Effect of processing strain rate and temperature on interfacial segregation of zinc in a magnesium alloy

Dudekula Althaf Basha, Ryoji Sahara, Hidetoshi Somekawa, Alok Singh, Koichi Tsuchiya

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

We show that, while interfaces formed in a Mg-3Zn-0.5Y (at%) magnesium alloy by severe plastic deformation (SPD) by high pressure torsion (HPT) at room temperature (RT) are segregated with Zn (without aid of any thermal treatment), only a small fraction of grain boundaries are segregated when extruded at 573 K (300 °C). We have examined the effect of strain rate and temperature on the diffusion behavior and segregation of zinc in magnesium alloys. At first, we have established the driving force for segregation by evaluating segregation energy and the interface energy gain by density functional theory calculations. The mechanism of segregation is established through calculation of excess vacancy concentration and critical dislocation velocity as a function of strain rate. It is estimated that Zn atoms are transported by SPD induced vacancy flux in case of HPT at RT, whereas the Zn atoms are dragged by equilibrium vacancies and dislocations on extrusion at 573 K (300 °C). The amount of segregation to the different twins and grain boundaries with different interfacial energies have been calculated by thermodynamic parameters and found to be in the range of 1–8 at% of Zn for the case of HPT process and 0.7–1.6 at% of Zn for extrusion processed specimens. These estimates correspond to the solute concentrations determined experimentally.

Original languageEnglish
Pages (from-to)54-67
Number of pages14
JournalMaterials Science and Engineering A
Volume703
DOIs
Publication statusPublished - 2017 Aug 4
Externally publishedYes

Keywords

  • Extrusion
  • First principles calculation
  • High-pressure torsion
  • Interface segregation
  • Magnesium alloys
  • Transmission electron microscopy

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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