What Metal Materials Are Used in 3D Printing?

Metals are materials with good electrical conductivity, thermal conductivity, and plasticity. They normally consist of metallic elements or alloys and offer high strength, hardness, and corrosion resistance. Metals are used throughout industrial manufacturing, construction, electronics, and aerospace. Their physical, chemical, and processing properties make them important not only in conventional manufacturing but also in metal 3D printing.

Metals currently used in 3D printing include stainless steel, titanium alloys, aluminum alloys, nickel alloys, copper alloys, and iron alloys. These materials generally have high strength and hardness and are often difficult to machine conventionally, making additive manufacturing attractive. Metal powders for 3D printing normally require high purity, good sphericity, a narrow particle-size distribution, and low oxygen content. Processes such as selective laser melting and electron-beam melting can rapidly produce customized metal parts with complex shapes.

Stainless Steel

Stainless steel is composed of iron, chromium, nickel, and other alloying elements, with chromium as the principal addition. It offers good weldability, chemical corrosion resistance, high-temperature resistance, mechanical performance, and hygienic properties suitable for food and pharmaceutical contact. Stainless-steel powder forms readily, is easy to prepare, and is relatively inexpensive, making it one of the earliest metals used in 3D printing.

Applications include structural and load-bearing parts, pipes, vessels, doors, windows, railings, decorative products, food-processing equipment, medical devices, and chemical equipment. Stainless-steel grades commonly used in metal 3D printing include austenitic 316L and 304L and martensitic precipitation-hardening grades 15-5PH and 17-4PH.

Aluminum Alloys

Aluminum alloys combine aluminum with elements such as copper, zinc, and magnesium. Their specific properties depend on the types and amounts of alloying additions. Aluminum alloys have low density, high specific strength and stiffness, good castability and plasticity, good corrosion resistance, and relatively high fatigue resistance. They are widely used in aerospace, transportation, construction, electromechanical products, light industry, and consumer goods.

Aluminum alloys used in metal 3D printing include AlSi12, AlSi10Mg, AlSi7Mg, Al-Si9Cu3, 6060, and 6061. AlSi12 is a lightweight powder with good thermal properties and is suitable for thin-walled aerospace and automotive parts such as heat exchangers. AlSi10Mg offers high strength and hardness for thin-walled parts and complex geometries, especially where good thermal performance and low mass are required.

Titanium Alloys

Titanium alloys combine high strength with low density, good toughness, corrosion resistance, and biocompatibility. They are important in medical, aerospace, and automotive applications. Titanium is a typical difficult-to-machine material: it cuts poorly and readily absorbs hydrogen, oxygen, nitrogen, and carbon during hot processing. Metal 3D printing is especially suitable because it can form complex structures while retaining useful mechanical properties. Its protective atmosphere limits reactions with oxygen and nitrogen, while localized rapid heating and cooling limits evaporation of alloying elements.

Current titanium materials for 3D printing include commercially pure titanium, Ti6Al4V (TC4), and Ti6Al17Nb. Principal applications include aerospace components and human implants such as bones and teeth.

Nickel-Based Alloys

Nickel-based alloys retain high strength and oxidation-corrosion resistance at 650 to 1000°C. Their mechanical properties and resistance to oxidation and hot corrosion suit high-temperature, high-stress service. Additively manufactured nickel alloys can be used for hot-section aero-engine components such as turbine disks and blades, improving engine stability and thermal efficiency. A nickel-based alloy containing 50% titanium by mass has a strong shape-memory effect and is used for spacecraft structures and artificial-heart motors. Mature nickel superalloys for 3D printing include Inconel 625 (IN625), Inconel 718 (IN718), and Inconel 939 (IN939).

Cobalt-Based Alloys

Cobalt-based alloys contain cobalt as the principal element with nickel, chromium, tungsten, and small amounts of molybdenum, niobium, tantalum, titanium, lanthanum, and other additions. Their high strength, corrosion resistance, and biocompatibility led to early use in artificial joints. They are now widely used for customized dental prostheses and engine components. Common 3D-printing grades include Co212, Co452, Co502, and CoCr28Mo6.

Copper Alloys

Copper alloys use copper as the base element. Because copper has antimicrobial properties, these alloys are used in medical equipment and frequently touched products such as public door handles. Copper powder has high laser reflectivity and low absorptivity, so it was long considered difficult to print. In recent years, however, many companies have achieved copper-alloy 3D printing. Available feedstocks include copper-alloy powders, copper-matrix composites, and copper-alloy wire.

Liquid Metals

Liquid metals used in 3D printing are typically nontoxic gallium-indium alloys that remain liquid at room temperature, including gallium-indium and gallium-indium-tin alloys. Their surface hardens when exposed to air while the interior remains liquid. Their electrical conductivity creates the possibility of printing liquid-metal circuit boards.

In 2017, the Laboratory of Cryogenics and Medical Science at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, proposed suspended liquid-metal 3D printing. The process uses a gallium-indium liquid alloy as the printing material and a self-curing hydrogel as support. A nozzle continuously extrudes room-temperature liquid metal, while the hydrogel supports and fixes its shape. Layer-by-layer deposition creates highly complex, flexible three-dimensional metal structures. Potential applications include flexible 3D electronics, soft-robot assembly, material encapsulation, and biomedicine.

Other Metals

Gold, silver, niobium, zirconium, magnesium alloys, and other metals can also be 3D printed.