooling rates of fusion AM may enable net-shape fabrication with a lower risk of reinforcement agglomeration.

Rapid Cooling–MMC Relationship

The high cooling rates of fusion AM may help reduce the tendency of reinforcing materials to agglomerate during fabrication.

Net-Shape Fabrication

Fabrication of a component close to its final intended geometry, reducing the amount of subsequent shaping or machining required.

Intermetallic Compound

A metallic material consisting of different metallic elements combined in a chemically ordered compound rather than behaving simply as a conventional random alloy mixture.

Titanium Aluminide

An intermetallic material based on titanium and aluminum that combines low density with excellent creep resistance.

Major Advantages of Titanium Aluminides

Low density combined with excellent creep resistance.

Why are titanium aluminides attractive for turbine components?

Their combination of low density and excellent creep resistance is useful for components exposed to sustained loading at elevated temperature.

Titanium Aluminide Creep Resistance

The ability of titanium aluminides to resist long-term deformation under sustained loading at elevated temperature.

AM and Titanium Aluminides

The source states that additive manufacturing has enabled the first widespread use of titanium aluminides.

EB-PBF

An electron-beam powder-bed-fusion process whose rapid solidification and high, stable build environment can enable fabrication of titanium-aluminide components.

Why is EB-PBF useful for titanium aluminides?

The rapid solidification and high, stable build environment enable fabrication of components such as titanium-aluminide turbine blades.

Titanium Aluminide Turbine Blade

A high-temperature component that can exploit titanium aluminide's low density and creep resistance and can be fabricated using EB-PBF as described in the source.

Special-Material Property–Process Relationship

Materials with exceptional properties can simultaneously present unusual processing difficulties, so manufacturing methods must be compatible with their specific material behavior.

Special-Material Selection

Selection among copper alloys, refractory metals, magnesium, metal-matrix composites, and intermetallics depends on the particular functional properties and processing constraints required by the application.