Page 96 - eBook_Proceedings of the International Conference on Digital Manufacturing V2

Proceedings of the International Conference on Digital Manufacturing –
Volume 2

Gain Refiner Addition

A study examined the effect of grain refines, especially AlTiB, on
the microstructural evolution of Al-Si alloys during SSMP. The
primary objective was to promote the development of fine,
spherical α-Al particles, which are essential for enhancing flow
characteristics and mechanical performance in semi-solid metal
applications (Nafisi, Szpunar, Vali & Ghomashchi, 2007). The
material used was A356 alloy with varying Ti and B content via
5/1TiBAl master alloy. The material was processed by
conventional casting (graphite cups) and SSMP via Swirled
Enthalpy Equilibration Device (SEED) technology.

Thermal analysis, optical microscopy, EBSD, and image
analysis were particularly conducted. Findings show grain refiners
increase nucleation temperature by 5 °C (Figure ) and
solidification range for α-Al widens (6 °C), aiding globule
formation, smaller grain size, and improved sphericity. EBSD and
image analysis confirm more uniform and globular
microstructures in refined samples (Figure ) (Nafisi, Szpunar,
Vali & Ghomashchi, 2007).

a) b)

Figure 33: Microstructural changes resulted from grain refinement:
(a) untreated sample without grain refinement addition, (b) with
1300 ppm Ti and 210 ppm B addition (Nafisi, Szpunar, Vali &
Ghomashchi, 2007).

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