This study investigated gas tungsten arc (GTA) welding of pure titanium sheets. Tensile, flexural, and microhardness tests were conducted on GTA welded samples. Microstructural analysis using optical microscopy and SEM was also performed. The results showed that the GTA welded samples had higher microhardness values and tensile/flexural strengths than the base pure titanium material. However, the strengths of the GTA welded samples were still lower than the base material due to cracks and oxide structures observed in the weld zone. Microstructural analysis revealed coarse columnar grains in the weld zone and finer equiaxed grains in the base material.

1. International Journal of Materials and Mechanics Engineering, Vol. 2, No. 1
Investigation gas tungsten arc welding of pure titanium
Gh. R. Razavi1a
, M. Masaeli1b
, M. Taheri2c
, M. Saboktakin1d
1
Department of Materials Engineering, Najafabad Branch, Islamic Azad University, Isfahan, P.O.
Box 517, Iran
2
Master of Materials engineering, nonprofitable university of kar Qazvin branch, Iran
a
R_Razavi@smt.iaun.ac.ir, b
mohammadmasaeli@yahoo.com, c
material65@yahoo.com,
d
mohsen.saboktakin@gmail.com
Keywords: Ti alloys, mechanical properties, GTA welding.
Abstract. Titanium alloys are widely used in many fields such as the automotive, aerospace and
chemical industries. In some applications, Titanium alloys are needed for use with particular
welding methods. These are GTAW, GMAW .In this study, Titanium Grade- 2 (Cp-Ti) plates
were welded using GTAW welding. Tensile and flexural tests were applied to the welded
samples. The microstructure and SEM images of main material and welded regions were studied
and microhardness measurements were performed.Tensile and flexural strengths of GTA welded
samples were higher than pure Ti welded samples. The microhardness values of the weld-zone of
GTA welded samples were higher than the pere Ti welded samples welding zone. In
microstructure and SEM investigations, oxide structures and the splashes of molten metal
appearing like drops were identified.
Introduction
Titanium has become an attractive material because of its low density and higher mechanical
properties/density ratio. Because of its high strength and high corrosion resistance, titanium and
titanium alloys have become the preferred engineering material in recent years. However, because
of its lower wear resistance it cannot be preferred in engineering applications which include
friction and wear[1-5].
Titanium-based materials gain preference by their low density, high strength, high corrosion
resistance and high fracture strength. They are also preferred in the aircraft and aerospace
industry, chemical industry,medicine, marine, automotive industry, and the biomedical
industry[6,7]. All traditional machining processes are applicable to these materials, but because of
their particular properties these materials have some difficulties in machining processes. Because
of its high corrosion resistance, titanium and its alloys are widely used in dental implants,
chemical industry apparatus, oil industry pipes, shipbuilding, fasteners and exhaust systems in the
automotive industry, jet engines in aircraft, and in the aerospace industry and construction
industries.
Although titanium and alloys have the feature of high corrosion resistance at low temperatures, it
is undesirable to weld them in atmospheric air as they have an increasing tendency to react
with oxygene, hydrogen, carbon and nitrogen[2,8,9]. Titanium is chemically reactive at high
temperatures. While welding, titanium alloys pick up oxygen and nitrogen from the atmosphere.
Choi and Choi investigated the effect of GTA welding condition according to mechanical
properties of pure titanium and they reported that if oxygen or nitrogen in the air infiltrates
into the WMZ (welding metal zone), the hardness of the titanium welding will increase. Therefore,
the welding of titanium requires complete gas shielding[2]. The welding processes recommended
for use when welding titanium and its alloys are; tungsten inert gas (GTA) welding, metallic inert

