Abstract
Microstructure of titanium joint made with developed Ti-Zr base alloy brazing fillers has been investigated by observation and microanalysis with TEM, STEM/EDX, SEM/EDX, and X-ray diffraction test. Effect of heating time on the structure of the joint area was also examined in connection with diffusion of alloy elements in the fillers.
TEM microscopy revealed that the acicular structure at the joint area consists of more fine lamellar and cellular structures which form colonies similar to those commonly observed in eutectic and eutectoid. The configurations and diffraction patterns suggseted that these fine structures were eutectoid of α-Ti and Ti2Cu containing Zr, and that the joint area was made of proeutectoid α-phase and the eutectoid.
Joint structure was remarkably affected by heating time. Particualrly the width of the region of these acicular structure at the joint area varies with heating time; firstly it increases to some extent, then decreases and finally disappears. According to the observation and analysis with SEM/EDX, the area of acicular structure was considered to correspond to such area as containing more amount of Cu and Ni than the solubility in Ti base metal. On this discussion, the width was also calculated by diffusion theory.
