scholarly journals Ultrasonic Welding of Nickel with Coarse and Ultrafine Grained Structures

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1800
Author(s):  
Elvina R. Shayakhmetova ◽  
Mariya A. Murzinova ◽  
Ayrat A. Nazarov
Keyword(s):  
High Pressure Torsion ◽  
Ultrasonic Welding ◽  
Coarse Grained ◽  
Shear Tests ◽  
Weld Joints ◽  
Lap Shear ◽  
Ultrafine Grained ◽  
Welding Interface ◽  
Optimal Values ◽  
First Time

Solid state joints of samples of coarse-grained (CG) and ultrafine-grained (UFG) nickel have been obtained for the first time using spot ultrasonic welding (USW). The UFG structure in disk-shaped samples was processed by means of high-pressure torsion (HPT). On the basis of lap shear tests, the optimal values of the clamping force resulting in the highest values of the joint strength are determined. The microstructures in the weld joints obtained at optimal parameters of USW are characterized by scanning electron microscopy. It is shown that during ultrasonic welding of coarse-grained nickel, a thin layer with an UFG microstructure is formed near the weld surfaces. The bulks of sheets retain the CG microstructure, but a significant dislocation activity is observed in these regions. During USW of samples having an UFG initial microstructure, significant grain growth occurs. Fine grains are observed only along the welding interface. An average lap shear strength of 97 MPa was obtained by welding the UFG samples, which was approximately 40% higher than the strength of samples processed by welding coarse-grained sheets (70 MPa). It is concluded that higher strength weld joints can be obtained by using sheets with the UFG structure as compared to the CG sheets.

scholarly journals Microstructure and strength of joints of nickel sheets produced by ultrasonic welding

2021 ◽  
pp. 75-81
Author(s):  
E. R. Shayakhmetova ◽  
◽  
M. A. Murzinova ◽  
A. A. Nazarov ◽  
◽  
...  
Keyword(s):  
Shear Strength ◽  
Solid Phase ◽  
Copper Alloys ◽  
Compressive Load ◽  
Ultrasonic Welding ◽  
Coarse Grained ◽  
Lap Shear Strength ◽  
Fine Grained ◽  
Weld Joints ◽  
Lap Shear

Ultrasonic welding (USW) is one of the methods for producing solid-phase joints of thin metal sheets, which in the future can be used to obtain laminated composite materials, for additive manufacturing and renovation of metallic articles. The quality of joints depends on both the processing conditions and the properties of welded metals and alloys. At present, the USW conditions, the properties, and structure of weld joints of strong metals, in particular, of nickel, are underexplored. In this work, the authors studied the influence of the compressive load magnitude on the lap shear strength and the structure of joints of annealed nickel sheets with a thickness of 0.5 mm produced by spot USW. The authors carried out USW at a vibration frequency of 20 kHz with an amplitude of 15 μm, the time of welding was equal to 2 s. The compressive load magnitude was varied from 3.5 to 7 kN. The study showed that with an increase in the compressive load in the considered range of values, the strength of weld joints increased, reached a maximum, and then decreased. The joints obtained at the compressive load of 6 kN demonstrated the highest lap shear strength of 1950 N. A zone of thermomechanical influence with a gradient microstructure is observed near the contact of the welded surfaces. In a layer with a thickness of 10–20 mm, the initial coarse-grained structure of nickel is transformed into an ultra-fine-grained one with a grain size of less than 1 mm. The ultra-fine-grained layer neighbors on crystallites, the size of which is several micrometers and increases with a distance from the contact surface of welded sheets. The authors compared the results of mechanical lap shear tests and structural studies with the data obtained after ultrasonic welding of nickel, aluminum, and copper alloys.

