Effect of anhydrous borax addition and manufacturing method on aluminium-based in-situ formed metal matrix composites

This study aims to fabricate cost-effective aluminium matrix composites reinforced with in situ formed aluminium diboride (AlB2) by incorporating 5 vol% micronised anhydrous borax (AHB) into the ET & Idot;AL 150 (EA150) aluminium alloy. Two manufacturing methods were compared: melting AHB and EA150 together in a single crucible (Method 1) and melting them separately before mixing them in a single crucible (Method 2). The influence of these methods on the physical, mechanical, and tribological properties of the composites was evaluated. Non-pressure casting was performed at 1000 degrees C with rapid water-bath cooling to promote AlB2 formation and suppress the brittle AlB12 phase. Characterisation included density, Brinell hardness, pin-on-disc wear, three-point bending, and microstructural analysis. The results show that Method 2 effectively reduced slag and inclusions, improved Brinell hardness (up to 16.33%) and flexural yield stress (up to 11.10%), and a reduced coefficient of friction (by 5%) compared to pure EA150. These findings demonstrate that the manufacturing method critically controls the composite quality and performance, validating untreated micronised borax as a cost-effective boron source for AlB2-reinforced aluminium composites suitable for structural and automotive applications. Cette & eacute;tude vise & agrave; fabriquer des composites & agrave; matrice d'aluminium & eacute;conomiques, renforc & eacute;s par du diborure d'aluminium (AlB2) form & eacute; in-situ, en incorporant 5% en volume de borax anhydre micronis & eacute; (AHB) dans l'alliage d'aluminium ETIAL 150 (EA150). On a compar & eacute; deux m & eacute;thodes de fabrication: la fusion simultan & eacute;e de l'AHB et de l'EA150 dans un creuset unique (M & eacute;thode 1) et leur fusion s & eacute;par & eacute;e avant de les m & eacute;langer dans un creuset unique (M & eacute;thode 2). On a & eacute;valu & eacute; l'influence de ces m & eacute;thodes sur les propri & eacute;t & eacute;s physiques, m & eacute;caniques et tribologiques de ces composites. On a r & eacute;alis & eacute; un moulage sans pression & agrave; 1000 degrees C avec refroidissement rapide au bain d'eau afin de favoriser la formation d'AlB2 et de supprimer la phase fragile AlB12. La caract & eacute;risation comprenait la densit & eacute;, la duret & eacute; Brinell, l'usure par pointe-sur-disque, la flexion en trois points et l'analyse microstructurale. Les r & eacute;sultats montrent que la m & eacute;thode 2 r & eacute;duisait efficacement le laitier et les inclusions, am & eacute;liorait la duret & eacute; Brinell (jusqu'& agrave; 16.33%) et la limite d'& eacute;lasticit & eacute; en flexion (jusqu'& agrave; 11.10%), et r & eacute;duisait le coefficient de frottement (de 5%) par rapport & agrave; l'EA150 pur. Ces r & eacute;sultats d & eacute;montrent que la m & eacute;thode de fabrication influence de mani & egrave;re critique la qualit & eacute; et les performances du composite, validant le borax micronis & eacute; non trait & eacute; comme une source de bore & eacute;conomique pour les composites d'aluminium renforc & eacute;s par l'AlB2, adapt & eacute;s aux applications structurelles et automobiles.