Dissimilar Metal Welding

M.Ekaditya Albar 1106154305

Rangga Agung 1106108942

Rhidiyan Waroko 0806331935

Rudiyansah 0806331973

Master Degree Program

Metallurgy and Material Engineering Department

Universitas Indonesia

7-Jan-13 1

Outline

Dissimilar Metal Welding

Journal Review

Enhanced mechanical properties of friction stir welded dissimilar Al–Cu

joint by intermetallic compounds

Dissimilar friction welding of induction surface-hardened steels and

thermochemically treated steels

Dissimilar friction stir welding between 5052 aluminum alloy and AZ31

magnesium alloy

Weldability and mechanical properties of dissimilar aluminum–copper lap

joints made by friction stir welding

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Dissimilar Metal Welding

The joining of dissimilar materials is becoming increasingly

important in industrial applications due to their numerous

advantages. These include not only technical advantages, such as

desired product properties, but also benefits in terms of production

economics.

Dissimilar metals are difficult to join with conventional fusion

welding due to their different chemical and physical

characteristics, thus solid state joining methods have received

much attention.

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Journal 1: Enhanced mechanical properties of friction stir welded dissimilar Al–Cu

joint by intermetallic compounds (May 2010)

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Introduction:

FSW has been shown to be an effective way of joining materials with poor fusion weldability, such as

high-strength aluminum alloys and magnesium alloys.

In Al-Cu joints, an intermetallic compound (IMC) layer usually formed on the Al–Cu interface.

IMCs were easily formed in the nugget zone due to severe plastic deformation and thermal exposure.

IMCs have been used as reinforcing particles in metal matrix composites (MMCs).

Control of the IMC layer between dissimilar metals and the size and distribution of the IMC particles in the

nugget zone becomes a key factor for FSW of dissimilar metals.

Experiment:

1060 Aluminum + Pure Copper (99.9%) Plate (p x l x t : 300 x 70 x 5 mm)

FSW machine (China FSW Center)

Tool traverse speed : 100 mm min−1 ; Rotation rate : 600 rpm

Microstructural Analysis : EPMA, XRD, SEM, TEM, EDS

Mechanical Testing : Tensile Test, Vickers Microhardness, Three-point Bending Test

Results and Discussions:

The nugget zone consists of a mixture of the aluminum matrix and Cu particles.

A continuous and uniform interface layer is formed with a thickness of ∼1 μm.

Reinforcing particles were mainly composed of Al2Cu, Al4Cu9, and few AlCu particles.

UTS of the composite structure was as high as 210 MPa.

The hardness increased substantially due to the strengthening effect of the Al–Cu IMC particles.

SEM

Re

sult

PRZ



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XR

D R

esu

lt

EPMA Result



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Hardness Vickers Te

nsi

le T

est

TEM Result



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Bending Test

Conclusions:

1060 aluminum alloy and commercial pure copper were successfully friction stir welded.

Reinforcing particles were mainly composed of Al2Cu, Al4Cu9, and few AlCu particles.

UTS of the composite structure was as high as 210 MPa.

The hardness increased substantially due to the strengthening effect of the Al–Cu IMC particles.

Bending without fracture was generated at the Al–Cu interface.

Journal 2: Dissimilar friction welding of induction surface-hardened steels and

thermochemically treated steels (April 2012)

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Background:

Friction welding is a highly productive process that relies on the conversion of mechanical energy into

thermal energy.

For friction joining of surface hardened steels, the distribution of the thermal gradient on the surfaces in

contact during the process is affecting the hardness at the interface.

This work is focused on the particularities of the conventional friction welding process of dissimilar steels for

joints in which one component is induction-hardened, using high frequency currents, and the other one is

subject to another heat or thermochemical treatment, such as carburization or nitriding.

