The list of printable metals is much shorter than the list of metals, because an alloy has to survive a very rapid melt and solidification cycle without cracking. That constraint, rather than availability or cost, is what decides which alloys appear on a machine's material list, and it is why some familiar wrought grades simply cannot be printed.
The available families
Stainless steels, both austenitic and precipitation hardening, are the workhorses. Tool steels for tooling inserts. Aluminium silicon casting alloys, because wrought aluminium grades hot crack. Titanium alloys for aerospace and medical. Nickel superalloys for high temperature parts. Cobalt chrome for dental and orthopaedic work. Copper and precious metals on suitably equipped machines.
Why some alloys will not print
Rapid solidification in a melt pool concentrates alloying elements at grain boundaries and can produce hot tearing as the last liquid solidifies under stress. Alloys with a wide freezing range are particularly prone. That is why the printable aluminium alloys are casting compositions rather than the high strength wrought grades most engineers would reach for first.
Powder is a specification, not a commodity
Particle size distribution controls how the recoater spreads the layer and how it packs. Sphericity controls flow. Oxygen and nitrogen content affect the finished properties, particularly in titanium. Satellites and irregular particles disrupt spreading. Powder is bought to a specification and lot traced in regulated work, exactly as bar stock is.
Reuse and its limits
Unfused powder is recovered, sieved and blended with virgin powder for the next build. That is normal and economically essential, and it is controlled: oxygen pickup and particle morphology change with each cycle, so a reuse ratio and a number of cycles are specified. An unlimited reuse policy is a quality problem waiting to appear in a fatigue test.
Questions people ask about metal 3d printing materials
Which metals can be 3D printed?
Stainless and tool steels, aluminium casting alloys, titanium alloys, nickel superalloys, cobalt chrome, and copper and precious metals on suitable machines.
Why can I not print my usual wrought aluminium grade?
High strength wrought aluminium alloys hot crack in a melt pool. The printable aluminium alloys are silicon bearing casting compositions that solidify without tearing.
Does powder quality matter?
A great deal. Particle size distribution, sphericity and oxygen content all affect spreading, density and the finished mechanical properties.
Can powder be reused?
Yes, with sieving and blending with virgin powder, under a controlled reuse ratio. Oxygen pickup and morphology change with each cycle, so reuse is limited rather than unlimited.