Effect of mechanical milling parameters on the properties of electrolytic pure copper powders and hot pressed billets fabricated from recycled copper wastes

This study was conducted to comprehensively investigate the effect of mechanical milling parameters on the properties of electrolytic pure copper powders and hot pressed billets fabricated from recycled copper wastes. Three different milling speeds, five different milling times and three different ball to powder weight ratios were used to fully reveal the effect of the mechanical milling process on the properties of recovered Cu powders. The results show that as the milling time and milling speed increased, the initial dendritic morphology of the copper was transformed into a flake-like structure. At 400 rpm and a 5:1 BPR parameters, the average particle sizes of C3, C4, and C5 after 2, 4, and 8h were ∼52 μm, 83 μm, and 71 μm, respectively. This suggests that particle size initially increases due to shape change and cold-welding, but at longer durations, fracture becomes dominant. The I5 with d(0.5) = 69.32 μm exhibited a high flow rate of 5.88 g/s with an apparent density of 2.9 g/cm3.While the hardness value of the Cu samples (A1-bulk sample) produced by exposure to the lowest deformation during the mechanical milling is 95.02 HB, the hardness value of the Cu specimens (F5-bulk sample) showing the highest apparent density, best flow rate and highest density values is 109.31 HB. The electrical conductivity values were determined to be approximately 52.2 MS/m, 57.4 MS/m and 44.3 MS/m for A1-bulk, F5-bulk and H5-bulk, respectively. This study offers valuable insights into the relationship between milling parameters, powder characteristics, and final material properties.