Abstract: A Compressive Torsion Processing (CTP) is a unique severe plastic deformation process
which can easily apply very large strain without shape change to a work piece. Hypereutectic Al-Si
alloys have good properties such as low thermal expansion and high wear resistance. It is important
for the alloys to control the size of second phase particles (primary and eutectic silicon,
intermetallic compounds) as well as grain size of aluminum matrix. In the present work, the CTP
was applied to hypereutectic Al-Si alloy (AA390) to investigate the possibility of microstructure
refinement of the alloy and the mechanical property of processed alloy was also investigated by
Abstract: The important role of dissolved elements, such as manganese or iron, in the production process of
rolled material was in the focus of this investigation.
In the AlMn-alloys the content of manganese in solid solution is first controlled by other alloying
elements such as silicon and iron. The addition of silicon or / and iron reduces the level of
manganese in solid solution in the as-cast condition as well as in the following preheating process
step. Another major parameter is the final annealing treatment of the rolled products. The
preheating treatment and the final annealing are the key parameters to control the level of
manganese in solid solution and the size and distribution of the fine dispersoids.
In the AlFe-series alloys the iron content in solid solution is first controlled by the casting process
DC or CC and the amount of iron in the alloy composition. In the as-cast condition the dissolved
iron level is normally higher in the CC-material than in the DC-material. The intermediate
annealing treatment also has a great influence on the content of iron in solid solution.
They recovery and recrystallisation behaviour is controlled by the content of manganese or iron in
solid solution. The precipitation of manganese or iron during thermal treatment leads to optimum
dislocation pinning and results in a high thermal stability. On the other hand, if the precipitation of
manganese or iron interacts with the occurence of recrystallisation, the resulting grain structure can
show coarse grain.
Abstract: The modelling of microstructure, and hence the properties, of cast alloys has so far been
attempted assuming the liquid metal is free from defects. The growing appreciation that bifilms, of
size measured in millimeters, are usually abundant in liquid metals, and control many features of
the casting, has led to this paper in which some of the known and some of the expected effects are
reviewed. It is suggested that bifilms cause major effects on microstructure and properties and their
presence can vastly overpower the effect of traditionally simulated structural features.
Abstract: Horizontal continuous casting process has been successfully implemented in Alcan for
the production of T-ingots of primary aluminium and foundry alloys. Ability to achieve increased
productivity targets and reduce production costs relies on a fundamental understanding of key
process characteristics and operating parameters. Thanks to the long-standing experience in vertical
DC Casting, numerical modelling appeared as a powerful approach to understand phenomena
related to metal flow, solidification and ultimately defect formation.
As part of a collaborative R&D program, a global model of horizontal casting process, integrating
specialized sub-models on critical aspects of the process such as meniscus dynamics, is being
developed. Experimental characterization of primary and secondary cooling is performed in parallel
with modelling work to provide the information necessary to properly characterize mould heat
transfer. This paper will present the development of a 3D process model of T-ingot casting along
with its application to solve specific process challenges that have emerged during the first years of
production in the plant.
Abstract: Age hardening is one of the most important processes to strengthen aluminium alloys. It
usually consists of the steps solution annealing, quenching and aging. For heat treatment
simulations as well as for the appropriate choice of quenching processes in heat treatment shops,
knowledge of the temperature- and time-dependent precipitation behaviour during continuous
cooling is required. Quenching should happen as fast as necessary to reach high strengths, but also
as slow as possible, to reduce residual stresses and distortion. This optimal quenching rate of an
aluminium component depends on its chemical composition, initial microstructure and solution
annealing parameters as well as on its dimensions. Unfortunately continuous cooling transformation
(CCT) diagrams of aluminium alloys do almost not exist. Instead isothermal transformation (IT)
diagrams or given average quenching rates are used to estimate quenching processes, but they are
not satisfying neither for heat treatment simulations nor for heat treatment shops.
Thermal analysis, especially Differential Scanning Calorimetry (DSC) provides an approach for
CCT-diagrams of aluminium alloys, if the relevant quenching rates can be realized in the DSCequipment.
