High-precision isothermal dilatometry as tool for quantitative analysis of precipitation kinetics: case study of dilute Al alloy

Abstract

An in-depth case study of precipitation kinetics for alloys is presented utilizing recent progress in high-precision isothermal dilatometry by measuring relative length changes down to the range of 10 À5 and covering large timescales exceeding 10 5 s. Using a dilute Al-Mg-Si alloy as model system, the different phases that form during isothermal heat treatment could quantitatively be analyzed both with respect to the absolute amount of precipitates and with respect to the underlying kinetics. Owing to the distinct length change features upon multi-step precipitation processes, the formation of the metastable b 00 -and b 0 -phases can unambigously be detected and furthermore can specifically be distinguished and resolved. From the reaction rate analysis of the precipitationinduced relative length change, that was isothermally measured for temperatures between 170 C and 260 C, the evolution with time of the atomic fraction of both the b 00 -and the b 0 -phase was determined. The results were also used to construct the isothermal time-temperature-precipitation diagrams which are important for technologically relevant processes.

Precipitation kinetics in metallic alloys: Experiments and modeling

“…However, below a certain size (around 1 nm), precipitates do have a significant impact on resistivity, and during the early stages of atomic clustering, the precipitation kinetics can be linked with the resistivity increase [53]. High sensitivity in-situ dilatometry can also provide information on the precipitation kinetics [54].…”

Microscopic Aspects of Artificial Ageing in Al-Mg-Si Alloys

“…As the precipitation sequence involves a transition from early GP zones to β" and/or β', the degree of lattice mismatch and lack of coherency increases in this order. β' formation is associated with a global shrinkage of a sample due to the removal of Mg from the matrix that overcompensates the expansion of β' [49,50] and tensile stresses around individual β' precipitates build up (other than for β" where the stresses are compressive). This facilitates the formation of open volume.…”

A Unique Quenching and Deformation Dilatometer for Combined In Situ Neutron Diffraction Analysis of Engineering Materials

“…[6] A detailed study of precipitation kinetics of a dilute Al-Mg-Si under isothermal dilatometry has revealed the evolution of the atomic fraction of two precipitates. [7] The result was used to construct the isothermal TTP diagrams which can be incorporated into technologically relevant processes. Using a DOI: 10.1002/adem.202100163 A modified quenching and deformation dilatometer (TA instruments DIL 805A/ D/T) is now in operation at the Heinz Maier-Leibnitz Zentrum (MLZ, Germany) neutron center.…”

“…[ 6 ] A detailed study of precipitation kinetics of a dilute Al–Mg–Si under isothermal dilatometry has revealed the evolution of the atomic fraction of two precipitates. [ 7 ] The result was used to construct the isothermal TTP diagrams which can be incorporated into technologically relevant processes. Using a quenching dilatometer at extraordinarily long isothermal aging times, the temperature–time–transformation (TTT) curves have been obtained for both a primary precipitation and an eutectoid decomposition in a Cu–Al–Ni shape memory alloy.…”