2. International Journal of Materials and Mechanics Engineering, Vol. 2, No. 1
gas (MIG) welding, diffusion welding, (both spot and seam) electron beam welding, friction stir
welding and laser welding[5,10]. Before the welding of titanium and alloys, it is necessary to
clean the oxide layer of the surface, and the welding zone must be prevented from making contact
with atmospheric air. In titanium built constructions, the material properties, weldability and
mechanical behavior of the different welding methods must be evident.
Kahraman et al. investigated the effect of welding current on the plasma arc welding of pure
titanium[10].
In this study, 2.5 mm thick commercially pure titanium sheets (Cp-Ti) were welded by TIG
welding methods. The mechanical properties of the titanium sheets which were welded by GTA
welding methods were investigated.
Experimental
1000x450x2.5 mm sized Titanium Grade 2 sheet which is the referred to material in the studies
250x450x2.5 mm sized piece, which are to be used in GTA welding 125x450x2.5 mm, and sized
two pieces were cut with a wire erosion cutting machine. The chemical compositionof the
titanium sheet (Grade-2) is shown in Table 1.
Table 1. chemical composition of Titanium used in the study.
Element Fe C N O H Ti
0.15 0.02 0.02 0.13 0.02 Bal.
The titanium plates were welded by using a ERTi-2 filler rod as one pass, but the double
surface was welded with GTA welding as is stated in AWS A5.16-70. The GTA welding
parameters are shown in Table 2.
Table 2. GTA welding parameters
Polarization) DC (+)
Voltage 220 V
Current 80 A
Filler rod ERTi-2
Shielding gas Argon
All tensile tests were carried out by using Shimadzu AG-IS (100 kN) tensile testing device and
extensometer. Experiments were conducted at room temperature and 1 mm/min pulling speed.
The bending tests of the samples were done by using a Shimadzu AG- IS 100 kN device,
according to support distances of BS EN ISO 5173. The bending speed of the machine was
1 mm/min. Vickers micro-hardness measurements of the samples are done by using 300 gf
force for 10 seconds 500 µm pause from the welding zone to the main material. Microscophic
studies are done by using Nikon stereo microscope. Samples are sanded with 220, 400, 600,
800, 1000 and 1200 grid SiC abrasives. Then they are polished with 3µ diamond paste. They are
etched by using 50 ml H2O, 40 ml HNO3 ve 10 ml HF solution.
Results and discussion
Each tensile test was repeated three times depending on the type of each sample, and then the
average value was taken as the tensile strength. The tensile test data is given in Table 3 & 4. The
test results of the samples are shown in Figure 1 & 2. The comperative microhardness

3. International Journal of Materials and Mechanics Engineering, Vol. 2, No. 1
measurement results of the samples are shown in Figure 3.
Table 3. Tensile test data’s of specimens
Specimen Yield Strength (N/mm2
) Tensile Strength (N/mm2
)
Base Material 368.7±12.5 410.3±7.9
GTA Welded 305.95±5.2 349.3±11.1
Figure 4 & 5 shows the joint area structures by the GTA welding methods. The surfaces of
the welded joints indicate structures composed of dendritic grains in the center of the welded
seam. The size of the grains by the GTA are larger than with Pure Ti. SEM studies of GTA
welded samples are shown in Figure 6-8. Studies are performed from welding zone to main
metal zone. As a result of the tensile test obtained from SEM studies of fracture surfaces of
samples taken from the example is shown in Figure 9. At the end of the tensile and bending
tests, the laser-welded samples had a higher tensile strength and a higher flexural strength than
the GTA welded samples (Table 4).
Figure 1.View of specimen after the tensile tests Figure 2. Welded seams
Table 5. Bending test data of samples
Flexural Strength (N/mm2)
Base Material 759±16.3
GTAW Welded 636±94.3
The comperative microhardness measurement results of the samples are shown in Figure 3. The
welding zone of GTA welded specimen's hardness is higher than the Pure Ti welded specimen's
hardness. Yunlian et al. Investigated the mechanical properties of laser-beam welding and gas
tungsten arc welding of titanium sheets and found that microhardness values of the welding zone
of GTA welded titanium specimens are higher than laser welded specimens[8]. Kahraman et al.
reported that the increasing welding current increased the hardness of weld metal and HAZ. This
increase was attributed to oxygen concentration in the weld[9,10].
Figure 3. Micro hardness measurements graphic

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Figure 4 shows that titanium grade 2 has a fine equiaxed microstructure. Figure 5 shows the weld
zone of the GTA welded sample has coarse columnar grains because of the prevailing thermal
conditions during the weld metal solidification. Growths of grains and distorted structures
observed in the GTA weld zone due to the high heat input during weldin[10].
Figure 4. Microstructure of main material
Figure 5. A)Structure of GTA welded sample’s main material-heat affected zone (HAZ)
B) Microstructure of GTA welded sample’s heat affected zone
White oxide grain structures are shown on the surface of GTA welded samples (Figure 7), and are
determined by elemental analysis. Ductile fracture occur after the tensile tests on the specimens.
(Figure 9). The quality of the surface of GTA welded specimens are degraded (Figure 8).SEM
examination of GTA welded samples have a narrow and short cracks. These caused the decrease
in the mechanical properties of the material.
Figure 6. GTA welded sample’s base metal- welding metal

5. International Journal of Materials and Mechanics Engineering, Vol. 2, No. 1
Figure 7. GTA welded specimen consisting cracks in the HAZ A) 100x B) 1200x
Figure 8. A) Measurement of the length of the cracks of GTA welded samples in HAZ
B) Measurement of the width of the cracks of GTA welded samples in HAZ
Figure 9. Fracture surface of main material
Conclusions
In this research, we studied gas tungsten arc welding of pure titanium, and the following results
were obtained:
1. Finer sizes and distribution of a phase within the grains are correlated to the highest strength that
could be observed in the weldments.

6. International Journal of Materials and Mechanics Engineering, Vol. 2, No. 1
2. Post weld heat treatment of weldments resulted in significant improvement in tensile strength and
a loss in ductility.
3. The gas tungsten arc welding is suitable for pure titanium sheets welding, and the welded seam
without defects can be obtained.
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