Grain Refinement and Deformation Behavior of Ultrafine Grained Pd and Pd-Ag Alloys Produced by HPT

2008 ◽  
Vol 584-586 ◽  
pp. 182-187
Author(s):  
Lilia Kurmanaeva ◽  
Yulia Ivanisenko ◽  
J. Markmann ◽  
Ruslan Valiev ◽  
Hans Jorg Fecht
Keyword(s):  
Mechanical Properties ◽  
Deformation Behavior ◽  
Materials Science ◽  
High Pressure Torsion ◽  
Uniform Elongation ◽  
Grain Structure ◽  
Coarse Grained ◽  
Ultrafine Grain ◽  
Ultrafine Grained ◽  
Ultrafine Grain Structure

Investigations of mechanical properties of nanocrystalline (nc) materials are still in interest of materials science, because they offer wide application as structural materials thanks to their outstanding mechanical properties. NC materials demonstrate superior hardness and strength as compared with their coarse grained counterparts, but very often they possess a limited ductility or show low uniform elongation due to poor strain hardening ability. Here, we present the results of investigation of the microstructure and mechanical properties of nc Pd and Pd-x%Ag (x=20, 60) alloys. The initially coarse grained Pd-x% Ag samples were processed by high pressure torsion, which resulted in formation of homogenous ultrafine grain structure. The increase of Ag contents led to the decrease of the resulted grain size and change in deformation behavior, because of decreasing of stacking fault energy (SFE). The samples with larger Ag contents demonstrated the higher values of hardness, yield stress and ultimate stress. Remarkably the uniform elongation had also increased with increase of strength.

Enhanced Thermal Stability and Mechanical Properties of Ultrafine-Grained Aluminum Alloy

2010 ◽  
Vol 667-669 ◽  
pp. 331-336 ◽  
Author(s):  
Rinat K. Islamgaliev ◽  
Marina A. Nikitina ◽  
Aidar F. Kamalov
Keyword(s):  
Thermal Stability ◽  
Aluminum Alloy ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Coarse Grained ◽  
Dynamic Precipitation ◽  
Ultrafine Grained ◽  
The Mean ◽  
Fatigue Endurance ◽  
Thermal Stability Of

The paper reports on microstructure, strength and fatigue of ultrafine-grained (UFG) samples of the Al-Cu-Mg-Si aluminum alloy processed by high pressure torsion (HPT) at various temperatures. Application of the HPT treatment led to strong grain refinement, as well as to a raise of the mean-root square strains and dynamic precipitation. In case of optimal HPT treatment the UFG samples have demonstrated the enhanced thermal stability, an increase in ultimate tensile strength in 2.5 times and enhancement in fatigue endurance limit by 20 % in comparison with coarse-grained alloy subjected to standard treatment. It is shown that the regime of the HPT treatment governs the volume fraction of precipitates and segregations, thereby affecting a grain size and thermal stability of ultrafine-grained structure.

scholarly journals Особенности упрочнения структурированного интенсивной пластической деформацией сплава Al-Cu-Zr

2021 ◽  
Vol 63 (10) ◽  
pp. 1572
Author(s):  
Т.С. Орлова ◽  
Д.И. Садыков ◽  
М.Ю. Мурашкин ◽  
В.У. Казыханов ◽  
Н.А. Еникеев
Keyword(s):  
High Pressure Torsion ◽  
High Strength ◽  
Coarse Grained ◽  
X Ray Diffraction ◽  
Microstructural Parameters ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Preliminary Annealing ◽  
Coarse Grained State ◽  
Additional Hardening

The effect of small additions of copper on the microstructure and physic-mechanical properties of an ultrafine-grained Al-1.47Cu-0.34Zr (wt%) alloy structured by high pressure torsion after preliminary annealing at 375 °C for 140 h has been studied. As a result of processing, high values of strength characteristics (conditional yield strength 430 MPa, ultimate tensile strength 574 MPa) with an acceptable level of electrical conductivity (46.1% IACS) and ductility (elongation to fracture ~ 5%) have been achieved. On the basis of the microstructural parameters determined by X-ray diffraction analysis and transmission electron microscopy, hardening mechanisms responsible for such high strength have been analyzed. It was shown that Cu plays the key role in strengthening. The addition of copper significantly contributes to grain refinement and, consequently, to grain-boundary hardening. Alloying with copper leads to significant additional hardening (~ 130 MPa) in the ultrafine-grained alloy, which is not typical for coarse-grained state. Segregation of Cu at grain boundaries and the formation of Cu nanoclusters are the most probable reasons for this hardening.

scholarly journals Влияние температуры деформации на эффект реализации высокой пластичности в ультрамелкозернистом сплаве Al-1.5Cu

