Meaning
Degree of metallic bonding at the contact points between adjacent powder particles defines the structural integrity of a sintered part.
Surface Diffusion
Surface and volume diffusion drive the movement of atoms toward the contact area to form the initial sintering neck density. As the temperature rises the atoms migrate from the particle surfaces to the narrow gaps between them to reduce the total surface energy. This process transforms a loose collection of particles into a coherent solid with a continuous metallic matrix.
Tensile Strength
Tensile and fatigue properties depend more on the sintering neck density than on the total porosity of the part during the early stages of sintering. If the necks are small or poorly developed the material will be brittle and prone to intergranular fracture. Increasing the sintering time or temperature allows these bridges to grow and coalesce which improves the toughness of the alloy.
Microscopic Control
Microscopic examination of the fractured surface of a part reveals the extent of the sintering neck density achieved during production. Ductile dimples on the fracture surface indicate that the bonds were strong and that the failure occurred through the metal rather than along the original particle boundaries. This analysis helps engineers optimize the sintering furnace settings to ensure consistent part quality.
