Open Collections

Constitutive behaviour of aluminium alloy B206 : in the as-cast and artificially aged states

University of British Columbia

The constitutive behaviour of the aluminum foundry alloy B206 has been investigated in both the as-cast and artificially aged states by combining compression, tension, hardness and calorimetry testing. Aluminum alloy B206 is a recently-developed high-strength foundry alloy that has strong potential for use in automotive, aerospace and energy applications. The results of the compression tests, performed on as-cast material and conducted on a Gleeble 3500 thermo-mechanical simulator over a broad range of temperature (50-530⁰C) and strain rates (10-³ ₋ 1s-¹), were used to develop an inclusive constitutive plastic flow behaviour model. A new unified constitutive model was introduced that combines a Ludwik model for flow stress description at low temperatures (50-300⁰C) with a Zener-Hollomon model at high temperatures (300-530⁰C) while accounting for the strain rate dependency of the transition between these two models. The results of the tensile tests, performed on the artificially aged material (ageing performed over a temperature range of 150-250⁰C and a heating duration range of 1-24h), were combined with the calorimetry experiments to develop a model that predicts yield strength. To fit the experimental data into a linear-fit type model that states the yield strength as a linear summation of the effective parameters, temperature and time dependency were introduced through a microstructural variable, precipitation fraction. The precipitation kinetics of B206 were described by an Avrami model that utilized the experimental data acquired from non-isothermal calorimetry followed by an analysis based on the Kissinger method. The remaining material constants in the linear-fit model were found by fitting the model against the tensile test results explaining the yield strength evolution up to the peak-aged state. The model predictions were then qualitatively compared to the results of the hardness measurements, restating the fast precipitation kinetics of B206 at the temperature range used during artificial aging and predicted by the Avrami model. Together, the developed models of B206 in the as-cast and artificially aged states can be used as part of a Through-Process model to optimize the performance of castings made from this alloy.

Text

2015-08-19

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/54534

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/