Experiment:

Hardness test (HVS – 10A1 hardness tester on longitudinal section, polished and nital-etch join)

Macroscopic (Olympus SZH-10 stereo microscope)

Microstructure (Olympus BH-2 metallographic microscope)

Bending test (Instron 250 kN universal testing machine)

Torsion test (Schenk-Trebel torsion testing machine 1600Nm)

Impact test (V-Notched, 300 J Charpy pendulum)



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Steel C Mn Si P S Cr Mo Ni

C45 0.48 0.63 0.25 0.029 0.028 - - -

C55 0.56 0.61 0.27 0.028 0.024 - - -

16MnCr5 0.17 1.14 0.31 0.025 0.026 1.07 - -

34CrNiMo6 0.36 0.61 0.28 0.027 0.027 1.52 0.24 1.54

Materials



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Treatments

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Fig. 1. Hardness gradient

of the C55 steel after high

frequency induction-

hardening Fig. 2. Macro and micrographic images of the dissimilar C55 induction-

hardened with a C45 quench-hardened steel friction welded joint

Fig. 3. Hardness gradients for two values of the friction/upsetting pressure across the joining plane for the

dissimilar C45 quench-hardened-C55 induction-hardened friction welded joint, measured in the marginal and

central areas, respectively

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Fig. 6. Hardness gradients in axial direction

across the joint plane for the induction-hardened

34CrNiMo6 steel with a 16MnCr5 carburized-

quenched-tempered steel joint for two values of

the friction/forging pressure.

Fig. 5. Macro and microscopic images of the friction

welded joints of induction-hardened 34CrNiMo6 and

16MnCr5 carburized-quenched-tempered steels.

Fig. 4. Details about the microstructure and hardness gradients

in pre-welding state for the 16MnCr5 (carburized) and

34CrNiMo6 (induction-hardened) steels used in the experiments.

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Fig. 7. Typical microstructure and hardness gradient

observed for the C45 after the nitriding operation and

the macroscopic image of the C55 induction-

hardened and C45 nitrided steel joint.


A biconcave HAZ forms for high

friction/forging pressures

(300/400 N/mm2), if one of the

components is thermomechanically

treated.

The decrease of the pressure did not

affect the process, neither the extent of

the softening area.

The nitride layer contributes to the

reduction of the relative friction

between the components in the vicinity of

the rotational axis.

The experimental results show that a

high quality joint can only be obtained if

the nitride layer is fully expunged from

the joint plane.

If such nitride debris are still present, a

quasi-cleavage fracture occurs due to

the high cooling rate during the

friction welding process, as also

observed for other combinations with

nitrided steels.



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Conclusions:

The friction pressure is limited to about 200 N/mm2, since higher values were

observed to lead only to minor reduction of the hardness on the induction-

hardened surface and can favor the presence of discontinuities in the center of the

joint plane.

Influenced by the presence hard layers in the join plane.

By increasing the axial pressure, the thermochemically hardened layer can be

expunged in the burr.

The presence of the nitride layer contributes to the reduction of the friction in

the vicinity of the rotational axis.

Regardless of the friction/forging pressures used (200/300 or 300/400 N/mm2) the

joints showed good mechanical properties, but the complete expulsion of the

nitride layer was observed only for 6 mm upset length.

Journal 3: Dissimilar friction stir welding between 5052 aluminum alloy and AZ31

magnesium alloy (January 2010)

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Background:

Al alloy (combination between mass reduction and high strength); Mg alloy (low density and high specific

strength).

Joining Al alloy and Mg alloy will be difficult if we use conventional fusion welding because of large

intermetallic compounds.

FSW is a potential candidate for dissimilar welding because of lower processing temperature and can

produced defect-free weld, i.e. joining Al 2024/Al 7075, Al/steel, Al/Cu, dan Al/Mg

Experiment:

5052 Al alloy + AZ31 Mg alloy, plate thickness 6 mm.

Surface of plate was grounded using grit paper to remove oxide layer then cleaned by ethanol.

5052 Al alloy (advancing side) and AZ31 Mg alloy (retreating side) from tool pin in FSW process.

FSW machine using FSW-3LM-003, vrot = 600 r/min and vwelding = 40 mm/min.

Butt join was resulted parallel to rolling path direction.

