Recent developments in fusion processing of

aluminium alloys

Professor Stewart Williams

Director Welding Engineering and Laser

Processing Centre

Presentation overview

Weld metal engineering for 2024 alloy

• Requirement for crack free welding

• Microstructural modelling of optimal compositions

• Production of crack free welds in 2024 alloy

Joining of aluminium to steel – seam welding

Additive manufacture of aluminium materials

• What is additive manufacture

• Additive manufacture of aluminium

• Latest developments in additive manufacture

New state of the art Al- alloys have substantially higher static

properties than standard armour alloys (30 - 150% greater)

Compositions and tempers designed to combat stress corrosion

0

100

200

300

400

500

600

700

0 20 40 60 80

Fracture Toughness (LT) MPa m

Yie

ld S

tre

ss

(L

) M

Pa

7055 T7751

Standard

Armour Alloys

1st gen.

3rd gen.

2nd gen.

5083H131

7020T651

2099 T8E67

Aluminium armour: new materials?

All V50

450

500

550

600

650

700

750

50 75 100 125 150 175 200

VHN (5kg)

V50 (

ms-1

)

FFV

Frag

Compromise position for

optimum FRAG performance

2024-T351

2124-T851

2624 –T851

7010-HAZ200

7010-T7+

7010-W51

7017-T6

No stress corrosion

cracking!

Ballistic testing – FFV and Frag summary.

FFV round – Bullet.. Frag. - 20mm diameter steel plug.

But it needs to be

fusion weldable

Problems in fusion welding 2024

2024 is highly crack sensitive and is considered unweldable

Filler wire issues

Available filler wires typically binary – base materials are ternary

No commercial aluminium filler wires have been developed and

marketed since 1960’s

Only filler for 2XXX series is binary 2319 (6%Cu) originally

developed for binary 2219 (6%Cu) base material.

Cost of development is prohibitive and one off prototype filler

wires have variable quality

Elemental recipe is highly subjective

A large range of fillers must be developed for the range of alloys

Solution – Combine modern developments in materials

modelling with technological welding advances to provide

a quick and cost effective method of defining near

optimum weld compositions

0

20

40

60

80

100

0 1 2 3Wt% Mg content for fixed 4.3 Wt% Cu

So

lid

ific

ati

on

Tem

p. R

an

ge (

oC

)

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

Vo

lum

e F

racti

on

Eu

tecti

c L

iqu

id

Approx’ target

composition

Avoidance of Cracking - Microstructural

Modelling

6% Cu

Filler

5% Mg

Filler

Large freezing range or small fraction of Eutectic

liquid leads to the likelihood of cracking

1 2 3 4 5 6

1

2

3

4

5

6

Alwt.% Mg

wt.% Cu

Target Compositions

Ideal 2024

composition

Binary 5% Mg wire

Highly crack susceptible

Binary 6%Cu wire

Crack susceptible

2024 mid range composition - 4.3% Cu, 1.5% MG

Summary compositions of Al/Cu/Mg

alloy System (2xxx series)

Weld metal engineering using a tandem torch with

different wire compositions, sizes and feed rates

C

Binary 6% Cu wire – cracks in sequence Binary 6% Cu wire – cracks in weld 2 & 3

Binary 5% Mg wire – severe cracking Mixed wire – no cracking in sequence

Fusion Welding – Avoidance of Cracking –

Multiple Wires

0

1

2

3

4

5

6

7

parent 2 4 6 8 10 12 14

Measured Distance Across Weld (mm)

% E

lem

en

tal

Co

mp

osit

ion

Binary Cu

Ternary Cu

Binary Mg

Ternary Mg

Maintenance of weld metal composition

throughout a multipass weld

Black – Binary wire – rapidly becomes Cu rich and Mg depleted – result is cracking

Red – Ternary mix – stable composition throughout weld – result is no cracking

Three wire configuration

6% Cu

Wire

5% Mg

WireCuSi3Wire

2319 Wire

0

20

40

60

80

100

120

140

160

-10 -8 -6 -4 -2 0 2 4 6 8 10

Fusion Welding – Improving Weld Metal Properties –

Three Wires

Standard single

wire weld

Position in weld (mm)

Hv

Al-8Cu-2.2Mg 1 m min spd

0

20

40

60

80

100

120

140

160

-8 -6 -4 -2 0 2 4 6 8

Three wire

weld 8% Cu

Position in weld (mm)

