Superplasticity and Superplastic Diffusion Bonding of a Fine-Grained TiAl Alloy

Abstract

Superplasticity and superplastic diffusion bonding in a TiAl alloy with a fine-grained duplex microstructure have been investigated in order to fabricate TiAl alloy products using a combination process of superplastic forming with diffusion bonding. Superplastic tensile tests were carried out at temperatures ranging from 1000 to 1100 C, and at strain rates ranging from 10 À5 to 10 À3 s À1 . A low superplastic flow stress of less than 25 MPa was observed at 1100 C and at a strain rate of 8:3 Â 10 À5 s À1 . Under this condition, a tensile elongation of 300% and a strain rate sensitivity coefficient of over 0.5 were obtained. Furthermore, superplastic diffusion bonding under a low pressure of 10 MPa was conducted. Defect-free bonds were achieved at 1100 C for holding 1 h. It is suggested that the low superplastic flow stress at 1100 C allows a significant plastic flow between the two contacted surfaces, resulting in a full contact of the surfaces, which is necessary for the sound bonds. Finally, a twosheet part of spherical dome was successfully produced from this alloy.

Structure and thermoelectric properties of nanocomposite bismuth telluride prepared by melt spinning or by partially alloying with IV–VI compounds

“…For comparison, samples with a concentration of PbTe of up to 10% were analyzed, a range where the miscibility is much less probable but remains unclear according to the different phase diagrams mentioned in Refs. [10][11][12][13][14]. ple.…”

“…PbTe/Bi 2 Te 3 . The miscibility in phase diagrams may even differ severely for different authors, also indicating a high uncertainty of the crystalline fine structure on the nanoscale [10][11][12][13][14].…”