Sebuah Kajian Pustaka:

JEMMME (Journal of Energy, Mechanical, Material, and Manufacturing Engineering)
Vol.6, No. 3, 2021

ISSN 2541-6332 | e-ISSN 2548-4281
Journal homepage: http://ejournal.umm.ac.id/index.php/JEMMME

Sari | Flow Rate Effects on Microstructure and Mechanical Properties for Titanium … 189

Flow Rate Effects on Microstructure and
Mechanical Properties for Titanium Weld Joint

Dewi Puspita Saria, Amir Arifinb, Gunawanb, Dendy Adantab, Ihsan Asurab, Imam Syofiia

aStudy Program of Mechanical Engineering Education, Universitas Sriwijaya
Indralaya – 30862, South Sumatra, Indonesia

bDepartment of Mechanical Engineering, Faculty of Engineering, Universitas Sriwijaya

Indralaya – 30862, South Sumatra, Indonesia
e-mail: amir@unsri.ac.id

Abstract

Titanium is a metal with a low density, has good heat transfer, and a high

melting point; hence widely used for various purposes, such as
petrochemicals, aerospace, medical, and reactors. The titanium welding
process is complicated because no absence of protection against air during
the welding process results in the high absorption of oxygen from free air. In
this work, ASTM Gr-1 Titanium is joining using Tungsten Inert Gas (TIG)
welding method. The effect of argon flow rate on the mechanical properties of
titanium welding and its microstructures is investigated by hardness and
tensile tests. Then, microstructure observation to explore the fusion zone and
heat-affected zone. Furthermore, phase formation during the welding process
is analysed using the X-ray diffraction (XRD) method. The tensile test
revealed that maximum tensile strength was obtained at a 60 l/m argon flow
rate while minimum tensile strength was received at 25 l/min. The hardness
test shows that maximum hardness was obtained at 25 l/min on the fusion
zone.

Keywords: CP Titanium; Argon flow rate; mechanical properties; microstructure

1. INTRODUCTION
Welding is a technique of joining two metal pieces permanently, in contrast to
connecting using bolts and nuts that can be removed or not permanent. According to
Deutsche Industrie Normen (DIN), welding can be defined as a metallurgical bond in
metal or metal alloy joints carried out in a melted or liquid state [1]. The need in the
fertilizer industry today cannot be separated from welding techniques as a method of
joining component structures. Many factors are considered in choosing the material to be
welded and the welding method, such as strength, toughness, lighter mass, and corrosion
resistance of materials.
Welding is the process of joining two or more metals using heat energy, so the metal
around the weld area experiences changes in its metallurgical structure, deformation, and
thermal stress [2]. Liquid welding is a method of welding in which the joint is heated until it
melts using a heat source with added materials or fillers. Types of liquid welding that are
often used are shield metal arc welding (SMAW) and gas tungsten arc welding (GTAW)
[3,4]. For this case, discuss the liquid welding type of GTAW.
Process GTAW or tungsten inert gas (TIG) is used non-consumable electrodes to be
used in autogenous welding, i.e., welding without filler metal. GTAW welding, a shielding
gas is used, i.e., an inert gas (argon, helium) or an active gas (CO2). The working
principle of GTAW is to melt and combine metals by heating them by an electric arc
obtained from the potential difference between the non-consumable tungsten electrode
and the metal. The weld pool is protected by a shielding gas supplied by the shield gas
cylinder. The main parameters of GTAW welding are arc length, welding current, welding
travel speed, and shielding gas [5]. Figure 1 is a schematic of GTAW process welding.

http://ejournal.umm.ac.id/index.php/JEMMME
mailto:xxxx@xxxx.xxx

JEMMME (Journal of Energy, Mechanical, Material, and Manufacturing Engineering)
Vol.6, No. 3, 2021 doi: 10.22219/jemmme.v6i3.19082

Sari | Flow Rate Effects on Microstructure and Mechanical Properties for Titanium … 190