The aluminium alloy Al-4.5Zn-1Mg (7020) is known for its relatively low quenching
sensitivity as well as for its technical importance. The complete CCT-diagram of 7020 with cooling
rates from a few K/min to some 100 K/min has been recorded. Samples have been solution
annealed and quenched with different cooling rates in a high speed DSC. The resulting precipitation
heat peaks during cooling have been evaluated for temperature and time of precipitation start, as
well as their areas as a measure for the precipitate amount. Quenched samples have been further
investigated regarding their microstructure by light and electron microscopy, hardness after aging
and precipitation behaviour during re-heating in DSC. The CCT-diagram correlated very well with
the microstructure, hardness and re-heating results. A critical cooling rate with no detectable
precipitation during continuous cooling 155 K/min could be determined for 7020. A model to
integrate the CCT-diagram in heat treatment simulation of aluminium alloys is under development.
Abstract: A mathematical model has been developed and validated to predict deformation,
temperature and microstructure evolution during multi-pass hot rolling of an AA5083 aluminum
alloy. The validated model was employed to examine the effect of changing the number of rolling
passes and the strain partitioning during multi-pass rolling on the material stored energy and the
resulting microstructure. Results indicate that the number of rolling passes has a significant effect
on the material stored energy. In addition, the way the strain is partitioned in two-pass rolling cases
affects the material stored energy with decreasing strain/pass providing the highest stored energy in
the material after rolling and vice versa. The reason behind these results was further investigated
indicating that the thermal evolution during rolling may significantly influence the material stored
energy and subsequent recrystallization kinetics.
Abstract: The effect of extrusion rate and ratio on the Al3Zr induced dynamic recrystallization
(DRX) that occurs during hot extrusion of RS-P/M Al-Zn-Mg-Cu-Zr alloys was investigated. An
increase in the logarithm of extrusion rate promoted DRX and lead to a monotonic increase in the
number of fine grains. Although DRX was also promoted and the grain size reduced by an increase in
extrusion ratio from 10 to 20, the DRX behavior hardly changed, even when the extrusion ratio
exceeded 20. However, with increasing extrusion ratio, the width of fibrous grain, i.e., the
unrecrystallized region, decreased and the tensile strength increased to 879 MPa.
When the extrusion rate and ratio exceeded 54 mm/min and 20, respectively, a marked grain
coarsening occurred upon solution treatment, and the tensile strength tended to decrease, because of
the high dislocation density induced by hot extrusion. By annealing at 563 K before solution
treatment, it was possible to prevent grain coarsening, and thus prevent the strength decrease.
Abstract: The process of severe plastic deformation (SPD) makes it possible to reduce the grain
size to the submicrometer or nanometer range in many metallic materials. When the SPD process is
applied to age hardenable alloys, it may also be possible to control aging behavior. In this study, a
technique of equal-channel angular pressing (ECAP) is used as an SPD process and aging behavior
is examined on the three selected Al alloy systems such as Al-Ag, Al-Mg-Si and Al-Si-Ge. The
microstructures are observed using transmission electron microscopy and the mechanical properties
including hardness are measured. It is shown that the SPD process introduces unusual phenomena
in the precipitation process and there should be a potential for enhancement of strength over the
conventional age-hardening process or for improvement of ductility while keeping the high
Abstract: Thermo-mechanical processing (TMP), coined 50 years ago for steels to describe
combined thermal and mechanical treatments that define both product shape and
microstructure/properties, has been practiced since the early industrial revolution. The improved
function and control in mechanical shaping equipment were easily adapted to newly discovered
aluminum, integrating hot forming, cold deformation and annealing. The TMP goals for Al alloys
were grain refinement, substructure preservation, texture control and enhanced precipitation. Hot
extrusion became widely employed with exploitation of elongated grains with substructure and
strong texture and of press heat treatment (solution during deformation, quenching upon exit).
Rolling schedules were tuned to generate desired grain size/shape, substructure and texture. This
historical account aims to enhance application of metallography to process optimization and
innovation that makes metals more competitive with other materials.