The Role of the Deformation Conditions in the Evolution of the Microstructure of the Ti-6Al-2Sn-4Zr-6Mo Alloy

2015 ◽  
Vol 641 ◽  
pp. 116-119 ◽  
Author(s):  
Janusz Krawczyk ◽  
Aneta Łukaszek-Sołek ◽  
Robert Dąbrowski
Keyword(s):  
Plastic Deformation ◽  
True Strain ◽  
Processing Temperature ◽  
Strain Rates ◽  
Two Phase ◽  
Β Phase ◽  
Fine Grain ◽  
Α Phase ◽  
Temperature Time

This work discusses the influence of the processing temperature, time and processing strain on the microstructure of the Ti6Al2Sn4Zr6Mo alloy. The Ti6Al2Sn4Zr6Mo alloy belongs to the two-phase (α+β) type of titanium alloys. The samples were compressed with the use of the Gleeble thermo-mechanical simulator at the temperatures of: 800, 900, 950, 1000 and 1100°C and at the strain rates of: 0.01; 0.1; 1; 10 and 100 s-1 to a total true strain of 1. The occurrence of the primary α phase in the Ti6Al2Sn4Zr6Mo alloy was investigated. The diagram showing the influence of the processing temperature and the strain rate on the dynamic recrystallization of the β phase was presented.The occurrence of the primary α phase precipitates blocks the grain growth. Therefore, the plastic deformation of this alloy should be carried out at a temperature at which the separation of the primary α phase occurs to finally obtain a material with a fine grain.

Effect of Strain Amounts on Cold Compression Deformation Mechanism of Ti-55531 Alloy with Bimodal Microstructure

2021 ◽  
Vol 1035 ◽  
pp. 182-188
Author(s):  
Jian Hua Cai ◽  
She Wei Xin ◽  
Lei Li ◽  
Lei Zou ◽  
Hai Ying Yang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Deformation Mechanism ◽  
True Strain ◽  
Bimodal Microstructure ◽  
Free Zone ◽  
Β Phase ◽  
Α Phase ◽  
Initial Stage ◽  
Pile Up ◽  
Dislocation Tangle

The plastic deformation mechanism of Ti-55531 alloy with bimodal microstructure was investigated by compression testing at room temperature. The bimodal microstructure was composed of equiaxed primary α phase (αp) and transformed β (βtrans) that consisted of acicular secondary α phase (αs) and residual β phase (βr). In the initial stage of deformation, the αp grains first underwent plastic deformation, the dislocations germinated and increased, forming the dislocation loop with the dislocation free zone in αp at the true stain of 0.083. With the true strain subsequently increasing to 0.105, the dislocation tangle and dislocation pile-up occurred in αp, and a lot of dislocations were also activated in most of αs. Moreover, the dislocation density was increasing gradually in βr with the adding of strain. Finally, the dislocation pile-up and dislocation tangle appeared in αs and βr at the true strain of 0.163. The whole deformation process was coordinated by αp, αs and βr. They accommodated mutually and completed deformation together.

The Effect of α-Phase Grains Morphology in Initial Microstructure on Superplasticity of Two-Phase Titanium Alloys

2016 ◽  
Vol 838-839 ◽  
pp. 143-149 ◽  
Author(s):  
Maciej Motyka ◽  
Jan Sieniawski
Keyword(s):  
Plastic Deformation ◽  
Titanium Alloys ◽  
Superplastic Deformation ◽  
Thermomechanical Processing ◽  
Ti6al4v Alloy ◽  
Two Phase ◽  
Fine Grained ◽  
Β Phase ◽  
Α Phase ◽  
Heating Up

It is generally accepted that fine-grained and equiaxed microstructure enables superplastic deformation of two-phase titanium alloys. Appropriate microstructure is usually developed in the thermomechanical processing with careful selection of the parameters of plastic deformation and heat treatment. Based on results of own research in this area increased superplasticity was found in Ti6Al4V alloy having microstructure containing highly deformed and elongated α-grains – considerably different from equiaxed ones. It was found that during heating up and first stage of superplastic deformation fragmentation of elongated α-phase grains occurred, followed by formation and growth of globular grains of that phase. Particular role of quenching of the Ti6Al4V alloy from the stable β-phase temperature range in thermomechanical processing was identified. It leads to increase of elongation coefficient of α-phase grains after plastic deformation but also restrains nucleation of the precipitates of secondary α-phase in further stages of thermomechanical processing. It was established that developed phase morphology of the alloy determined its hot plasticity – especially in the range of low strain rates typical for superplastic deformation.