Figure 1. Schematic of the GTAW equipment used

From Figure 1, metal will experience the effect of heating the welding result and
changing the weld area's microstructure. The shape of the microstructure depends on the
temperature achieved in the welding, the welding speed, and the welding cooling rate.
Metal areas that experience changes in microstructure due to welding (heating) are called
the Heat Affected Zone (HAZ) [6].
Welding TIG works with high-alloy steel and metals (non-ferrous) such as aluminium,
copper, titanium, and alloys thereof; because of the high arc stability, TIG welding is the
best of modern electric welding due to its high heat dispersion. Excess on the workpiece
is reduced by adding an inert shielding gas also a cooling gas [1].
Titanium is a metal with a low density where it is 60% lower than the density of steel
and can be strengthened again by adding alloys and special treatment. Titanium has
good heat transfer properties with a conductivity value of 11.4 W/m·K and a thermal
coefficient (8.41 µm/m·K), which is lower than steel and non-magnetic. Titanium is
generally silver with a density of 4.51 g/cm3 (0.163 lb/in3), a melting point of 1668 ± 10 °C
(3035 °F), and a boiling point of 3260 °C (5900 °F). Titanium at a temperature of less
than 882.5 °C has a close-packed hexagonal (α phase) crystal form, whereas when it is
above 882.5 °C, it has a body-centred cubic (β phase) crystal form [7].
Titanium and its alloys have a higher melting point than steel, but temperatures
useful for structural applications generally only range from 427 - 595 °C. Titanium with
aluminide alloys can be used for applications up to 760 °C, where it is widely used for
various purposes, such as petrochemicals, spacecraft, medical devices, and reactors [8].
Commercially pure (CP) titanium is ductile enough (15-25% elongation) and has an
ultimate tensile strength of 30 ksi (207 MPa) at room temperature. Adding the elements
nitrogen and oxygen will strengthen the titanium (interstitial solid solution) but will cause
embrittlement due to the dissolution of these elements. Carbon is also an impurity in
titanium, but its effect does not exceed oxygen and nitrogen. Hydrogen can cause
embrittlement if it is over the limit. These elements will naturally dissolve during the
welding process [9]. The addition of the aforementioned alloys causes the tensile strength
to increase and the ductility to decrease; the combination of high tensile strength and light
density is needed in various work structures and good corrosion resistance properties up
to temperatures below 650 °C [7].
Hydrogen, oxygen, carbon, and nitrogen in pure titanium and its alloys are
impurities. The mechanical properties quality of CP titanium without alloy is seen from
many interstitial elements, especially the amount of oxygen. The interstitial element is
contaminated by oxygen which can cause impurities during the welding process. The
absence of protection against air during the welding process results in the high
absorption of oxygen from free air. Hydrogen, nitrogen, and oxygen are absorbed in
humid and wet conditions during the welding process. Residual cleaning material, oil, and

JEMMME (Journal of Energy, Mechanical, Material, and Manufacturing Engineering)
Vol.6, No. 3, 2021 doi: 10.22219/jemmme.v6i3.19082

Sari | Flow Rate Effects on Microstructure and Mechanical Properties for Titanium … 191

other material contamination to be welded cause carbon and hydrogen contamination
[10]. Therefore, this study investigates the effect of argon flow rate on mechanical
properties and microstructures in titanium welding.

2. METHODS
Chemical element composition on CP titanium material has been obtained by doing
XRF testing at a fertilizer plant. Table 1 is the chemical composition element of CP
titanium (ASTM Gr-1 titanium). Table 1 indicates that the material is a commercially pure
titanium ASTM Grade 1.

