1. Optical microstructure of AZ80 alloy after heat treatment - Unetched
MS&T’08 Materials Science & technology Conference October 5-9 , 2008, Pittsburgh, Pennsylvania
Thermophysical Properties and Microstructural Analysis of AZ80 Magnesium Alloys Designed for Automotive Industry
Gabriela Popescu, Petru Moldovan, Dionezie Bojin, Simona Bejan, Mihai Manea University “Politehnica” of Bucharest, Materials Science and Engineering Department, Romania
Abstract
Introduction
Magnesium alloys are considered to be the lightest metals available and are of major interest in automotive industry due to their advantage in component’s weight reducing.
Thermo-physical properties of AZ80 magnesium alloy were determined: the variation of diffusivity (α), the variation of thermal expansion coefficient and its mean value in the temperature interval 60 – 400 0C. Knowing the density of AZ80 and using the obtained results it can be determined the thermal conductivity (λ) of the alloy.
The microstructural analysis was determined by OM, SEM and EDS microanalysis for two bars of AZ80 alloy.
Thermal diffusivity is an important property, required for such purposes as design applications under transient heat flow conditions, determination of safe operating temperature, process control, and quality assurance.
The flash method is used to measure values of thermal diffusivity, α, of a wide range of solid materials. It is particularly advantageous because of simple specimen geometry, small specimen size requirements, rapidity of measurement and ease of handling, with a single apparatus, of materials having a wide range of thermal diffusivity values over a large temperature range.
Thermal diffusivity results, together with specific heat capacity (Cp) and density (ρ) values, can be used in many cases to derive thermal conductivity (λ), according to the relationship: xxxxxxxrelatia?????
Experimental results
(a)
(b)
Sample no.1 (P1), bar of φ = 28 mm in T5 state
Sample no.2 (P2), wire of φ = 5 mm in F state
Variation curve of thermal diffusivity with temperature for sample 1
a- test 1; b – test 2
Dependency curve for coefficient of thermal linear expansion to temperature
Optical microstructure of AZ80 alloy after heat treatment - Unetched
Untreated sample
Treated sample
Aged:1 80 0C – 18 h
Aged:1 80 0C –21 h
Aged:1 80 0C – 24 h
MgMnAl compound
Forged bar
Forged
Microstructures of transversal section P1 samples. Attack 4% nital / 20 sec
The microstructure details of sample P1
Conclusion
The microstructures were determined for two types of AZ80 extruded alloy bars with diameters of φ5mm and φ28mm sent by GKSS (Germany), from TIMMINCO Enterprise.
The study of the microstructures was done by Optical Microscopy (OM) and Spectral electron Microscopy SEM and EDS microanalysis.
For AZ80 alloy the study pointed out a series of fine precipitates in continuous rows shape or polyhedral particles, their chemical composition being identified by EDS analysis.
Acknowledgments
This work is supported by the FP 6 Program under Contract No (MagForge).
The authors would like to thank to the Coordinator of this project, Dr. W. Sillekens, TNO Nederland, for the financial support under the MagForge Project.