Effect of liquid phases on the tensile elongation of superplastic aluminum alloys and composites

Journal Article · Sat Apr 01 04:00:00 EST 1995 · Scripta Metallurgica et Materialia

DOI:https://doi.org/10.1016/0956-716X(94)00003-Z· OSTI ID:39886

Higashi, K ^[1]; Nieh, T G; Wadsworth, J ^[2]; Mabuchi, M ^[3]

---

1. Univ. of Osaka Prefecture (Japan). Dept. of Mechanical Systems Engineering
2. Lawrence Livermore National Lab., CA (United States)
3. National Industrial Research Inst., Nagoya (Japan)

One of the major drawbacks of conventional superplastic forming is that the phenomenon is only found at relatively low strain rates, typically about 10{sup {minus}4} to 10{sup {minus}3} s{sup {minus}1}. Recent studies, however, have demonstrated that superplasticity can in fact be found at considerably higher strain rates than 10{sup {minus}3} s{sup {minus}1}, i.e. at strain rates of up to 10{sup 0} to 10{sup 2} s{sup {minus}1}. This high-strain-rate superplasticity (HSRS) phenomenon was originally observed in metal matrix composites and then found in mechanically alloyed materials. The phenomenon was then studied in some detail, principally in metal matrix composites but was also pursued in the mechanically alloyed materials. More recently the effect has also been observed in metallic alloys produced by more conventional methods. Technologically, HSRS in metal matrix composites is expected to result in a viable, near-net-shape forming technique for the automobile, aerospace, and even semi-conductor industries. It was initially pointed out by Nieh et al. that the observed HSRS phenomenon may be related to the presence of some liquid phases at interfaces or grain boundaries as a result of, or at least accompanied by, the segregation of solutes to such regions. Recently, Mabuchi and Higashi, using an in situ TEM technique, have directly observed solute segregation at interfaces or grain boundaries and the preferential melting of these enriched grain boundaries. In the current paper, the authors present further evidence, through the analysis of existing data, to illustrate that the elongation to failure of many superplastic materials is associated with the presence, or the likelihood of the presence, of liquid phases at boundary interfaces. The materials and experimental procedures have been described previously in various papers.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 39886
• Journal Information: Scripta Metallurgica et Materialia, Journal Name: Scripta Metallurgica et Materialia Journal Issue: 7 Vol. 32; ISSN 0956-716X; ISSN SCRMEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
CALORIMETRY
COMPOSITE MATERIALS
GRAIN BOUNDARIES
GRAIN SIZE
INTERFACES
LIQUIDS
MELTING
METALLURGICAL EFFECTS
PLASTICITY
STRAIN RATE
TENSILE PROPERTIES