The Four Main Morphologies
Dendritic particles are tree-like, branched structures produced by electrolytic deposition. Spherical particles are produced by gas or water atomisation. Irregular particles are sponge-like, typically reduced from oxides. Flake particles are flat platelets produced by milling.
Dendritic Morphology
Dendritic copper powder (e.g. CU-ED) provides excellent green strength and compressibility in cold-pressed parts. The branched structure mechanically interlocks during pressing, holding the green part together before sintering. Apparent density is low (0.65 to 2.7 g/cm³). Used in diamond tool segments and powder metallurgy pressing.
Spherical Morphology
Gas-atomised spherical powders (e.g. CU-AT, AL-SP) have excellent flowability and high apparent density (4.0+ g/cm³). Essential for additive manufacturing, thermal spray and cold spray where powder must flow uniformly through nozzles or across a powder bed. Poor green strength when pressed.
Irregular / Sponge Morphology
Reduced iron powder (e.g. FE-RED) has a porous, sponge-like structure. High compressibility for sintered friction materials and PM components. Apparent density between dendritic and spherical (2.2 to 3.0 g/cm³).
Flake Morphology
Milled flake powders (copper, bronze, brass flake) have a high aspect ratio and large surface area. Used in metallic paints, liquid metal coatings, and decorative cold-casting. The platelet shape orients parallel to the substrate during application, creating a continuous metallic film.
Choosing the Right Morphology
If pressing and sintering parts: dendritic or irregular. If flowing through a 3D printer or thermal spray gun: spherical. If creating a metallic surface coating or paint: flake. For brazing pastes: spherical for consistent rheology.
Morphology Sets Apparent Density
Shape and packing are the same question asked twice. Spheres pack efficiently and land high: CU-AT sits at 4.0 to 4.8 g/cc. Dendrites cannot nest, so they trap air between branches and land low, from 0.65 to 2.7 g/cc for CU-ED. Sponge iron falls between at 2.2 to 3.0. If you know the morphology you can predict the apparent density band before reading the certificate.
Morphology Sets Flow
Flow follows the same logic. A sphere presents minimal contact area to its neighbours and rolls; a dendrite interlocks with everything around it and does not. This is why spherical powders are specified wherever material must move unattended, through a nozzle, across a recoater, into a die at speed, and why dendritic powder is specified where it must stay put and hold shape.
The Trade-off You Cannot Escape
Green strength and flow pull in opposite directions, and morphology is the reason. The interlocking that gives dendritic powder its green strength is precisely what stops it flowing; the smoothness that lets spherical powder flow is precisely why it falls apart when pressed. No single morphology optimises both, which is why segment formulations blend powders rather than seeking one perfect grade.
Choosing by Process
Pressing and sintering favours dendritic or irregular. Additive manufacturing, thermal spray and cold spray require spherical. Decorative coatings favour fine flake or fine spherical for coverage and burnish. Match the shape to the mechanism the process relies on, and the properties follow.