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Microstructure and mechanical properties of ZA62 Mg alloy by equal-channel angular pressing

Authors
Journal
Materials Science and Engineering A
0921-5093
Publisher
Elsevier
Publication Date
Volume
528
Issue
3
Identifiers
DOI: 10.1016/j.msea.2010.09.096
Keywords
  • Equal-Channel Angular Pressing (Ecap)
  • Magnesium Alloys
  • Bimodal
  • Severe Plastic Deformation
  • Superplasticity

Abstract

Abstract The Mg–6Zn–2Al alloy was processed by ECAP and microstructure and mechanical properties of the alloy before and after ECAP were studied. The results revealed that the microstructure of the ZA62 alloy was successfully refined after two-step ECAP (2 passes at 473K and 2–8 passes at 423K). The course bulk interphase of Mg51Zn20 was crushed into fine particles and mixed with fine matrix grains forming “stripes” in the microstructure after the second step of ECAP extrusion. A bimodal microstructure of small grains of the matrix with size of ∼0.5μm in the stripes and large grains of the matrix with size of ∼2μm out of stripes was observed in the microstructure of samples after 4–8 passes of ECAP extrusion at the second step. The mechanical properties of the alloy studied were significantly improved after ECAP and the highest yield strength and elongation at room temperature were obtained at the samples after 4 and 8 ECAP passes at the second step, respectively. Tensile tests carried out at temperature of 473K to 573K and strain rate of 1×10−3s−1 to 3×10−2s−1 revealed that the alloy after 8 ECAP passes at the second step showed superplasticity and the highest elongation and strain rate sensitivity (m-value) reached 520% and 0.45, respectively.

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