Nucleation and growth mechanism of crystalline phase for fabrication of ultrafine-grained Ti_(66)BNb_(13)Cu_8Ni_(6.8)Al_(6.2) composites by spark plasma sintering and crystallization of amorphous phase

摘要

Ductile ultrafine-grained Ti_(66)BNb_(13)Cu_8Ni_(6.8)Al_(6.2) composites with in situ precipitated β-Ti(Nb) phase were fabricated by spark plasma sintering and crystallization of amorphous phase. Microstructure analysis indicates that hard β-Ti(Nb) forms the matrix and soft (Cu, Ni)-Ti_2 acts as the reinforced phase, but the two phase regions have different scale, morphology and distribution. Fracture strength and fracture strain of the composites reach as high as 2415 Mpa and 32.6%, respectively. Theoretical bases of fabricating the ultrafine-grained composites, and nucleation and growth mechanism of crystalline phase during the crystallization process were elucidated. The results obtained provide a promising method for fabricating large-sized crystallized phase-containing bulk composites with excellent mechanical property by powder metallurgy.