Page 87 - eBook_Proceedings of the International Conference on Digital Manufacturing V2

Fabrication and Characterization of a Low-Cost Piezoelectric using Rochelle
Salt for Energy Harvesting and Sensor Applications

Figure presents the fundamentals concept of thixoforming,
wherein a solid metal billet is reheated to a semi-solid state and
subsequently injected into a mould. Meanwhile, rheocasting
involves directly casting the metal into a mould from the semi-
solid state, often using electromagnetic stirring to achieve the
desired slurry consistency (Alshekhly, Omar, Salleh & Alhawari,
2014; Ji, Wang & Dong, 2022).

SSMP differs from standard methods, like casting and forging.
While both casting and forging use solid materials, forging can
also involve metal slurries, which are made of a liquid matrix and
small, non-dendritic solid particles. Casting is generally cheaper,
but forgings are mechanically stronger due to their structural
integrity. SSMP is a middle ground, offering better defect
management and properties than casting. SSMP components are
often free from shrinkage, gas porosities, segregation, and surface
defects, which improve processes like heat treatment, welding,
and mechanical tasks (Mohammed, Omar, Salleh, Alhawari &
Kapranos, 2013; Kim, Kim & Kang, 2005; Winklhofer, 2019;
Flemings, Riek & Young, 1976).

Figure 30 shows two microstructures of metallic materials,
likely alloys, observed under a microscope. The microstructure on
the left (a) exhibits a dendritic structure, characterised by
branched, tree-like crystals. This type of structure typically forms
during solidification when the cooling rate is relatively slow,
allowing crystals to grow preferentially along certain
crystallographic directions. The microstructure on (b) shows a
more globular or spheroidal structure, where the crystals are more
rounded and less branched (Ji, Wang & Dong, 2022). This type of
structure can be achieved through various processing techniques,
such as SSMP or the addition of grain refiners, which promote
nucleation and limit dendritic growth. The scale bar is in the
bottom right corner of each image, indicates a length of 100 μm,
providing a sense of the microstructural scale.

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