The Effect of Selective Laser Melting Conditions on the Structure of an Alnico Alloy

Additively Manufactured Alnico Permanent Magnet Materials—A Review

“…A similar scenario was observed when Alnico-8 was processed via LPBF with a heated stage at 800 °C, with evident porosity [34,59]. In contrast, Shakirov et al demonstrated that meticulous optimization of process parameters, specifically employing settings at 190 W and 700 mm/s, resulted in Alnico-5 samples with reduced porosity and cracks [57]. Remarkably, Alnico-8 samples crafted using the L-DED technique exhibited a defect-free profile with a geometrical density of 7.25 g/cc [4].…”

“…A study conducted by Fuhui et al successfully generated Alnico-5 samples through LPBF with a heated stage at 160 °C, achieving material density in excess of the 98% threshold [55,56]. However, despite these noteworthy density enhancements, the samples displayed surface defects, notably porosity and cracks in LPBF-processed Alnico-5 [56,57]. A similar scenario was observed when Alnico-8 was processed via LPBF with a heated stage at 800 °C, with evident porosity [34,59].…”

“…Understanding and controlling all these thermokinetics and composition-related parameters are therefore essential for tailoring microstructures to achieve specific material characteristics and performance attributes. Although the combined effects of all these parameters are very complex, several researchers have attempted to break down such complexity by approaching it in the most simplistic manner by separating the effect of each of these parameters [57,66,73,[75][76][77][78]. Majority of these efforts have emphasized the effect of solidification range on grain morphologies.…”

“…This explains why both Alnico-8H and Alnico-8H (with reduced Co content), when fabricated using the L-DED process, exhibited a consistent equiaxed microstructure across the entirety of the sample. Meanwhile, Alnico-5, whose solidification range is around 24 °C (obtained from the CALPHAD database), developed an elongated grain morphology when processed through LPBF [57]. The large thermal gradient and localized melt pool characteristics of the LPBF process frequently result in a substantial anisotropic, columnar grain morphology [47,79].…”

“…Figure 15. Schematic of quasi-binary phase diagram of Alnico-8 with (α 1 ) and (α 2 ) [5].Table 6.The phases observed in Alnico samples fabricated through various processes for both the as-processed and post-heat treatment conditions[1,4,34,[54][55][56][57][58][59]91].ProcessingAs Processed (Microstructure)…”