Post on 03-Feb-2022
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