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Lecture

Strengthening and corrosion properties of a biodegradable Mg-Zn-Ca alloy ZX50 after processing by HPT and heat treatment

Thursday (27.09.2018)
18:15 - 18:30 S1/03 - 23
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This study investigates a biodegradable Mg-5Zn-0.3Ca alloy (ZX50) during HPT-processing and long-term heat treatments, the latter with respect to the evolution of intermetallic precipitates and vacancy clusters. These precipitates are to achieve both a strength increase and a decrease of corrosion rate, which is often found as being too high in this alloy type [1] to suggest it for use as biodegradable implant.

The thermomechanical procedure used in this work follows that of Orlov et al. [2] applied to Mg-Zn-Zr alloy ZK60. Both the precipitates as well as the vacancy clusters achieve strength increases; in case of the latter, the Zn atoms may act as potential trapping sites not only for HPT-induced dislocations but also for vacancies. So far, overall increases of strength of up to 250% were reached. Quantitative estimations show that the vacancy clusters contribute far more to the total strength increase than the precipitates. Furthermore a vacancy concentration of at most 10-5 can cause the hardness increase measured [3]; the experimental results, however, showed vacancy concentrations till to even 10-3 which means that a significant part of the HPT induced vacancies stays single and thus does not affect hardening.

The corrosion rate as well as the Young’s modulus remain unchanged during the processing history consisting of both HPT deformation as well as heat treatments, thus making this alloy a very attractive biodegradable material.

This work has been supported by projects J2-7157 of the Slovenian Research Agency ARRS, and I2815-N36 of the Austrian Science Fund FWF.


Reference:

[1] Hofstetter J., Becker M., Martinelli E., Weinberg A.M., Mingler B., Kilian H., Pogatscher S., Uggowitzer P.J., Löffler J.F. (2014) JOM, 66, 566–572

[2] Orlov D., Pelliccia X., Fang L., Bourgeois L., Kirby N., Nikulin A.Y., Ameyama K., Estrin Y. (2014) Acta Mater. 72, 110-124.

[3] H.O.K. Kirchner, Loop hardening of hexagonal metals, Z. Metallkd. 67 (1976) 525-532.

 

Speaker:
Andrea Ojdanic
University of Vienna
Additional Authors:
  • Prof. Dr. Erhard Schafler
    University of Vienna
  • Dr. Jelena Horky
    Austrian Institute of Technology
  • Dr. Bernhard Mingler
    Austrian Institute of Technology
  • Prof. Dr. Dmytro Orlov
    Lund University
  • Prof. Dr. Michael Zehetbauer
    University of Vienna