Microstructure analysis at cross section of weld direction by OM (KEYENCE VHX-600) and SEM (Quata200)

Etch solution: picric acid (4,2 g), acetic acid (8 ml), distilled water (10 ml), ethanol (70 ml).

Hardness measurement by HVS-100 digit hardness tester, load ! N, dwell time 20 sec.

Materials



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Defect-free using FSW (vrot = 600 r/min, vwelding = 40 mm/min).

Interface Mg alloy + Al alloy

Fig. 1. Surface appearance of dissimilar weld prepared by

FSW

Fig. 2. Optical approach of cross-section of dissimilar weld

Defect-free



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In Fig. 2 we can see typical microstructural zone, like Base Material (BM),

Heat-Affected Zone (HAZ), Thermomechanical Affected Zone (TMAZ), and

Stir-Zone (SZ).

Fig. 2. Optical approach of cross-section of dissimilar

weld

Simple bond interface

Intermixed structure



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Fig. 3. SEM images of AZ31 in different

regions, marked with letters in Fig.2:

(a) BM; (b) HAZ;

(c) Interface of TMAZ/SZ;

(d) SZ in Mg side;

(e) SZ in Al side;

(f) Intercalated microstructure.

Fig. 2. Optical approach of cross-

section of dissimilar weld

BM terdiri dari large equiaxed grains

(50 μm) dan fine grains (10 μm).



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(a) BM;

(b) HAZ; (c) Interface of TMAZ/SZ;

(d) SZ in Mg side;

(e) SZ in Al side;


Fig. 2. Optical approach of cross-section

of dissimilar weld



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(a) BM; (b) HAZ;

(c) Interface of TMAZ/SZ; (d) SZ in Mg side;

(e) SZ in Al side;



of dissimilar weld

Dynamic rekristalisasi terjadi di SZ

dikarenakan deformasi plastis dan efek

termal siklik yang disebabkan rotational

tool.



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(a) BM; (b) HAZ;


(d) SZ in Mg side; (e) SZ in Al side;



of dissimilar weld

Grain dengan ukuran rata-rata 5,4 μm

(daerah d / sisi Mg) dimana lebih kecil

dibandingkan BM.

Fine equiaxed rekristalisasi grains

menghasilkan struktur yang berbeda pada

lokasi yang berbeda dari SZ, seperti pada

daerah d, e, f. (Fig. 2)



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(a) BM; (b) HAZ;


(d) SZ in Mg side;

(e) SZ in Al side; (f) Intercalated microstructure.


of dissimilar weld

Grain dengan ukuran rata-rata 6,9 μm

(daerah d / sisi Al) dimana lebih kecil

dibandingkan BM.







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(a) BM; (b) HAZ;


(d) SZ in Mg side;

(e) SZ in Al side;



of dissimilar weld

Struktur interkalasi terbentuk dan

ukuran grains rata-rata dari AZ31

Mg alloy (2,8 μm)







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Fig. 2. Optical approach of cross-section of dissimilar weld

Fig. 4. Microstructures of onion ring in dissimilar weld:

(a) Optical microstructure; (b) EDS maps of Mg;

(c) EDS maps of Al;

(d) Distribution in onion ring.

Fig. 4 (a) menunjukkan mikrostruktur terdiri dari

dua pita dengan beda kontras.

Menurut hasil analisis EDX, pita gelap (Mg) dan pita putih (Al), dimana mirip onion ring,

namun bentuknya berbeda dari monolitik FSW.

Hal menarik dapat diamati

pada daerah g (Fig. 2)

dimana berlokasi di SZ

dekat sisi 5052 Al alloy dan

dikelilingi oleh Mg alloy.



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Fig. 2. Optical approach of cross-section of

dissimilar weld


(a) Optical microstructure;

(b) EDS maps of Mg; (c) EDS maps of Al;


Fig. 4 (b) menunjukkan peta EDX dari distribusi Mg pada daerah g.








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dissimilar weld



(c) EDS maps of Al; (d) Distribution in onion ring.

