DEVELOPMENT OF BIODEGRADABLE MG-ZN-CA ALLOYS FOR BIOMEDICAL APPLICATIONS

In the present study, Mg-8at.%Zn- 1at.%Ca alloys were fabricated via T4 and T6 solid solution treatment technique for biomedical applications. The alloys were prepared at three different temperatures: 400 degrees C, 465 degrees C and 530 degrees C followed by water or liquid nitrogen quenching. The microstructure of Mg-Zn-Ca alloys was characterized using X-ray diffraction (XRD) analysis, optical and electron microscopes, and energy dispersive spectroscopy, respectively. The examination of mechanical properties was conducted on micro hardness tester. The following differences can be concluded from the results: In water quenched samples, the following three phases were identified from XRD pattern: alpha -Mg matrix, binary Mg2Zn3 and ternary Ca2Mg6Zn3, the secondary phases are more agglomerated. At higher solution treatment temperature, the secondary phases became more dissolved to the Mg-matrix which creates better homogenized material. Higher treatment temperatures cause grains to grow and to a limited extent, samples quenched in liquid nitrogen have smaller grains than those quenched in water. The sample heat treated at the temperature of 465 degrees C reaches a minimum hardness. While in liquid nitrogen quenched samples, the alloys consisted of four phases: alpha -Mg matrix, binary Mg2Zn3 and MgZn2 and ternary Ca2Mg6Zn3, the secondary phases are more distributed in a network form, at higher magnification, there are some secondary phases precipitated in rod/needle shape in the samples, the hardness of the samples decreases with the temperature increases.