Constitutive and stochastic models to predict the effect of casting defects on the mechanical properties of High Pressure Die Cast AlSi9Cu3(Fe) alloys

Abstract

The effect of casting defects on mechanical
properties of a high-pressure die-cast
AlSi9Cu3(Fe) alloy is reported. A series of Ushaped
structural components are cast using
a combination of injection parameters and
pouring temperatures in order to generate
different types and amount of casting defects
throughout the casting. It has been found that
castings contain defects, primarily pores and
oxides, and that the presence and distribution
of these defects are highly sensitive to the
process conditions. Moreover, significant
variations of the defect distribution have,
however, been found in castings produced
under the same conditions, indicating the
stochastic nature of defects in die castings.
The tensile properties are affected by the
amount and distribution of defects and are
determined by the defect area fraction. The
influence of casting defects on mechanical
properties are investigated through a
theoretical verification based on constitutive
and stochastic models. The analytical
approach, based on the Ghosh constitutive
model of tension instability, correctly indicates
the trends of the experimental results, while
the Weibull statistics evidences how the scale
parameter and the Weibull modulus are
strongly affected by the casting conditions.
An integrated stochastic-analytical approach
is then proposed and it appears to be
applicable to describe the tensile properties in
terms of fractographic defects and cumulative
failure probability Pi.