Magnesium Die Casting
International Summer School on High-Integrity Die Castings
28 Jul.-1 Aug., 2008, WPI, Worcester, USA
K. U. Kainer, Z. Zhen, Y. Huang, N. Hort
Magnesium Innovation Centre MagIC, GKSS Forschungszentrum
Geesthacht GmbH
PAGE 1
Challenges for Magnesium R&D
Sheets, outside
Magnesium for consumer products
Early application in 1940’s and 1960’s Sheets, inside
(VW Beetle)
Revival since 1990’s; main application
Challenge
Extrusions
areas:
– Automotive (see figure) Thixo-/ foring parts
for chassis
– 3C industries
computer, Complex thin-walled
communication, casting parts for body
consumer electronics Casting for high
thermal and
mechanical load
Casting
Time
Friedrich H., Schumann S., Proc. of the Second Israeli International Conference (2000): 9–18.
PAGE 2
Magnesium in Automotive Today
Global emissions standards are getting more stringent
Reduced emissions ~ Cleaner Air
Chart courtesy of CSM Worldwide
PAGE 3
Weight Savings: Materials
Steering Column
Support
Engine V-4 Mg: 1,4 kg Tailgate
Mg: 16 kg Steel: 2,3 kg Mg: 3,2 kg
Al: 22 kg 40 % Al: 5,5 kg
Fe/Steel: 60 kg 42 %
22 - 73 %
Seat frame
Mg: 1,8 kg
Steel: 5 kg
64 %
Wheel case
Mg: 11,4 kg Inner Door
Steel: 15,6 kg Steering Column Mg: 5,4 kg
28 % Mg: 0,9 kg Al: 8,2 kg
Steel: 1,4 kg 33 %
33 %
Quelle: www.magnesium.com
PAGE 4
Potential Weight Savings
Component
Currently used Additional Potential Use of Mg
on e.g. VW / short term medium term long term
Audi vehicles < 5 years > 5 years > 10 years
Power Train 18 kg 24-29 kg 38-49 kg
4 kg 12-16 kg 14-20 kg
3 kg 23-37 kg 31-49 kg 46-69 kg
4-6 kg 34-40 kg
59-82 kg 87-130 kg 132-184 kg
Grand Total 25 kg
After Volkswagen AG, K-EFWM/Dr. Schumann/Sinomag11.2002
PAGE 5
Use of Magnesium in the Past
1939 Before WW II
1924
1941
1939
After WW II
1952
1995 1946-1978
PAGE 6
Magnesium Applications Today
Interior Parts Interior Parts
Seat Components Sunroof Components
Instrument Panels Mirror Frames
Knee Bolsters Headlight Retainers
Inner Door Frames
Steering Column Comp.
Steering Wheels Drive train Parts
Brake & Clutch Pedal Manual Transmission Housings
Brackets 4 WD Transfer Case
Airbag Retainers
Brackets
Radio Frames
Radio and HVAC Covers
Engine Parts
Crankcase
Cylinder head Covers
Intake Manifolds
Drive Brackets
Electrical Connectors
Engine Cradle
Oil pans
PAGE 7
Magnesium Applications Today: High
Pressure Die Casting
PAGE 8
Temperatures for Power Train Use
suspension,
crank shaft engine block
T > 200 °C
piston
T > 250 °C
fan, gaskets
T < 100 °C
filter boxes
T = 150-200 °C
ignition plug, gear box housing
catalyst T < 175 °C
source: Volkswagen AG
PAGE 9
Applications in Power Train: High
Pressure Die Casting
PAGE 10
Forecast High Pressure Die Casting
Casting ,000 tons
Source: Hydro Magnesium intern: Probability Forecast
*) China domestic demand on die casting is included as of 2004
PAGE 11
Forecast: Applications HPDC-Parts
80
Powertrain
Structural Components
60
[m etric ktons]
40
20
0
2005 2006 2007 2008 2009 2010
Year
Source:D. Webb http//www.intlmag.org
PAGE 12
Use of Magnesium Alloys
• Casting
- Die casting (AZ, AS, AE, AM)
