Fabrication of bulk ultrafine-grained materials through intense plastic straining

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 1998-09, Vol.29 (9), p.2237-2243
• Main Authors: Berbon, Patrick B., Langdon, Terence G., Tsenev, Nikolai K., Valiev, Ruslan Z., Furukawa, Minoru, Horita, Zenji, Nemoto, Minoru
• Format: Article
• Language: English
• Subjects: Alloys; Aluminum; Aluminum base alloys; Elongation; Experiments; Grain growth; Grain size; Hot rolling; Magnesium base alloys; Microstructure; Plastic deformation; Pressing; Room temperature; Solid solutions; Strain rate; Superplasticity; Temperature; Ultrafines; Zirconium base alloys
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-998-0101-6

Ultrafine grain sizes were introduced into samples of an Al-3 pct Mg solid solution alloy and a cast Al-Mg-Li-Zr alloy using the process of equal-channel angular (ECA) pressing. The Al-3 pct Mg alloy exhibited a grain size of ∼0.23 µm after pressing at room temperature to a strain of ∼4, but there was significant grain growth when the pressed material was heated to temperatures above ∼450 K. The Al-Mg-Li-Zr alloy exhibited a grain size of ∼1.2 µm, and the microstructure was heterogeneous after pressing to a strain of ∼4 at 673 K and homogeneous after pressing to a strain of ∼8 at 673 K with an additional strain of ∼4 at 473 K. The heterogeneous material exhibited superplastic-like flow, but the homogeneous material exhibited high-strain-rate superplasticity with an elongation of >1000 pct at 623 K at a strain rate of 10−2 s−1. It is concluded that a homogeneous microstructure is required, and therefore a high pressing strain, in order to attain high-strain-rate superplasticity (HSR SP) in ultrafine-grained materials.