Abstract: Phase transformations in 6XXX alloys with Mn, Cu and Cr additions have been studied in
the process of homogenization annealing at different temperatures. The continuous cooling
transformation diagrams of decomposition of solid solution during the cooling of ingots from the
homogenization temperature have been plotted. The effect of the cooling rate after homogenization
on the properties of ingots during extrusion has been studied.
Abstract: In creep-ageforming a material experiences continuously variable bending stresses
through its thickness, from tensile to compressive, which are maximum at the surfaces. This can
potentially result in through thickness microstructural gradients, due to interactions between the
bending stresses, creep, and precipitation occurring during ageing, that can alter a component’s
performance. The aim of the work reported here was to develop an understanding of these effects in
an industrial creep ageforming process. For this purpose two aerospace alloys, 7475 and 2022, were
ageformed by Airbus UK using industrial scale ageforming tools. Their microstructures were
analysed in detail by TEM, and SAXS, which revealed significant through thickness microstructural
changes after forming.
Abstract: The formation of eutectics in Al–Zn–Mg–Ni and Al–Zn–Mg–Si systems is studied by
means of metallography, DSC, EPMA, X-ray spectroscopy and thermodynamical calculations.
Polythermal sections of the corresponding phase diagrams are constructed. The concentrations and
temperatures of binary eutectic reactions L → (Al) + Al3Ni and L → (Al) + Mg2Si in quaternary
alloys are determined. Nonequilibrium solidification in Al–7% Zn–3% Mg-based alloys ceases at
approximately 480 °C. The alloys close by composition to binary eutectics have considerably
improved casting properties as compared to the base Al–7% Zn–3% Mg composition. In particular,
hot tearing susceptibility is much less in alloys with Al3Ni or Mg2Si. These results are corroborated
by measurements of thermal contraction during solidification. The alloys containing binary
eutectics exhibit much lower temperatures of contraction onset and less thermal strain is
accumulated in the solidification range. Fine eutectic morphology enables fragmentation and
spheroidization of intermetallic particles during annealing. The presence of Al3Ni and Mg2Si
particles does not decrease the precipitation hardening effect associated with precipitation of the T′
(AlMgZn) phase. Improved casting properties and good mechanical properties of castings allow the
application of Al–Zn–Mg alloys with binary eutectics formed by Al3Ni or Mg2Si as foundry alloys.
Abstract: In order to improve the high-temperature strength of an Al-Cu-Mg alloy, Mn was added at
supersaturation to form a high-density dispersion of an intermetallic phase. In the P/M Al-3.6Mn-
6.4Cu-3.6Zn-1.7Mg alloy (mass%), rod-like Al-Mn-Cu-Zn quaternary intermetallic phases (Q phase)
several hundred nanometers in length were dispersed in the matrix. The chemical composition of the
Q phase was determined by TEM/EDX to be 78.8Al-12Mn-8Cu-1.2Zn (at%). The crystal system,
space group, and lattice parameters of the unit cell were identified to be orthorhombic, Cmcm and a =
0.76, b = 2.11, c = 1.25 nm, respectively, by Rietveld analysis. Since the matrix of the alloy obtained
was of the Al-Cu-Mg-(Zn) system, age-hardening occurred by formation of a GPB zone at room
temperature and 448 K. At the peak level of age-hardening at room temperature, the tensile strength
at room temperature was 704 MPa, and the elongations were 8.0%. The high temperature strengths at
523 and 573 K were 319 and 141 MPa, respectively, and the elongations were 17 and 34%,
Abstract: In this study, we investigated the effects of a small addition of Cu (0.1%) or Ge (0.1%) on the
microstructure and mechanical property of Al-Si alloys. The results are as follows. The size of
precipitates in the Cu-added or Ge-added alloys is smaller than that in the binary alloy. The size of
the precipitates at the grain boundary in the Cu-added or Ge-added alloys is larger than the size of
the precipitates in the binary alloy. However, the number of the precipitates at the grain boundary in
the Cu-added and Ge-added alloys is smaller than that in the binary alloy. It was found that a small
addition of Cu or Ge has the effect of raising the fatigue strength under repeated tensile loading as
well as the tensile strength.