Table 1. Composition of ASTM Gr-1 Titanium

Element Composition
(%)

Titanium (Ti) 99.38
Iron (Fe) 0.548
Tin (Sn) 0.065

The TIG machine used for CP titanium (ASTM Gr-1 titanium material) welding is the
PANA-TIG TSP 500 with ERTi-1 filler rods. Before welding, the titanium is cleaned using
acetone so that the impurities that stick to the material disappear and do not diffuse when
the welding process. Furthermore, the titanium metal is placed on the backing shield. The
welding process is carried out in an open space. The details on TIG welding parameters
can be seen in Table 2. After all, preparations have been completed, welding can be
carried out according to a predetermined procedure. The welding procedure to be carried
out refers to the welding procedure specification (WPS). GTAW welding process on
titanium can be seen in Figure 2.

Table 2. GTAW welding parameters on titanium

Specimens Argon flow
rate (l/min)

Current (A) Voltage(V) Inert
Gas

Root fill and cap

A 15

120 100 110

Argon
UHP

99.99%
B 25

C 60

Figure 2. GTAW welding process on titanium

Then, the hardness test was carried out using the Vickers hardness method with the
diamond as the indenter. Tensile strength was determined through the universal testing
machine (Hung Ta Type HT 9502). The surface morphology of the sample fracture was
observed using an optical microscope.

JEMMME (Journal of Energy, Mechanical, Material, and Manufacturing Engineering)
Vol.6, No. 3, 2021 doi: 10.22219/jemmme.v6i3.19082

Sari | Flow Rate Effects on Microstructure and Mechanical Properties for Titanium … 192

3. RESULT AND DISCUSSION
From Figure 3, an increase in the hardness in the fusion zone area of each sample
was obtained. The hardness increased for a 25 l/min argon flow rate of 162 VHN and 15
l/min of 146 VHN. The hardness increase is suspected because of the maximum
protection from inert argon gas during the welding process. From Figure 3, the hardness
in the base metal area tends to be stable at 118 VHN, and in the HAZ area, there is a
decrease in the hardness by an average of 108 VHN.

0 5 10 15 20
100

110

120

130

140

150

160

170

H
a
rd

n
e
ss

(
V

H
N

)

Hardness test position

15 l/min

25 l/min

60 l/min

Figure 3. Hardness profile on welded joints

25,2915

23,5458

26,2865

1 2 3
20

T
e
n
si

le
s

tr
e
n
g
th

(
k
g
/m

m
2
)

Samples

15 l/min

25 l/min

60 l/min

Figure 4. The profile of the tensile strength

JEMMME (Journal of Energy, Mechanical, Material, and Manufacturing Engineering)
Vol.6, No. 3, 2021 doi: 10.22219/jemmme.v6i3.19082

Sari | Flow Rate Effects on Microstructure and Mechanical Properties for Titanium … 193

Figure 4 shows the tensile strength of samples A, B, and C. Based on Figure 4, the
lowest average tensile strength obtained in sample B of 23.5485 kg/mm2. Based on
Figure 4, the lowest average tensile strength obtained in sample B of 23.5485 Kg/mm2;
the lowest tensile strength occurred allegedly because of minim protection in welding
when the temperature is above 800 °C so that the outside air (oxygen, hydrogen, and
nitrogen) enters and cause embrittlement. Consequently, it affects the welding strength of
the titanium material; this condition is proportional to the hardness profile in sample B,
which tends to increase in the area of base metal and weld metal [11].
Figure 5 shows the morphology fracture of samples B and C. From Figure 8-a, the
fracture surface of the tensile test specimen C undergoes plastic deformation; it is
characterized by fractures that form a uniform dimple caused by crack propagation in the
grain boundaries (intergranular) on the fracture surface; this indicates ductile fracture
characteristics. From Figure 8-b, the surface fractures in specimen B are mortar tends to
be wider and has a fracture that tends to be smooth and has little plastic deformation; this
indicates that the fracture is less ductile in the material.

(a) (b)

Figure 5. Morphology of fracture: (a) The fracture surface is ductile, (b) The broken surface is less

ductile

Figure 6 shows the microstructure of the parent metal. The microstructure of pure
titanium in the base metal consists of a fine equiaxed α grain structure and tends to be
uniform / hexagonal closed packed (HCP) phase (Figure 6). The microstructure is
generally formed at room temperature or below 882.5 °C [10].

