Page 92 - eBook_Proceedings of the International Conference on Digital Manufacturing V2

Proceedings of the International Conference on Digital Manufacturing –
Volume 2

This structure gives the slurry thixotropic behaviour, meaning
its flow changes with shear and time (Ji, Wang & Dong, 2022;
Mohammed, Omar, Salleh, Alhawari & Kapranos, 2013;
Megalingam, Ahmad, Alang, Muhammad & Muduli, 2024; Fei,
Xu, Yao & Zhou, 2022). The formation of a globular
microstructure is essential for achieving thixotropic behaviour,
which can be controlled by adjusting the pouring temperature and
holding time (Tajudin, Ahmad, Alias, Razak & Alang, 2023;
Ahmad, Naher & Brabazon, 2014; Li, Wang, Li, Liu & Zhao,
2023; Hirt et al., 2006).

In SSMP, ferrous metals, like steel, and non-ferrous metals,
like aluminium and magnesium, show different thixotropic
behaviours. Ferrous metals initially become more fluid under
shear stress (shear thinning), but can thicken again over time
(shear thickening). Temperature, initial structure, and alloying
elements all affect this behaviour (Mohammed, Omar, Salleh,
Alhawari & Kapranos, 2013). Figure shows a steel sample with
rounded grains in a liquid phase, designed to support thixotropic
flow during forming.

Figure 32: Dendritic and globular structures in a semi-solid alloy,
along with a basic eutectic phase diagram for X210CrW12 steel
(Tajudin, Ahmad, Alias, Razak & Alang, 2023).

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