Fig. 4 (c) menunjukkan peta EDX dari distribusi Al pada daerah g.








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dissimilar weld








(c) EDS maps of Al;


Komposisi kimia : 83% Al + 17 % Mg (mass

fraction), dimana struktur lamella merupakan

komposisi dari pita Al + Mg.



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Distribution of Microstructure

Fig. 2 .Optical approach of cross-section of dissimilar weld

o Nilai Vickers microhardness

dari dissimilar weld diukur

sepanjang garis yang ditandai

pada Fig. 2 dimana posisinya

1,5 mm (atas), 3 mm

(tengah), 4,5 mm (bawah)

dari permukaan atas.

o Hasilnya → Fig. 5

Fig. 5. Microhardness profiles of microstructure

from Mg to Al with different locations

Microhardness menunjukkan distribusi tidak seragam.

Hardness SZ > BM.

Nilai maksimum hardness: posisi tengah SZ dimana 2x

lebih besar dari BM.

Struktur onion-ring dan mikrostruktur interkalasi

penyebab variasi tajam hardness di weld zone.



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Fig. 6 menunjukkan lokasi patah tarik dan morfologi patahan dari dissimilar weld yang

diuji tegak lurus dari arah welding.

Spesimen uji tarik gagal pada lokasi 2,5 mm dari pusat sambungan pada sisi

advancing. Fig. 6 (a)

Pada lokasi ini, gradien hardness merupakan yang paling tajam, menurut Fig. 5.

Fig. 6 (b) menunjukkan morfologi patahan SEM yang diamati dari arah normal

terhadap permukaan patahan.

Bentuk cleavage-like dapat ditemukan pada permukaan patahan (patah brittle).

Fig. 6. Fracture section of AZ31/5052 dissimilar friction stir weld: (a) Tensile

fracture location; (b) SEM image of fracture surface

Ten

sil

e T

esti

ng



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Conclusions:

Sound weld 5052 Al alloy + AZ31 Mg alloy dapat dihasilkan melalui FSW

dengan vrot = 600 r/min dan vwelding = 40 mm/min.

Mikrostruktur BM menjadi bentuk equiaxed dan fine grains pada SZ.

Dimana pada bagian atas SZ, 5052 + AZ31 alloy simply bonded,

sedangkan struktur onion-ring (komposisi pita Al + Mg) terbentuk di

bagian bawah SZ.

Profil microhardness menunjukkan distribusi tidak seragam, dengan nilai

maksimum microhardness SZ dua kali lebih besar dibandingkan BM.

Posisi patahan berada pada jarak 2,5 mm dari pusat sambungan (pada

sisi Al), dimana gradien hardness merupakan yang paling tajam.

Journal 4: Weldability and mechanical properties of dissimilar aluminum–copper

lap joints made by friction stir welding (October 2009)

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Background:

Lap joints of 1060 aluminum alloy and commercially pure copper by FSW

Usually a large void formation, cracks and other distinct defects throughout the weld

Mechanically mixed region in weld nugget consisting Mainly CuAl2, CuAl, and Cu9Al4, brittle nature of the

Inter Metallic Compound (IMC)

The effect of welding speed on interface morphology (lap joint configuration), microstructure, and joint

strength

Lowering the amount of heat in interface may result in limited formation of IMC

Experiment:

Rolled plates of 1060 aluminum alloy (top) and commercially pure copper (bottom) in lap joint

Dimension of sample 20 mm length and 10 mm width and before welding, the samples were degreased using

acetone

Make lap joints, a FSW adapted milling machine was used

The couple samples were friction stir welded with the pin rotating clockwise at speed of 1180 rpm and

welding speeds of 30, 60, 95, 118, 190, 300, and 375 mm/min

Microstructural analysis : Metallographic analysis (OM + SEM + EDS)

Mechanical testing : Tensile Shear Test



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Extremely high welding speeds in the present work (300 and 375 mm/min), produced very poor metallic

bonding (higher welding speed caused less vertical transport of interface).

