scholarly journals Slippage during high-pressure torsion of commercially pure titanium and application of accumulative HPT to it

2022 ◽  
Vol 1213 (1) ◽  
pp. 012003
Author(s):  
D V Gunderov ◽  
A A Churakova ◽  
A V Sharafutdinov ◽  
V D Sitdikov ◽  
V V Astanin
Keyword(s):  
High Pressure ◽  
High Pressure Torsion ◽  
Pure Titanium ◽  
Phase Changes ◽  
Phase Content ◽  
Commercially Pure Titanium ◽  
Micro Hardness ◽  
Ω Phase ◽  
Commercially Pure ◽  
First Time

Abstract A new efficient method was used to find that in the case of high-pressure torsion of commercially pure titanium, accumulation of shear strain in Ti does not occur due to slippage of anvils. Despite this, micro-hardness increases as the number of turns n increases, and Ti structure is refined more intensively. High-pressure torsion is accompanied by a high-pressure ω-phase formation. However, the content of ω-phase changes non-monotonously with an increase in the number of turns. First, while number of turns is less than n=5, the ω-phase content reaches 50%. Upon further deformation, the ω-phase content decreases to 15% for n=20. A new accumulative high-pressure torsion method is applied to commercially pure titanium for the first time. Accumulative high-pressure torsion leads to the strongest transformation of the structure and an increase in hardness, since stronger real deformation occurs due to composition of compression and torsion strain cycles.

scholarly journals Influence of HPT and Accumulative High-Pressure Torsion on the Structure and Hv of a Zirconium Alloy

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 573
Author(s):  
Dmitry Gunderov ◽  
Andrey Stotskiy ◽  
Yuri Lebedev ◽  
Veta Mukaeva
Keyword(s):  
High Pressure ◽  
Zirconium Alloy ◽  
High Pressure Torsion ◽  
Ti Alloy ◽  
Micro Hardness ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ω Phase ◽  
First Time ◽  
Torsion Deformation

The authors previously used the accumulative high-pressure torsion (ACC HPT) method for the first time on steel 316, β-Ti alloy, and bulk metallic glass vit105. On low-alloyed alloys, in particular, the zirconium alloy Zr-1%Nb, the new method was not used. This alloy has a tendency to α → ω phase transformations at using simple HPT. When using ACC HPT, the α → ω transformation can be influenced to a greater extent. This article studies the sliding effect and accumulation of shear strain in Zr-1%Nb alloy at various stages of high-pressure torsion (HPT). The degree of shear deformation at different stages of HPT was estimated. The influence of various high-pressure torsion conditions on the micro-hardness and phase composition by X-ray diffraction (XRD) of Zr-1%Nb was analyzed. It is shown that at high-pressure torsion revolutions of n = 2, anvils and the specimen significantly slip, which is a result of material strengthening. It was found that despite sliding, regular high-pressure torsion resulted in the high strengthening of Zr-1%Nb alloy (micro-hardness more than doubled), and after high-pressure torsion n = 10, up to 97% of the high-pressure ω-phase was formed in it (as in papers of other researchers). Accumulative high-pressure torsion deformation leads to the strongest transformation of the Zr-1%Nb structure and Hv and, therefore, to a higher real strain of the material due to composition by upsetting and torsion in strain cycles.

The Influence of Laser Irradiation Parameters on Tribological Behaviour of Commercially Pure Titanium for Dental Prostheses

2016 ◽  
Author(s):  
Karibeeran Shanmuga Sundaram ◽  
Gurusami Kiliyappan ◽  
Senthil Kumaran Selvadurai
Keyword(s):  
Surface Roughness ◽  
Wear Resistance ◽  
Pure Titanium ◽  
Laser Surface ◽  
Commercially Pure Titanium ◽  
Laser Shock ◽  
Micro Hardness ◽  
Dental Prostheses ◽  
Commercially Pure ◽  
Cp Ti

