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International Journal of Latest Trends in Engineering and Technology
Vol.(8)Issue(3), pp.121-126
6061 T6
H.M.Anil Kumar1 and Dr.V.Venkata Ramana 2
Abstract- Friction stir welding is a solid state welding process where in two materials are joined without melting the
material. The process is well suited for non ferrous materials such as aluminum, copper, magnesium, zinc etc. It is an
effective technique for joining dissimilar metal and alloys and finds its application in various fields such as aerospace
and automotive industries. In this attempt is made to join aluminum alloy AA 7075 T651 and AA 6061 T6 condition
by friction stir welding technique under different process parameters such as tool rotation speed (750 rpm to 1250
rpm), welding speed (90 mm/min to 110 min) and using five different tools pin profiles –threaded cylindrical (TC),
triangular profile (TP), conical profile (CP), square profile (SP) and hexagonal profile (HP). The outcome of the
experimentation indicated that square tool pin profile and hexagonal tool pin profile at the tool rotation speed of
1250 rpm and the welding speed of 110 mm/min respectively yielded good quality welds in contrast to other tool pin
Keywords – Dissimilar Friction stir welding, tool pin profile, tensile strength, microstructure
Friction stir welding (FSW) is a solid state joining process developed at The Welding Institute (TWI), Cambridge,
UK, in 1991. The process uses rotating tool which provides frictional heat and mixing to produce a weld between two
metallic surfaces below their melting point. Since the process works below the melting point of the metals some of the
defects like cracks, porosity and blow holes arising out of fusion welding process are eliminated. Koilraj et al [1]
investigated the optimum values of dissimilar friction stir welding process parameters such as tool rotational speed,
transverse speed, tool geometry and ratio between tool shoulder diameter and pin diameter for aluminium AA2219T87 and AA5083-H321 alloy. The results indicated that optimum levels of the rotational speed, transverse speed, and
D/d ratio are 700 rpm, 15 mm/min and 3 respectively. The cylindrical threaded pin tool profile was found to be the
best in contrast to other profiles. The D/d ratio contributes 60% to the satisfactory welds.Govind Reddy et al [2]
optimized the process parameters on the work on dissimilar frictions stir welding using AA2024-AA7075 aluminum
alloy. In this work effect of tool rotation speed and welding speed on the tensile strength is investigated by developing
mathematical model using response surface methodology and Nelder Mead algorithm.R Palanivel et al [3] studied the
effects of tool rotational speed and pin profile on microstructure and tensile strength of two different aluminum alloys
AA5083-H111 and AA6351-T welded by using friction stir welding under varying process parameters with different
tool pin profiles. The results showed that the joint fabricated by Straight Square at the tool rotational speed of 950 rpm
yielded highest tensile strength of 273 MPa. The two process parameters affected the joint strength due to variations
in material flow behavior, loss of cold work in the HAZ of AA5083 side, dissolution and over aging of precipitates of
AA6351 side and formation of macroscopic defects in the weld zone.D. A. Dragatogiannis et al [4] did the work on
Department of Mechanical Engineering Ballari Institute of Technology & Management, Ballari, Karnataka, India
Department of Mechanical Engineering Ballari Institute of Technology & Management, Ballari, Karnataka, India
Effect Of Tool Pin Profile On Dissimilar Friction Stir Welding Of Aluminum Alloy Aa 7075
T651 And Aa 6061 T6
dissimilar friction stir welding between 5083 and 6082 Al alloys reinforced with TiC Nanoparticles. The optimum
parameters selected are traverse speed of 60 to 85mm/min, rotational speed of 600 to 1180RPM and tool tilt angle
0°to 4°. The results shown that the hardness, elastic modulus, ultimate tensile strength, percentage of elongation, and
yield values increase with the presence of TiC nanoparticles.D. M. Rodrigues et al [5] conducted the experiments on
non-heat treatable AA 5083-H111 and heat treatable AA 6082-T6 aluminum alloys, which are widely used in
welding fabrication. Welding is done under a large range of welding conditions with varying tool dimensions, rotation
and traverse speeds, axial loads and tilt angles. Based on the various experiments, it is investigated that differences in
friction stir weldability, weld defect and weld strength, is related to plastic behaviors of both base materials. Finally
methodology for determining suitable friction stir welding parameters is proposed Hariharan et al [6] investigated the
mechanical properties of Al 6061 & 7075 alloy using Computerized Numerical Control Machine by friction stir
welding concept. The cylindrical & taper pin profile are selected and welding is carried out between 1600 to 1250
rpm at the rate of 120 mm/min with the tool tilt angle of 2°. High tensile strength of 485 MPa is produced at 1250
rpm,120mm/min and 2° tilt angle. The maximum hardness of 131 BHN is obtained at 1600 rpm. The taper tool at
1250 rpm has shown very fine grain structure 100µm due to the dynamic recrystallisation process.
Work Material Details–
The two dissimilar aluminum alloys AA7075-T651 and AA6061-T6 are cut by milling machine of dimension
200x60x6.35mm. After the cutting the process work pieces are cleaned by acetone solution to remove the dust, dirt
etc. The chemical composition of AA70705-T651is 0.05 %wt Si, 0.07 %wt Fe, 1.30 %wt Cu, 0.03%wt Mn,
2.69%wt Mg, 0.20%wt Cr, 0.01%wt Ni, 5.78%wt Zn, 0.06%wt Ti, 0.01%wt Pb, 0.01%wt Sn and balance
aluminum. The mechanical properties of AA7075-T651 are 583.34 MPa ultimate tensile strength, 526.24 MPa Yield
tensile strength, 11.26 total percentage elongation and 183.9 Vickers Hardness. Now the chemical composition of
AA6061-T6 is 0.4 %wt Si, 0.7%wt Fe, 0.2%wt Cu, 0.15 %wt Mn, 1.20 %wt Mg, 0.35 %wt Cr, 0.15 %wt Ti,
0.25%wt Zn and balance aluminium. The mechanical properties of AA6061- T6 are 300 MPa ultimate tensile
strength, 260 MPa yield strength, 19 percentage elongation and 110 Vickers Hardness.