Figure 6. Parent metal microstructure

Figure 7-a is the microstructure of the HAZ where there is the deformation of item α.
Initially uniformly turns into coarse serrated and acicular α. Figure 7-b is the
microstructure of the fusion zone for welding with a flow rate of 15 l/min. From Figure 7-b,

JEMMME (Journal of Energy, Mechanical, Material, and Manufacturing Engineering)
Vol.6, No. 3, 2021 doi: 10.22219/jemmme.v6i3.19082

Sari | Flow Rate Effects on Microstructure and Mechanical Properties for Titanium … 194

the microstructure changes from serrated α coarsely transforming into serrated α fine.
The transformation is caused in the welding process the rapid cooling and oxygen
diffusion occur [12]. Figure 7-c is the microstructure for sample 25 l/min. From Figure 7-c,
the growth of acicular and alpha platelets is increasingly dominant; this is proportional to
the hardness testing results in the FZ area. Figure 7-d is the area of the fusion zone for
the C sample (60 l/min), where the arrows that serrate and platelet alpha are more
dominant, with the least acicular alpha being formed; this is due to high protection from
extensive air contamination by argon during the welding process.

(a) (b)

Figure 7. The microstructure of titanium welding: (a) HAZ is formed by serrated and acicular alpha,
(b) FZ for welding with a flow rate of 15 l/min, (c) FZ for welding with a flow rate of 25 l/min, and (d)

FZ for welding with a flow rate 60 l/min

From Figure 8, form Ti 90 phases are formed in the base metal area, HAZ, and weld
metal; no other phases are formed. This indicates that the welding procedure is correct
and meets welding standards titanium. The welding of specimen C using the argon
discharge of 60 l/min, the maximum protection against outside air contamination is when
welding is carried out so that there is no Ti02 phase or titanium oxide (easily formed when
titanium is heated to 882 °C), and other phases are formed [13].

20 40 60 80
0

500

1000

1500

In
te

n
si

ty
(

c
p
s)

2-theta (deg)

Meas. data: BSr_Theta_2-Theta

Figure 8. XRD results at HAZ and Fusion Zone

JEMMME (Journal of Energy, Mechanical, Material, and Manufacturing Engineering)
Vol.6, No. 3, 2021 doi: 10.22219/jemmme.v6i3.19082

Sari | Flow Rate Effects on Microstructure and Mechanical Properties for Titanium … 195

4. CONCLUSION
Testing the mechanical properties in this research includes hardness and tensile

testing. They are testing the hardness of the Vickers using a load of 20 Kgf. Based on the

results, the argon flow significantly affects the welding results; a high UHP argon flow rate

protects the welding from oxygen so that the hardness is not too high increased

compared to low flow rates. Furthermore, it increases the hardness and decreases the

strength of the material and ductility when fractured. The results show that the C

specimen obtained by TIG welding treatment using the 60 l/min argon flow rate

experienced the lowest hardness addition of 144 VHN. In contrast, the B sample

experienced the highest average addition of the hardness of 162 VHN (25 l/min), the A

sample of 146 VHN (15 l/min). Based on the tensile test, the C sample is the highest

tensile strength C with an average of 26.2865 kg/mm2, while the lowest is the B sample B

of 23.5485 kg/mm2.

Based on metallographic testing, the main metal area of commercially pure titanium

has a uniform grain size with a hexagonal closed packed (HCP) phase. In contrast, the

grain forms become elongated like straw, called platelet and acicular alpha in the HAZ

and weld metal.

ACKNOWLEDGEMENT
Thanks to Universitas Sriwijaya for the facilities for this research.

REFERENCES
1. Dadang. Teknik Las GTAW. Tarkina, Sukaini, editors. Jakarta: Kementerian

Pendidikan dan Kebudayaan Republik Indonesia; 2012.

