Materials processing is the practice of transforming raw materials into useful forms with specific shapes, structures, and properties. It covers everything from pouring molten metal into a mold to depositing a coating just nanometers thick onto a microchip. The field sits at the heart of manufacturing, turning metals, ceramics, polymers, and composites into the components that make up cars, medical devices, buildings, and electronics.
How Processing Connects to Performance
In materials science, four factors are tightly linked: processing, structure, properties, and performance. This relationship is often drawn as a tetrahedron, with each corner connected to every other. The processing route you choose determines a material’s internal structure at the atomic and microscopic level, which dictates its properties (strength, conductivity, flexibility), which in turn dictate how it performs in real-world use.
A simple example: steel that is heated and then cooled slowly develops a different grain structure than steel that is rapidly quenched in water. The two pieces have identical chemistry but very different hardness and toughness. That difference is entirely a product of processing. This principle applies across every class of material, from plastics to advanced ceramics, and it’s why choosing the right processing method matters as much as choosing the right material.
Shaping: Casting, Forging, Molding, and Machining
Most materials processing falls into a few broad categories, starting with shaping. The goal is to get a material into the geometry you need, and the method depends on the material, the complexity of the shape, and how many parts you need to make.
Casting involves pouring molten metal into a mold and letting it solidify. Sand casting uses a sand mold for large, rough parts. Investment casting (also called lost-wax casting) produces finer detail and smoother surfaces. Die casting forces molten metal into a mold under high pressure for high-volume production. Engine blocks, turbine housings, and ship propellers are all commonly cast because their complex internal geometries can be formed in a single step.
Forging deforms solid metal under enormous pressure rather than melting it. Hot forging heats the metal above the temperature where its crystal grains can rearrange, allowing large shape changes without cracking. Cold forging works below that temperature, which requires more force but produces a harder, stronger part through a phenomenon called strain hardening. In both cases, the metal’s internal grain structure aligns along the direction of force, giving forged parts exceptional strength. That’s why crankshafts and aircraft landing gear, components that endure repeated stress cycles, are forged rather than cast.
Injection molding is the workhorse for plastics. Molten polymer is injected into a metal mold, cooled, and ejected as a finished part. It’s suited for producing thousands or millions of identical consumer products with a consistent finish.
Machining takes the opposite approach: instead of adding or reshaping material, it removes it. Mills, lathes, and drills cut away material from a solid block. Computer-controlled (CNC) machining can hold tolerances as tight as 0.025 mm, making it essential for aerospace parts, medical devices, gears, and bearings where precision is critical.
How Different Materials Require Different Approaches
Not every processing technique works for every material. Metals can be deformed and cut into new shapes without breaking, which is why they’re well suited to forging and machining. That flexibility comes at a cost: extracting metals from their ores requires energy-intensive chemical reduction, making them generally more expensive than nonmetallic alternatives.
Ceramics follow a fundamentally different path. A mixture of ceramic powders, water, and binder materials is molded into a temporary shape called a “green body.” That green body is dried, then baked at high temperature so the binder burns away and the ceramic particles fuse together. Once fired, ceramics are extremely hard but brittle, and with the exception of glasses, they can’t easily be reshaped. You get one shot at the geometry.
Polymers are the most forgiving when it comes to shaping. They can be readily formed into complex geometries through molding, extrusion, and thermoforming. Composites, which combine two or more materials (like carbon fiber embedded in a polymer matrix), require their own layup and curing processes designed to preserve the arrangement and orientation of the reinforcing material.
Surface Processing and Coatings
Sometimes the goal isn’t to shape an entire part but to modify its surface. A turbine blade might need a heat-resistant coating. A medical implant might need a biocompatible layer. A tool might need a hard surface to resist wear. Surface processing addresses all of these needs without changing the bulk material underneath.
The main techniques fall into three categories. Vapor deposition methods, including physical vapor deposition (PVD) and chemical vapor deposition (CVD), work by depositing material from a gas phase onto a surface, one thin layer at a time. Solution-based methods like electroplating and sol-gel coating deposit material from a liquid. Molten and semi-molten methods, such as thermal spraying and laser cladding, apply material in a melted or partially melted state. Each method offers different trade-offs in coating thickness, adhesion, temperature resistance, and cost.
Additive vs. Subtractive Manufacturing
Traditional machining is subtractive: you start with a block and cut away everything that isn’t the final part. Additive manufacturing, commonly called 3D printing, builds parts layer by layer, using only the material that ends up in the finished piece. This distinction has major practical consequences.
Subtractive methods produce parts from a solid, uniform block, which gives them isotropic mechanical properties, meaning the part is equally strong in every direction. Additive parts, built layer by layer, can have microscopic variations at the boundaries between layers. This often creates anisotropy, where strength depends on the direction of force relative to the build orientation. Subtractive machining also achieves tighter tolerances (around 0.025 mm versus roughly 0.1 mm for advanced additive processes) and produces smoother surface finishes straight off the machine. Additive parts almost always need secondary finishing to reach comparable smoothness.
Where additive manufacturing shines is geometric freedom. Internal channels, lattice structures, and organic shapes that would be impossible to machine from a solid block are straightforward to print. This makes it ideal for prototyping, custom one-off parts, and designs with complex internal features. Subtractive manufacturing remains dominant for high-volume production and high-stress structural components like landing gear, engine mounts, and hardened steel injection molds, where maximum material integrity is non-negotiable.
Nanoscale Processing
At the smallest scales, materials processing looks very different. Nanomaterials, with features measured in billionths of a meter, are synthesized through two broad strategies. Top-down methods start with bulk material and break it down: ball milling grinds particles to nanoscale dimensions, while laser ablation and sputtering strip material from a surface atom by atom. Bottom-up methods build nanostructures from individual atoms and molecules, assembling them into larger architectures through chemical or physical processes.
The choice between these approaches matters because the technique itself influences the structure of the final material. A thin film grown by plasma sputtering, for instance, can have an amorphous (non-crystalline) structure that would be difficult to achieve with thermal evaporation. Nanomaterials produced by these methods are already used in medicine, electronics, biosensors, cosmetics, and packaging, valued for magnetic, optical, catalytic, and mechanical properties that only emerge at the nanoscale.
Energy and Environmental Scale
Materials processing is one of the most energy-intensive human activities. In the U.S., the industrial sector accounted for 35% of total end-use energy consumption in 2022, and manufacturing alone represented 76% of that industrial total. Six subsectors, chemicals, petroleum and coal products, paper, primary metals, food, and nonmetallic mineral products, consumed 87% of all manufacturing energy.
The numbers are staggering. In 2018, chemical manufacturing alone used 7.1 quadrillion BTU of energy, much of it as feedstock (raw material inputs like hydrocarbon gas liquids used to make plastics). Primary metals manufacturing, which includes iron and steelmaking, consumed 2 quadrillion BTU, with coal serving as both fuel and a chemical reducing agent. Together, chemicals, petroleum and coal products, and paper manufacturing accounted for nearly 70% of total manufacturing energy use. These figures explain why efficiency improvements and process innovation in materials processing have outsized effects on global energy consumption and emissions.