- Gravity casting (AZ, K, ZK, ZE, EZ, QE, WE)
- Squeeze casting (AZ, AS, AE, AM, K, ZK, ZE, EZ, QE)
- Semi-solid (AZ, AS, AE, AM)
• Extrusion (AZ31, AZ61, AZ80, WE54, WE43)
• Rolling (AZ31, HK31, HM21, ZK60)
• Forging (AZ31, AZ60, AZ80, ZK)
• Corrosion protection
• Welding
PAGE 13
Magnesium Alloy Systems
• AZ (Mg-Al-Zn) • AE (Mg-Al-SE)
• good room temperature • AJ (Mg-Al-Sr)
properties
• small properties at elevated • MRI (Mg-Al-Mn-Ca-RE)
temperatures • good properties at elevated
• low ductility temperatures
• good creep resistance
• AM (Mg-Al-Mn) • constricted castability
• better ductility
• moderate room temperature
properties
• constricted castability
• AS (Mg-Al-Si)
• better strength
• improved creep resistance
• constricted castability
PAGE 14
Magnesium Casting Alloys
• Die casting
- AZ, AS, AE, AM
• Gravity casting
- AZ, K, ZK, ZE, EZ, QE, WE
• Squeeze casting
- AZ, AS, AE, AM, K, ZK, ZE, EZ, QE
• Semi-solid
- AZ, AS, AE, AM
PAGE 15
Patents/Modifications for Pressure Die
Cast Magnesium Alloys
Chemical Composition
Year/
Originator Al Zn Mn SE Ca others
1994 Nissan/Ube 1.5-10 <2 0.25-5.5
1996 MEL < 0.1 0-0.4 0-0.5 0.05 0-1
1996 Hyundai 5.3-10 0.7-6.0 0.4-5 Si
1996 ITM Inc. 2-6 0.1-0.8
1996 Noranda 4.9 0.26-0.30 1.74-1.94 Sr
4.7-4.9 0.27-0.29 1.23-1.35 Sr
1997 Honda 4.5-10 4.5- 0.2-1 1-3 0.1-3
6 0.2-1 1-3 1.2-2.2
1997 Mazda 2-6 0.5-4
1997 IMRA America 2-9 6-1 0.2-0.5 0.1-2.0
1997 Hyundai 5.3-10 0.7-6.0 0.15-10 0.5-5 Si
1999 VW/DSM 6-9 0.7-0.9 0.18-0.37 0.15-0.92 0.45-1.1 0.03-0.11 Sr
2000 Norsk Hydro 1.9-2.5 0.25 0.05-0.15 0.06-0.25 0.7-1.2 Si
Source: Pekgüleryüz, 2000, King, 1998, Norsk Hydro, 2003
PAGE 16
VW Objectives For HPDC High
Temperature Magnesium Alloys
• Room temperature characteristics at least as good
as AZ91.
• Elevated strength better than AZ91 beyond 120ºC.
• Minimum creep rate better than AE42.
• Castability similar to AZ91.
• Corrosion resistance similar to HP AZ91.
• Cost ≤ 1.2 x AZ91
PAGE 17
Castability of Mg-Al-Zn Alloys
alloy-
groups
AZ-Base 1
AZ-Base 2
ZA-Base
castable
difficult
Zn-content (wt.-%)
Source: Foerster
PAGE 18
Castability and Creep Resistance
180 1: AZ91
°C
10 2: AS21X
8 9 3: MRI153M
7 4: AJ62X
6 5: AE42
Resistance
5 4 3 6: AJ52X
Creep
2 7: ACM522
8: AX52J
150 1 9: MRI230D
°C
10: AM-HP2
Castabilit
Source: Aghion et al., Dunlop et.
PAGE 19
y
Al.
Die Casting of Magnesium Alloys
• Filling time 30 % shorter compared to Al
• Life time of tools higher
• Ingate speed appr. 90-100m s-1
• Ingate thickness > 0.8 mm
• Temperature of the die: 220-240 ºC
• Die casting alloys
- Hot chamber: AZ, AM
- Cold chamber: AZ, AM, AE, AS
• Not all Mg-alloys can be used for die casting!!
PAGE 20
Illustration of die casting process
Source: www.ekkinc.com
PAGE 21
Cold Chamber Die Casting Process
moving platen
fixed platen moving die
part
ejector
ejector die
plunger
chamber
PAGE 22
Hot Chamber Die Casting Process
hydraulic closing die
die
piston
melt
chamber
PAGE 23
HPDC Unit
Source: www.rauch-ft.com
PAGE 24
HPDC and Vacuum HPDC
PAGE 25
Cover Gases
Unsolved status in the EU:
Fluor containing gases are likely to be abandonned.
