TIG welding of Ti6Al4V alloy: Microstructure, fractography, tensile and microhardness data

Titanium alloy is widely used in many industries due to its unique weight to strength ratio and high corrosion resistance. A suitable method of joining Titanium and its alloys is using Tungsten Inert Gas (TIG) welding. A significant advantage of TIG welding over other fusion welding is its ability to use non-consumable electrodes. This research was carried out on Ti6Al4V alloy of 2-3 mm thickness using TIG welding. Current and gas flow rates were varied, with Argon used as the inert gas for the welding. The data and images presented in this article account for the mechanical (tensile and microhardness), fractography, and microstructural properties of the welded samples. This article will foster simulation of heat input and flux and mechanical properties of TIG-welded Ti6Al4V alloy.


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Titanium alloy is widely used in many industries due to its unique weight to strength ratio and high corrosion resistance. A suitable method of joining Titanium and its alloys is using Tungsten Inert Gas (TIG) welding. A significant advantage of TIG welding over other fusion welding is its ability to use non-consumable electrodes. This research was carried out on Ti6Al4V alloy of 2-3 mm thickness using TIG welding. Current and gas flow rates were varied, with Argon used as the inert gas for the welding. The data and images presented in this article account for the mechanical (tensile and microhardness), fractography, and microstructural properties of the welded samples. This article will foster simulation of heat input and flux and mechanical properties of TIG-welded Ti6Al4V alloy. ©

Value of the Data
• In conjunction with the images, the dataset will further give an insight into the simulation and analysis of the strength of the material. • Industries such as automobile, chemical, marine, and aerospace will benefit from the data supplied since the primary material used by these industries is Titanium due to its unique properties over other metals.

• The dataset and images can give the welders/engineers vital information in various industries
where Titanium alloy is used. • The experiment was carefully selected and designed using the Taguchi design of experiment method. Hence, It will guide the engineers/welders on designing, planning, and executing welding operations. • The data can aid in the development an empirical model for predicting and optimizing TIG welding of Ti6Al4V alloy.

Data Description
A commercial mill annealed titanium grade 5 alloy sheet measuring 100 × 60 × 3 mm and 100 × 60 × 2 mm were the material used in this experiment. Tables 1 and 2 show the chemical composition of the Ti6Al4V sheets and the Ti6Al4V ELI filler rod used for this experiment, which was obtained from the material safety data sheet from the supplier. The materials conforms with ASTM B265 [1] and ASTM F136 [2] , respectively. Table 3 presents the mechanical properties of the Ti6Al4V sheet and Ti6Al4V ELI filler rods used at room temperature. Tables 4-5 show the experimental design for welding 3 mm and 2 mm thick sheets, respectively. The experimental   design was adopted based on the optimum range of parameters recommended by Muncaster [3] , and the parameters were randomized using the Taguchi L4 (2 2 ) design of experiment. The ASTM E8 [4] sub-size was used for the tensile test, as shown in Figure 1 . There is a provision for gas flow beneath the welded plate to prevent back purging and contamination of weld, as shown in the experimental setup Figure 2 . Figure 3 -10 shows the images of the microstructure of each sample. Each image shows the microstructure at three different zones, namely, heat affected zone (HAZ), base metal (BM), and fusion zone (FZ). The bead geometry measured using the Olympus Stream Essentials software is shown in Table 6 , and the fractography Images of the failed samples at FZ are shown in   Figures 13 and 14 shows the stress-strain relationship for 2 and 3 mm thick alloy, derived from the raw data in the supplementary file. Lastly, Figures 15 and 16 present the microhardness profile derived from the raw data presented in the supplementary file for 2 and 3 mm thick alloy, respectively.

Experimental Design, Materials and Methods
The TIG welding done in this experiment was carried out using the Afrox industrial 175 multiprocess welding machine and were done in two categories, Ti6Al4V sheets of 100 × 60 × 3 mm were joined as category A and Ti6Al4V sheets of 100 × 60 × 2 mm as category B. The two categories were joined using Ti6Al4V ELI as filler metal. Pure Argon of 99.99% purity was used as      the inert gas to prevent the weld's back purging and oxygen contamination [5] . Before welding, each sheet was cleaned with acetone to remove oxide films and contaminations from its surface [6] . Four welds were done, varying current and gas flow rate for each category. Each sample's microstructural examination was done using a cut out of 25 × 10 mm for each thickness. Each sample was ground using Silicon Carbide (SiC) papers of different sizes (#320-50 0-80 0-120 0). They were then polished and etched using Kroll's reagent containing 85% H 2 O + 10% HNO 3 + 5% HF for 18s [ 7 , 8 ]. The images were captured at 50X magnification at the heat affected zone (HAZ), base metal (BM), and the fusion zone (FZ) for each thickness. Furthermore, macrostructure images were taken at 1X to view the weld zone (WZ) and measure the bead geometry using the Olympus Stream Essentials software.
A Microhardness test was conducted at different WZ to create a hardness profile. Twenty indentations were done at a 1mm interval from each other, with a force of 4.9 N and a dwell time of 15s, following ASTM E384 [9] .
Tensile tests were carried out using the UTM Zwick Roell 2250, and following ASTM E8 [ 4 , 10 , 11 ], three samples were used for this test for each welding parameter. The samples were further analyzed at the failure point by obtaining the fractography images using the TESCAN SEM to study the manner of failure of the material.