Quantification of volume fraction of precipitates in an aged Al-1.0 mass%Mg2Si alloy

Abstract

An Al-1.0 mass%Mg2Si alloy was aged at 473 K for 36 ks. Using the same sample, resistivity (ρ) measurements, tensile tests and TEM observations were carried out. The volume fraction (Vfρ) of precipitates was estimated from the decrement in resistivity due to aging. Length (λ), diameter (d) and number density (NP) per unit volume of the needle-shaped precipitates were measured on TEM micrographs. Perhaps because of initiation of overaging in the present aging condition, λ and NP showed a wide scatter and differed significantly in two equivalent samples, independently heat treated and tested. However, proof stress and Vfρ in the two runs well coincided with each other and the volume fraction estimated from TEM micrographs (VfTEM) matched within a factor of 2 for the two runs.