Laser shock peening (LSP) is one of the innovative technique that produces a compressive residual stress on the surface of metallic materials, thereby significantly increasing its fatigue life in applications where failure is caused by surface-initiated cracks. The specimens were treated with laser shock waves with different processing parameters, and characterization studies were made on treated specimens. The purpose of the present study was to investigate the influence of Nd:YAG laser on commercially pure titanium (CP-Ti) used in prosthetic dental restorations. The treatment influenced change in microstructure, micro hardness, surface roughness, and wear resistance characteristics. Though CP-Ti is considered as an excellent material for dental applications due to its outstanding biocompatibility, it is not suitable when high mastication forces are applied. In the present study, pulsed Nd:YAG laser surface treatment technique was adopted to improve the wear resistance of CP-Ti. The wear test pin specimens of CP-Ti were investment cast with centrifugal titanium casting machine. The wear properties of specimens were evaluated after LSP on a “pin-on-disc” wear testing tribometer, as per ASTM G99-05 standards. The results of the wear experiment showed that the treated laser surface has higher wear resistance, micro hardness, and surface roughness compared to as-cast samples. The improvement of wear resistance may be attributed due to grain refinement imparted by LSP processes. The microstructure, wear surfaces, wear debris, and morphology of the specimen were analyzed by using optical electron microscope, scanning electron microscope, and X-ray diffraction (XRD). The data were compared using ANOVA and post-hoc Tukey tests. The characteristic change resulted in increase in wear resistance and decrease in wear rate. Hence, it is evident that the more reliable and removable partial denture metal frameworks for dental prostheses may find its applications.

X-Ray Analysis of High Pressure Torsion Induced Nanostructures in Ti and Ni

2006 ◽  
Vol 114 ◽  
pp. 329-336 ◽  
Author(s):  
A.R. Kilmametov ◽  
Ruslan Valiev ◽  
Igor V. Alexandrov
Keyword(s):  
High Pressure ◽  
High Pressure Torsion ◽  
Applied Pressure ◽  
Orientation Distribution ◽  
Nanocrystalline State ◽  
Cubic Symmetry ◽  
X Ray ◽  
Ω Phase ◽  
Commercially Pure ◽  
Pressure Phase

X-ray investigations revealed that the increase in the applied pressure during high pressure torsion (HPT) of commercially pure Ti leads not only to substructure refinement with an increase of the dislocation density and microstrain level but also to an α→ ω phase transition at room temperature. The coexistence of both α and ω phases, the latter known as a high pressure phase, in the ratio approximately of 1:3 has been obtained after removal of thehigh pressure. Texture analysis of electodeposited Ni after HPT discovered a new form of crystallite orientation distribution in the nanocrystalline state. A nearly random orientation crystallite distribution has been observed unlike the “traditional” case of a shear texture forming in cubic symmetry metals. The crystallographic texture data obtained were considered as experimental evidence of the changed plastic deformation mechanisms in nanocrystalline Ni produced by HPT.

scholarly journals Influence of Inhomogeneity on Mechanical Properties of Commercially Pure Titanium Processed by HPT

2018 ◽  
Vol 385 ◽  
pp. 284-289 ◽  
Author(s):  
Alexander P. Zhilyaev ◽  
Yi Huang ◽  
Jose María Cabrera ◽  
Terence G. Langdon
Keyword(s):  
Mechanical Properties ◽  
High Pressure Torsion ◽  
Structural Phase ◽  
Pure Titanium ◽  
High Strength ◽  
Alpha Phase ◽  
Commercially Pure Titanium ◽  
Omega Phase ◽  
Commercially Pure ◽  
Ti Powder

Already for fifteen years many researchers have been trying to discover metallic materials with unusual combinations of strength and ductility: with high strength and enhanced ductility. This combination may be achieved through different ways: alloying, nanostructuring, etc. This report is an attempt to analyze the influence of inhomogeneity of different types (structural, phase and space) on mechanical properties of commercially pure titanium (bulk and powder) subjected to high-pressure torsion. Experimental results for HPT bulk and powder titanium have demonstrated that mechanical behavior of CP titanium strongly depends on phase inhomogeneity (alpha + omega phases), structural inhomogeneity (bimodal grain size distribution) and space inhomogeneity (retained porosity) in case of cold consolidated Ti powder. High strength in HPT bulk titanium due to the formation of hard omega phase during HPT processing at room temperature was detected. The strong omega phase transforms back to nanograined alpha phase domains during short annealing at elevated temperature. HPT consolidation of titanium powder leads to the formation of brittle specimens showing high strength but almost zero plasticity.