Hv

Al-7Cu-2Mg 1/2m min spd

0

20

40

60

80

100

120

140

160

-10 -8 -6 -4 -2 0 2 4 6 8 10

Three wire

weld 7% Cu

Position in weld (mm)

Hv

2024 Mix

0

20

40

60

80

100

120

140

160

-10 -8 -6 -4 -2 0 2 4 6 8 10

Optimised two

wire weld

Position in weld (mm)

Hv

Summary of fusion welding of high

strength aluminium

Microstructural modelling can be used to determine optimum

weld metal compositions – in this case to avoid cracking

Tandem welding methods can be used to explore different weld

metal chemistries

By using an optimum composition with 2024 alloy crack free

welds are obtained

By adding a 3rd wire an even wider range of compositions is

possible

From this welding wire compositions can be specified for either

welding or additive manufacture applications

Joining of aluminium to steel – seam

welding

Objective is to use the laser in conduction mode

A correlation is sought between the intermetallic layer thickness

and the fundamental laser interaction parameters

• Power density - power/area

• Interaction time – beam diameter/travel speed

• Specific process energy – Power Density X interaction time X area

Correlate the intermetallic layer thickness with joint strength

Aluminium 5083

6mm thick

Steel XF350

2mm thick

•Plate dimensions

138 x 150 mm

Experimental setup

8kW Fibre

Laser

After

Shielding gas

20 l/min pure Argon

Clamping system

Toggle clamps & bars

Surface conditionSurface finishing, ground

& not prepared

Cu bar Samples clamped always with the same load

Results

• Samples were cut in two different positions to check if

penetration and IML thickness were constant along the

weld seam.

Aluminium

Steel

Sample

BSample

A

Results

Sample

B

Sample

A

No difference

observed between

the ends

Results – Intermetallic compounds

Sample U11 B

Welding parameters:

Power = 4.0 kW; Interaction time = 3.9 s; Travel speed = 20 cm/min;

Spot size = 13 mm

Fe2Al5

FeAl3

20 µm

Intermetallic

layer

St

Al

Microhardness test(Load = 200g, time = 10s)

Distance [mm]

0 1 2 3 4 5 6 7

Mic

roh

ard

ne

ss [

HV

]

0

100

200

300

400

500

600

Sample U11-B

Base material - Steel

Base material - Aluminium

Results – Vickers microhardness test

St

Al

1.6 mm

St

Al

Intermatallic layer thicknes vs Specific point energy (point A)

Specific point energy [kJ]

9 10 11 12 13 14

Inte

rme

talli

c layer

thic

kne

ss [

µm

]

0

5

10

15

20

25

Manually ground

Surface ground

Results: Intermetallic layer thickness

evolution

Intermatallic layer thicknes vs Specific point energy(point A, manually ground)

Specific point energy [kJ]

9 10 11 12 13 14 15 16

Inte

rme

talli

c la

ye

r th

ickn

ess [

µm

]

0

5

10

15

20

25

Power density = 0.0030 [MW/cm2]

Power density = 0.0038 [MW/cm2]

Results: Intermetallic layer thickness

evolution

Summary aluminium to steel joining

By using the laser fundamental interaction parameters a good

understanding and control of the intermetallic layer can be

obtained

Continuous seam welds can be produce without porosity or

defects

Properties are yet to be determined

What is Metal Additive Manufacture - Basic

Process

Slice an object into layers

Programme a robot or

machine tool to trace out

the layers

Using a

deposition

tool to build

up your part

What is a (metal) deposition tool Also known as

• Additive (Layer) Manufacture (A(L)M)

• (Laser) Cladding

• Buttering

• Digital manufacture

• Direct Light Fabrication

• Direct Metal Casting (DMC)

• Direct Metal (Laser) Deposition (DM(L)D)

• Laser Direct Casting or Deposition

• Laser casting

• Laser clad casting

• Laser consolidation

• Laser cusing

• Laser Engineered Net Shaping (LENS)

• Lasform

• (Metal) Rapid Prototyping

• Net shape manufacture

• Net shape engineering

• Shaped deposition manufacturing

• Shaped melting

• Selective Laser Sintering (SLS)

• Selective Laser Melting (SLM)

• Shaped Metal Deposition (SMD)

• Shape Melting Technology (SMT)

• Shape welding

• Solid freeform fabrication (SFF)

• Weld build up

• + several more since I put this list together a couple of year ago

Very Simply

And we have ours

Wire + Arc Additive Manufacture

WAAM

Metal Additive Layer Manufacture - History

1926 Baker – patented “The use

of an electric arc as a heat

source to generate 3D objects

depositing molten metal in

superimposed layers”

1971Ujiie (Mitsubishi) Pressure vessel fabrication using SAW,

electroslag and TIG, also

multiwire with different wires to

give functionally graded walls

1983 Kussmaul used Shape

Welding to manufacture high

quality large nuclear structural steel (20MnMoNi5 5) parts –

deposition rate 80kg/hr – total

weight 79 tonnes

This has been around awhile!

