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conferenceseries .com
November 13-15, 2017 | Las Vegas, USA
14th International Conference and Exhibition on
Materials Science and Engineering
RRJOMS | Volume 5 | Issue 7 | November, 2017
Accelerated corrosion test for exhaust gas recirculation exchangers
Anne-Gaëlle Villemiane1, Josselin Paturaud2, Armelle Danielou3, Jean-Yves Buffière2 and Damien Fabregue2
1Valeo THS France
2INSA Lyon, France
3Constellium Ing. C-Tec, France
Economic and environmental drivers are leading to exchanger weight reduction for automotive applications. The consequence is
a material downgauging and some critical conditions reached. One of the exchanger’s main failure modes is induced by transient
differential dilatations between the exchanger components. In this work, a detailed characterization of the cyclic damage mechanisms
in car heat exchangers has been undertaken in order to improve their reliability. The studied material is a very thin (<0.3 mm)
aluminum sheet composed of 3 layers (4XXX /3XXX/ 4XXX) (figure 1) compared to the same aluminium sheet made of 1 layer
(3XXX), brazed in similar conditions to those of real components. Fatigue tests at constant stress amplitude have been performed
at room temperature to show the influence of the clad in the fatigue resistance. Tensile properties between the clad alloy and the
unclad alloy are strictly identical. However, the Wölher curve shows a high fatigue resistance for the unclad material compared to
the cladded one. (Figure 2). Fractography analysis on the 3 layer alloy reveals that the crack initiation is intergranular on the clad
side and occurs on the specimen face because the clad is harder than the core which weakened the grain boundaries leading to
multifissuration initiation and propagation. Cracks stopped for about 50% of the fatigue life then there is a transgranular propagation
of the crack until failure. Concerning the unclad material, the elements Cu, Fe, Si, Mn and Ti are better distributed in the alloy
thickness leading to a less modified surface state and decreasing the site initiation number and therefore the multifissuration. Thanks
to microstructure, tomography and surface rupture analysis a fatigue damage mechanisms can be proposed, showing the residual clad
layer key influence on the crack initiation.
Biography
Anne-Gaëlle Villemiane is an expert in fatigue and fractography. She has been working for Valeo for 10 years and she is head of the Material Laboratory. She has worked
on 3 phDs specialising in fatigue and has written 8 publications on the topic applied on automotive problematic. She has obtained a phD in 2006 on the determination of
the niobium effect on the oxidation mechanisms of ternary titanium aluminides. This study was conducted from first seconds (20 s) to long term oxidation times (2000 h).
Anne-Gaëlle Villemiane et al., Res. Rev. J Mat. Sci. 2017, 5:7
DOI: 10.4172/2321-6212-C1-011