Cover gas components:
SF6, SO2, R134a (HFC134a)
New protective gases:
Novec 612, Fluorokethone, Hydro-Fluorether
Global warming potential (GWP):
FK < HFC134a < SF6
0,05% 5% 100%
PAGE 26
Relationship Between Magnesium Die Casting
Defects And Processing Parameters
Metal Metal Die Gating Die vent Die lubricant Metal Ejection Casting rate
velocity Pressure Temperature system Temperature defect
Incomplete
filing
● ● ● ● ● ● ●
Cold shuts
● ●
Pores
● ● ● ●
Gas bubbles
Shrinks
● ●
Blisters
● ● ●
Flow marks
● ● ● ● ●
Surface
Swirls
● ●
Hot cracks
● ● ● ●
Cracks/fract
ures
● ● ●
Deformation
● ●
PAGE 27
Quality Control
Alleviation of pre-solidification in the shot
sleeve:
• Reduce the heat transfer from the melt to the sleeve wall
by insulating the inner sleeve wall.
• Reduce the heat conductivity in the sleeve wall.
• Reduce the heat transfer by maintaining a higher temperature
in the sleeve wall.
Source: Gjestland et al. Adv Eng Mater,
2007
PAGE 28
Microstructure
Secondary dendrite arm spacing and grain size as a function of
solidification rate in AZ91D
Source: Gjestland et al. Adv Eng Mater,
2007
PAGE 29
Creep Properties Of Mg-al-ca Alloy Produced
By Die Cast, Squeeze Cast And Gravity Cast
Die cast
Squeeze cast
Die cast
Source: Zhu et al, Mater.Sci.Eng.A,2008
PAGE 30
Numerical Simulation Methods
Finite Difference Method (FDM) and Finite Element Method (FEM)
FDM is easy on programming and gives result with reasonable accuracy, while FEM
shows advantages on simulating complex and thin-wall castings, due to its better
geometry replication.
FEM FDM
Thin-wall casting geometry modeled by using FEM and FDM methods
Source: Marty McLaughlin, www.ekkinc.com
PAGE 31
Mold Filling Simulation Of Hot-chamber
Diecast AM60B
Filling time:
11ms
Cast temp.:
650oC
Software:
self-developed
3D FDM
program
Mold filling simulation results of diecast AM60B alloy, showing that the melt enters a cylindrical bar
in the way of a jet and is “bounced” backward along the wall when striking the filled part
Source: Li and Zhou, Materials Technology, 2003
PAGE 32
A Mold Filling Simulation Case
Source: Song and Xu, North Hengli Sci. and Tech Co.
PAGE 33
Ltd.
Solidification Simulation Of HPDC
Magnesium Alloys
Source: Song and Xu, North Hengli Sci. and Tech Co.
Ltd.PAGE 34
Flow Simulation Within Shot Sleeve
Magnesium die casting part is usually very thin and the
heat capacity (combining the specific heat and latent
heat of fusion) of magnesium is small compared with that
of aluminum. Therefore, magnesium die castings solidify
during the die filling more remarkably than aluminium die
castings. It also indicates that the accuracy of mold filling
simulation for magnesium die castings is more significant
than that of aluminium alloys. To further improve the
accuracy of flow simulation, recently, melt motion within
shot sleeve had been integrated into the mold filling
simulation for magnesium alloys.
Source: www.ekkinc.com
PAGE 35
Solidification Simulation Of Low Pressure Die
Cast Magnesium Wheel
Source: NERC-LAF, Shanghai Jiaotong
Uni.PAGE 36
Solidification Simulation Of Low Pressure Die
Cast Wheel
Source: NERC-LAF, Shanghai Jiaotong
PAGE 37
Uni.
Solidification Simulation Of Low Pressure Die
Cast Engine Block
Source: NERC-LAF, Shanghai Jiaotong
PAGE 38
Uni.
