Study on joining of single crystals of refratory metal by using brazing material with high melting-point

1.用Mo-40%Ru合金钎焊单晶钼用粉末冶金法制备Mo-40%Ru或Mo-40%Ru-B合金板，但没有成功。然后采用粉末与有机溶剂的混合物对单晶钼进行钎焊。当硼的加入量为2%时，接头强度逐渐提高，并达到了Mo晶体的强度。此外，接头被“全弯曲”，直到弯曲角为100 °，并且在室温下没有失效。这一结果表明，Mo-40%Ru合金中加入少量的硼后，其韧性得到了显著的提高.单晶钼与碳陶瓷的钎焊采用钯、铂或锆作为钎焊剂，单晶钼与碳陶瓷的钎焊接头强度高达100 MPa。电子探针分析表明，接头强度不仅与成分有关，而且与孔隙有关，特别是与表面附近的孔隙有关.模拟大气环境下接头强度的退化上述钎焊接头应在相对高温的环境中长期使用。在高温真空条件下保持试样，观察钎焊接头组织、成分和强度的变化。Mo-40%Ru-1%B合金钎焊接头的强度高于Mo-40%Ru合金钎焊接头的强度，但韧性较小。用钯或铂钎焊的单晶钼与碳陶瓷的接头在热处理后约有原来强度的一半。

1.Brazing of single-crystalline molybdenum by using Mo-40%Ru alloyPreparation of sheets of Mo-40%Ru or Mo-40%Ru-B alloys by powder metallurgy was not successful. Then brazing of single-crystalline molybdenum was performed by using mixture of powders and organic solvent. The joint strength gradually increased by adding boron as small as 2%, and was as high as that of the bulk Mo crystal. Additonally the joint was "full-bended" until a bend angle of 100ﾟand was not failed at room temperature. This result reggests the toughness of Mo-40%Ru alloy was substantially improved by a small addition of boron.2. Brazing between single-crystalline molybdenum and carbon-ceramicsBy using palladium, platinum or zirconium, the brazed joint between single-crystalline molybdenum and carbon-ceramics demonstrated a strength as high as 100MPa. Investigation by EPMA suggested the joint strength depends on both composition and pores particularly near the surface.3. Degradation of the joint strength in a simulated atmosphereThe brazed joints mentioned above should be used in a relatively high-temperature circumstance for a prolonged period. Thereby the specimen was kept in a vacuum at high temperature and the change of structure, composition and strength of the brazed joint was examined. The brazed joints by using Mo-40%Ru-1%B alloy demonstrated a ductility, though small, and a higher strength than that by using Mo-40%Ru alloy. The brazed joint between single-crystalline molybdenum and carbon-ceramics by using palladium or platinum demonstrated approximately a half of the original strength after heat treatment.