2021 ◽  
Vol 63 (10) ◽  
pp. 1585
Author(s):  
А.М. Мавлютов ◽  
Т.С. Орлова ◽  
Э.Х. Яппарова ◽  
Н.А. Еникеев ◽  
М.Ю. Мурашкин
Keyword(s):  
Low Temperature ◽  
High Pressure Torsion ◽  
Additional Treatment ◽  
Mechanical Tension ◽  
Low Temperature Annealing ◽  
Commercially Pure ◽  
Ultrafine Grained ◽  
First Time ◽  
Temperature Side ◽  
High Ultimate Tensile Strength

For the first time the influence of temperature of mechanical tension on the plastification effect (PE) in ultrafine-grained (UFG) Al-1.5Cu (wt.%) alloy was studied. The UFG structure in the material was formed by high pressure torsion (HPT). A significant increase in the plasticity (from ~ 3% to 22%) of the UFG alloy while maintaining high ultimate tensile strength (450 MPa) was achieved by additional treatment, including low temperature annealing and subsequent small additional HPT deformation. The temperature range of the PE implementation was revealed. It was shown that decrease of the deformation temperature leads to a gradual decrease of the PE and its disappearance at –20 oC. Cu alloying led to a significant narrowing of the range of PE implementation from low temperature side compared to the UFG commercially pure Al. Possible reasons of the influence of Cu alloying on temperature dependence of the PE are discussed.

The Effect of Ultrafine-Grained Structure of Al-30Zn on the Shape Forming Ability at Sheet Metal Forming

2018 ◽  
Vol 385 ◽  
pp. 228-233
Author(s):  
Elena V. Bobruk ◽  
Denis G. Tyulenev ◽  
Oleg V. Golubev ◽  
Maxim Y. Murashkin
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Aluminum Matrix ◽  
Test Method ◽  
Coarse Grained ◽  
Angular Pressing ◽  
Ultrafine Grained

High pressure torsion (HPT) and equal channel angular pressing in parallel channels (ECAP-PC) at room temperature are used to form homogeneous ultrafine-grained (UFG) structure with a grain size of the aluminum matrix of 350 and 700 nm, respectively, in Al-30Zn (wt. %) specimens. The UFG samples with special geometry produced from the specimens processed by SPD techniques were subjected to sphere-shaped dimple extrusion testing (via the Erikson test method) and bended plate extrusion to determine the material formability during cold sheet metal forming. The same tests were performed on the material with coarse-grained (CG) structure for the sake of comparison. The obtained results are discussed.

scholarly journals Effect of Grain Boundaries on the Electron Work Function of Ultrafine Grained Aluminum

2018 ◽  
Vol 57 (1) ◽  
pp. 110-115 ◽  
Author(s):  
T.S. Orlova ◽  
A.V. Ankudinov ◽  
A.M. Mavlyutov ◽  
N.N. Resnina
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Work Function ◽  
High Pressure Torsion ◽  
Electron Work Function ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Different Temperatures ◽  
First Time ◽  
Specific Length

Abstract The electron work function (EWF) of ultrafine grained (UFG) aluminum structured by high pressure torsion (HPT) has been investigated. For the first time, the dependence of the EWF on the specific length of grain boundaries (or the grain size) for UFG Al has been obtained. The change of average grain size was achieved by short term annealing of HPT-processed aluminum at different temperatures from the range 90-400 °C. It has been shown that the state of grain boundaries (GBs) affects the magnitude of the EWF. It has been found that the transformation of GBs due to annealing at 90 °C from a nonequilibrium to more equilibrium state while maintaining the specific length of GBs and their average misorientation is accompanied by a decrease in average GB specific energy by 0.3 J m-2. This transition provides a sharp increase in the EWF of the UFGAl by 0.25 eV.