Hot Deformation Behavior of Near-α Ti-Fe Alloy in (α+β) Two-Phase Region with Different Fe Content

2010 ◽  
Vol 638-642 ◽  
pp. 310-314
Author(s):  
Behrang Poorganji ◽  
Makoto Yamaguchi ◽  
Yoshio Itsumi ◽  
Katsushi Matsumoto ◽  
Tomofumi Tanaka ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Deformation Temperature ◽  
Interlamellar Spacing ◽  
Phase Region ◽  
Strain Rates ◽  
Two Phase ◽  
Β Phase ◽  
Α Phase ◽  
Fe Content

In the present study, microstructure evolution of Ti-Fe alloys with different Fe content between 0.2-1.5mass% during hot deformation in (α+β) two-phase region is studied with focusing on effect of phase volume fraction at different deformation temperatures and strain rates. Hot deformation was conducted on the specimens quenched after β solutionizing at 1173K for 1.2ks at 1108, 1073 and 948K, by uniaxial compression by 50% at various strain rates ranged from 1 to 10-4 s-1. Initial structures are (α+β) lamellar structures of fine interlamellar spacing and colony sizes. Increase in Fe content results in increasing the fraction of the β phase at the given deformation temperature. Either colony size or interlamellar spacing is coarser at higher temperatures. At the higher deformation temperature where β phase fraction is larger, dynamic recovery of β phase is a major deformation mechanism while at a lower temperature, i.e., a higher α fraction, dynamic recrystallization of α phase occurs predominantly. It is concluded that critical strain needed for occurrence of dynamic recrystallization is decreased by increasing fraction of the α phase at the same deformation temperature, i.e., by decreasing Fe content. Furthermore, by increasing strain rate grain size of the recrystallized α is decreased.

Phase Transformations of the Ti-40% Nb Alloy Under External Influence

2016 ◽  
Vol 683 ◽  
pp. 174-180 ◽  
Author(s):  
Yuri P. Sharkeev ◽  
Zhanna G. Kovalevskaya ◽  
Margarita A. Khimich ◽  
Vladimir A. Bataev ◽  
Qi Fang Zhu ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Phase Transformation ◽  
Severe Plastic Deformation ◽  
Phase Transformations ◽  
Optical Metallography ◽  
External Influence ◽  
Β Phase ◽  
Α Phase ◽  
Pressing Operation ◽  
Loading Axis

The phase transformations of the alloy Ti-40 mas % Nb after tempering and severe plastic deformation are studied. The phase transformations of the alloy according to the type and conditions of external influences are analyzed using methods of XRD, SEM and optical metallography. It is determined that inverse phase transformation of the metastable α''-phase to equilibrium β-phase is carried out after severe plastic deformation. Complete phase transformation α'' → β is typical for the mode, which consists of three pressing operation with the change of the loading axis in cramped conditions, followed by a multi-pass rolling in grooved rolls.

The Role of Martensitic Transformation in Thermomechanical Development of Microstructure and Plasticity of Two-Phase Ti-6Al-4V Titanium Alloy

2016 ◽  
Vol 687 ◽  
pp. 3-10 ◽  
Author(s):  
Maciej Motyka ◽  
Jan Sieniawski ◽  
Waldemar Ziaja
Keyword(s):  
Plastic Deformation ◽  
Titanium Alloy ◽  
Martensitic Transformation ◽  
Titanium Alloys ◽  
Thermomechanical Processing ◽  
Solution Treatment ◽  
Phase Morphology ◽  
Two Phase ◽  
Α Phase ◽  
Hot Plasticity

Phase constituent morphology in microstructure of two-phase α+β titanium alloys is determined by conditions of thermomechanical processing consisting of sequential heat treatment and plastic deformation operations. Results of previous research indicate that particularly solution treatment preceding plastic deformation significantly changes α-phase morphology and determines hot plasticity of titanium alloys. In the paper thermomechanical processing composed of β solution treatment and following hot forging of Ti-6Al-4V titanium alloy was analysed. Development of martensite plates during heating up and hot deformation was evaluated. Microscopic examinations revealed that elongated and deformed α-phase grains were fragmented and transformed into globular ones. Significant influence of martensitic transformation on elongation coefficient of α-phase grains after plastic deformation was confirmed. Based on results of elevated temperature tensile tests it was established that α-phase morphology in examined two-phase α+β titanium alloy, developed in the thermomechanical processing, can enhance their hot plasticity – especially in the range of low strain rates.

