A. García-Escorial

Mechanical properties of some PM aluminide and silicide reinforced 2124 aluminium matrix composites

Tensile properties of PM 2124 aluminium composites reinforced with Ni3Al, NiAl, Cr3Si and MoSi2 intermetallic powder particles have been investigated in tempering conditions T1 and T4. Intermetallics were produced by selfpropagated high-temperature synthesis and composite powders consolidated by extrusion. 2124/MoSi2 showed the highest thermal stability, and the best mechanical properties even after comparison with those of 2124/SiC composite after processing through the same route. 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

Containerless Solidification and Characterization of Industrial Alloys (NEQUISOL)

Containerless solidification using electromagnetic levitator (EML), gas atomization and an instrumented drop tube, known as impulse atomization is investigated for Al-Fe and Al-Ni alloys. The effects of primary phase and eutectic undercooling on the microstructure of Al-Fe alloys are investigated using the impulse drop tube and parabolic flight. The TEM characterization on the eutectic microstructure of impulse-atomized Al-Fe powders with two compositions showed that the metastable AlmFe formed in these alloys. Also, the growth undercooling that the dendritic front experiences during the solidification of the droplet resulted in variation of dendrite growth direction from to . For Al-4 at%Fe, it was found that in reduced-gravity and in the impulse-atomized droplets the primary intermetallic forms with a flower-like morphology, whereas in the terrestrial EML sample it has a needle like morphology. For Al-Ni, the effect of primary phase undercooling on dendrite growth velocity under terrestrial and reduced-gravity condition is discussed. It is shown that under terrestrial conditions, in the Ni-rich alloys with increasing undercooling the growth velocity increases, whereas in the Al-rich alloys the growth velocity decreases. However, the Al-rich alloy that was studied in reduced-gravity showed similar behavior to that of Ni-rich alloys. Furthermore, the effect of cooling rate on the phase fractions and metastable phase formation of impulse-atomized Al-Ni alloys is compared with EML. A microsegregation model for the solidification of Al-Ni alloys is applied to impulse atomized powders. The model accounts for the occurrence of several phase transformations, including one or several peritectic reactions and one eutectic reaction.