PAGE 1

K. U. Kainer, Z. Zhen, Y. Huang, N. Hort

Magnesium Innovation Centre MagIC, GKSS Forschungszentrum Geesthacht GmbH

Magnesium Die Casting

International Summer School on High-Integrity Die Castings

28 Jul.-1 Aug., 2008, WPI, Worcester, USA

PAGE 2

Challenges for Magnesium R&D

Magnesium for consumer products Early application in 1940’s and 1960’s

(VW Beetle) Revival since 1990’s; main application

areas:– Automotive (see figure)– 3C industries

computer, communication,consumer electronics

Friedrich H., Schumann S., Proc. of the Second Israeli International Conference (2000): 9–18.

Sheets, outside

Sheets, inside

Extrusions

Thixo-/ foring parts for chassis

Complex thin-walled casting parts for body

Casting for high thermal and

mechanical load

Casting

Time

Cha

lleng

e

PAGE 3

Reduced emissions ~ Cleaner AirChart courtesy of CSM Worldwide

Global emissions standards are getting more stringent

Magnesium in Automotive Today

PAGE 4

Weight Savings: Materials

Steering ColumnMg: 0,9 kgSteel: 1,4 kg33 %

Wheel caseMg: 11,4 kgSteel: 15,6 kg28 %

TailgateMg: 3,2 kgAl: 5,5 kg42 %

Steering Column SupportMg: 1,4 kgSteel: 2,3 kg40 %

Seat frameMg: 1,8 kgSteel: 5 kg64 %

Inner DoorMg: 5,4 kgAl: 8,2 kg33 %

Engine V-4Mg: 16 kgAl: 22 kgFe/Steel: 60 kg22 - 73 %

Quelle: www.magnesium.com

PAGE 5

Potential Weight Savings

4 kg

4-6 kg 34-40 kg

3 kg 23-37 kg

18 kg 38-49 kg

25 kg 59-82 kg 132-184 kg87-130 kg

Component

Grand Total

Power Train

Currently used on e.g. VW / Audi vehicles

short term< 5 years

long term> 10 years

medium term> 5 years

After Volkswagen AG, K-EFWM/Dr. Schumann/Sinomag11.2002

Additional Potential Use of Mg

24-29 kg

14-20 kg12-16 kg

31-49 kg 46-69 kg

PAGE 6

Before WW II

After WW II

1924

1941

1939

1952

1946-19781995

1939

Use of Magnesium in the Past

PAGE 7

Magnesium Applications Today

Interior PartsSeat ComponentsInstrument PanelsKnee BolstersSteering Column Comp.Steering WheelsBrake & Clutch Pedal BracketsAirbag RetainersBracketsRadio FramesRadio and HVAC Covers

Drive train PartsManual Transmission Housings4 WD Transfer Case

Engine PartsCrankcaseCylinder head CoversIntake ManifoldsDrive BracketsElectrical ConnectorsEngine CradleOil pans

Interior PartsSunroof ComponentsMirror FramesHeadlight RetainersInner Door Frames

PAGE 8

Magnesium Applications Today: High Pressure Die Casting

PAGE 9

suspension,crank shaft

fan, gasketsT < 100 °C

ignition plug, catalyst gear box housing

T < 175 °C

engine blockT > 200 °C

source: Volkswagen AG

pistonT > 250 °C

filter boxesT = 150-200 °C

Temperatures for Power Train Use

PAGE 10

Applications in Power Train: High Pressure Die Casting

PAGE 11

Forecast High Pressure Die Casting

Source: Hydro Magnesium intern: Probability Forecast

*) China domestic demand on die casting is included as of 2004

Casting ,000 tons

PAGE 12

2005 2006 2007 2008 2009 20100

20

40

60

80

[me

tric

kto

ns

]

Year

Powertrain Structural Components

Source:D. Webb http//www.intlmag.org

Forecast: Applications HPDC-Parts

PAGE 13

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 14

• AZ (Mg-Al-Zn)• good room temperature

properties• small properties at elevated

temperatures• low ductility

• AM (Mg-Al-Mn)• better ductility • moderate room temperature

properties• constricted castability

• AS (Mg-Al-Si)• better strength• improved creep resistance • constricted castability

• AE (Mg-Al-SE)• AJ (Mg-Al-Sr)• MRI (Mg-Al-Mn-Ca-RE)

• good properties at elevated temperatures

• good creep resistance• constricted castability

Magnesium Alloy Systems

PAGE 15

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 16

Patents/Modifications for Pressure Die Cast Magnesium Alloys

Year/Originator

Chemical Composition

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 4.94.7-4.9

0.26-0.300.27-0.29

1.74-1.94 Sr1.23-1.35 Sr

1997 Honda 4.5-10 4.5-6

0.2-1 0.2-1

1-3 1-3

0.1-3 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 17

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 18

Castability of Mg-Al-Zn Alloys

Zn-content (wt.-%)

AZ-Base 1AZ-Base 2ZA-Base

alloy-groups

castabledifficult

Source: Foerster

PAGE 19

78 9

10

6

1

5 42

3

1: AZ91

2: AS21X

3: MRI153M

4: AJ62X

5: AE42

6: AJ52X

7: ACM522

8: AX52J

9: MRI230D

10: AM-HP2

Castability

Cre

ep

Res

ista

nce

180 °C

150 °C

Source: Aghion et al., Dunlop et.

Al.

