scholarly journals The Temperature and Strain Rate Dependence of the Flow Stress of Single Crystal Nial Deformed Along

1994 ◽  
Vol 364 ◽  
Author(s):  
Stuart A Maloy ◽  
George T Gray
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Single Crystal ◽  
Work Hardening ◽  
Rate Dependence ◽  
Temperature Sensitive ◽  
Strain Rates ◽  
Slip Bands ◽  
Work Hardening Rate ◽  
Slip Traces

AbstractSingle crystal NiAl and Ni-49.75Al-0.25Fe have been deformed along <110> at temperatures of 77, 298 and 773K and strain rates of 0.001/s, 0.1/s and 2000/s. The flow stress of <110> NiAl is rate and temperature sensitive. A significant decrease in the work hardening rate is observed after deformation at 77K and a strain rate of 2000/s. Coarse {110} slip traces are observed after deformation at a strain rate of 2000/s at 77K, while no slip traces were observed after deformation under all other conditions. TEM observations reveal distinct {110} slip bands after deformation at 77K and a strain rate of 2000/s.

Effect of Hot Extrusion on the Flow Behaviour of a Nickel-Based P/M Superalloy

2019 ◽  
Vol 298 ◽  
pp. 43-51
Author(s):  
Jia Yong Si ◽  
Song Hao Liu ◽  
Long Chen
Keyword(s):  
Activation Energy ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Rate Sensitivity ◽  
Hot Extrusion ◽  
Turbine Disk ◽  
Flow Behaviour ◽  
Strain Rates ◽  
Work Hardening Rate

This research investigated the effect of hot extrusion on the flow behaviour of nickel-based superalloy FGH4096 by hot compression experiments in the temperature range from 1020 to 1110 °C and strain rates ranging from 0.1 to 0.001 s-1. The influence of the hot extrusion on the initial microstructures, work hardening rate, strain rate sensitivity, and activation energy of deformation were discussed. The results show that the extruded microstructure is constituted by the fine dynamic recrystallisation of grains. The true strain-true stress curves show that the as-HIPed and as-HEXed FGH4096 superalloy present double flow stress peaks and discontinuous flow softening. The as-HEXed FGH4096 is easily dynamically softened at high temperatures and high strain rates compared with as-HIPed microstructures. As for the work hardening rate, the as-HEXed FGH4096 exhibits higher θ values than that of as-HIPed. It is beneficial to the homogenous deformation and grain refinement during subsequent turbine disk forging. Comparing to as-HIPed FGH4096, the highest strain rate sensitivity value of as-HEXed is 0.306 at 1110 °C. The isothermal superplastic forging of a P/M turbine disk may be carried out at this temperature. The deformation activation energy value of the as-HIPed FGH4096 is lower which means that dislocation sliding and climbing can be easily initiated in the as-HIPed alloy.

On the Mechanical Threshold Stress of Aluminum: Effect of the Alloying Content

2001 ◽  
Vol 123 (2) ◽  
pp. 155-161 ◽  
Author(s):  
Eli S. Puchi-Cabrera ◽  
Crisanto Villalobos-Gutie´rrez ◽  
Gonzalo Castro-Farin˜as
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Working Conditions ◽  
Threshold Stress ◽  
Solute Concentration ◽  
Strain Rates ◽  
Solute Content ◽  
Mechanical Threshold ◽  
Work Hardening Rate ◽  
Aluminum Effect

The mechanical behavior of aluminum with different alloying contents up to 1 wt percent, deformed under hot-working conditions, has been analyzed in terms of the exponential saturation equation proposed by Voce for the description of the evolution of the mechanical threshold stress, σ^, and the model advanced by Kocks for the description of the ratio, sε˙,T, between the flow stress at any strain rate and temperature and σ^. It has been determined that the increase in the alloying content of aluminum gives rise to an increase in the mechanical threshold stress mainly due to the effect of the solute content on the saturation stress, σ^s and less markedly on the athermal stress, σ^a. On the contrary, it has been found that the increase in the alloying content gives rise to a decrease of the Stage II or athermal work-hardening rate, θ0. Also, it has been concluded that the increase in the solute content of the material gives rise to a significant increase in the parameters ε˙K and g0 that enter into the expression of sε˙,T. Therefore, the dependence of the flow stress at any temperature and strain rate with the alloying content evolves from the dependence of both sε˙,T and σ^ on solute concentration. Also, it has been found that, for the present analysis, the factor sε˙,T derived from Kocks model is more satisfactory than that derived from the Follansbee and Kocks model since the latter predicts negative values of the flow stress below approximately 10 MPa, that is to say, under conditions of elevated deformation temperatures and low strain rates.

The Effect of Strain Rate on the Mechanical Properties of Single Crystal NiAl

1990 ◽  
Vol 213 ◽  
Author(s):  
D.F. Lahrman ◽  
R.D. Field ◽  
R. Darolia
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Single Crystal ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Deformation Mechanisms ◽  
Strain Rates ◽  
Test Results ◽  
Work Hardening Rate ◽  
Crystallographic Orientations

ABSTRACTIn this study, the strain rate sensitivity of single crystal NiAl has been investigated by performing tensile tests as a function of temperature and two strain rates. Three crystallographic orientations, [100], [110], and [111] were studied. The tensile test results investigated include yield strength, work hardening rate and plastic strain to failure. The data are discussed in terms of deformation mechanisms in NiAl.

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