Microstructures of brazings and welds using grade 2 commercially pure titanium

Purpose: Microstructural analyses of commercially pure titanium (CpTi) are scarce. The present report presents the micrographs, fractographs, elementa l characteristics, and hardness profiles of brazed joints and weldments usi ng machined rods of CpTi. Materials and Methods: CpTi rods were joined usin g four techniques: laser welding, electric-arc welding, electron-beam weldi ng, and gold- and Ti-filler brazing. The specimens were then subjected to t ensile and fatigue loading. After sectioning and patterning, optical microg raphs of intact joints were obtained. Fractured surfaces were investigated using scanning electron microscopy (SEM). The joint's composition was deter mined by SEM-energy dispersive x-ray analysis. Hardness was determined at s pecific locations using a microindenter. Results: While laser welding left the parent metal's equiaxed structure fairly intact, electric-arc welding, electron-beam welding, and brazing created a heat-affected zone in the vici nity of the joint. The extent and characteristics of the heat-affected zone depended on the amount of heat transferred to the specimens. In this respe ct, brazing essentially increased grain size and altered their shape. Elect ron-beam welding augmented this phenomenon, yielding grains that encompasse d the full diameter of the joint. Electric-arc welding disrupted the granul ar pattern and generated highly lamellar/acicular structures. Conclusion: H ardness was not a good indicator of mechanical resistance, nor was the join t's structural continuity with the parent substrate. Still, acicular micros tructures were characterized by a peculiar behavior in that such joints wer e highly resistant to tensile stresses while their fatigue strength ranged among the lowest of the joints tested.