Abstract
In the present research, a Mg–4Zn–1.2Y–0.8Nd (wt.%) alloy was heat treated and hot extruded with different passes. XRD, SEM, TEM and tensile testing were employed to characterize the microstructure evolution and mechanical properties. The results exhibited that the semi-continuously distributed W-Mg3Zn3Y2 phases formed the skeleton structure which separated the α-Mg matrix into a dual-size grain structure. In addition, the Mg24Y5, Mg41Nd5 and Y2O3 phase was also observed in the heat-treated alloy. Moreover, it was found that the Mg24Y5 phase had an orientation relationship with the α-Mg matrix of α[111]Mg24Y5//[0001]α-Mg and α(101¯)Mg24Y5//(101¯0)α-Mg, and the Mg41Nd5 phase had an orientation relationship with the α-Mg matrix of α[001]Mg41Nd5//[0001]α-Mg. The one-pass hot extrusion segmented the secondary phases into small ones and refined the α-Mg matrix. Due to the partly recrystallization and crystal orientation difference, the coarse elongated grain surrounded by fine recrystallized grain and secondary phase was the main feature of the one-pass hot extruded alloy. Furthermore, the secondary phases exhibited the linear distribution along the direction of hot extrusion. The two-pass hot extrusion refined the secondary phase and matrix further, which produced the ultrafine α-Mg matrix with uniform grain size and a well redistributed secondary phase. Due to the microstructure optimization by the multi-pass hot extrusion, the ductility and strength of the Mg–Zn–Y–Nd alloy were well improved, especially the two-pass hot extruded alloy which was significant improved in ductility and strength simultaneously.
Highlights
Mg-based alloys have attracted much attention as one of most promising candidates for biomedical implants due to their high specific strength, low elastic modulus, relatively good biocompatibility and bio-absorbability [1,2,3]
The study of Němec et al [6] demonstrated that the Mg alloy with an appropriate Zn addition would obtain better mechanical properties and the Mg–12Zn alloy prepared by equal-channel angular pressing possessed the best ductility and strength
The secondary phase could be divided into two kinds
Summary
Mg-based alloys have attracted much attention as one of most promising candidates for biomedical implants due to their high specific strength, low elastic modulus, relatively good biocompatibility and bio-absorbability [1,2,3]. The relative low ductility and strength of Mg-based alloys have severely impeded their medical applications. It is necessary to enhance the mechanical properties of the Mg-based alloys before their application. According to the previous research [4,5], the Zn doped Mg-based alloy has been considered the most potential candidate for biomedical implants, because of its relatively good balance between biocompatibility and mechanical properties. The study of Zn addition in Mg–Y–Nd alloy revealed that propriate Zn content could improve the strength and ductility simultaneously when its addition is less than
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