Fracture Behavior of Ultrafine-Grained Titanium Under Tension at Elevated Temperatures

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
S. V. Sajadifar ◽  
H. J. Maier ◽  
T. Niendorf ◽  
G. G. Yapici
Keyword(s):  
Fracture Behavior ◽  
Elevated Temperatures ◽  
Rate Sensitivity ◽  
Void Coalescence ◽  
Strain Rates ◽  
Enhanced Diffusion ◽  
Deformation Response ◽  
Ultrafine Grained ◽  
Highly Sensitive ◽  
Comprehensive Recovery

Abstract This investigation focused on the deformation response and microstructural changes of severely deformed titanium during post-severe plastic deformation tension, at temperatures of 300–600 °C and at strain rates of 0.001–0.1 s−1. The obtained results suggest that SPD enhances the strength of grade 4 titanium up to 500 °C. At above 600 °C, the severely deformed microstructure showed comprehensive recovery. Severely deformed titanium was seen to be highly sensitive to the deformation rate, where strain rate sensitivity increased with the increase of test temperature. Analysis of fracture surfaces reveals that at elevated temperatures, growth of dimples and void coalescence occurs due to the enhanced diffusion rate and occurrence of recrystallized grains.

Local Investigations of the Mechanical Properties of Ultrafine Grained Metals by Nanoindentations

2006 ◽  
Vol 503-504 ◽  
pp. 31-36 ◽  
Author(s):  
Johannes Mueller ◽  
Karsten Durst ◽  
Dorothea Amberger ◽  
Matthias Göken
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Fcc Metals ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Indentation Strain

The mechanical properties of ultrafine-grained metals processed by equal channel angular pressing is investigated by nanoindentations in comparison with measurements on nanocrystalline nickel with a grain size between 20 and 400 nm produced by pulsed electrodeposition. Besides hardness and Young’s modulus measurements, the nanoindentation method allows also controlled experiments on the strain rate sensitivity, which are discussed in detail in this paper. Nanoindentation measurements can be performed at indentation strain rates between 10-3 s-1 and 0.1 s-1. Nanocrystalline and ultrafine-grained fcc metals as Al and Ni show a significant strain rate sensitivity at room temperature in comparison with conventional grain sized materials. In ultrafine-grained bcc Fe the strain rate sensitivity does not change significantly after severe plastic deformation. Inelastic effects are found during repeated unloading-loading experiments in nanoindentations.

A Model for the Effects of Strain Rate and Temperature on the Deformation Behavior of Ultrafine-Grained Metals

2011 ◽  
Vol 291-294 ◽  
pp. 1173-1177
Author(s):  
Zi Ling Xie ◽  
Lin Zhu Sun ◽  
Fang Yang
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Boundary Diffusion ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Dislocation Slip ◽  
Deformation Response ◽  
Ultrafine Grained ◽  
Boundary Sliding

A theoretical model is developed to account for the effects of strain rate and temperature on the deformation behavior of ultrafine-grained fcc Cu. Three mechanisms, including dislocation slip, grain boundary diffusion, and grain boundary sliding are considered to contribute to the deformation response simultaneously. Numerical simulations show that the strain rate sensitivity increases with decreasing grain size and strain rate, and that the flow stress and tensile ductility increase with either increasing strain rate or decreasing deformation temperature.

Strain Rate Sensitivity of Commercial Aluminum Alloys

2019 ◽  
Author(s):  
R.C. Picu
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Solid Solutions ◽  
Elevated Temperatures ◽  
Rate Sensitivity ◽  
Solute Diffusion ◽  
Rate Dependent ◽  
Ultrafine Grained ◽  
Using Data

This article presents a review of the strain rate-dependent mechanical behavior of aluminum and its commercial alloys. The importance of strain rate sensitivity (SRS) stems from its relation with ductility and formability. Plastic deformation is stable and localization less likely in alloys with higher SRS. After discussing the basic formulation used to interpret experimental data, the methods used to measure the SRS parameter are presented. This is followed by a brief review of the main mechanisms that render the flow stress sensitive to the deformation rate, including mechanisms leading to positive and negative SRS. The generic dependence of the SRS parameter on the strain, temperature, and strain rate are further presented using data for pure Al. The effect of alloying is analyzed in the context of solid solutions and precipitated commercial alloys. Results on solid solutions are discussed separately at low and elevated temperatures in order to evidence the role of solute diffusion on SRS. This article ends with a brief discussion of the grain size dependence of SRS, with emphasis on recent efforts to produce nanocrystalline and ultrafine-grained materials by severe plastic deformation.

Developing High Strain Rate Superplasticity in Aluminum Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 2949-2954 ◽  
Author(s):  
Cheng Xu ◽  
Minoru Furukawa ◽  
Z. Horita ◽  
Terence G. Langdon
Keyword(s):  
Elevated Temperatures ◽  
High Strain ◽  
Superplastic Forming ◽  
Ultrafine Grain ◽  
Strain Rates ◽  
Cast Aluminum ◽  
Grain Sizes ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Materials Used

The conventional materials used in superplastic forming operations generally have grain sizes of ~2 µm or larger and they exhibit superplasticity at relatively low strain rates. Processing by equal-channel angular pressing (ECAP) produces materials having ultrafine-grain sizes, usually in the submicrometer range. If these ultrafine grains show reasonable stability at elevated temperatures, the alloys may exhibit a capability for achieving superplastic elongations at high strain rates. This paper examines the development of ultrafine-grained structures and superplastic ductilities in a spray-cast aluminum 7034 alloys through ECAP. The results show that ECAP is a very effective procedure for achieving grain refinement and superplasticity at rapid strain rates.

