OPTIMISATION OF STRAIN RATE SENSITIVITY DURING SUPERPLASTIC DEFORMATION OF Al-Li-ALLOY LITAL A

1987 ◽  
Vol 48 (C3) ◽  
pp. C3-251-C3-256 ◽  
Author(s):  
N. RIDLEY ◽  
D. W. LIVESEY ◽  
J. PILLING
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Rate Sensitivity

Investigation of Superplastic Behavior of NiAI and Ni3Al Duplex Alloy

1996 ◽  
Vol 460 ◽  
Author(s):  
Liu Zhenyun ◽  
Lin Dongliang ◽  
T. L. Lin ◽  
Gu Yuefeng ◽  
Shan Aidang
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Empirical Equation ◽  
Tensile Elongation ◽  
Rate Sensitivity ◽  
Superplastic Behavior ◽  
Narrow Temperature Range ◽  
Optical Microstructure ◽  
Duplex Alloy

ABSTRACTThe superplastic behavior of a NiAI and Ni3Al duplex alloy was investigated. It was found that the alloy exhibits superplastic behavior over a narrow temperature range, from 975 °C to 1025°C at the strain rate of 1.52 × 10-4 s-1. A maximum tensile elongation of 149% was obtained at 1000°C with the strain rate sensitivity up to 0.375. The superplastic deformation of the duplex alloy can be approximately described by an empirical equation of the form: ε = Ao2.67 exp(-303,000 / RT). Optical microstructure and TEM observation show that the superplastic behavior mechanism of the investigated alloy is a process of continuous recovery and recrystallization during deformation.

The Influence of Microstructure on Superplastic Behaviours of γ-TiAl Alloys

1998 ◽  
Vol 552 ◽  
Author(s):  
J. Sun ◽  
J. S. Wu ◽  
G. X. Hu ◽  
Y. H. He ◽  
B. Y. Huang
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Maximum Elongation ◽  
Tial Alloys ◽  
Different Temperatures ◽  
Incremental Strain

ABSTRACTIn this work, superplastic behaviours in Ti-33A1–3Cr-0.5Mo (wt%) γ-TiAl alloys with two different initial microstructures of near gamma (NG) and duplex (DM) structure were investigated with respect to the effect of testing temperatures and strain rates. At 1050°C and a strain rate of 8×10–5 S–1, a maximum elongation of 570% was observed for NG-TiAl and a maximum elongation of 467% for DM-TiAl. The relations of flow stress and strain rate sensitivity vs. strain rates at different temperatures were also determined by incremental strain rate tests. The results showed that the value of strain rate sensitivity is higher and the flow stress is lower for NG than those for DM at the same condition. The microstructural evolution during superplastic deformation was examined and correlated to the mechanical properties for these two alloys. The influence of microstructure on the superplastic behaviours of γ-TiAl alloys, and possible superplastic deformation mechanisms were finally discussed.

Superplastic Deformation Mechanisms in a Fine-Grained, Yttria-stabilized Tetragonal Zirconia Polycrystal (Y-TZP)

1990 ◽  
Vol 196 ◽  
Author(s):  
T. G. Nieh ◽  
J. Wadsworth
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Grain Growth ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Boundary Triple ◽  
Sliding Mechanism ◽  
Boundary Sliding

ABSTRACTConcurrent grain growth, and in particular, dynamic grain growth, was observed to take place during superplastic deformation of Y-TZP. As a result of this concurrent grain growth, the measured strain rate sensitivity was found to be lower than that measured under constantstructure conditions. In the present paper, data obtained from the superplastic deformation of YTZP under constant-structure conditions are presented. It is demonstrated that the strain rate sensitivity values are generally higher than 0.5, when measured from the grain size-compensated data; this result suggests a grain boundary sliding mechanism. Microstructures from samples prior to and after superplastic deformation reveal grains which are essentially equiaxed; this observation is also consistent with a grain boundary sliding mechanism. Both high-resolution images of grain boundary triple points using transmission electron microscopy, and fracture surface studies using Auger electron spectroscopy and X-ray photoelectron spectroscopy indicate that there is no evidence for the presence of glassy phases at grain boundaries in Y-TZP.

Common Mechanism for Superplastic Deformation in Different Classes of Materials

2012 ◽  
Vol 735 ◽  
pp. 26-30 ◽  
Author(s):  
K. Anantha Padmanabhan ◽  
Herbert Gleiter
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Physical Mechanism ◽  
Rate Sensitivity ◽  
Common Mechanism ◽  
Sensitivity Index ◽  
Strain Rate Sensitivity Index ◽  
Definition Of

An earlier proposal is generalized to explain superplasticity in different classes of materials and grain size ranges. A definition of “superplasticity” as due to a unique physical mechanism, rather than in terms of extreme elongations and/ or strain rate sensitivity index, m, being more than or equal to 0.30 emerges.

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