Effect of melt conditioning on heat treatment and mechanical properties of AZ31 alloy strips produced by twin roll casting

In the present investigation, magnesium strips were produced by twin roll casting (TRC) and melt conditioned twin roll casting (MC-TRC) processes. Detailed optical microscopy studies were carried out on as-cast and homogenized TRC and MC-TRC strips. The results showed uniform, fine and equiaxed grain structure was observed for MC-TRC samples in as-cast condition. Whereas, coarse columnar grains with centreline segregation were observed in the case of as-cast TRC samples. The solidification mechanisms for TRC and MC-TRC have been found completely divergent. The homogenized TRC and MC-TRC samples were subjected to tensile test at elevated temperature (250-400 °C). At 250 °C, MC-TRC sample showed significant improvement in strength and ductility. However, at higher temperatures the tensile properties were almost comparable, despite of TRC samples having larger grains compared to MC-TRC samples. The mechanism of deformation has been explained by detailed fractures surface and sub-surface analysis carried out by scanning electron and optical microscopy. Homogenized MC-TRC samples were formed (hot stamping) into engineering component without any trace of crack on its surface. Whereas, TRC samples cracked in several places during hot stamping process.EPSRC – LiME, UK and Towards Affordable, Closed-Loop Recyclable Future Low Carbon Vehicle Structures – TARF-LCV(EP/I038616/1), Department of Mechanical Engineering, Imperial College London, UK, Mr. Steve Cook, Mr. Peter Lloyd, Mr. Graham Mitchell and Mr. Carmelo and BCAST, Brunel University London

Twin-Roll Cast Al-clad Mg Alloy

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Twin-Roll Cast Al-Clad Magnesium Alloy

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Cladding of Mg alloy with Al by twin-roll casting

Cladding of Mg alloy with Al has been conducted by simultaneous casting, cladding and rolling a using twin-roll casting process. The as-cast microstructure shows the presence of Mg17Al12 in the reaction zone with good interfacial bonding between the Al and the base Mg alloy. Annealing of the clad sheet results in the additional formation of Mg2Al3 along the Mg/Al interface. Subsequent rolling of the as-annealed sheet reduces the thickness of the reaction zone with a resultant improvement in the formability of the clad sheet. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.X116766sciescopu

The determination of accessible Pt metal fraction in Pt±Sn/Al2O3 reforming catalyst

An attempt has been made to provide a simple method for the determination of accessible Pt metal fraction in Pt±Sn/Al2O3 catalyst. The complications in Pt±Sn/Al2O3 system arise mainly due to uncertainties involved in the oxidation states of tin: Sn0, Sn2 and Sn4 in the reduced catalyst. H2, O2 chemisorption/titrations originally applied to Pt/Al2O3 were extended to the Pt±Sn/Al2O3 system. Two oxygen titration cycles OT1 and OT2 at room temperature were carried out using a dynamic pulse ¯ow technique. Only part of the total Sn in the catalyst is reduced to Sn0 (15%), which contributes to oxygen uptake. While OT1 is a linear function of the Sn content in the catalyst, the second oxygen titration OT2 gives the accessible Pt metal fraction only. It has been concluded that oxygen chemisorption/titrations at temperatures higher than ambient under dynamic conditions are not reliable for the determination of metal dispersions. # 1998 Elsevier Science B.V

Twin-Roll Cast Al-Clad Magnesium Alloy

An attempt has been made to clad Mg alloy with AI by twin-roll casting. This was clone by inserting an Al sheet between the roll and the Mg alloy melt during twin-roll casting. Microstructural investigation across the transverse section of the as-cast Al-clad Mg alloy sheet reveals a very good interfacial bonding between AI and the base Mg alloy. Annealing of the AI-clad Mg alloy sheet results in the formation of layers of various intermetallic phases along the Mg/Al interface. Subsequent rolling of the as-annealed sheet significantly improves the formability of the reaction zone, as evidenced by the cracking of the base Mg alloy before the cracking of the reaction zone.113Nsciescopu