Emission Nuclear Gamma-Resonance Spectroscopy of Grain Boundaries in Coarse-Grained and Ultrafine-Grained Polycrystalline Mo

2015 ◽  
Vol 364 ◽  
pp. 147-156 ◽  
Author(s):  
Vladimir V. Popov ◽  
A.V. Sergeev ◽  
A.V. Stolbovsky
Keyword(s):  
High Pressure ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
High Pressure Torsion ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Coarse Grained ◽  
Resonance Spectroscopy ◽  
Nuclear Gamma Resonance ◽  
Ultrafine Grained

Grain boundaries in coarse-grained Mo with grain boundaries of recrystallization origin and in ultrafine-grained (UFG) Mo obtained by high pressure torsion have been studied by the emission Mössbauer spectroscopy on the57Co (57Fe) nuclei. It is demonstrated that Co atoms diffuse along grain boundaries by interstitials. The temperature dependence of grain-boundary segregation factor of Co in coarse-grained Mo has been determined. It is shown that the state of Co atoms in grain boundaries and near-boundary areas in UFG Mo differs from that in coarse-grained Mo.

scholarly journals Phase Transformations upon Ageing in Ti15Mo Alloy Subjected to Two Different Deformation Methods

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1230
Author(s):  
Kristína Bartha ◽  
Josef Stráský ◽  
Anna Veverková ◽  
Jozef Veselý ◽  
Jakub Čížek ◽  
...  
Keyword(s):  
High Pressure Torsion ◽  
Positron Annihilation Spectroscopy ◽  
Lattice Defects ◽  
Coarse Grained ◽  
Two Phase ◽  
Rotary Swaging ◽  
Α Phase ◽  
Ultrafine Grained ◽  
Isothermal Ageing ◽  
Α Particles

Ti15Mo alloy was subjected to two techniques of intensive plastic deformation, namely high pressure torsion and rotary swaging at room temperature. The imposed strain resulted in the formation of an ultrafine-grained structure in both deformed conditions. Detailed inspection of the microstructure revealed the presence of grains with a size of around 100 nm in both conditions. The microstructure after rotary swaging also contained elongated grains with a length up to 1 µm. Isothermal ageing at 400 °C and 500 °C up to 16 h was applied to both conditions to investigate the kinetics of precipitation of the α phase and the recovery of lattice defects. Positron annihilation spectroscopy indicated that the recovery of lattice defects in the β matrix had already occurred at 400 °C and, in terms of positron trapping, was partly compensated by the precipitation of incoherent α particles. At 500 °C the recovery was fully offset by the formation of incoherent α/β interfaces. Contrary to common coarse-grained material, in which the α phase precipitates in the form of lamellae, precipitation of small and equiaxed α particles occurred in the deformed condition. A refined two-phase equiaxed microstructure with α particles and β grain sizes below 1 μm is achievable by simple rotary swaging followed by ageing.

scholarly journals Fatigue Behavior of Ultrafine Grained Medium Carbon Steel with Different Carbide Morphologies Processed by High Pressure Torsion

2014 ◽  
Vol 891-892 ◽  
pp. 428-433 ◽  
Author(s):  
Christoph Ruffing ◽  
Eberhard Kerscher
Keyword(s):  
High Pressure ◽  
Crack Initiation ◽  
High Pressure Torsion ◽  
Fatigue Behavior ◽  
Coarse Grained ◽  
Initial Microstructure ◽  
Fracture Surfaces ◽  
Carbide Morphology ◽  
Ultrafine Grained ◽  
1045 Steel

The increased attention that ultrafine grained (UFG) materials have received over the last decade has been provoked, not least, by their high strength in combination with remarkable ductility. The main focus of our investigation was the evaluation of the effect of different carbide morphologies in the initial microstructure on the fatigue behavior after high pressure torsion (HPT) treatment of SAE 1045 steel. In our case HPT increased the hardness by a factor of 1.75 - 3.2 compared to the initial states. The achieved hardness maximum was 726 HV. The amount of increase depended on the initial carbide morphology. By stress controlled cyclic four point bending tests with a load ratio of 0.1 endurance limits were determined for the initial and HPT states. The endurance limit increased linearly with hardness until 500 HV and independently of the carbide morphology. All fracture surfaces were investigated by SEM after the fatigue tests. They revealed pretty flat fatigue fracture surfaces with crack initiation at the surface or rather at non-metallic inclusions for the UFG states. Morphology and crack initiation mechanisms were changed by severe plastic deformation compared with the coarse grained initial state. Residual fracture surfaces with a spheroidal initial microstructure showed well-defined dimple structures also after HPT at high fatigue limits and high hardness values. In contrast, the specimens with initial tempered microstructure showed rather brittle and rough residual fracture surfaces.

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