CP-Ti Processed for Multiple Passes by ECAP at Room Temperature

2010 ◽  
Vol 667-669 ◽  
pp. 779-784
Author(s):  
Xi Rong Yang ◽  
Xi Cheng Zhao ◽  
Xiao Yan Liu
Keyword(s):  
Room Temperature ◽  
Elevated Temperatures ◽  
Pure Titanium ◽  
Commercially Pure Titanium ◽  
Micro Hardness ◽  
Angular Pressing ◽  
Commercially Pure ◽  
Series Of Experiments ◽  
Ram Speed ◽  
Cp Ti

A series of experiments were conducted to evaluate the feasibility that commercially pure titanium (CP-Ti) was pressed for multiple passes by equal channel angular pressing (ECAP) at room temperature. Samples of CP-Ti were processed at room temperature using the dies with channel angles of 90° and 120°, respectively. First, each billet was processed 4 passes by ECAP using a die with an angle of 120° and a ram speed of 0.5mm s-1. And in order to eliminate residual stress, immediate annealing at 473 K for an hour was conducted between two adjacent passes. Second, CP-Ti was successfully processed by ECAP for up to 8 passes using the same die and a ram speed of 2 mm s-1 by controlling the flow of metal. Finally, CP-Ti was successfully achieved using a conventional die with an angle of 90° between the channels at room temperature. Each billet was processed for two passes with a ram speed of 26 mm s-1. These experiments show that CP-Ti may be processed by ECAP at room temperature and special attention was paid on improvements in the yield stress, ultimate strength and micro-hardness of ECAPed-Ti that are slightly higher than the improvements attained after pressing at elevated temperatures.

scholarly journals Structural and Mechanical Properties of Ti–Co Alloys Treated by High Pressure Torsion

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 426 ◽  
Author(s):  
Boris Straumal ◽  
Anna Korneva ◽  
Askar Kilmametov ◽  
Lidia Lityńska-Dobrzyńska ◽  
Alena Gornakova ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Annealing Temperature ◽  
High Pressure Torsion ◽  
Pure Titanium ◽  
Eutectoid Transformation ◽  
Ω Phase ◽  
Preliminary Annealing ◽  
Increasing Temperature ◽  
Co Alloys

The microstructure and properties of titanium-based alloys can be tailored using severe plastic deformation. The structure and microhardness of Ti–4 wt.% Co alloy have been studied after preliminary annealing and following high pressure torsion (HPT). The Ti–4 wt.% Co alloy has been annealed at 400, 500, and 600 °C, i.e., below the temperature of eutectoid transformation in the Ti–4 wt.% Co system. The amount of Co dissolved in α-Ti increased with increasing annealing temperature. HPT led to the transformation of α-Ti in ω-Ti. After HPT, the amount of ω-phase in the sample annealed at 400 °C was about 80­85%, i.e., higher than in pure titanium (about 40%). However, with increasing temperature of pre-annealing, the portion of ω-phase decreased (60–65% at 500 °C and about 5% at 600 °C). The microhardness of all investigated samples increased with increasing temperature of pre-annealing.

TiC/Ti Composite Layers Fabricated by Laser Surface Alloying

2007 ◽  
Vol 336-338 ◽  
pp. 1148-1150
Author(s):  
Jian Bin Zhang ◽  
Ding Fan ◽  
Jing Jie Dai ◽  
Yao Ning Sun
Keyword(s):  
Continuous Wave ◽  
Composite Layer ◽  
Pure Titanium ◽  
Surface Hardness ◽  
Laser Surface ◽  
Commercially Pure Titanium ◽  
Surface Alloying ◽  
Micro Hardness ◽  
Laser Surface Alloying ◽  
Commercially Pure

Laser surface alloying is an attractive processing to improve surface hardness, wear and corrosion resistance. In this paper, a continuous wave CO2 laser was used to irradiate commercially pure titanium surface with pre-placed active carbon powders in argon atmosphere. A compact, well-adherent, and crack-free TiC/Ti composite layer was obtained. The microstructure and phase constitution of the alloyed layers were determined and analyzed, and the micro-hardness was measured. The result of X ray diffraction (XRD) analysis shows that the alloyed layers contain TiC and Ti (martensite). The scanning electron microscopy (SEM) observation shows TiC growth morphologies have a well-developed dendrite, cellular dendrite, globular microstructure and cross-petal microstructure. The mechanism of the formation of titanium carbides is discussed. Micro-hardness of the laser surface alloyed layer was improved to 420 Hv as compared to 200 Hv of the as-received commercially pure titanium.

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