| In this investigation, Al2O3/Cu composite material was prepared by Al2O3 particle addtion. The effect of the size, mass fraction and distribution of the secondary particle on the characteristics of arc movement was discussed, and the effect of microstructure on the arc erosion of Al2O3/Cu composite material was disclosed. The relation between microstructure and material properties was studied, and the breakdown process was investigated in the vacuum high voltage as well. The relationship between the the movement characteristiss of cathode spots and microstructure was understood, and the factors which affect breakdown and chopping current were analyzed. The following conclusions can be drawn from the investigation:The smaller Al2O3 particles increase the hardness of the Al2O3/Cu composite material and decreases the electrical conductivity slightly. The larger mass fraction of Al2O3 increases the hardness sharply and decreases the electrical conductivity sharply. The more uniform distribution of particles can improve the hardness and the electrical conductivity. The uniformity of the Al2O3/Cu composite material increases with increasing the milling time. However, longer time results in aggregation and non-uniformity of the namo-powders.The smaller Al2O3 particle increases the breakdown of the Al2O3/Cu composite material significantly, prolong the arc life and decreases the chopping current. With increasing the mass fraction of Al2O3, the breakdown voltage increases, then decreases; the arc life increases, then decreases; and chopping current decreases. The more uniform distribution of Al2O3 particle is helpful to increase the characteristics of the vacuum breakdown.The erosion of the Al2O3/Cu composite material mainly depends on the particle size, mass fraction and uniformity. Within a centain range of Al2O3 mass fraction, the smaller paricle and more uniform distribution alleviate the arc erosion, increase the eroding area, and decreases the erosion pits significantly. However, the excessive Al2O3 addition will cause the smaller particle spacing, thus results in the concentrated erosion and smaller eroding area and deeper erosion pits.From the theory of arc generation mechanism and the arc movement behavior, the arc energy, arc movement modes and the characteristics of molten location on the surface of the contact material are the main factors to affect erosion. When arc is generated simultaneously on many locations, it can move rapidly and expand from center to the edge. The too large spacing among the prefered breakdown mini-area will cause the stagnation of arc. However, the too small spacing will form a single arc with high energy, thus causes the concentration erosion. The increase of molten viscosity may alleviate arc erosion on some degree. |