B. Tool Details –
The joints of aluminum alloys are produced by five different tool profiles are used: threaded cylindrical (TC),
triangular profile (TP), conical profile (CP), square profile (SP) and hexagonal profile (HP). High Carbon and high
chromium steel is used as a tool material with shoulder diameter of 20 mm, tool pin diameter of 6.3 mm and pin
length of 5.3mm. Tool material is an air hardened which has high wear and abrasion resistant properties. It is heat
treatable and will offer hardness in the range 55-62 HRC, and is machinable in the annealed condition. Because of
high chromium content it has mild corrosion resistance properties in the hardened condition.
C. Selection of Process ParametersThe friction stir welding is carried out under three different process parameters, such as tool rotational speed of
750 RPM to 1250 RPM, welding speed of 90 mm/min to 110 mm/min and five different tool pin profiles as
mentioned above. The photographic image of the welded specimens is shown in the Figure1.
Figure 1. Welded Specimens
A. MacrostructureReferring to the figure 1, visual examination itself reveals that only two welds performed using square pin profile
(Figure 1C) and hexagonal profile (Figure 1D) appears to be a good welded joint than any other pin profiles. Further
it is observed that, during the welding process at 1000 rpm and 100 mm/min triangular profile tool has broken due to
the lack of hardness, insufficient clamping force on the work piece, tool geometrical dimension and other parameters
such as welding speed, tool rotation could be the possible reasons for the tool pin rupture. The five different types of
tools used for friction stir welding and broken triangular profile is shown in Figure 2. The nugget zone and heat
affected zone of welds produced from dissimilar aluminum alloys AA 7075 and A6061welded specimen are shown
in Figure 3. The macro structure of the specimen 3 has no defect whereas the macro structure of specimen 4 has
defect. The photographic images of the macrostructure of both the specimens are shown in Figure 4
Figure 2. Five different tool profiles
Figure 3. Different zones of Welding
Figure 4. Macrostructure of the Specimens 3 and 4
Effect Of Tool Pin Profile On Dissimilar Friction Stir Welding Of Aluminum Alloy Aa 7075
T651 And Aa 6061 T6
B. M icro structural StudiesMicro structural studies and tensile tests are envisaged for the two specimens (3 and 4) which appeared good quality
welds through visual inspection as shown in Figure 5. Further specimen 3 is welded at 1250 rpm and 110 mm/min
using square tool pin profile, whereas specimen 4 is welded at 1000 rpm and 100 mm/min using hexagonal tool pin
profile. The interface zone between 7075 & 6061 shown for the specimen 3 in this, 7075 has undergone
fragmentation and dynamic re-crystallization but 6061 has not changed its morphology. Similarly the interface zone
between 7075 & 6061is shown for the specimen 4, in this, the 7075 undergone fragmentation and dynamic recrystallization, 6061 has not changed its morphology. By this it is understood no proper intermixing of alloys has
taken place which will not give high joint strength. The photographic image of Microstructure of the specimens 3
and 4 are shown in Figure 6.
Figure 5. Good Welds
Figure 6. Microstructure of the Good quality welds
C. Tensile StrengthThe ultimate tensile strength of the two specimens 3 and 4 are evaluated by preparing the tensile specimens as per
ASTM E8M-04 standard. The prepared samples were tested on universal testing machine with a capacity of 50kN,
make from Associate Scientific Engineering Works, New Delhi with gear rotation speed for gradual loading of 1.25,
1.5 and 2.5 mm/min. The prepared tensile specimen are shown in Figure 7. The specimen which is joined using
hexagonal profile at 1000 rpm and 100 mm/min produced 35.46MPa and the specimen which is joined using square
tool pin profile at 1250 rpm and 110 mm/min produced 125.41MPa. The stress-strain graphs of the specimen are
shown in Figure 8.
Figure 7. Tensile Specimens
Figure 8. Stress – Strain Graph of Specimen 3 and 4
Effect Of Tool Pin Profile On Dissimilar Friction Stir Welding Of Aluminum Alloy Aa 7075
T651 And Aa 6061 T6
The experimental investigation to find out the effect of tool pin profile on the on dissimilar friction stir welding on
Aluminum alloys AA 7075 T651 and AA 6061 T6 which are used extensively in the aeronautical applications is
successfully conducted using different process parameters like tool rotational speed, welding speed and tool pin
profile. The following conclusions are drawn from the experimentation.
The tool pin profile has greater impact on the tensile strength of the friction stir welded component.
The good quality welds are possible with the application of sufficient clamping force on the work piece,
proper design of tool geometrical dimensions with required tool hardness to avoid wreckage of tool, as in this case
triangular tool profile has damaged. It is also seen that effect of tool pin profile augmented with tool rotational
speed and welding speed on the tensile strength and micro structure of the material.
The square tool pin profile and hexagonal tool pin profile at the tool rotation speed of 1250 rpm and the
welding speed of 110 mm/min respectively produced good quality welds with tensile strength of 35kN and 125kN
respectively in contrast to other tool pin profiles.
The proper selection of tool pin profile, rotational speed, feed and other necessary parameters will give the
better results.
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Welding of dissimilar
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