Jul
23
2007
Light alloys
A study of double oxide film defect behaviour in a quiescent aluminium melt
R. Raiszadeh* and W D Griffiths
Department of Metallurgy and Materials Science, The University of Birmingham
67th World Foundry Congress
The change in the volume of an air bubble held within commercially pure
liquid aluminium was recorded by real time x-ray radiography, to estimate
the behaviour of double oxide film defects after entrainment in liquid
aluminium. This showed that first oxygen and then nitrogen were
consumed by the melt to produce Al2O3 and AlN respectively. Varying the
initial hydrogen contents of the melt also showed that hydrogen could
diffuse into the a...
Jul
23
2007
Heat treatments
The influence of heat treatment on the structure and tensile properties of cast titanium alloy Ti-5111
A.C. Robinson1, E.J. Czyryca1, and D.A. Koss2
1Naval Surface Warfare Center, Carderock Division, USA. 2The Pennsylvania State University, USA
67th World Foundry Congress
The influence of heat treatment on the microstructure and tensile
properties of the cast Ti-5111 alloy has been examined. The effects of
annealing temperature and cooling rate on the microstructural evolution in
this near-alpha alloy are assessed, and the relationships between
microstructure and the corresponding tensile properties and fracture
behavior are explored. The results indicate good strength in both the ascast
condition and aft...
Jul
23
2007
Moulding methods and materials
Wicking of liquid polystyrene degradation products into the pattern coating in the lost foam casting process
P J Davies and W D Griffiths
Department of Metallurgy and Materials, School of Engineering, University of Birmingham, UK
67th World Foundry Congress
Entrapment of liquid polystyrene degradation products during filling is
detrimental to the quality of Aluminium Lost Foam castings. In this study,
the degradation of expanded polystyrene under different heating
conditions, and the ability of two pattern coatings of different permeability
to absorb the partially degraded liquid polymer, was determined using gel
permeation chromatography and scanning electron microscopy. It is
suggested th...
Jul
23
2007
Moulding methods and materials
A comparison of thixocasting and rheocasting
Stephen P. Midson* and Andrew Jackson**
The Midson Group, Inc. Denver, Colorado. USA* and Arthur Jackson & Co., Ltd. UK**
67th World Foundry Congress
The first semi-solid casting process to be commercialized was
thixocasting, where a pre-cast billet is re-heated to the semi-solid solid
casting temperature. Advantages of thixocasting include the production of
high quality components, while the main disadvantage is the higher cost
associated with the production of the pre-cast billets.
Commercial pressures have driven casters to examine a different
approach to semi-solid casting, where ...
Jul
23
2007
Light alloys
Strontium effect on the solidification path of a 319-type aluminum alloy
M. Castro-Román, J. J. Montes-RodrÃguez, M. Herrera-Trejo.
CINVESTAV Unidad Saltillo, Carr. Saltillo-Monterrey km 13, 25000 Saltillo,
67th World Foundry Congress
The sequence of phase precipitation during solidification of a 319-type
aluminum alloy was studied by thermal analysis. Melts of the alloy with
different Sr contents were prepared in a gas-heated furnace. The liquid
metal was poured into graphite cups fitted with two thermocouples.
Special attention was paid in the experimental setup in order to obtain
cooling curves with low noise. Thermogram data were analyzed using the
derivative of c...
