Processing by high-pressure torsion (HPT) leads to the formation of an ultrafine-grained (UFG) structure in the biodegradable  Mg-1%Zn-0.13%Ca magnesium alloy with an average grain size of 150 nm, containing two types of particles: Mg2Ca with a size of 20 nm and Ca2Mg6Zn3 with a size reaching 1 µm. As a result of heat treatment of the UFG Mg alloy at a temperature of  200оС, ductile samples have been produced, having an increased ultimate tensile  strength of 270 MPa as compared with the initial coarse-grained sate (140 MPa). Biodegradable Mg alloys with a UFG structure are of great interest as the materials for making medical implants that degrade in human body a few months after surgery. 

 Typical structures of the UFG Mg-1%Zn-0.13%Ca magnesium alloy: (а) bright-field image of the structure with an average grain size of 150 

nm; (b) dark-field image of the Mg2 Ca particles with a size of 20 nm

Properties of the ultrafine-grained Mg-1%Zn-0.13%Ca magnesium alloy:

State and billet dimensions Ultimate tensile strength,MPa Yield stress, MPa Elongation to failure, %
UFG, diameter 20 mm, thickness 1 mm 270 235 9
Coarse-grained 140 35 14

Main publications:

1.  O.  Kulyasova, R.  Islamgaliev, Y.  Zhao, R.  Valiev. Microstructure and mechanical properties of ultrafine-grained Mg-Zn-Ca alloy. JOP Conf. Ser.: Mater. Sci. Eng. 63 (2014) 012142.
2.  J.  Cizek, I.  Procházka, B.  Smola, I.  Stulíková, V.  Očenášek, R.K.  Islamgaliev, O.B.  Kulyasova. Microstructure development and ductility of ultrafine-grained Mg-Gd alloy prepared by high pressure torsion. Materials Science Forum. 633-634 (2010) 353-364.
3.  O.  Kulyasova, R.K.  Islamgaliev, B.  Mingler, M.  Zehetbauer.  Microstructure and fatigue properties of the ultrafine-grained AM60 magnesium alloy processed by ECAP. Mat. Sci. Eng. A503 (2009) 176-180