Castability and Creep Resistance

PAGE 20

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 21

Illustration of die casting process

Source: www.ekkinc.com

PAGE 22

Cold Chamber Die Casting Process

plunger

chamber

partejector

fixed platen

ejector die

moving platen

moving die

PAGE 23

Hot Chamber Die Casting Process

hydraulic closing die

piston

chamber

melt

die

PAGE 24

HPDC Unit

Source: www.rauch-ft.com

PAGE 25

HPDC and Vacuum HPDC

PAGE 26

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%

Cover Gases

PAGE 27

Relationship Between Magnesium Die Casting Defects And Processing Parameters

Metal velocity

Metal Pressure

Die Temperature

Gating system

Die vent Die lubricant Metal Temperature

Ejection defect

Casting rate

Incomplete filing

● ● ● ● ● ● ●

Cold shuts ● ●Pores ● ● ● ●

Gas bubbles

Shrinks ● ●Blisters ● ● ●

Flow marks ● ● ● ● ●Surface Swirls

● ●

Hot cracks ● ● ● ●Cracks/

fractures● ● ●

Deformation ● ●

PAGE 28

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 29

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 30

Creep Properties Of Mg-al-ca Alloy Produced By Die Cast, Squeeze Cast And Gravity Cast

Source: Zhu et al, Mater.Sci.Eng.A,2008

Die

cast

Sq

uee

ze ca

stD

ie

cast

PAGE 31

Numerical Simulation Methods

Thin-wall casting geometry modeled by using FEM and FDM methods

FEM FDM

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.

Source: Marty McLaughlin, www.ekkinc.com

PAGE 32

Mold Filling Simulation Of Hot-chamber Diecast AM60B

Source: Li and Zhou, Materials Technology, 2003

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

Filling time:

11ms

Cast temp.:

650oC

Software:

self-developed

3D FDM

program

PAGE 33

A Mold Filling Simulation Case

Source: Song and Xu, North Hengli Sci. and Tech Co.

Ltd.

PAGE 34

Solidification Simulation Of HPDC Magnesium Alloys

Source: Song and Xu, North Hengli Sci. and Tech Co.

Ltd.

PAGE 35

Flow Simulation Within Shot Sleeve

Source: www.ekkinc.com

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.

PAGE 36

Solidification Simulation Of Low Pressure Die Cast Magnesium Wheel

Source: NERC-LAF, Shanghai Jiaotong

Uni.

PAGE 37

Solidification Simulation Of Low Pressure Die Cast Wheel

Source: NERC-LAF, Shanghai Jiaotong

Uni.

PAGE 38

Solidification Simulation Of Low Pressure Die Cast Engine Block

Source: NERC-LAF, Shanghai Jiaotong

Uni.

PAGE 39

Microstrutural Simulation Of Die Cast AM50

Source: Fu et al, Mater.Sci.Forum, 2008

Microstructure of die cast AM50 simulated by using a 2D Cellular Automaton based

model coupling with macro heat transfer calculation

PAGE 40

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 41

Recycling Alloys

PAGE 42

Que

lle: I

MA

, ME

L, H

ydro

Mag

nesi

um

19

91

19

92

19

93

19

94

19

95

19

96

19

97

19

98

19

99

20

00

20

01

20

02

20

03

20

04

20

05

20

06

20

07

0

50

100

150

200

Secondary Magnesium

PAGE 43

New Secondary Alloy

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

Composition and microstructure of the new secondary alloy compared to AZ91D

AZC1231 (~100 µm)AZ91D (600-800 µm)

PAGE 44

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 (after 1h in 5%NaCl, pH11)

0.43 ± 0.04 mm/year

1.81 ± 0.59 mm/year

Lin. polarisation resistance(after 24h in 5%NaCl, pH11)

247 cm2 80 cm2

Impedance (after 36h in 3.5%NaCl, pH7)

263 cm2 149 cm2

Saltspray (after 48h in 5%NaCl, pH7)

1.07 ± 0.23 mm/year

0.99 ± 0.58 mm/year

Immersion* (average after 400 h in 3.5%NaCl, pH6)

1.49 mm/year

1.42 ± 0.26 mm/year

PAGE 45

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 46

Casting Properties

Thelix

[°C]

angle [°]

filled length of the helix

[cm]

completely filled length of the helix

[cm]

AZ91D 159.0± 5.7

256.8± 36.1

48.6± 7.4

23.0± 1.8

AZC1231 158.8± 2.5

408.8± 28.4

66.1± 5.6

39.5± 6.0

Helix casting experiments* (700°C melt temperature, release agent Demotex S)

Better casting properties compared to AZ91D, thus no limitations in the possible casting processes

gravity die casting HPDCNRC

* C. S

charf, P

. Živan

ovic, A

. Ditze, K

. Ho

rny, G

. Fran

ke, C. B

lawert, K

.U. K

ainer, E

. M

orales,

Giesserei 94, N

r. 11 (2007), S.20-33

PAGE 47

Research into the Industrial Use

Gravity die casting6 kg melt volume (Lab)

HPDC housing1000 kg melt volume (Industry)

ingot (AZ91D)

ingot (AZC)

housing (AZ91D)

housing (AZC)

Rm (MPa) 198 189 258 250

Rp0,2 (MPa) 81 152 187 187

A5 (%) 5,6 0,5 2,8 1,4

CRsalt spray (mm/year)

1 1 2,5 5

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.: 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.

25 mm

250 mm

PAGE 48Source: Institut fuer Fahrzeugkonzepte,

DLR

PAGE 49Source: Institut fuer Fahrzeugkonzepte,

DLR

PAGE 50

Source: Institut fuer Fahrzeugkonzepte,

DLR

PAGE 51Source: Institut fuer Fahrzeugkonzepte,

DLR

PAGE 52Source: Institut fuer Fahrzeugkonzepte,

DLR

PAGE 53

Thank you for your attention!