Research On The Technology Of Molybdenum Crystals Of Refractory Metals Prepared By Electron Beam Floating Zone Melting

Refractory metals and intermetallic alloys with outstanding properties play an unsubstituted role in the fields of national defence, aerospace, electron technology, energy science, chemical-resistent science, metallurgy and nuclear industry and received high recognition from worldwide countries, have become one of the most warm-up field in material science. The technology of preparing refectory metal molybdenum single crystal is researched by electron beam floating zone melting in this paper, Microstructure of directional solidification and growth mechanics for molybdenum single crystals prepared by seed crystals and without seed crystals are investigated. The relation of mechanical property, processing parameter and structure of solidification is investigated.Three parts was include in this paper: First, a new electronic gun was designed, this make it possible for a fast .uniform and stable directional solidification process using electron beam floating zone melting .Second ,the polycrystal Mo with the orientation of (110) made with high purity sintered and arc-melting Mo was prepared by the method of electron beam floating zone melting without a seed.It can be concluded that it agrees competitive growth mechanics during direct solidification processing using this method. The grain with the orientation that deviate with the heat flow was restricted, and grain boundary of wide-angle had a visible decrease ; the small angle increase with the scan rate; the composition gets more homogeneous ;The hardness is homogeneous inside the crystal grain ,and the microhardness is higher inside the grain than that on the grain boundary; the microhardness has a inverse ratio with the scan rate. The last part of this paper gives a introduction of technology with seed using electron beam floating zone melting. The Mo-Nb seed had the orientation of (111 ).The crude materials was high purity arc-melt Mo. When it had a scan rate of 1.5, 2.0 and 2.5mm/min, the single crystal with the orientation of (111) was got after one scanning. When the rate is 20.mm/min, the best quality single crystal was got .The microhardness also decreases with the scan rate increasing.