1. Nucleation kinetics and grain growth during aluminum solidification
Naveed Iqbal
Materials Research Society (fall meeting, 2004), Boston, MA, USA
Niels van Dijk, S. E. Offerman, G. J. Kearley (IRI, TU Delft, The Netherlands)
L. Katgerman (TNW, TU Delft, The Netherlands)
Mona Moret - ESRF, Grenoble, France
10 November 2018

2. Pure Al: Liquid to solid transformation
Liquid Al
Solid Al
( FCC) T
Solid
Liquid
10 November 2018

3. Al+grain refiners:
Substrate(TiB2)
Liquid
Solid
10 November 2018

4. 3D X-Ray Diffraction Microscope
2D detector
Furnace
Sample w
slits
Bent crystal
Synchrotron
Beam line European Synchrotron Radiation Facility
10 November 2018

5. Liquid to solid phase transformation
Al-0.1Ti-0.1TiB2
t =0.0 sec
t =40sec
t =200 sec
t =168 sec
• T = 973 oK
• Before transformation
• Beam size: 300  300 m2
• Energy = 70 keV
10 November 2018

6. Liquid to solid phase transformation
Al-0.1Ti-0.1TiB2
10 November 2018

7. Nucleation Rate
Solid fraction fS
10 November 2018

8. Nucleation during phase transformation
10 November 2018

9. Metastable TiAl3 and aluminum grain growth during solidification
TiB2
TiAl3 Al
Metastable TiAl3 and aluminum grain growth during solidification
TiB2 particles nucleate
the TiAl3 phase that
ultimately nucleate the aluminum grains.
10 November 2018

10. Growth of individual aluminum grains
Diffusion Controlled growth:
R(t)=S(Dt):
Theory
Theory
Cooling 1 K/min
10 November 2018

11. Growth of individual aluminum grains
Industrial Sample: Al-0.25Ti-0.04 TiB2 (0.20 Fe)
Theory
Cooling 1 K/min
10 November 2018

12. Conclusions
• The increased nucleation during solidification of aluminum
alloys is due to the metastable TiAl3 phase formed on the
surface of TiB2 particles.
• Grain growth in AL-Ti system is controlled by titanium
diffusion in the beginning, by latent heat in the middle and the
free growth at the end of solidification.
• The latent heat plays a vital role during solidification
by restricting both the nucleation and grain growth.
10 November 2018