High Rate Superplastic Deformation Mechanisms in IN90211 Mechanically Alloyed Aluminum

1990 ◽  
Vol 196 ◽  
Author(s):  
Thomas R. Bieler ◽  
Amiya K. Mukherjee
Keyword(s):  
Strain Rate ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
High Rate ◽  
Temperature Dependent ◽  
Mechanically Alloyed ◽  
Rate Limiting Step ◽  
Orowan Stress ◽  
Apparent Strain ◽  
Rate Limiting

ABSTRACTIN90211 has exhibited superplastic elongations above 500% at high homologous temperatures (0.76–0.82 Tm). A high strain rate and flow stress for optimum elongation was measured (1–5/sec, 20–60 MPa, 425–485 °C). The apparent strain rate sensitivity of m≈0.25 differs from the usual m≈0.5 observations of superplastic deformation. An analysis of the data at several strains indicates a highly temperature dependent threshold stress is present, with either a n=2 or n=3 assumption for the stress exponent. The magnitude of the threshold stresses in IN90211 are smaller than usually observed in a dispersion strengthened matrix (1–20% instead of ≈50% of the Orowan stress). Experimental evidence from creep experiments supports the n=3 deformation mechanism as the rate limiting step of deformation.

scholarly journals Strain rate and thermal softening effects in shear testing of AA7075-T6 sheet

2018 ◽  
Vol 183 ◽  
pp. 02037 ◽  
Author(s):  
Taamjeed Rahmaan ◽  
Ping Zhou ◽  
Cliff Butcher ◽  
Michael J. Worswick
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Rate Sensitivity ◽  
Thermal Conditions ◽  
Shear Loading ◽  
Image Correlation ◽  
High Rate ◽  
Strain Rates ◽  
Shear Testing ◽  
Plane Shear

Shear tests were performed at strain rates ranging from quasi-static (0.01 s-1) to 500 s-1 for AA7075-T6 sheet metal alloy at room temperature. A miniature sized shear specimen was used in this work to perform high strain rate shear testing. Digital image correlation (DIC) techniques were employed to measure the strains in the experiments. At maximum in-plane shear strains greater than 20%, the AA7075-T6 alloy demonstrated a reduced work hardening rate at elevated strain rates. At lower strains, the AA7075-T6 alloy showed mild positive rate sensitivity. The strain to localization (using the Zener-Holloman criterion), measured using the DIC technique, decreased with strain rate in shear loading. The strain at complete failure, however, exhibited an increase at the highest strain rate (500 s-1). The current work also focused on characterization of the thermal conditions occurring during high rate loading in shear with in situ high speed thermal imaging. Experimental results from the highest strain rate (500 s-1) tests showed a notable increase in temperature within the specimen gauge region as a result of the conversion of plastic deformation energy into heat.

Dislocation Mechanics of Extremely High Rate Deformations in Iron and Tantalum

2021 ◽  
pp. 1-30
Author(s):  
Mu'Tasem Shehadeh ◽  
Pascale El Ters ◽  
Ronald W. Armstrong ◽  
Werner Arnold
Keyword(s):  
Strain Rate ◽  
Weak Shock ◽  
Rate Sensitivity ◽  
High Rate ◽  
Dislocation Dynamic ◽  
Dislocation Generation ◽  
High Deformation ◽  
Rate Analysis ◽  
Dislocation Mechanics ◽  
Dynamic Plasticity

Abstract High strain rate simulations were performed using the multiscale dislocation dynamic plasticity (MDDP) method to calculate different rise times and load durations in mimicking high deformation rate shock or isentropic (ramp) testing of a-iron and tantalum crystals. Focus for both types of loading on both materials was on the inter-relationship between the (dislocation-velocity-related) strain rate sensitivity and the (time-dependent) evolution of dislocation density. The computations are compared with model thermal activation strain rate analysis (TASRA), phonon drag and dislocation generation predictions. The overall comparison of simulated tests and previous experimental measurements shows that the imposition of a rise time even as small as 0.2 ns preceding plastic relaxation via the MDDP method is indicative of relatively weak shock behavior.

Superplasticity of AlCoCrCuFeNi High Entropy Alloy

2012 ◽  
Vol 735 ◽  
pp. 146-151 ◽  
Author(s):  
Andrey V. Kuznetsov ◽  
Dmitry G. Shaisultanov ◽  
Nikita Stepanov ◽  
Gennady A. Salishchev ◽  
Oleg N. Senkov
Keyword(s):  
Particle Size ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
Tensile Ductility ◽  
Rate Sensitivity ◽  
Particle Growth ◽  
High Entropy Alloy ◽  
Superplastic Behavior ◽  
High Entropy ◽  
Elongation To Failure

An AlCoCrCuFeNi high entropy alloy was multiaxially isothermally forged at 950°C to produce a fine equiaxed structure with the average grain/particle size of ~1.5 µm. The forged alloy exhibited superplastic behavior in the temperature range of 800-1000°C. For example, during deformation at a strain rate of 10-3 s-1, tensile ductility increased from 400% to 860% when the temperature increased from 800°C to 1000°C. An increase in strain rate from 10-4 to 10-2 s-1 at T = 1000°C did not affect ductility: elongation to failure was about 800%. The strain rate sensitivity of the flow stress was rather high, m = 0.6, which is typical to the superplastic behavior. The equiaxed morphology of grains and particles retained after the superplastic deformation, although some grain/particle growth was observed.

The Phenomenon of Superplasticity in Feal-Ti Alloy with Large Grains

1994 ◽  
Vol 364 ◽  
Author(s):  
Dingqiang Li ◽  
Aidang Shan ◽  
Yi Liu ◽  
Dongliang Lin
Keyword(s):  
Strain Rate ◽  
Superplastic Deformation ◽  
Dynamic Recovery ◽  
Rate Sensitivity ◽  
Strain Rate Range ◽  
Ti Alloy ◽  
Maximum Elongation ◽  
Rate Range ◽  
First Time ◽  
Range Of Values

AbstractThe phenomenon of superplasticity in an ordered FeAl based alloy is reported in this paper for the first time. The behavior of superplastic deformation for the FeAl based alloy (Fe-36.5at.%-2at.%Ti) with large grains of above 300 μm has been examined at 1000°C in a strain rate range from 1.39×10− 4 /s to 2.78×l0−2 /s. The maximum elongation of 208% for the FeAl based alloy with large grains has been obtained and the index of strain rate sensitivity, the m value, has a range of values from 0.25 to 0.42. The reason for the large elongation is ascribed to the dynamic recovery and recrystallization during deformation in this large grained alloy at high temperatures.

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.

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