ON THE STUDY OF FUSED-BREAKING OF DOPED TUNGSTEN WIRE

The hole-structure of doped or undoped W wire in close vicinity to the fused-breaking was observed by metallography. It was found that the K contained in the W wire plays an important role on the formation of hole. The K atoms may move and accumulate along the grain boundaries first. The residual K-bubbles from which the K atoms had lost may be disintegrated into many micropores under high temperature. These micropores migrate in the crystal lattice and collect themself at the grain boundaries where the K atoms accumulated already. A series of holes with various sizes are, therefore, formed. The fused-breaking will take place at the section where the local temperature raised rapidly to an unallow able limit due to the unadaptable increasing of electrical resistance across such section occurring holes.