MCAST Melt Conditioning by Advanced Shear Technology

MCAST Melt Conditioning by Advanced Shear Technology

BCAST (Brunel Centre for Advanced Solidification Technology)Brunel University

UK

Introduction to MCASTIntroduction to MCAST

MCAST (Melt Conditioning by Advanced Shear Technology) is an innovative technology developed by BCAST at Brunel University for conditioning liquid alloys prior to solidification processing.MCAST uses the dispersive mixing power of the twin-screw mechanism to provide conditioned melt with uniform temperature, uniform chemical composition and well dispersed heterogeneous nucleation sites.The conditioned melt will solidify with enhanced heterogeneous nucleation to produce a solidified object with fine and uniform microstructure, uniform composition and reduced cast defects.MCAST process operates in batch for shape casting or continuously for continuous castingMCAST process is applicable to Al-alloys, Mg-alloys, Zn-alloys, Sn- alloys, Pb-alloys.

Melt Conditioning by Advanced Shear Technology

MCAST ProcessMCAST Process

Fluid flow characteristics in MCASTFluid flow characteristics in MCAST

Uniform temperature fieldUniform composition fieldWell dispersed nucleation sitesRapid heat exchange rateEnhanced kinetic conditions

Sheared, 800rpm,45s

Effect of shearing and superheatEffect of shearing and superheat

No Shear

650oC

605oC

AZ91D

AZ91D, sheared at 800rpm for 45s

0

100

200

300

400

500

600

700

800

600 610 620 630 640 650 660

Shearing temperature (°C)

Gra

in s

ize

(µm

) No ShearSheared

Effect of shearing and superheatEffect of shearing and superheat

AZ91D, sheared at 800rpm for 45s

Resting after shearingResting after shearing

0

100

200

300

400

500

600

700

800

1 10 100 1000Relaxation time, s

Gra

in s

ize,

mic

ron 605oC 800rpm 45s

650oC 800rpm 45s

AZ91D, re-melted at 650oC

Re-melting experimentRe-melting experiment

0 1 2 3

0 1 2 3

With shearing

Without shearing

AZ91D, re-melted at 650oC

Re-melting experimentRe-melting experiment

ShearedNo shear

Effect of shearing and superheatEffect of shearing and superheat

0

100

200

300

400

600 610 620 630 640 650 660

Temperature ( oC)

Gra

in s

ize

(m

)

Sheared

No Shear

Al-10Mg, sheared at 800rpm, 60s

Shearing vs. grain refinerShearing vs. grain refiner

No TiB2No Shear No TiB2

Shear

TiB2No Shear

TiB2 +Shear

5754-0.25Fe, sheared at 650oC, 800rpm, 60s

T P1

mo u

l d

Al-15Si

Gra

phite

mou

ldM

etal

lic m

ould

Shearing vs. cooling rateShearing vs. cooling rate

50ppm P, no shear 50ppm P, shearedNo P, no shear No P, sheared

0

20

40

60

80

100

120

140

160

Ave

rage

siz

e of

prim

ary

Si (m

icro

n)

TP1 mouldGraphite mouldMetallic die

No P, no shear P, No shear No P, shear P + shear

Modification mechanism

Al-15Si

Physical grain refining

LM24, Filtered at 640oC

Oxide in liquid metal

No shear Sheared

Filter Filter

Intermetallics and OxidesIntermetallics and Oxides

AZ91D, filtered at 640oC

50m 50m

Non-sheared Sheared

Oxide in non-sheared meltOxide in non-sheared melt

AZ91D, No shear, filtered at 640oC

2 m

300nm

5 m

1 m 300nm

10m

Young oxide film Old oxide film Oxide skin

Dispersed oxides in sheared meltDispersed oxides in sheared melt

AZ91D, sheared, filtered at 640oC

400nm

How Does MCAST Work?How Does MCAST Work?

MCASTProcessing

DispersedOxide

Particles

EnhancedNucleation

Refined Structure

Reduced Defects

EnhancedProperties