PSI - Issue 23

Jaroslav Čapek et al. / Procedia Structural Integrity 23 (2019) 3 –8 Jaroslav Čapek et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction

Recently, zinc-based materials have been extensively studied as candidates for the fabrication of various cardiovascular and orthopedic implants Niu, et al. (2016), Bowen, et al. (2013), Mostaed, et al. (2016). In order to enhance the mechanical, corrosion and biological properties, zinc is often alloyed by others elements Niu, et al. (2016), Mostaed, et al. (2016), Murni, et al. (2015), Li, et al. (2015a). For the orthopedic applications, the elements of the second group of the periodic table are considered as the most suitable, because those elements occur in bone tissues and are necessary for a good bone growth Liu, et al. (2016), Vojtěch, et al. (20 11), Li, et al. (2015b), Li, et al. (2015a). The main disadvantage of those elements is that they are insoluble in zinc and form intermetallic phases which can significantly deteriorate the ductility Vojtěch, et al. (2011) , K ubásek, et al. (2016) .

Nomenclature wt.%

Weight % AAS Atomic absorption spectrometry XRD X-ray diffraction LM Light microscopy SEM Scanning electron microscopy EDX Electron dispersive spectroscopy TEM Transmission electron microscopy CYS Compressive yield strength HV1 Vickers hardness, load 1 kg

2. Materials and Methods

2.1. Material preparation

The alloys were prepared by the melting of appropriate amounts of pure elements (99.999 wt.% Zn, 99.95 wt.% Mg, 99 wt.% Ca and 99 wt.% Sr) in an MgO crucible at 520 °C under a protective Ar atmosphere. After homogenization, the melt was poured into a steel mold with a diameter of 50 mm and length of 400 mm. A part of the ingots was annealed at 350 °C for various time periods (4, 8, 16 and 24 h) in a muffle furnace and subsequently quenched in water.

2.2. Material characterization

The exact chemical composition of the prepared alloys was determined by atomic absorption spectrometry (AAS) using an atomic absorption spectrometer GBC 932Plus. For the analysis, the materials were dissolved in nitric acid and diluted by deionized water. The phase composition of the studied materials was measured by X-ray diffraction (XRD) using a PANalytical X’Pert PRO powder diffractometer with a Co anode. Metallographic cross-sections were prepared in a standard way and the microstructure of the samples was observed using a Zeiss Observer D1m light metallographic microscope (LM) and a TESCAN Vega 3 LMU scanning electron microscope (SEM) equipped with an Oxford Instruments INCA 350 EDX analyzer (EDX). Thin foils transparent for electrons were prepared by grinding and subsequent ion milling. Those foils were examined by a transmission electron microscope FEI Tecnai F20 X-Twin (TEM). From the point of view of mechanical properties, the microhardness HV1 was measured using a Struers Duramin2 microhardness tester and compressive properties were measured on 4x4x6 mm cuboids using an Instron 5882 universal loading machine at a strain rate of 10 -3 s -1 .