1994-99 Cranfield University develop Shaped Metal Deposition (SMD) for

Rolls Royce for engine casings, various processes and materials were

assessed

Metal Additive Layer Manufacture - History

High deposition rates (several kg/h)

High material efficiency (90%)

No defects

Low part cost

x Medium to low level of complexity

Powder based Wire based

X Low deposition rates (0.1-0.2 kg/h)

X Low material efficiency (10-60%)

X Quality and flaw issues

X Very high part cost

High level of complexity

Weld based Additive Layer Manufacturing - METALS

MALM – Process Options

Primary Objective:

large scale structural

components

WAAM

machine

RUAMRob 2.0

Slicing and path generation

(within a couple of minutes)

WAAM

workpiece

CAD STL

WAAM Process

Example application - Ti Stiffened panel

Initial weight (kg) Final weight (kg) Buy to fly ratio

Machining 27.5 5.6 4.9

WAALM + Finishing 5 + 1.2 (wire) = 6.2 5.6 1.1

Development of aluminum CMT

process algorithms

Example aluminum application –

satellite launch vehicle component

Building cylinder on a 5 Axis

system

800mm

Variable wall thickness 6-8mm

WAAM - Large parts Variable wall thickness

cylinder – example satellite launch vehicle part

As deposited – 6 hours

After machining

WAAM - Large parts Intersecting Stiffened Panels

Aluminium

Design Handbook - Horizontal Unsupported

walls -aluminium

Enclosed structure (steel)

WAAM – Latest results – mixed material

systems Steel/bronze (CuSi3%) parts

100

105

110

115

120

125

130

135

140

145

150

-3000 -2000 -1000 0 1000 2000 3000

Vic

kers

Hard

ness

Distance in µ

Vertical hardness - Cu to Steel

Yield 140 MPa, UTS 300 MPa,

elongation 12%, failure in bronze

WAAM – latest results – rolling* - setup

SUBSTRATE

GTAW

TORCH

ROLLER

*Patent applied for

WAAM – latest results – rolling - effect on

distortion and bead geometry

0

1

2

3

4

5

6

7

8

Control 50 kN 75 kN

Dis

tort

ion

[m

m]

• Plates are 450 mm long

75 kN50 kN

CONTROL

Average

L.H.

[mm]

Std. Dev. Average

reduction

after

rolling

[mm]

Control 1.13 0.19 -

50 kN 1.04 0.12 0.25

75 kN 0.93 0.09 0.37

Effect on

Geometry

Rolling improves process repeatability

WAALM – latest results – rolling - effect on

microstructure

Rolling introduces deformation, nucleation

sites and stored energy into the large beta

grains, thus inducing recrystallisation when

layers are reheated during the subsequent

deposition

Reduction in grain size

Control 50 kN 75 kN

Grain size Control 50 kn 75 kN

Primary grains 3 x 30 mm 240 μm 83 μm

Alpha Lathes length 21.1 15.5 7.7

Alpha Lathes Width 1.2 1.0 0.7

40

• HiVE Technology

demonstrator system

implemented for large

scale WAAM

incorporating milling,

and rolling (to be

completed)

Installation of large scale ALM facility now

complete – HiVE (old Airbus FSW machine)

Welding

power

source

Welding

torch

Milling

cutter

Large scale WAAM – 1st part

3m long aluminium stiffener, deposited and

machined on the HiVE system

Summary additive manufacture

Wire + arc based additive manufacture is suitable for producing

large structural metal parts in a very cost effective manner

It can used for a wide variety of materials including aluminium

titanium and tool steel

New developments such as rolling, mixed materials and

integrated machining are rapidly evolving

This will be a very important technology for high value

manufacturing

Thanks you for your attention

Professor Stewart Williams

s.williams@cranfield.ac.uk

+44 (0)1234 754693