Study of heat-affected zone and mechanical properties of Nd-YAG laser welding process of thin titanium alloy sheet

Abstract

Titanium alloy (Ti–6Al–4V) is a subject of this research because it has high strength and oxidation resistance in a wide range of temperature. As a result of its resistance to high-temperature corrosion, the alloy is used for catalyst-grid. In the present study, full penetration welding of 1 mm thick titanium alloy sheet in a butt configuration was carried out by using an Nd-YAG laser welding machine. The influence of different welding, parameters, such as, welding speed, welding power on the heat affected zone (HAZ) morphology, metallurgy and mechanical properties, has been discussed in detail. Microstructures have been assessed by optical microscopy and by field emission scanning electron microscope (FESEM). The mechanical behavior has been analyzed in terms of Vickers micro-hardness compared with specimens under different welding conditions and base materials. A microstructure with different welding parameters has been scrutinized by FESEM. Hardness of the base metal has been found to be lower in comparison with the fusion zone due to rapid cooling. The weld size has been found to increase with a decreasing welding speed and decrease with an increasing welding speed. The hardness spreads from the parent metal to the HAZ and it is the maximum at the center of the weld region. It has been found that tensile strength of the specimen with different process parameters is approximately equal to the tensile strength of the parent metal.

Keywords:

• Microstructure
• microhardness
• tensile strength
• laser material processing