Superplasticity in laminated metal composites

Conference · Tue Oct 20 04:00:00 EDT 1998

OSTI ID:3379

Lesuer, D ^[1]; Sherby, O; Syn, C

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1. LLNL

Several studies have shown the possibility of achieving superplastic behavior in laminated metal composites consisting of alternating layers of superplastic and non-superplastic materials. Achieving high rate sensitivity in such a laminate requires the appropriate choice of component materials and component volume fraction as well as deformation under appropriate conditions of strain rate and temperature. The first investigators to study this behavior were Snyder et al. [1], who demonstrated that a non-superplastic material (interstitial free iron) could be made superplastic by lamination with a superplastic material (fine-grained ultrahigh carbon steel (UHCS)). Other laminates in which superplasticity has been observed in a non-superplastic material include UHCS/stainless steel and UHCS/aluminum bronze. In these studies, tensile tests were conducted with the tensile axis parallel to the layers. High strain rate sensitivities were observed and are associated with high tensile ductilities. However, as observed by Tsai et al. [2], obtaining high strain rate sensitivity is a necessary but not sufficient condition for high elongations. Tsai et al. studied the UHCS/brass laminate and found that, despite a strain rate sensitivity exponent of 0.5, only about 60% elongation was obtained. The low tensile ductility resulted from brittle, intergranular fracture of the brass. Once cracking started in the brass, cracks penetrated into the UHCS and premature failure resulted. Thus high elongations requires achieving high strain rate sensitivity as well as avoiding brittle fracture in the less ductile layer. In addition to tension, other deformation modes, including compression [3] and co-extrusion [4], have been studied for deformation response under conditions of high strain rate s

• Research Organization: Lawrence Livermore National Laboratory, Livermore, CA
• Sponsoring Organization: USDOE Office of Defense Programs (DP)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 3379
• Report Number(s): UCRL-JC-131939; ON: DE00003379
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Aluminium Alloys
Brass
Bronze
Carbon Steels
Composite Materials
Experimental Data
Iron
Plasticity
Stainless Steels