Product Code: ICAL09_1006

Phase Evolution in Laser Solid Formed Compositionally Graded Ti60-Ti2AlNb Alloys
Authors:
Xin Lin, Northwestern Polytechnical University; Xi'an Peoples Republic of China
Mocong Yang, State Key Laboratory of Solidification Processing, Northwestern Polytechnical University; Xi\'An Peoples Republic of China
Xiaojing Xu, State Key Laboratory of Solidification Processing, Northwestern Polytechnical University; Xi\'An Peoples Republic of China
Haiou Yang, -; -
Jing Chen, State Key Laboratory of Solidification Processing, Northwestern Polytechnical University; Xi\'An Peoples Republic of China
Weidong Huang, State Key Laboratory of Solidification Processing, Northwestern Polytechnical University; Xi\'An Peoples Republic of China
Presented at ICALEO 2009

A thin-wall Ti60-Ti2AlNb alloy, with continuous composition gradient along the deposited direction, was fabricated by laser solid forming (LSF). The microstructure and phase evolution along the deposited direction were investigated. With the increase of aluminum and niobium contents, a series of phase evolutions along the compositional gradient occurred: α + β α + '' + β + β/B2+2 β/B2 +2 β/B2+ 2 + OB2+OB2.There is a large composition range from Ti60 to Ti60-60wt.%Ti2AlNb for the existence of phase. The hardness of the graded material increases with the increase of aluminum and niobium contents, and reaches the maximum with the formation of B2+O phases, then decreases sharply as obtaining the whole B2 phase at the top of Ti2AlNb parts. Based on the non-equilibrium phase diagram of the Ti-rich corner, the phase evolution during laser solid forming of the graded materials is explained on combining with the analysis of the influence of the Al and Nb on the stabilities of , 2, β/B2 and O phases in titanium alloys and the effects of recurrent tempering/annealing and heat accumulation in laser solid forming.