Abstract: The quantitative correlation between strength, ductility and precipitate microstructures in
the vicinity of grain boundaries with precipitate free zones (PFZ) was evaluated for Al-Zn-Mg(-Ag,
Cu) alloys using transmission electron microscopy (TEM), three-dimensional atom probe (3DAP)
and tensile test. In the Al-Zn-Mg ternary and Cu-added alloys aged at 433K, larger widths of PFZ
were observed by TEM and resulted in lower elongations to fracture, independent of the size of grain
boundary precipitates. On the other hand, the elongation of the Ag-added alloy was higher, if
compared at the same levels of proof stress, due to the much smaller width of PFZ. This strongly
suggests that PFZ is harmful to fracture of the investigated alloys. From a 3DAP analysis,
furthermore, it was revealed that Ag and Cu atoms are incorporated in the nanoclusters from the
initial stage of aging. In this work, the elongation was well correlated to the width of PFZ, size of
grain boundary precipitates and the level of proof stress, enabling to predict ductility of the alloys
from known microstructural factors.
Abstract: The formation of nanoclusters in the early aging stage is not fully clarified due to their
extremely small sizes. To clarify the atomic-scale clustering of solute atoms, a three-dimensional
atom probe (3DAP) analysis and a Monte Carlo computer simulation have been conducted together
for Al-Zn alloys. The nanoclusters in the alloy aged at room temperature were successfully detected
in the obtained 3DAP maps. From these maps the growth behavior of nanoclusters during aging was
experimentally examined. In the Monte Carlo simulation, on the other hand, many-body nearest
neighbor interactions between atoms and between atoms and a vacancy were taken into account.
The Zn concentration of the clusters calculated in the 4-body interaction model best agreed with
that obtained experimentally, suggesting the importance of many-body interactions. Therefore, it
was confirmed that the combined analysis of 3DAP and the well-constructed Monte Carlo
simulation is useful to make clear the nanocluster formation in alloys.
Abstract: A diffusion controlled precipitation model based on classical nucleation and growth
theory has been implemented to simulate the precipitation kinetics in a hot rolled supersaturated Al-
Mn alloy (AA3103). The modelling approach explicitly includes the effect of concurrent
recrystallisation on precipitation and considers the simultaneous evolution and interaction of two
precipitate populations that vary significantly in size, i.e. constituent particles and dispersoids.
Comparison with experimental results shows that this classical modelling approach predicts
incorrect nucleus density and too high precipitation rates, which cannot be simply corrected by
parameter fitting. Reasons for this discrepancy are discussed in terms of selection of nucleation
sites, the effect of diffusion in a multi-component system, various diffusion paths and the possible
influence of precipitate shape and size distribution.
The model is subsequently altered by introducing two additional parameters that control the Mn
solute concentration at the particle-matrix interface. This more phenomenological model is
successful in reproducing the experimental precipitation kinetics, both in deformed and undeformed
aluminium matrix, and the effect of concurrent recrystallisation for a wide temperature range.
Abstract: The new structural applications of aluminum materials are determined by
intelligent lightweight design: the demand of safety, ecology, recycling and by
economics. Al-Si alloys allow complex shapes to be cast. Metallurgical a high volume
fraction of fine dispersoid which are less about 0.1 microns in size are useful for
retaining a fine grain. In the 6061 series of alloys, iron combines with aluminium and
silicon to form two types of commune inter-metallic, (beta AlFeSi and alpha
AlFeSi).The type of inter-metallic that is present these alloys will have an important
bearing on the homogenization time, workability and quality of the surface finish.
The microstructure of the as-cast samples was evaluated by electronic microscopy
and the morphology of inter-metallic compounds related to the efficiently modification.
Mn-Ti-Sr modification of Al-alloys is normally accompanied by an increase in porosity
in the casting.
Abstract: The microstructural evolution has been investigated in three alloys of the 7000 series possessing
increasing zinc contents by combining small-angle X-ray scattering, differential scanning
calorimetry and transmission electron microscopy, in order to gain understanding on the evolution
of the compromise between yield strength and corrosion resistance. We show that the three
materials show qualitatively identical precipitation sequences; however the precipitated volume
fraction is shown to increase in parallel to the Zn content. Moreover, the precipitate size evolution is
faster in the high Zn alloy. The precipitate composition is inferred to vary in the three materials, and
this difference is shown to explain the differences in calorimetric behavior, precipitation kinetics
and corrosion resistance.