ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
This paper addresses the effect of microstructure on the formability of aluminium alloysof interest for automotive sheet applications. The bulk of this work has been on the alloy AA5754 –both conventional DC cast alloys and continuous cast alloys made by twin belt casting. It is knownthat alloys such as these contain Fe as a tramp impurity which results in Fe-based intermetallicparticles distributed through microstructure as isolated particles and in stringers aligned along therolling direction. It is thought that these particles are the cause, both of the reduced ductility that isobserved as the Fe level rises, and the relatively poor formability of strip cast alloys, as comparedwith those made by DC cast. Conventional wisdom suggests that the reduction of ductility is due tothe effect of particles as nucleating sites for damage. However, most studies show that thesematerials are resistant to damage until just before fracture. We now believe that effect is actuallyrelated to the development of shear bands in these materials. We present experimental data whichsupports this conclusion. We then show how the FE models we have developed demonstrate therole of shear instability on fracture and the role played by hard particles. We show how a unit cellapproach can be used to incorporate the effect of particle density and morphology on shearlocalization in a way that includes statistical variability due to microstructural heterogeneity. Thisleads to a set of constitutive equations in which the parameters are distributed from one region toanother. These are then fed into a macroscopic FE model at the level of the specimen or thecomponent in order to determine the effect of microstructural variability on shear instability andductility
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/13/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.519-521.183.pdf
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