Low temperature superplasticity in a magnesium-based composite

Journal Article · Sat Jan 01 04:00:00 EST 2000 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(99)00357-7· OSTI ID:20013340

Watanabe, H; Mukai, T; Nieh, T G; Higashi, K

High tensile ductility associated with superplasticity occurs when grain size is small and typically less than {approximately} 10 {micro}m. The conventional superplasticity in pseudo single-phase alloys is observed at relatively low strain rates of < 10{sup {minus}3} s{sup {minus}1} and at temperatures of {approximately} 0.8T{sub m}, where T{sub m} is the melting point of the material. Experimental evidence suggests that a reduction in grain size will increase the strain rate and/or decrease the temperature for optimum superplastic flow. Recently, high-strain-rate superplasticity (HSRS) has been investigated extensively in magnesium-based materials. It has been found that the composite used in the present study was also shown to exhibit HSRS at high temperatures of {approximately} 623 K. On the other hand, few works are available for the study of low temperature superplasticity (LTSP) in alloys. A lower forming temperature enables reduction in energy cost, reducing surface oxidation and preventing selective depletion of the alloy additions. Another reason for focusing on the lower temperature is to probe the low temperature limits of superplasticity. To date, it has been reported that the dominant deformation mechanism for LTSP in unreinforced magnesium alloy was the same as that at high temperatures. On the other hand, LTSP has not been reported in metal-matrix composites (MMCs). In the present study the authors investigated the low temperature superplastic behavior in a magnesium-based composite. First, they demonstrate that the fine-grained magnesium-based composite behaved in a superplastic manner even at low temperatures of about half the absolute melting point. Second, the low temperature superplastic behavior was characterized, and the deformation mechanisms was discussed.

• Research Organization: Osaka Municipal Technical Research Inst., Osaka (JP)
• OSTI ID: 20013340
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 3 Vol. 42; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPOSITE MATERIALS
DEFORMATION
ELONGATION
GRAIN SIZE
MAGNESIUM ALLOYS
PLASTICITY
SILICON CARBIDES
STRAIN RATE
TEMPERATURE DEPENDENCE