Precipitation hardening and microstructures of rapidly solidified Mg−Zn−Ca−X alloys

Abstract

Two quaternary magnesium alloys based on ternary Mg-5wt.%Zn-4wt.%Ca containing either Co(2wt.%) or Zr(0.5wt.%) were rapidly solidified using melt spinning. The nano-scale second phase distribution and thermal stability were studied using TEM, STEM and EDS system. Microhardness measurements conducted in the aged condition have identified that the Mg-Ca-Zn-Co alloy presented a peak value at 150 o C followed by a hardness decrease. The Mg-Ca-Zn-Co alloy showed refined quaternary precipitates distributed along the cell boundary and a refined grain structure, yielding higher hardness values than the Mg-Ca-Zn-Zr alloy at all aging temperatures.

Production and Precipitation Hardening of Mg-Ca-Zn-Co Alloy for Tissue Engineering

“…Mg shows poorer corrosion resistance in Clcontaining environments. As a result, Mg alloys could be developed as a biodegradable metal, with their fast corrosion rate in physiologic environment [1][2][3][4][5][6][7].…”

“…For these alloys, Al, Mn, Zr elements are employed to improve mechanical and corrosion properties. However, these products result in negative effects on humans [2][3][4][5][6].…”

“…Also, since maximum solubility of Zn in Mg is 8.4 wt. %, a considerable amount of Zn can be retained in a solid solution in Mg [3][4][5]. Mg-Zn alloys offer constant degradation rate owing to homogeneous microstructure.…”

“…Ca is an element in refining the microstructure and precipitates in Mg alloys, and in improving strength and corrosion resistance. Formation of a calcium-phosphate layer was observed during immersion in simulated body fluid beneficial on cell adhesion and corrosion protection [3][4][5]. Mg-Zn is a precipitation hardenable alloy, in which solubility of Zn in the Mg decreases with increasing temperature.…”

“…In this study, the Mg-Ca-Zn-Co alloy was produced for biomedical applications by the powder metallurgy method. Although cast Mg-Ca-Zn/Mg-Ca-Zn-Co alloys were studied [3][4][5], studies on powder metallurgy Mg-Ca-Zn-Co alloy are limited. Corrosion behavior of the specimens was examined in a simulated body fluid.…”