Translated Abstract
Commercially pure titanium has a high specific strength, good corrosion resistance and biocompatibility. Because of its excellent properties, the metal has been widely used in biological, chemical, medical fields. Compared with the traditional fusion welding, the laser beam welding has a series of features, which are the high energy density, high weld Depth-to-width ratio, narrow heat-affected zone, small deformation, high production efficiency, and control flexibility. A large number of researches have been conducted to investigate the laser beam welding of commercially pure titanium, and many achievements have been obtained. The strength of commercially pure titanium laser beam welded joints have been improved greatly, whereas the plasticity of joints reduced significantly. Therefore, the research on heat treatment of laser beam welded joints of commercially pure titanium is important.
Using the IPG-4000W fiber laser welding machine, the joints of commercially pure titanium TA2 under different welding speed were obtained. Then, different temperature and time of heat treatment were been done, by high temperature muffle furnace. The microstructure and the microhardness of the welded joints was examined and tested with the aid of optical microscope, scanning electron microscopy (SEM) and electron back scattering diffraction and microhardness experiment. The influence of different welding speed and different heat treatment on microstructure and properties of commercially pure titanium TA2 had been studied.
According to the results, with the increase of welding speed, the size of the laser beam welded joints’ heat affected zone and fusion zone of commercially pure titanium TA2 decrease; Laser beam welded joints’ heat-affected zone (HAZ) and fusion zone contains a lot of low angle grain boundary, the grain of the joints’ HAZ under 1 m/min welding speed is various. The heat treatment at 650℃ have no obvious effect on the microstructure and performance of the joint. While at 700℃, recrystallization has appeared in HAZ, as the holding time increased, the recrystallization region is increasing; At 750℃ and 800℃, the joint HAZ had complete recrystallization. Hence, with the increase of temperature and time, the grain size of the HAZ increases; At higher temperature and longer time of heat treatment conditions, the base metal (BM) grain grew up, and recrystallization phenomenon has appeared in the fusion zone of recrystallization phenomenon; The low-angle grain boundaries inside the grain gradually disappear, while the neighboring grain orientation difference distribution changed from centralized random normal distribution to random distribution; With the enlargement of the crystalline regions and grain size, the microhardness joint HAZ decreases. In this experiment, the optimum process was: holding for 30min after heat treatment at 750℃, but the base metal grain has grown up slightly.
Translated Keyword
[Commercially pure titanium, Heat treatment temperature, Holding time, Laser beam welding, Microstructure and properties]
Corresponding authors email
