Microstructure And Propertie Evolutiom Of TiBW/TC4 Composites With Network Microstructure After Hot Compressed Deformation

In this paper, Ti Bw/TC4 composites with a network microstructure were fabricated through low energy ball milling and hot-pressing sintering process based on spherical TC4 powders and fine Ti B2 powders. Hot compessed deformation behavior of the composites was investigated. Microstructure evolution of the composites after hot deformation under different parameters was analyzed by optical microscope, scanning electron microscope and electron backscatter diffraction system. Rockwell hardness of the composites after hot compression was tested. Room temperature tensile test was performed on d ifferent parts of the samples after hot deformation and further annealing. The corresponding relationship between microstructure evolution and properties transformation was established.Hot compression testes were carried out in the temperature range from 900 to 1000℃ and in the strain rate range of 0.001~0.1s-1 with a reduction range from 20% to 60% in height. Flow stresses decreased with increasing temperatures and declining strain rates.Microstructure analysis of the specimens after hot compression reveals that different deformation regions correspond to various microstructures. In deformation center region with maximum plastic strain, the spherical TC4 particles were torn and crushed dramatically, while Ti B whiskers broke up and directionally oriented. The deformation of center region and volume fraction of dynamic recrystallization increased with increasing deformation reduction. Primary α phase constantly spheroidizing during compression through a way of low angle boundaries transform to high angle boundaries. Ti B whiskers are beneficial to sphe roidizing. In higher strain-rate condition, the spheroidizing tends to occur in Ti Bw rich-region. A fiber texture components occurs shows <11 2—0>//ND. In lower strain-rate condition, the structure is homogeneous.Rockwell hardness test showed that with increase compression, the HRC increased. With the increase of temperature and decreasing of strain rate HRC increased firstly and then decreased. HRC are lower of Ti Bw/TC4 composites after comperession at high temperature and low strain rate.Room temperature tensile test results that tensile strength and elongation all increased with the compression increasing. After compression the tensile strength and elongation of V5D200 and V5D110 composites are higher than that of the as-sintered composites. After annealed, the tensile strength is lower than as-sintered composites respectively. Elongations of V5D200 and V5D110 composites increase to 13.2% and 14.3% respectively. After compression the tensile strengt h of V5D110 composites decreased and continued decreasing after annealed.