The interface in the central region has moved considerably into the bottom plate. This vertical transport of

interface is attributed to the ring-vortex flow of materials created by pin threads.

In the aluminum close to the Al/Cu interface, a dark area was observed (higher welding speeds, this are a was

limited to a narrower region and extended toward the advancing side of the joints).

Cavity defects which are formed outside the optimum FSW conditions, caused by an insufficient heat input

(with increasing the welding speed, this type of defect is more likely to occur). As a matter of fact, decreasing

the welding speed gives effective influence on the plastic flow and consequently increasing the heat input).

Lowering the amount of heat in interface may result in limited formation of IMC.

Macroscopic overviews of the FSW joint

cross sections at constant tool

rotational speed of 1180 rpm and

welding speeds of (a)30, (b)60, (c)95,

(d)118, and (e)190mm/min



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The microstructure of the aluminum stir zone was characterized by the equiaxed fine grains (that the equiaxed

fine grains were formed through the dynamic recrystallization during FSW)

The TMAZ area characterized by elongated grains and layers which is between stir zone and the HAZ areas

Copper particles with irregular shape and inhomogeneous distribution were observed in the aluminum dark

area (copper plate near interface was unable to sustain very large vertical elongation and tore apart into the

small-elongated particles that were found in various places in the dark area)

Microstructures showing different regions of (a) fine equiaxed grains in stir zone of aluminum near Al/Cu

interface,(b) elongated aluminum grains in the TMAZ of advancing side



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SEM image of copper particle surrounded by equiaxed

grains of Al 1060 Alloy in the weld nugget for the joint

produced by rotational speed of 1180 rpm and welding speed

of 90 mm/min

The back scattered electron (BSE) image of a coarse particle

existing in the nugget shows as tacked layer structure inside;

the EDS spectra for positions A (light gray layers), B (dark

gray layers), C (white layers) shows possible existence of

Al4Cu9, Al2Cu, and base copper, respectively (welding

condition: 95mm/min, 1180rpm)



7-Jan-13 35

The failure loads ranged from 1902 to 2642 N.

One can find that with increasing the welding

speed, failure load increases up to a maximum

value and then decreasing behavior is

appeared. The shear load of the joint is probably

affected by two factors: the amount of

microcracks, and cavity formation.

General tensile fracture surface of a

specimen friction stir welded at

rotational and welding speed of 1180

rpm and 95 mm/min, respectively.

The fracture occurred at the

advancing side of aluminum plate

containing copper fragments (white

colored particles)



7-Jan-13 36

Conclusions:

The maximum tensile shear strength has been achieved at welding speed

of 95 mm/min

Due to formation of high amount of micro cracks in the dark area at

welding speeds of 30 and 60 mm/min, the tolerable tensile shear was

lower than that of 95 mm/min

Higher welding speeds of 118 and 190 mm/min, the cavity defects are

produced and again tensile shear strength is decreased in compare with

95 mm/min

Lower welding speed caused more vertical transport, while a higher

welding speed caused less vertical transport on the retreating side

References Ion Mitelea, Victor Budau, Corneliu Craciunescu. Dissimilar friction welding of induction

surface-hardened steels and thermochemically treated steels. Journal of Materials

Processing Technology 212 (2012) 1892–1899.

P. Xue, B.L. Xiao, D.R. Ni, Z.Y. Ma. Enhanced mechanical properties of friction stir

welded dissimilar Al–Cu joint by intermetallic compounds. Materials Science and

Engineering A 527 (2010) 5723–5727.

T. Saeid, A. Abdollah-zadeh, B.Sazgari. Weldability and mechanical properties of

dissimilar aluminum–copper lap joints made by friction stir welding. Journal of Alloys

and Compounds 490 (2010) 652–655.

Yan Yong, Zhang Da-tong, Qiu Cheng, Zhang Wen. Dissimilar friction stir welding

between 5052 aluminum alloy and AZ31 magnesium alloy. Trans. Nonferrous Met. Soc.

China 20 (2010) s619-s623.

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Dissimilar Metal Welding

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