Presentation on theme: "Innovative approach to structure control in light alloys Dmitry Eskin, Hari-Babu Nadendla Brunel Centre for Advanced Solidification Technology."— Presentation transcript:
Innovative approach to structure control in light alloys Dmitry Eskin, Hari-Babu Nadendla Brunel Centre for Advanced Solidification Technology
BCAST: Vision BCAST is an international leader in liquid metal engineering with focus on solidification research, strategic technology developments and user-led industrial applications. We conduct fundamental research to generate world-class knowledge in solidification science. We develop and exploit innovative and sustainable technologies and enable the metal casting industry and its customers to improve their competitiveness in global markets. Brunel University 8 constituent academic schools 10 research institutes 15,200 full-time students 2,500 staff BCAST 3 Professors 5 Lecturers 11 Research Fellows 8 PhD students 5 Support staff
Research Fundamental research: Fundamental research: Nucleation–based solidification research including the structure of liquid metal, mechanisms of heterogeneous nucleation and the generic approach for enhancing and controlling nucleation through both physical and chemical methods. Technology development: Technology development: Innovative generic technologies for liquid metal treatment and applications of developed to the existing shape casting and continuous casting processes. Industrial applications: Industrial applications: Proprietary applied research with individual industrial partners to exploit fundamental research and generic technological development to support the metal casting industry in implementing innovative processing technologies and new products.
Outline Why we think that metals are underestimated in European programmes Scandium – ultimate addition to Al alloys Grain refinement using designed master alloys Ultrasonic cavitation processing – universal technology Conclusions
What is the age we are living now in? Stone age 2.5 mln BC-2000 BC Bronze age 3300 BC-600 BC 1300 BC-300 BC Iron age Middle age Renaissance Industrial age Electronic age Nano- age?
What are the important materials? MetalAnnual production, mln tAnnual production, mln m 3 Iron and steel1921243 Plastic*245190 Aluminium33.912.5 Copper15.231.7 Zinc10.761.5 Magnesium0.4290.24 Zirconium0.90.138 Titanium0.090.02 Niobium0.0819.45 x 10 -3 Scandium10 x 10 -9 (2 x 10 -6, oxide) 3.39 x 10 -11 m 3
What can be called extreme processing conditions? Temperature: 700-800 °C for Al melting and casting Speed: cm/s Pressure: 1 atm Time-scale: minutes to hours Length-scale: cm to meters
What can be called extreme processing conditions? Temperature: more than 5000 K Speed: faster than 1500 m/s Pressure: up to 10000 atm Time-scale: less than 100 µsec Length-scale: 5 to 500 µm “The conditions inside the collapsing bubbles are theoretically extreme enough to allow nuclear fusion to take place.” Nature 440, p.132 (9 March 2006)
Potential of Scandium Al-Sc master alloy Al alloy billet
Effects of Scandium Sc is prone to supersaturation in (Al) Al 3 Sc is the only one phase in Al-based systems: Equilibrium L1 2 phase Lattice parameters perfectly matching Al – can be coherent Precipitates at 200-300 °C Primary: perfect grain refiner Secondary: powerful, coherent, equilibrium hardener Secondary: powerful, equilibrium, stable grain blocker L. Toropova et al.
How to realize the potential of scandium in aluminium alloys Scandium is expensive so a much cheaper master alloy produced directly from oxides is an alternative Scandium can be added in combination with other elements, e.g. Zr, with resulting 2-3 times lower addition level Scandium is not a rare metal, it is scattered. Increased bulk demand would result in lower costs and price
Designed grain refiners based on less-common transition elements 0.384 nm 0.405 nm Al Al (face centred cubic) New grain refiner has Higher melting temperature than Al Good lattice matching (with Al and Al-Si matrix crystals) Chemical stability with Al and other commonly used alloying elements No compounds with alloying elements (no poisoning) Al-Si alloys are the base for most castings used in cars, aircrafts, pumps, engines etc
Al-Si binary alloys Tp1 test 700 O C Practical alloys composition M. Nowak & N. Hari Babu Patent application
LM6 20 mm LM6 with Grain refiner addition Slow cooling rate 0.07 K/s With NGR additionWithout addition M. Nowak & N. Hari Babu
Cavitation Cavitation zone Acoustic streaming Non affected area (D. Eskin et al., 2010) (N. Alba-Baena et al., 2011) (Garcia-Rodriguez et al, 2011)
Structure refinement in light alloys In the liquid state: activation of nonmetallic inclusions In the liquid state: dispersion and refinement of nucleating substrates, e.g. intermetallics In the solidification range: fragmentation of dendrites and dispersion of fragments Primary intermetallics: fragmentation, nucleation Al 2 O 3 wetting Al 3 (Zr, Ti) D. Eskin et al.
Degassing in Al (GA 286344) N. Alba Baena & D. Eskin, 2012
Conclusions The potential of advanced “conventional” metal is great and is related to less-common and scattered metals and to extreme processing. Advances bring about economical, technical, societal and environmental impact. There is large potential for fundamental scientific advances for support of advanced metallic materials.
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