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mMINING METALLURGY MATERIALS
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Heterogeneous Nucleation
Mechanisms in Al Alloys
Universitätslehrerverband der
Montanuniversität Leoben (ULV)
This study employs the metallic glass technique to investigate nucleation mechanisms
on heterogeneous TiB 2 particles in Al alloys with an aim to develop more potent grain
refiners.
Grain refined and non
grain refined sample
Melt-spinner
Al-5Ti-1B rod: (a) TiB 2 particle; (b) Al 3 Ti particle; (c) Al matrix
Results indicate that Al nucleates on the basal faces of boride
particles. Dissolved Al 3 Ti particles from the rod provide excess
Ti in the melt. HRTEM of the boride interface has revealed
Al 3 Ti monolayers approximately 1 nm thick. Microchemical
STEM analysis shows that Ti seggregates to the boride interface.
The Al 3 Ti layers are believed to be a requisite for potent
nucleation at low undercoolings due to a reduction in lattice
mismatch with the Al.
Brian McKay
Chair of Casting Research
at MUL since: 2003
Zur Person:
1997-2001 DPhil. Oxford University
2002- 2003 Postdoc University of Manchester
Institute of Science and Technology (UMIST)
2003 - Present University Assistant MUL
In cast houses and foundries it is common to grain refine Al
alloys. This results in a small uniform equiaxed grain structure
which can facilitate casting practice and improve mechanical
properties in the final as-cast product. The most common grain
refiner used in industry is Al-5Ti-1B rod. The rod contains
hexagonal TiB 2 platelets and Al 3 Ti particles distributed within an
Al matrix.
Heterogeneous nucleation on the boride particles has been
examined using the metallic glass technique. This technique
freezes the growth of the nuclei at an early stage within a glass
matrix by rapidly quenching the melt using a melt-spinner.
The nuclei are embedded within a glass which readily permits
examination of the nucleation events by electron microscopy.
TEM micrograph of Al nucleating
on boride particle
HRTEM micrograph of boride
interface.
Forschungsschwerpunkte:
Characterisation techniques: HRTEM, TEM, STEM, SEM, FIB,
EDX, EBSD, DSC, and XRD.
Casting Techniques
Grain Refinement
Metallic Glasses
Al and Mg Aerospace Alloys