High strength and fatigue properties of Mg-Zn-Ca alloys after severe plastic deformation

Abstract

Magnesium alloys are the lightest metallic structural materials with an outstanding specific strength. This makes them appealing for a wide range of applications in "green" transportation where weight saving is of major concern. Another emerging application area for modern Mg-based alloys is in the biomedical domain where they are considered as bioabsorbable temporary implants, and where the worldwide market is expanding particularly rapidly in parallel with the surging research. Requirements for mechanical properties-strength, ductility and fatigue resistance-of implants in orthopaedics are stringent. Therefore, a broad variety of processing routes have been proposed in the past decade to tailor the microstructure in order to optimize the properties. In the present brief communication, we demonstrate that using a hybrid deformation processing schedule involving warm equal-channel angular pressing (ECAP) on the first stage and cold rotary swaging on the second dramatically improves the tensile and fatigue properties of the magnesium alloy ZX40. Due to a combined effect of significant grain refinement and dislocation storage after rotary swaging, the ultimate tensile strength and the conventional fatigue limit achieved very high values (for this class of alloys) of 380 MPa and 115 MPa, respectively. Preliminary results of the microstructural investigations are discussed briefly.

Regulation of corrosion damage of magnesium alloys through the use of vacuum zirconium coatings

“…Эта проблема сейчас успешно решается за счет использования комплексной обработки, включающей такие передовые методы интенсивной пластической деформации, как изотермическая прокатка, ротационная ковка, всесторонняя изотермическая ковка, равноканальное угловое прессование и др. [5]. Однако вторая проблема, связанная с невысокими коррозионно-усталостными свойствами магниевых сплавов, до сих пор остается нерешенной.…”

Developing trends in Mg alloys for biomedical implant applications

“…Additionally, excessive amounts of Mg2Ca reduces ductility and renders the alloy susceptible to localized degradation. Nevertheless, this phase reportedly does not form beyond a Zn/Ca atomic ratio of ~ 1.3 [16], [17], but was detected in an MZC alloy with 1.82 Zn/Ca ratio [10]. The nobler Ca2Mg6Zn3 phase on the other hand can act as a temporary barrier to localized corrosion [10].…”

“…A ten-fold grain size reduction was achieved from 220m to ~ 20 -30 m. Post ECAP rotary swaging successfully increased the ultimate tensile strength of the alloy from 245 to 381 MPa, however this resulted in a reduction in ductility from about 28 -5 % elongation [16].…”

Severe Plastic Deformation of Mg–Zn–Zr–Ce Alloys: Advancing Corrosion Resistance and Mechanical Strength for Medical Applications

“…Furthermore, study [36] showed that rolling followed by ECAP can increase the mechanical strength, ductility, and corrosion resistance of pure magnesium. In similar research [37], it has been demonstrated that a combination of ECAP and rotary forging in the magnesium alloy Mg-Zn-Ca (ZX40) led to significant grain refinement and accumulation of dislocations. This, in turn, resulted in increased tensile strength and fatigue limit values of 380 MPa and 115 MPa, respectively.…”