and effective element that enhances various properties of Mg alloys. It
was found that small amount of Ca addition increases the non-
flammability and corrosion resistance of Mg alloys , but a larger addition
above 1% decreases the strength and elongation of Mg–Ca binary
alloy . Upon addition of Ca in Mg–Al alloys, Al2Ca phase is formed
by reducing the Mg17Al12 eutectic phase which has a low melting
point. However, a major problem with calcium addition is that the
castability is largely degraded and ambient-temperature mechanical
properties are decreased . In order to overcome these disadvantages,
the liquid forging and extrusion processes were explored and
analysed in this paper.
Liquid forging (LF) process is also known as direct squeeze casting,
which is a combination of casting and forging where the molten metal
is solidified under high squeezing pressure. This changes the melting
point, heat transfer and solidification rate, which would optimise the
microstructure and reduce the gas and shrinkage porosities [10,12,13].
As a result, the liquid forged components usually exhibit better mechanical
properties and casting soundness compared to the conventional
casting methods. Goh et al studied the liquid forging parameters for
AZ91–Ca alloy and found an optimised setup for this process . As
the mechanical properties degrade with increasing calcium percentages,
the extrusion process was introduced in the current study to compensate
for this disadvantage. Hot extrusion significantly modifies the
microstructure and rearranges the secondary phase in Mg–Al alloys