Mechanical performance of lamellar structured composites of magnesium–calcium deficient hydroxyapatite produced by ball milling and sintering for biomedical applications

Abstract

In the current study, magnesium (Mg) based micro-lamellar composites were produced by using calcium deficient hydroxyapatite (CDHA) as the reinforcing phase in different fractions (1, 2 and 4% by weight) by ball milling and vacuum sintering. Ball milling resulted in development of thin Mg flakes. Microstructural studies after sintering clearly revealed the developed Mg flakes with oxide CDHA phases at the lamellar interfaces. X-ray diffraction studies demonstrated the basal (002) dominated texture in the composites. Higher hardness (91.9 ± 3.7 HV0.1) was measured for the composite due to the lamellar structure. Compression tests revealed higher strength (308.4 ± 5.3 MPa) for the composite with the increased CDHA content compared with ball milled and sintered Mg with 0% CDHA (248.5 ± 6.8 MPa) with marginal loss in % of elongation. Fracture toughness measurements carried out by indentation method exhibited increased fracture toughness up to 2% CDHA and then deterioration with 4% CDHA due to the increased brittleness. Cell viability tests carried out by using African Green Monkey kidney (VERO) cells showed excellent viability for all the composites which demonstrated non-toxicity. The results suggest the potential of ball milling and sintering in producing micro-lamellar Mg-CDHA composites for degradable bone implant applications with enhanced mechanical properties and suggest to limit CDHA content to lower fraction (up to 2%) to achieve better fracture toughness.