Prediction of compressive strength of biodegradable Mg-Zn/HA composite via response surface methodology and its biodegradation

Abstract

This work aimed to fabricate magnesium zinc/hydroxyapatite (Mg-Zn/HA) composite via powder metallurgy method and to develop a mathematical model to predict the compressive strength of the composite using response surface methodology method. The effect of various mechanical milling parameters, milling speed (200-300 r/min), ball-to-powder weight ratio (5-12.5) and HA content (2.6-10 wt%) on the compressive strength of Mg-Zn/HA composite was investigated. The model shows that high compressive strength of Mg-Zn/HA composite was achieved when the powders were prepared with high milling speed and ball-topowder weight ratio and low HA content. The mathematical model was adequate with error percentage lower than 3.4%. The microstructure of Mg-Zn/HA composite with different process parameters revealed that fine microstructure was observed at high milling speed and ball-to-powder weight ratio while agglomeration of HA was found in composite with 10 wt% HA. The agglomeration of HA led to degradation of interfacial bonding strength between matrix and reinforcement phases and hence decreased the overall compressive strength of Mg-Zn/HA composite. Biodegradation test revealed that sample with higher HA content had more weight gain and there was more formation of hydroxyapatite. Mg-Zn/HA composite with 8 wt% HA was found to be the best candidate for implant application because it had considerable compressive strength and good biodegradation properties. � 2016 The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg.