Mg for transportation systems

Magnesiumfor transportation systems

Peter J. UggowitzerInstitute of MetallurgyMaterials Department

ETH Zürich

Helmut KaufmannLight Metals Center

of CompetenceLKR Ranshofen

Mg for transportation systems

1 History

2 Mg renaissance

3 Mg properties

4 Processing & alloys:new developments

content

Mg for transportation systems

Source:IG Farben, 1939

1 History

Frames for airplane seats

Airplane body planking

Car bodies

Mg for transportation systems 1 History

Racing bike; Opel 1922Total weight 69 kg.Piston and crankcase made of Mg.

VW beetle used 21 kg Mgof die castings in its gear box and engine block.In the 1970’s Mg demandreaches 42’000 tons

Mg for transportation systems 1 Statistics

Mg consumption

0

100

200

300

400

500

600

1990 1995 2000 2005

total die casting

X 1

000 t

Source:Mg Alloy Corp., IMA

Mg for transportation systems 1 Statistics

Mg consumption

Source:Mg Alloy Corp., IMA

Today: 3 kg average magnesium content in cars.Target for 2005: 40 kg Mg per vehicle.

Today:Porsche 911 uses 52 kg Mg per vehicle.Audi A2 uses 20 kg, A4 and A6 have about 14 kg.VW Passat platform uses 14 kg Mg. In 2005 thisplatform will incorporate between 28 to 42 kg,projected at 2 million units per year.

⇒ Requires tripling of existing capacity - from current 420 tpa to over 1.5 million tpa.

Mg for transportation systems 1 Statistics

Auto companies buy into Mg projects

• VW has invested € 108 in Dead Sea Magnesium Ltd.

• Ford is participating in Australian Mg Corp by investing € 3.107 and placing a € 1,5.109 order for Mg metal.

• General Motors and Norsk Hydro have announced a long -term supply agreement.

• Toyota is in joint venture with Noranda starting the € 5.108 Magnola (Serpentin debris) plant in Quebec.

Mg for transportation systems

0

2

4

6

8

10

Mg Al Ti Fe

den

sity

, ρ

[ gcm

-3]

Mg-alloys1.2<ρ<1.9

2 Renaissance

Why the renaissance of Mg ?Lightweight construction of cars,railed vehicles, cabins, cable cars,roboting systems,..

Components for audio, video,computer, communication (AVCC)systems.

0 10 100 10000

4

8

12

Nickel

Iron

Copper

content in ppm

corr

osi

on r

ate,

[m

m/a

]

Mg for transportation systems

Mg automotive application today 2 Mg in t.s.

Mg light weightinner door; VW Lupo.

Mg tailgate, wheel rims

Fuel tankprotector; MercedesSLK

Mg

hat

rack

Mg

inst

rum

ent

pan

el, A

cla

ssM

erce

des

Ste

erin

g w

hee

lst

eeri

ng

wh

eel

lock

s; V

W

Mg gear box BMW

Sea

t st

ruct

ure

,≈5

0%w

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savi

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Mg for transportation systems

Mg automotive application today 2 Mg in t.s.

High Pressure Die Cast componentsfor structural application at T <130°Cwhere damage tolerance and pressure tightness is not required.

and tomorrowMg components for high-performance gear boxes, crankcases, engine blocksand hydraulic parts -require improved creepresistance, pressure tightness and thicker walls.

The solution:

New alloys and processes

Mg for transportation systems

Mg alloys for elevated temperature

0

0,4

0,8

1,2

1,6

2

AZ91 AS41 AE42 Nor.A1 ETH/LKR AlSi8.5Cu

cree

p e

longat

ion [

%]

35 MPa, 175°C, 200 hETH/LKR:MgAlSrX

3 Mg properties

new creep resistant Mg alloysfor high-performance application

Mg for transportation systems

ρρρρ

[g/cm3]

E

[GPa]

Rm[MPa]

αααα

[10-6K-1]

λλλλ

[Wm-1K-1]

Fe 7.87 208 70 (3500)* 11.8 80

Ti 4.50 120 235 (1500)* 8.4 26

Al 2.70 62 45 (750)* 23.6 247

Mg 1.74 44 55/90 (500)* 26.1 157

* maximum strength

3 Mg properties

Mg physical and mechanicalproperties

Problem: limited ductility (fracture toughness) due to hexagonal crystal structure; solidification in non-equilibrium;gas content in die cast components (heat treatment, welding ?)

Mg for transportation systems

non-equilibrium AZ91 die cast, dT/dt ↑↑↑↑

Non-equilibrium: formation ofeutectic β-phase (Mg17Al12)

3 Mg properties

0

0.2

0.4

0.6

0.8

1

420 460 500 540 580 620

temperature, T, [°C]

solid

fra

ctio

n, f

S, [

-]

eute

ctic

tem

per

atu

re, T

E=

437°

C

Al-content

3%6%9%so

lid f

ract

ion

, fs

[-]

eute

ctic

tem

per

atu

re,

TE =

437

°C

Mg for transportation systems 4 processing

Semi-solid processing

0

0.2

0.4

0.6

0.8

1

420 460 500 540 580 620

temperature, T, [°C]

eute

ctic

tem

per

atu

re, T

E=

437°

C

solid

fra

ctio

n, f

S, [

-]

Al-content3%6%9%so

lid f

ract

ion

, fs

[-]

eute

ctic

tem

per

atu

re,

TE =

437

°C

AZ91 AZ71 AM60 AE42 AlSi7Mg

∆TSL [°C] 148 126 74 45 52

∆∆∆∆T40/60 [°C] 22 18 13 9 17

less brittle β-phase, no gas entrapment

Mg for transportation systems 4 processing

200µm 200µm

AZ91 AZ71

as cast as cast

no gas entrapment

⇒ solution heat treatment possible400°C/24h

Mg for transportation systems 4 processing

100µm 100µmT4400°C/24h

T4400°C/24h

200µm 200µm

AZ91 AZ71

as cast as cast

Mg for transportation systems 4 processing

Mechanical propertiesNRC

AZ71

as cast

NRC

AZ71

T4

Die cast

AZ91

as cast

Rp0.2 [MPa] 120±15 115±15 125±15

Rm [MPa] 195±8 270±25 215±30

A [%] 5.2±1.2 11.5±2.5 2±1.5

KJC [MPa√m] 14±2 44±4 10.7

excellent ductility in T4 condition

Mg for transportation systems 4 processing

Steering rodalloy: AZ71, shot weight 1850 g

Outlook: • NRC adapted AZ alloys

• Heat resistance AZ-X alloys

• Heat treatment optimization

• Implementation of Mg recycling

Mg for transportation systems

Thixocasting

New Rheocasting

Semi-Solid Casting

Semi-Solid Melt

Semi-Solid Melt

Melting

Cutting Heating

Slurrymaking

Melting Stirring Billet casting

Out-Source-Recycling

In-house-Recycling

4 processing

Mg in-house recycling