Quantitative in situ X-ray powder diffraction studies of phase transformations in Al alloys

In situ synchrotron X-ray powder diffraction is a powerful tool for
studying phase transformations in engineering alloys, which, when
combined with Rietveld-based data analysis methods, allows the phase
composition of an alloy to be quantified as a function of variables such
as time or temperature. This approach has recently been used to gain
new insights into phase transitions within two Al alloy systems. In
situ isothermal aging experiments have confirmed that the
decomposition sequence in Al-Cu-Mg alloys involves a metastable
variant of the S (Al2CuMg) phase, and enabled the kinetics of the
transformation between metastable and equilibrium S phases to be
investigated. In addition, continuous heating experiments have been
used to investigate crystallisation pathways in Al-Ni-Y metallic glasses,
and have revealed that the mechanism switches from a two stage
process involving α-Al, to a three stage process involving Al9Ni2 and a
transient excess of Al3Ni, with increasing Ni concentration.