2. Setiawan A, Wardana YAY. Analisa Ketangguhan dan Struktur Mikro pada Daerah

Las dan HAZ Hasil Pengelasan Sumerged Arc Welding pada Baja SM 490. JURNAL

TEKNIK MESIN: Jurnal Keilmuan dan Terapan Teknik Mesin. 2006;8(2).

3. Pratiwi DK, Arifin A, Suhada RA. WELDING ANALYSIS OF GRAY CAST IRON

ASTM A48 CLASS 40 USING SMAW. Indonesian Journal of Engineering and

Science. 2021 Sep 8;2(3):043–9. doi: https://doi.org/10.51630/ijes.v2i3.26

4. Nagy M, Behúlová M, Pérez MR. Microstructural and mechanical properties of

dissimilar Al-Ti joints prepared by GTAW welding-brazing. IOP Conference Series:

Materials Science and Engineering. 2019 Jan 4;465:012006. doi:

https://doi.org/10.1088/1757-899X/465/1/012006

5. Perdana D. Analisa Pengaruh Variasi Arus Pengelasan GTAW pada Material Plat

SS 400 disambung dengan Material Plat SUS 304 terhadap Sifat Mekanis. In:

Prosiding Seminar Nasional ReTII ke-11 2016. Yogyakarta: Sekolah Tinggi

Teknologi Nasional Yogyakarta; 2016.

6. Sireesha M, Shankar V, Albert SK, Sundaresan S. Microstructural features of

dissimilar welds between 316LN austenitic stainless steel and alloy 800. Materials

Science and Engineering: A. 2000 Nov;292(1):74–82. doi:

https://doi.org/10.1016/S0921-5093(00)00969-2

7. Donachie MJ. Introduction to Selection of Titanium Alloys. In: Titanium. ASM

International; 2000. p. 5–11. doi: https://doi.org/10.31399/asm.tb.ttg2.t61120005

8. Gospodinov D, Ferdinandov N, Dimitrov S. Classification, properties and application

of titanium and its alloys. In: Proceeding of University of Ruse . 2016.

9. Habashi F. ASM Metals Handbook Vol 2 10th Edition: Properties and Selection Non-

Ferrous Alloys and Special Purpose Mate. Ohio ASM Int. 1992;

10. Kou S. Welding Metallurgy. 3rd ed. New York: Johm Wiley and Sons; 2020.

11. ASM. Metals Handbook 10th Edition Volume 2.pdf. 1990.

12. Li X, Xie J, Zhou Y. Effects of oxygen contamination in the argon shielding gas in

laser welding of commercially pure titanium thin sheet. Journal of Materials Science.

2005 Jul;40(13):3437–43. doi: https://doi.org/10.1007/s10853-005-0447-8

13. Gu D, Hagedorn YC, Meiners W, Meng G, Batista RJS, Wissenbach K, et al.

http://repositori.kemdikbud.go.id/9528/1/TEKNIK-LAS-GTAW-XI-1.pdf
https://jurnalmesin.petra.ac.id/index.php/mes/article/view/16525
https://doi.org/10.51630/ijes.v2i3.26
https://doi.org/10.1088/1757-899X/465/1/012006
https://journal.itny.ac.id/index.php/ReTII/article/view/456
https://doi.org/10.1016/S0921-5093(00)00969-2
https://doi.org/10.31399/asm.tb.ttg2.t61120005
https://doi.org/10.1007/s10853-005-0447-8

JEMMME (Journal of Energy, Mechanical, Material, and Manufacturing Engineering)
Vol.6, No. 3, 2021 doi: 10.22219/jemmme.v6i3.19082

Sari | Flow Rate Effects on Microstructure and Mechanical Properties for Titanium … 196

Densification behavior, microstructure evolution, and wear performance of selective

laser melting processed commercially pure titanium. Acta Materialia. 2012

May;60(9):3849–60. doi: https://doi.org/10.1016/j.actamat.2012.04.006

https://doi.org/10.1016/j.actamat.2012.04.006