SELECTIVE ELECTRON BEAM MELTING OF TITANIUM AND TITANIUM ALUMINIDE ALLOYS

Selective electron beam melting (SEBM) with an additive-layer thickness similar to 100 pm has been used to fabricate two titanium alloys (Ti-6Al-4V and Ti-6Al-2. 75Sn-4Zr-0.4Mo-0.45Si-0.1Y, designated Ti600 in China) and two TiAl alloys (Ti-48Al-2Nb-2Cr (TiAl), and Ti-45Al-7Nb-0.2W (TiAl-7Nb)). The as-fabricated Ti-6Al-4V and Ti600 alloys showed excellent tensile properties. Both alloys displayed a fullcolumnar microstructure parallel to the additive solidification direction with the transverse section showing an increasingly coarse microstructure towards the bottom of each cuboidal sample. Fine yttrium oxide dispersoids were observed in the matrix of the asfabricated Ti600 alloy. In order to utilize additive manufacturing (AM) for the two brittle TiAl alloys, an anneal-accompanied SEBM process was developed, which allowed thermal stresses to relax during the AM process. In addition, the formation of various types of defects during SEBM is briefly discussed.