Investigation On The Relationships Between Electric Properties And Microstructures Of CuWCr Composites

A series of CuWCr composites were prepared by sintering-infiltration method. The relationships between microstructures of CuWCr materials and electric properties such as breakdown voltage, chopping current and eroding endurance have been investigated in three groups of samples, varied in the size of Cr particle, weight ratio of W to Cr, and Cu content. The main conclusions including:1. The weak-breakdown phase is related to the content of Cr substituted by Cu and the effect of Cr reinforced. The large-scale spreading CrW solute and bubbly Cu change the contacting-voltage distribution on the boundary among Cu, Cr and W. Chromium phase is the first-breakdown phase when Cr is partly replaced by Cu or it conglomerates in large-scale; the first-breakdown phase takes place on the Cr-ring when Cr is incompletely substituted by Cu and appears Cr-ring on the boundary of Cu phase; Cu phase is the first-breakdown phase when Cr is full substituted by Cu.2. The breakdown voltage of CuWCr composite mainly depends on effect of CrW solute and its microstructure. Increasing Cr solubility in W, decreasing the weak-breakdown phase and the size of Cr can deduce the probability of being breakdown.3. The main factors of influencing the chopping current of CuWCr composites are conductivity, contribution of Cu phase, grain size of Cu. Increasing the conductivity is harmful to decrease chopping current, reducing the gain size of Cu and increasing the dispersion of Cu are in favor of decreasing chopping current.4. Thermo-conductivity and electro-conductivity are main aspects to change the eroding endurance. While electro-conductivity is improved, the quantity of heat decrease, which results in enhancing heat conduction and alleviating arc-erosion. Small grain size of Cu, high conductivity and uniform contribution of Cu are beneficial to eroding endurance.5. The breakdown mechanism is not same while the composites is as cathode and as anode. The breakdown voltage is 7-10 times lower while as anode. The chopping current of anode is little higher and eroding velocity is faster than cathode. Particle-transference and electric-emission are basic factors in the...