Spark-Sintered W Alloys Doped with LaB_6(Materials, Metallurgy & Weldability)

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LaB_6 doped W alloys were experimentally produced with the aim of developing new arc cathode materials by SPS. SPS is a new sintering method that applies a uniaxial stress and a pulse DC current to material powder to perform sintering. Alloys of three compositions, 25vol%LaB_6-W, 50vol%LaB_6-W, and 75vol%LaB_6-W were sintered at three different sintering temperatures, 1670K, 1870K, and 2070K for a sintering time of 600s. Pure W and pure LaB_6 powder was sintered in the same condition for comparison. At a sintering temperature of 2070K, sintered blocks of high density were obtained for every composition. Produced alloys were metallographically analyzed, and it was found that in every alloy reactions of La and W occurred during sintering, and in 25vol%LaB_6-W alloys W_2B and W, in 50vol%LaB_6-W and 75vol%LaB_6-W alloys WB, LaB_4 and LaB_6 existed after sintering. In the 25vol%LaB_6-W alloy, La isolated by decomposition of LaB_6 was found to form complex oxides with W. Discharge tests of electrodes made of sintered alloys were performed. The consumption of electrodes of 50vol%LaB_6-W and 75vol%LaB_6-W was very rapid. Those alloys contained LaB_4 generated by reactions of W and LaB_6. The low melting point of LaB_4 might have a bad influence on the resistance of those alloys to high temperature. On the other hand, electrodes of 25vol%LaB_6-W showed rather good properties, in spite of the fact that 25vol%LaB_6-W alloys contained no LaB_6 after sintering. This alloy contained complex oxides of La and W, and its major component, W_2B, is a material of high melting point and low work function. These components might improve performance of the 25vol%LaB_6-W alloy as an electrode material.
大阪大学の論文

Spark-Sintered W Alloys Doped with LaB_6(Materials, Metallurgy & Weldability)

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