Influence of the Ageing Temperature on the Selected Mechanical Properties of the Ti6Al7Nb Alloy

2015 ◽  
Vol 641 ◽  
pp. 120-123 ◽  
Author(s):  
Robert Dąbrowski ◽  
Janusz Krawczyk ◽  
Edyta Rożniata
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Volume Fraction ◽  
Heating Temperature ◽  
Ageing Temperature ◽  
Sample Length ◽  
Two Phase ◽  
Β Phase ◽  
Α Phase ◽  
The Impact

The results of investigations of the influence of the ageing temperature on the selected mechanical properties i.e. hardness, fracture toughness (examined by the linear elastic fracture mechanics - KIctest) and impact strength (KV) of two-phase Ti6Al7Nb alloy, are presented in the hereby paper. Investigations were performed in the ageing temperatures range: 450÷650°C of the alloy previously undercooled from the selected heating temperature (in two-phase range) - equal 970°C. The heating temperature was determined on the basis of the dilatometric curve of the alloy heating in the system ΔL = f ((T), where: ΔL – change of the sample length, T – temperature, which was then differentiated in the system: ΔL/ΔT = f (T). The dilatometer L78 R.I.T.A of the LINSEIS Company was used in the tests. Investigations of the alloy microstructure in the ageing temperatures range 450÷650°C were carried out by means of the light microscope Axiovert 200 MAT of the Carl Zeiss Company. It was found that nearly equiaxial grains of the primary α phase occur in the microstructure (of the volume fraction app. 30%) and that the volume fraction of the new lamellar α phase - formed from the supersaturated β phase - increases. With an increase of the alloy ageing temperature, in the mentioned above range, a small increase of its hardness from 305 to 324HV as well as a decrease of stress intensity factor KIcfrom 67.3 to 48.6 MPa x m1/2and impact strength (KV) from 40.2 to 31.3 J. The impact tests results were supplemented by the fractographic documentation. It was found, that the characteristic features of the fractures of impact test samples do not exhibit essential differences in dependence of the ageing temperature and material hardness. The fractographic investigations were performed by means of the scanning electron microscope NovaNanoSEM 450.

Monotonic and Cyclic Behavior of Ultrafine Grain Metals:Overview

2006 ◽  
Vol 503-504 ◽  
pp. 267-274 ◽  
Author(s):  
Alexei Vinogradov
Keyword(s):  
Plastic Deformation ◽  
Cyclic Stress ◽  
Grain Boundary Sliding ◽  
Cyclic Behavior ◽  
Ultrafine Grain ◽  
Strain Behavior ◽  
Fine Grain ◽  
Boundary Sliding ◽  
The Common

The available to date experimental results are reviewed with regard to the common aspects and features of monotonic and cyclic stress-strain behavior of various ultra-fine grain materials produced by severe plastic deformation (SPD). Some possible mechanisms of plastic flow and degradation during monotonic and cyclic testing are discussed from the standpoint of initial SPD structure and its evolution upon loading. The role of two strengthening mechanisms – dislocation accumulation and grain reduction - is highlighted. The key importance of grain boundaries for the mechanical behavior, strain localization and fracture of ultra-fine grain metals is argued and the experimental evidence is presented on the significance of grain boundary sliding in their plastic deformation. The results of phenomenological modeling of the monotonic and cyclic response of ultra-fine grain metals are presented in terms of dislocation kinetics and a satisfactory agreement with experimental data is demonstrated.

