Spark plasma sintering of functionally graded material in the Ti–TiB2–B system

A six-layer functionally gradient material (FGM) of Ti–TiB–TiB2 was rapidly fabricated by spark plasma sintering (SPS) in vacuum. Both B and TiB2 were used and reacted with Ti to synthesize TiB. Adjusting the content ratio of B to TiB2 in individual layers could control the amount of synthesized TiB by two steps during sintering. The composition and microstructure of the layers in FGM were investigated by XRD, SEM and TEM. The synthesized TiB has needle-like, agglomerated and elongated morphologies. The content of agglomerated TiB increased and that of needle shape TiB decreased with increasing the target TiB volume fraction ranging from 20 to 60%. The elongated TiB was observed in the other two layers with higher target TiB volume fraction, which structure is similar to the agglomerated TiB. The FGM with Ti on one side to Ti–TiB–TiB2 on the other were fabricated at relative low sintering temperature and short dwelling time by spark plasma sintering.