Effect of Al addition on the microstructure, tensile properties, and bendability of extruded Mg-7Sn-1Zn alloy

Sang Hoon Kim, Jong Un Lee, Ye Jin Kim, Jae Ok Choi, Jeong Hun Lee, Sung Hyuk Park

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

The effect of Al addition on the microstructure and mechanical properties of extruded Mg-Sn based alloy is investigated by adding 1 wt% Al to the Mg-7Sn-lZn alloy and indirectly extruding the billets with and without the Al addition. The Al addition promotes dynamic recrystallization (DRX) behaviour during hot extrusion, which results in an increase in the area fraction of dynamically recrystallized (DRXed) grains and a decrease in the width of unDRXed grains of the extruded alloy. In addition, dynamic precipitation during extrusion is also accelerated by the Al addition owing to the decrease in Sn solubility in the Mg matrix, thereby increasing the amount of Mg2Sn precipitates and decreasing their size. The increased amount of fine precipitates, and the reduced amount of coarse unDRXed grains, lead to a reduction in the average grain size of the extruded alloy. The Al addition significantly improves tensile properties (i.e., strength and ductility) and 3 point bending strength of the extruded alloy. The improvement in the tensile and bending strengths is attributed to the combined effects of grain-boundary hardening by the reduced grain size, precipitation hardening by more abundant precipitates, and solid-solution hardening by dissolved Al atoms. The increase in the tensile elongation results from the decrease in the amount and size of the coarse unDRXed grains because {10-11} contraction and {10-11}-{10-12} double twins, which can act as initiation sites of microcracks, easily occur under tension along the extrusion direction in the coarse grains. However, the increased amount of precipitates and the reduced grain size accelerate the formation of shear bands and suppress the activation of {10-12} twinning in the upper side of the bending sample, which consequently results in a deterioration in the bending formability of the extruded alloy.

Original languageEnglish
Pages (from-to)40-48
Number of pages9
JournalJournal of Korean Institute of Metals and Materials
Volume56
Issue number1
DOIs
StatePublished - Jan 2018

Keywords

  • Extrusion
  • Magnesium alloy
  • Precipitation
  • Recrystallization
  • Tensile properties

Fingerprint

Dive into the research topics of 'Effect of Al addition on the microstructure, tensile properties, and bendability of extruded Mg-7Sn-1Zn alloy'. Together they form a unique fingerprint.

Cite this