Role of analytical transmission EM in the study of Zr Pressure-tube alloys

1992 ◽  
Vol 50 (1) ◽  
pp. 206-207
Author(s):  
G.G. Weatherly ◽  
A. Perovic ◽  
V. Perovic ◽  
G.R. Purdy
Keyword(s):  
Heat Treatment ◽  
Nuclear Power ◽  
Cold Work ◽  
Neutron Cross Section ◽  
Zirconium Alloys ◽  
Stress Relief ◽  
Two Phase ◽  
Β Phase ◽  
Pressure Tubes

Zirconium alloys are widely used in the Candu nuclear power generating system because of their unique combination of creep and corrosion resistance properties coupled with a low neutron cross section. The Zr-2.5 wt%Nb alloy has been extensively studied because it is the key component in pressure tubes. Pressure tubes are fabricated by extrusion in the two phase (α + β) field in the binary phase diagram, followed by cold work and stress relief heat treatments. As a result of this treatment, the alloy has a complex microstructure consisting of a duplex α + βzr or α + βNb structure (depending on the particular heat treatment), superimposed on which is a dislocation structure associated with the working operation. Typical microstructures are shown in Figs.l and 2. If the alloy is quenched from the β phase field (1000° C), a Widmanstätten α-βzr microstructure is produced (Fig.la). In the extruded state (Fig.lb), the βZr phase is now elongated and linked by a substructure which contains both <a> and <c> dislocations. Cold working followed a stress relief heat treatment at 400°C for 24 hrs introduces predominantly <a> dislocations, while the βZr phase (which is metastable) has decomposed to form discrete arrays of βNb (Fig-lc). Examples of the dislocation substructure are shown in Fig.2. Boundaries containing both <a> and <c> dislocations are observed. The misorientation at the boundaries is typically a few degrees. They are often stepped or faceted. In Fig.2 the steps correspond to a <c> dislocation which has dissociated to form two <c>/2 dislocations.

scholarly journals Effect of Third-Stage Heat Treatments on Microstructure and Properties of Dual-Phase Titanium Alloy

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2776
Author(s):  
Xiqin Mao ◽  
Meigui Ou ◽  
Desong Chen ◽  
Ming Yang ◽  
Wei Long
Keyword(s):  
Tensile Strength ◽  
Titanium Alloy ◽  
Aging Treatment ◽  
Air Cooling ◽  
Phase Zone ◽  
Two Phase ◽  
Β Phase ◽  
Solution Treated ◽  
Α Phase ◽  
Third Stage

Two-phase TC21 titanium alloy samples were solution-treated at 990 °C (β phase zone) and cooled by furnace cooling (FC), air cooling (AC), and water quenching (WQ), respectively. The second solution stage treatment was carried out at 900 °C (α + β phase zone), then aging treatment was performed at 590 °C. The influence of the size and quantity of the α phase on the properties of the sample were studied. The experimental results showed as the cooling rate increased after the first solution stage treatment, wherein the thickness of primary layer α gradually decreased, and the tensile strength and yield strength gradually increased. After the second solution stage treatment, the tensile properties of samples increased due to the quantity of layers α increased. The aging treatment promoted the precipitation of the dispersed α phase and further improved the tensile strength. After the third solution stage treatments, the FC samples with more β-phase had the best comprehensive mechanical properties.

Microstructural Features and Mechanical Properties of the Ti-6Al-4V ELI Alloy Processed by Severe Plastic Deformation

2006 ◽  
Vol 503-504 ◽  
pp. 757-762 ◽  
Author(s):  
Irina P. Semenova ◽  
Lilia R. Saitova ◽  
Georgy I. Raab ◽  
Alexander Korshunov ◽  
Yuntian T. Zhu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Volume Fraction ◽  
Structure Refinement ◽  
Β Phase ◽  
Microstructure Stability ◽  
Α Phase ◽  
Initial Billet ◽  
Temperature Ageing ◽  
Preliminary Thermal Treatment

This paper investigates microstructures and mechanical properties of the TI-6AL-4V ELI alloy processed by ECAP and extrusion with various morphology of α and β-phase. Preliminary thermal treatment consisted of quenching and further high-temperature ageing. The present work reveals that the decrease of volume fraction of α-phase globular component in the initial billet results in a more homogeneous structure refinement during SPD, lower internal stress, enhancement of microstructure stability and mechanical properties. An ultimate strength of UTS ≥1350 MPa was obtained in the Ti-6Al-4V ELI alloy while maintaining a ductility of δ≥11%.

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