Diffusive and Displacive Phase Transformations Under High Pressure Torsion

Straumal, Boris B.; Kilmametov, Askar; Мазилкин, А. А.; Kogtenkova, Olga Kogtenkova; Baretzky, B.; Korneva, Anna; Zięba, P.

doi:10.12776/ams.v25i4.1368

Cited by 5 publications

(3 citation statements)

References 164 publications

(261 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, it is necessary to explore the relationship between microstructural parameters and their properties. The strength of SPD-deformed materials can be further improved by alloying, as the solute atoms and precipitates have a pinning effect on dislocations and grain boundaries, as shown in previous studies [18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 67%

The Influence of Severe Plastic Deformation and Subsequent Annealing on the Microstructure and Hardness of a Cu–Cr–Zr Alloy

et al. 2020

View full text Add to dashboard Cite

A Cu–1.1%Cr–0.04%Zr (wt.%) alloy was processed by severe plastic deformation (SPD) using the equal channel angular pressing (ECAP) technique at room temperature (RT). It was found that when the number of passes increased from one to four, the dislocation density significantly increased by 35% while the crystallite size decreased by 32%. Subsequent rolling at RT did not influence considerably the crystallite size and dislocation density. At the same time, cryorolling at liquid nitrogen temperature yielded a much higher dislocation density. All the samples contained Cr particles with an average size of 1 µm. Both the size and fraction of the Cr particles did not change during the increase in ECAP passes and the application of rolling after ECAP. The hardness of the severely deformed Cu alloy samples can be well correlated to the dislocation density using the Taylor equation. Heat treatment at 430 °C for 30 min in air caused a significant reduction in the dislocation density for all the deformed samples, while the hardness considerably increased. This apparent contradiction can be explained by the solute oxygen hardening, but the annihilation of mobile dislocations during annealing may also contribute to hardening.

show abstract

Section: Introductionmentioning

confidence: 67%

The Influence of Severe Plastic Deformation and Subsequent Annealing on the Microstructure and Hardness of a Cu–Cr–Zr Alloy

et al. 2020

View full text Add to dashboard Cite

show abstract

“…The amount of ω-phase indeed increases at the beginning of HPT process. However, it saturates after 2-3 anvil rotations together with grain size and torsion torque [20,40]. Thus, the initial instabilities during HPT evolve into the steady state [25,[41][42][43][44][45] It should be noted that decreased amount of the ω-phase after HPT was also observed in Ti-Fe alloys with 0.5, 1, 2.2 and 4wt.% Fe, if the initial state consists of mostly α -martensite in the (α/α )-phase mixture [20,28].…”

Section: Discussionmentioning

confidence: 99%

Influence of β-Stabilizers on the α-Ti→ω-Ti Transformation in Ti-Based Alloys

et al. 2020

Self Cite

View full text Add to dashboard Cite

The development of next generation Ti-based alloys demand completely new processes and approaches. In particular, the Ti-alloys of next generation will contain not only α-Ti and β-Ti phases, but also small amounts of ω-phase and intermetallic compounds. The β→ω phase transformation induced by high-pressure torsion (HPT) has been studied in detail recently. In this work, we investigated the HPT-induced α→ω phase transformation. For this purpose, we added various β-stabilizers into α-Ti matrix of studied Ti-alloys. Ti-alloys with 4% Fe, 2% Cr, 3% Ni, and 4% Co (wt. %) have been annealed at the temperatures below their point of eutectoid decomposition, from β-Ti to α-Ti, and respective intermetallics (TiFe, Ti2Co, Ti2Ni, TiCr2). Volume fraction of HPT-driven ω-phase (from ≤5 up to ~80%) depended on the amount of alloying element dissolved in the α-matrix. Evaluation of lattice parameters revealed accelerated mass transfer during HPT at room temperature corresponding to bulk diffusion in α-Ti at ~600 °С.

show abstract

“…In contrast to conventional metal forming processes, many SPD processes do not practically change the shape of the original specimen. The most widely used processes of this type are equal-channel angular pressing (ECAP) (for example, [ 2 , 3 , 4 , 5 ]) and high-pressure torsion (HPT) (for example, [ 6 , 7 , 8 , 9 , 10 ]). The distribution of material properties is quite uniform in specimens produced by such processes because the state of stress and strain is quite uniform in the plastic region.…”

Section: Introductionmentioning

confidence: 99%

Effect of Rotation of the Principal Stress Axes Relative to the Material on the Evolution of Material Properties in Severe Plastic Deformation Processes

et al. 2020

View full text Add to dashboard Cite

Severe plastic deformation (SPD) processes are widely used for improving material properties. A distinguishing feature of many SPD processes is that the principal axes of the stress tensor intensively rotate relative to the material. Nevertheless, no measure of this rotation is involved in the constitutive equations that predict the evolution of material properties. In particular, a typical way of describing the effect of SPD processes on material properties is to show the dependence of various parameters that characterize these properties on the equivalent strain. However, the same level of the equivalent strain can be achieved in a process in which the principal axes of the stress tensor do not rotate relative to the material. It is, therefore, vital to understand which properties are dependent and which properties are independent of the rotation of the principal axes of the stress tensor relative to the material. In the present paper, a new multistage SPD process is designed such that the principal stress axes do not rotate relative to the material during each stage of the process but the directions of the major and minor principal stresses interchange between two subsequent stages. The process is practically plane strain, and it may be named the process of upsetting by V-shape dies. In addition, axisymmetric compression by Rastegaev’s method is conducted. In this case, the principal stress axes are fixed in the material throughout the entire process of deformation. Material properties and microstructure generated in the two processes above are compared to reveal the effect of the rotation of the principal stress axes relative to the material on the evolution of these properties.

show abstract

Diffusive and Displacive Phase Transformations Under High Pressure Torsion

Cited by 5 publications

References 164 publications

The Influence of Severe Plastic Deformation and Subsequent Annealing on the Microstructure and Hardness of a Cu–Cr–Zr Alloy

The Influence of Severe Plastic Deformation and Subsequent Annealing on the Microstructure and Hardness of a Cu–Cr–Zr Alloy

Influence of β-Stabilizers on the α-Ti→ω-Ti Transformation in Ti-Based Alloys

Effect of Rotation of the Principal Stress Axes Relative to the Material on the Evolution of Material Properties in Severe Plastic Deformation Processes

Contact Info

Product

Resources

About