Low Temperature Superplasticity in Ultrafine-Grained AZ31 Alloy

2018 ◽  
Vol 385 ◽  
pp. 59-64 ◽  
Author(s):  
Roberto B. Figueiredo ◽  
Pedro Henrique R. Pereira ◽  
Terence G. Langdon
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
High Strain ◽  
High Pressure Torsion ◽  
Rate Sensitivity ◽  
Az31 Alloy ◽  
Strain Rates ◽  
Ultrafine Grained

The mechanical behavior of an AZ31 magnesium alloy processed by high-pressure torsion (HPT) was evaluated by tensile testing from room temperature up to 473 K at strain rates between 10-5 – 10-2 s-1. Samples tested at room temperature and at high strain rates at 373 K failed without any plastic deformation. However, significant ductility, with elongations larger than 200%, was observed at 423 K and 473 K and at low strain rates at 373 K. The high elongations are attributed to a pronounced strain hardening and a high strain rate sensitivity. The results agree with reports for a similar alloy processed by severe plastic deformation. However, the level of flow stress is lower and the strain rate sensitivity and the elongations are larger than observed in this alloy processed by conventional thermo-mechanical processing.

Enhanced Plasticity of WE54/SiC Composite Prepared by Powder Metallurgy

2011 ◽  
Vol 465 ◽  
pp. 419-422 ◽  
Author(s):  
Zoltán Száraz ◽  
Zuzanka Trojanová
Keyword(s):  
Powder Metallurgy ◽  
Strain Rate ◽  
Elevated Temperatures ◽  
High Strain ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Strain Rates ◽  
Deformation Characteristics ◽  
Powder Metallurgy Technique

The deformation characteristics of the WE54 magnesium alloy reinforced by 13% of SiC particles have been investigated in tension at elevated temperatures. Composite material was prepared by powder metallurgy technique. The strain rate sensitivity parameter m has been estimated by the abrupt strain rate changes (SRC) method. SRC tests and tensile tests with constant strain rate ( ) were performed at temperatures from 350 to 500 °C. Increased ductility has been found at high strain rates. The corresponding m value was 0.3. The activation energy Q has been estimated. Microstructure evolution has been observed by the light microscope and scanning electron microscope.

Low-Temperature Superplasticity in an Al-Mg-Sc Alloy Processed by ECAP

2016 ◽  
Vol 838-839 ◽  
pp. 422-427 ◽  
Author(s):  
Diana Yuzbekova ◽  
Anna Mogucheva ◽  
Rustam Kaibyshev
Keyword(s):  
Strain Rate ◽  
Rate Sensitivity ◽  
Sensitivity Coefficient ◽  
Strain Rates ◽  
Maximum Elongation ◽  
Superplastic Behavior ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Elongation To Failure ◽  
Average Size

The ultrafine grained structure of an AA5024 with an average size of ∼0.7 μm was produced by equal-channel angular pressing (ECAP) at 300°C with a total strain of ~12. Superplastic behavior of this alloy was examined in the temperature interval 175 - 300°C at strain rates ranging from 10-4 to 10-1 s-1. The maximum elongation-to-failure of ~1200% with the corresponding strain rate sensitivity coefficient, m, of ∼0.49 was attained at a temperature of 275°C and a strain rate of 5.6×10–3s–1. At 175°C (~0.53Tm, where Tm is the melting point), the elongation-to-failure of ~370% with the m value of ~0.3 was found at ε̇=1.4×10–4 s–1.

Effect of Ultrasonic Treatment on the Characteristics of Superplasticity of Titanium Alloy Ti-6Al-4V

2018 ◽  
Vol 385 ◽  
pp. 53-58 ◽  
Author(s):  
Asiya Samigullina ◽  
Mariya Murzinova ◽  
Aygul Mukhametgalina ◽  
Alexander P. Zhilyaev ◽  
Ayrat A. Nazarov
Keyword(s):  
Ultrasonic Treatment ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Sensitivity Coefficient ◽  
Strain Rates ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Elongation To Failure ◽  
Induced Defects

Effect of ultrasonic treatment (UST) with an amplitude of oscillating tension-compression stresses 100 MPa on the characteristics of superplastic deformation of Ti-6Al-4V alloy with an ultrafine grained (UFG) structure processed by equal-channel angular pressing (ECAP) is studied. During tensile tests at 600°C with initial strain rates in the interval from 10-4 to 10-3 s-1, ultrasonically irradiated samples exhibit a reduced flow stress, higher values of the strain rate sensitivity coefficient and elongation to failure as compared to the samples tested directly after ECAP. Detailed studies of the microstructure of samples subjected to ECAP only and ECAP followed by UST revealed no considerable differences. It is suggested that the UST affected fine structure of the material bringing them to a state with a higher ability of relaxation of deformation-induced defects.

Evaluating the Flow Properties of Ultrafine-Grained Materials

2013 ◽  
Vol 829 ◽  
pp. 3-9
Author(s):  
Megumi Kawasaki ◽  
Terence G. Langdon
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Elevated Temperatures ◽  
Strain Rates ◽  
Flow Properties ◽  
Ultrafine Grained ◽  
Recent Developments ◽  
Flow Mechanisms ◽  
Small Grains ◽  
Ultrafine Grained Materials

Processing through the application of severe plastic deformation (SPD) provides an opportunity for achieving significant grain refinement, typically to the submicrometer or even the nanometer level. If these small grains are reasonably stable at elevated temperatures, it is possible to achieve excellent superplastic capabilities at very rapid strain rates. Recent developments on the flow properties of ultrafine-grained materials are examined and it is shown that the flow mechanisms can be readily depicted using deformation mechanism maps. Examples of maps are presented for materials processed by SPD techniques.

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