Effect of ultrasonic assisted sintering on mechanical properties and degradation behaviour of Mg15Nb3Zn1Ca biomaterial

Abstract

The present work investigates the effect of ultrasonic power (%) and the time of ultrasonic vibration on the sintered density and ultimate compressive strength (UCS) of Mg15Nb3Zn1Ca fabricated using ultrasonic assisted conventional sintering (UACS). The customized UACS setup was designed and manufactured to conduct the experimentations. A customized ultrasonic stepped horn assembly was used for providing vibrations to the sample during sintering. Further, to evaluate the efficacy of ultrasonic vibration parameters, the developed setup was used to sinter Mg15Nb3Zn1Ca composite material. The study unveiled an increased sintered density and UCS of the fabricated sample by the increase in ultrasonic power (%). Moreover, a decrease in sintered density and UCS was observed with an increase in the time of ultrasonic vibration beyond a certain limit. Samples sintered with the assistance of ultrasonic vibration at 100% ultrasonic power, and 20 min of ultrasonic vibration resulted in a sintered density of 1.928± 0.062 g·cm −3 and UCS of 234.9± 12.3 MPa. The obtained mechanical properties of the fabricated sample were comparable to the properties of cortical bone. The surface morphology and elemental compositions of samples fabricated using UACS declared a fair dispersion of reinforcement in the matrix containing merely the source elements. The results of corrosion test have showed that the assistance of ultrasonic vibration suppressed the degradation behaviour of the sintered sample after performing electrochemical study of samples using 3-electorde cell voltammetry. Mg15Nb3Zn1Ca fabricated using UACS showed a 50.18% and 9.08% of reduction in corrosion rate over conventionally sintered pure Mg and Mg15Nb3Zn1Ca respectively. In addition, electrochemical impedance spectroscopy (EIS) results indicated an enhanced corrosion resistance of the Mg15Nb3Zn1Ca composite material when fabricated at 100% of ultrasonic power with 20 min of vibration time. Apart from that, electrochemical equivalent circuits also resulted in good fitting of the experimental data obtained from EIS.