Extrusion of Cu feed materials

Experimental works have been carried out to determine (i) extrusion limits (ii) feed materials property (flowability of the extrudable feed materials) and (iii) mechanical properties of sintered Cu rods shaped by extrusion. The works were divided into 4 processing steps such as (i) preparation of particulate-binder mixtures (feed materials), (ii) shaping of the feed materials by extrusion, (iii) removal of the binders and (iv) sintering of the debinded parts. In the step of feed material preparation, Cu powders with different shapes and sizes were mixed with a binder, comprising of low density polyethylene (LDPE): paraffin wax (PW): stearic acid (SA). Volume ratios between the Cu powder and the binder were varied, e.g., 60:40, 65:35 and 70:30. Shaping of the feed materials was performed by downwardly direct extrusion, with an extrusion ratio of 10:1, into a rod-shape part with a diameter of 5.0 mm. Extrusion, limits were determined. For spherical Cu powders, feed materials prepared from different Cu particle sizes ( < 45 mum, 45-75 mum and 75-125 mum) could be extrudable when the metal powder charges were < 70 vol. %. For irregular Cu powders, feed materials prepared from the powder with particle sizes < 45 mum could be extrudable when the metal powder charges were up to 65 vol. %. When the irregular Cu powders with particle's sizes of 45-75 mum were employed, the powder to binder ratio was limited at 60:40. Rheological property test results showed that all extrudable feed materials exhibited pseudo-plastic behavior, i.e., their viscosity values decreased with increasing shear rates. The extrudates were further debinded and sintered. Mechanical properties of the sintered Cu extrudates depended on original Cu particle size and shape and sintering time.