Effect of Microstructure Transformations on Fatigue Properties of Laser Beam Welded Ti‐6Al‐4V Butt Joints Subjected to Postweld Heat Treatment

Abstract

The efect of postweld heat treatment PWHT) on 2.6-mm-thick Ti-6Al-4V but joints that were welded using a continuous-wave 8-kW yterbium ibre laser was studied in terms of the microstructure, microtexture, number of welding defects, microhardness, residual stress distribution and high cycle fatigue HCF) properties. Five types of heat treatments in the temperature range of 540-920°C are investigated. The main reasons leading to fatigue life deterioration after the laser welding process are discussed, and possible guidelines for further improvement of the HCF behaviour by a subsequent suitable type of PWHT are provided. Low-temperature annealing T < 600°C) tends to harden both the base material and the welding zone without any signiicant efect on the fatigue properties. Heat treatments at higher temperatures T > 50°C) lead to the transformation of a strong martensitic structure in the fusion zone FZ) into more ductile coarse lamellar, which is more beneicial for fatigue performance. A suitable type of PWHT can increase the fatigue limit of a laser-welded Ti-6Al-4V but joint by 10%; however, a slight decrease in static strength should be considered. The efect of stress relief at elevated temperatures is studied.

Metallurgical aspects of joining commercially pure titanium to Ti-6Al-4V alloy in a T-joint configuration by laser beam welding

“…Thus, the fraction of the transformed martensitic structure gradually decreases from 100% in the HAZ near the fusion line to zero in the BM. Comprehensive analysis of the HAZ formation in the laser beam-welded Ti-6Al-4V alloy can be found elsewhere [29].…”

Comparison of different titanium alloys welded by Yb:YAG fibre laser for thin sheet applications used for T-ducts in bleed air systems

“…Butt-joint welding was performed for all three alloys with a continuous laser power of 1.4 kW, focal plane on the surface of the sheets, and a welding velocity of 5.0 m/min transverse to the rolling direction of the sheets. The basic welding parameters were extracted from studies of Nd:YAG-and Yb:YAG-laser beam welding of Ti6Al4V sheets with thickness between 1.0 and 2.54 mm and Ti Grade 1 sheets with 2.0 mm [13][14][15]. A ratio of 1.6 to 2.1 kW/mm thickness was identified.…”

Annealing Heat Treatment for Homogenizing the Microstructure and Mechanical Properties of Electron-Beam-Welded Thick Plate of Ti-6Al-4V Alloy

“…Titanium (Ti) alloys are extensively used in the aerospace industry due to their high specific strength, corrosion resistance, and high-temperature properties [1][2][3][4]. To enhance productivity efficiency in aerospace component manufacturing and reduce aircraft weight, fusion welding processes can be employed for joining components [4].…”

“…Titanium (Ti) alloys are extensively used in the aerospace industry due to their high specific strength, corrosion resistance, and high-temperature properties [1][2][3][4]. To enhance productivity efficiency in aerospace component manufacturing and reduce aircraft weight, fusion welding processes can be employed for joining components [4]. Among the various fusion welding processes, the electron beam welding (EBW) method not only prevents oxidation by providing a vacuum shield but also offers the advantages of a large welding depth, small welding width and deformation, and high welding speed [5][6][7][8][9].…”