Microstructural characterization and optimization of the ZnMg0.8(CaO)0.26 alloy processed by ball milling and subsequent extrusion

Abstract

Zinc is one of the most promising elements for the preparation of biodegradable metallic implants. Despite low mechanical performance for load-bearing applications, the degradation characteristics of pure zinc belong to the best from all significant biodegradable metals (Zn, Mg, Fe). The enhancement of the mechanical properties is often reached using various methods of material processing, leading to grain refinement and subsequent enhancement of the mechanical properties. In this study, the microstructure, phase composition and the possible mechanisms of intermetallic phase formation in the ZnMgCaO alloy prepared by high energy ball milling and consolidated by extrusion were studied. Formation of the Mg2Zn11, MgZn2 and CaZn13 phases during the material processing was confirmed. The creation of the phases was, with high probability, significantly affected by the magnitudes of individual components of internal energy. The increment of the internal energy led to the formation of stable Mg2Zn11 phase as well as to CaZn13 formation. Based on our results and the characterization of the microstructure, the most suitable conditions for the preparation of a ZnMgCaO alloy were found.

Microstructural and Mechanical Characterization of Newly Developed Zn-Mg-CaO Composite

“…The only exception was the group of samples milled at 300 RPM, where the interrow distance was similar at both milling times. The composition of the intermetallic phases and their quantitative analysis were already published in our previous publication concerning these materials [ 39 ]. Briefly, the presence of Mg 2 Zn 11 , MgZn 2 , and CaZn 13 phases was found in the materials with changes in mutual ratios.…”

“…The mutual distance between individual rows of intermetallic phases ( Figure 2 ) was connected predominantly with the milling conditions. As was described in our previous publication concerning these alloys [ 39 ], the particles of zinc were deformed with different intensities depending on milling conditions. Generally, two important factors played a significant role, namely, the formation of the intermetallic phases on the surface of the Zn particles and the flattening of the Zn particles during the milling process.…”

“…To minimize the influence of the environment, the processes connected with the mixture manipulation were performed in the glovebox under an argon atmosphere (filling of the milling jar, pressing, etc.). The details of preparation of powder mixture are described in our previous work [ 39 ]. The conditions of the milling process are summarized in Table 1 .…”

Advanced Zinc–Magnesium Alloys Prepared by Mechanical Alloying and Spark Plasma Sintering

“…During the mechanical alloying, the RPM parameter affects the energy that is generated when two grinding balls collide. This energy can be calculated for E-max mills according to their parameters from the equations for the deformation energy for the collision of grinding balls ( E C )—(1) and for angular speed ( ω D )—(2) [ 37 ]. …”

“…In these equations, R d specifies the distance between the middle of the disk to the second one (0.11 m), is the density of the material of the milling balls (5730 g/cm 3 ), E corresponds to the modulus of elasticity of the material of the milling balls (1.75·10 11 Pa), d b is the diameter of the milling balls (0.01 m), reflects the surface density of the powder that was stuck to the milling balls (approximately 0.1 kg/m 2 ) and RPM corresponds to the rotation of the milling vessel [ 37 ]. The design of the high energy Retch E-max mills is shown in the diagram ( Figure 2 ) and the calculated results are presented in Table 2 .…”