Microstrutural Simulation Of Die Cast AM50
Microstructure of die cast AM50 simulated by using a 2D Cellular Automaton based
model coupling with macro heat transfer calculation
Source: Fu et al, Mater.Sci.Forum, 2008
PAGE 39
Magnesium Recycling
• Driving force is saving energy:
- 35 kWh/kg for prime-production
- 3 kWh/kg for remelting magnesium-scrap
• Prime scrap: casting alloys, crap of production
• Old scrap: alloys, partly polluted
• Alloy mix
- Definition of recycling alloys
- Base alloy system
- Influence of alloying elements, impurities on property
profile
PAGE 40
Recycling Alloys
PAGE 41
Quelle: IMA, MEL, Hydro Magnesium
2007
2006
2005
2004
2003
Secondary Magnesium
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
0
200
150
100
50
PAGE 42
New Secondary Alloy
Composition and microstructure of the new secondary alloy compared to AZ91D
Alloy Al Zn Mn Si Cu Fe Ni
AZ91D 8.75 0.67 0.2 0.054 0.008 0.0022 0.0006
AZC1231 11.7 3.04 0.48 0.39 0.47 0.0087 0.0032
AZ91D (600-800 µm) AZC1231 (~100 µm)
PAGE 43
Corrosion Properties
Corrosion properties of AZ91D and AZC1231 determined in various corrosion tests
(gravity die casting except * HPDC housing)
Corrosion test condition AZ91D AZC1231
Pot.dyn. polarisation 0.43 ± 0.04 1.81 ± 0.59
(after 1h in 5%NaCl, pH11) mm/year mm/year
Lin. polarisation resistance 247 cm2 80 cm2
(after 24h in 5%NaCl, pH11)
Impedance 263 cm2 149 cm2
(after 36h in 3.5%NaCl, pH7)
Saltspray 1.07 ± 0.23 0.99 ± 0.58
(after 48h in 5%NaCl, pH7) mm/year mm/year
Immersion* 1.49 1.42 ± 0.26
(average after 400 h in 3.5%NaCl, pH6) mm/year mm/year
PAGE 44
Mechanical Properties
Comparison of the mechanical properties of the new alloy AZC1231 and AZ91D
Property AZ91 AZC1231
Hardness (HV5)** 83,2 ± 3,3 104,9 ± 2,8
Friction coefficient** 0.27 0.23
Wear volume** (mm3/N/m) 11.5 * 10-4 6.7 * 10-4
Rm* (MPa) 263 ± 14 246 ± 17
Rp* (MPa) 198 ± 15 187 ± 27
A5* (%) 2.1 ± 0.5 0.7 ± 0.5
Creep rate ** (s-1) 4,38 * 10-8 1,74 * 10-8
SCC threshold stress*** (MPa) 90 130
* HPDC housing, ** HPDC test specimen, *** gravity die cast
PAGE 45
Casting Properties
Helix casting experiments* (700°C melt temperature, release agent Demotex S)
Giesserei 94, Nr. 11 (2007), S.20-33
* C. Scharf, P. Živanovic, A. Ditze, K. Horny, G. Franke, C. Blawert, K.U. Kainer, E. Morales,
Thelix angle filled length completely filled
[°C] [°] of the helix length of the helix
[cm] [cm]
AZ91D 159.0 256.8 48.6 23.0
± 5.7 ± 36.1 ± 7.4 ± 1.8
AZC1231 158.8 408.8 66.1 39.5
± 2.5 ± 28.4 ± 5.6 ± 6.0
Better casting properties compared to AZ91D,
thus no limitations in the possible casting processes
gravity die casting NRC HPDC
PAGE 46
Research into the Industrial Use
Gravity die casting ingot ingot housing housing
6 kg melt volume (Lab) (AZ91D) (AZC) (AZ91D) (AZC)
Rm (MPa) 198 189 258 250
Rp0,2 (MPa) 81 152 187 187
A5 (%) 5,6 0,5 2,8 1,4
25 mm
CRsalt spray 1 1 2,5 5
(mm/year)
HPDC housing
1000 kg melt volume (Industry)
AZC secondary alloy has similar properties
(casting behaviour, strength and corrosion
resistance) compared to AZ91D
Patent application:
Ditze, A. Scharf, C., Blawert, C., Kainer, K. U., Morales, G.E.D.:
250 mm Magnesiumsekundärlegierung. DE 10 2005 033835 A1, 2005.
Ditze, A. Scharf, C., Blawert, C., Kainer, K. U., Morales, G. E. D.:
Magnesium Alloy. WO 2007/009435 A1, 2006.
PAGE 47
Source: Institut fuer Fahrzeugkonzepte,
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DLR
Source: Institut fuer Fahrzeugkonzepte,
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DLR
Source: Institut fuer Fahrzeugkonzepte,
PAGE 50
DLR
Source: Institut fuer Fahrzeugkonzepte,
PAGE 51
DLR
Source: Institut fuer Fahrzeugkonzepte,
PAGE 52
DLR
Thank you for your attention!
PAGE 53
