Development of an extruded Mg–Zn–Ca-based alloy: new insight on the role of Mn addition in precipitation

Abstract

An age hardenable Mg–2.5Zn–0.1Ca–0.1Mn (mol%) alloy has been developed. The extruded sample followed by a T5 treatment reveals 290 and 269 MPa of tensile and compressive proof stresses, respectively. Elongation to failure in tension and compression were 22 and 13%, respectively. The stresses were comparable to those in an as-extruded Mg–2.4Zn–0.1Ca–0.1Zr (mol%) and a T6-treated 6063 Al alloys. and phases appeared in the extruded samples, and these precipitates enhanced the proof stresses. Mn was detected in the fine precipitates, which may lead to dense distribution of the fine precipitations. The precipitates pinned the grain growth of dynamic recrystallisation and, therefore, fine grain size could be obtained. The fine precipitates suppressed the occurrence of tensile twinning in unrecrystallised regions, resulting in a high value associated with yield anisotropy.

Keywords:

• Mg alloy
• mechanical property
• precipitate
• TEM, Mn

Acknowledgements

This work was in part supported by a Grant-in-Aid for Scientific Research (A), 17206076, 2007, Grant-in-Aid for Young Scientists (B), 23760691, 2011 and Sankyo Tateyama Aluminum Co. Ltd. S. Hanaki and T. Takahashi of Sankyo-Material, Inc., Japan and R. Yoshimasu of Nagaoka University of Technology, Japan are thanked for their fruitful comments and support.