Plastic Flow Of Metals Research Articles

Study on the bonding mechanism of multilayer copper with nickel sheet in ultrasonic welding process

The metal-plastic flow and bonding strength of three-layer copper (Cu) with single-layer nickel (Ni) joints via ultrasonic welding were investigated in this study. With the increase of welding time from 0.3 to 0.5 s, the weld bonding density between different layers’ interface increased gradually and approached about 95 ± 1.5%. Electron backscatter diffraction (EBSD) analysis of different regions of the welded joint revealed that the metal grains in the 1st layer became relatively small and elongated, while the 2nd and 3rd layers tended to be equiaxed grains. The joint bonding strength of T-peel tests changed with welding time and had two kinds of fracture models (nugget pullout and interfacial fracture). Compared with the bonding strength of the 1st-2nd and 3rd-4th interface, the 2nd-3rd interface of joints had the highest bonding strength of 400.6 N with nugget pullout fracture model at welding time of 0.4 s. In addition, the much higher hardness of the 1st layer is attributed to the strong plastic deformation of the 1st layer, while the dynamic recovery and dynamic recrystallization of the metal of the 2nd layer resulted in the decrease of hardness.

Development of methodology and technical equipment for study of metal plastic flow in processing processes. Part 1. Design and manufacture of special bench-type milling CNc mashine for study of plastic flow of metal

Experimental evaluation of the metal plastic flow in the mechanical processing processes is an important task both to substantiate the correctness of the solutions obtained by finite element modeling, and to formulate reasonable recommendations for establishing modeling boundary and initial conditions. One of the effective methods for estimating of the material particles movement during various processes is the particle image velocimetry method (PIV). To implement this method for the processes of cutting and deep rolling, it is necessary to ensure high requirements for experimental equipment. Analysis of the existing CNC machines characteristics has shown the required characteristics are not fully provided. Therefore, a special CNC machine was developed and manufactured for experimental research, providing high drive power, rigidity, vibration resistance and accuracy.

Justification of the Application of Resource-Saving Technology for the Restoration of Metal-Intensive Rear Semi-Axles of Trucks Using Hot Plastic Deformation

The article is devoted to the substantiation of technological foundations for the restoration of extremely worn-out, metal-consuming, and resource-consuming parts, in a method consisting of applying a compensating metal wear with subsequent plastic deformation. Currently, there are no technologies for their restoration in a repair facility that guarantee the resilience of the factory product. The proposed technological process of repair consists of butt welding onto the end of the spline semi-axle shank, compensating for the wear of the metal, the volume of which takes into account the losses resulting from the wear of the slots, as well as allowances for their machining. In the example of forging the axle shaft of a truck’s driving axle, the regularities of the plastic flow of metal during part deformation in the stamp are revealed. In the process of hot volumetric upsetting of long cylindrical parts with a variable diameter, it is important to know the possible directions of metal movements, as well as the energy-power characteristics of the process at various stages of forging. The evaluation criteria of the level of perfection of the technology were indicators of resource conservation and efficiency of the recovery route. The technological direction of the conducted research was analyzed, step by step, from the standpoint of saving repair materials and energy resources. The results of theoretical studies are crucial in the design of die tooling, for the manufacture of blanks, when restoring the rear axle shafts of trucks with pressure. Production tests carried out on the models, obtained as a result of mathematical processing of experimental data, confirmed the reliability of the experimental information. The introduction of the proposed set of repair equipment for the restoration of semi-axles will allow the formation of additional production in the region for the recycling of worn-out metal-intensive steel parts of agricultural machinery.

Interface Characteristics and Bonding Performance of the Corrugated Mg/Al Clad Plate.

In this paper, a corrugated Mg/Al clad plate was successfully manufactured by an upper corrugated roller and a lower flat roller at 400 °C rolling temperature and 35% reduction ratio. Interface bonding performance of the corrugated Mg/Al clad plate was studied by tensile-shear test. The finite element method was used to simulate the corrugated rolling process. Experiment results revealed that the Mg/Al clad plate fabricated by corrugated roller had a tight bonding interface, no crack, and no intermetallic compounds. The transverse tensile-shear strength at the trough position reached 31.22 MPa, and the tensile-shear strength at the peak position was 17.61 MPa. It can be found that the stress and strain of interface metal at the trough position were the largest through numerical simulation results. Two cross-shear zones can be formed in the rolling deformation zone of the corrugated Mg/Al clad plate, which can accelerate the metal plastic flow and promote interface close bonding.

Effects of pin morphology on the interface defects of the FSWed lap joints of 2A12 aluminum alloy

The current work aims to study the effects of stirring pin morphology on the FSWed lap joints defects and mechanical properties. The 2A12 aluminum alloy friction stir welding lap joints were obtained using two shapes and three thread lengths of stirring pins by experiments. Besides the interface defects forming mechanism were studied by joints plastic metal flow numerical simulation. The results show that the conical pin can lead to uniform and continuous plastic metal velocity field which forms a Hook defect with sharp end, smaller deflection angle (minimum 8°) and larger size (maximum 0.18mm). It also will lead to a larger failure load (maximum is 9.5kN), and the fracture position easily occurs at the Advancing side (AS) of lower plate. The three section pin has a periodic shearing effect causing velocity difference between the arc edge and cutting section of the pin which forms a Hook defect with thicker end, larger deflection angle (maximum 42°) and smaller size (minimum 0.06mm). It also causes discontinuous wavy debris forms in the AS. The three section pin leads to a lower failure load (maximum is just 7.6kN), and the fracture position turns to occur at the lap interface. The increase of the thread length can promote the exchange of plastic metal in the thickness direction and interface materials flow velocity. So the angle (from 20°to 150°) and size (from 0.1mm to 0.6mm) of Hook increases but the height of Cold Lap reduces (increasing the effective sheet thickness of retreating side from 0.69mm to 0.95mm). In addition, the increase of the thread length can make the periodic shear effect of three section pin gradually weak. It is also found that the fracture position is closely related to the shape and the thread length of pins. When using conical pin, the fracture occurs at AS of lower plate or Retreating Side of Nugget Zone (NZ-RS) of upper plate; When using three section pin, the fracture occurs at the bonding interface. And with the increase of the thread length, the fracture position changes from the bonding interface to the NZ-RS of upper plate, and finally to the AS of lower plate.

APPLICATION OF CURRENT LINES IN DETERMINING KINEMATIC CHARACTERISTICS IN STATIONARY PROCESSES OF PLASTIC FLOW OF METAL

Methods of theoretical solution of problems in the processing of metals by pressure are insufficiently developed for practical use in the development and implementation of new technologies and improvement of existing ones. To meet the stringent requirements for the accuracy of determining the stress-strain state, it is necessary to have reliable information about the evolution of the development of the plastic deformation process at each point of the metal from the very beginning of the deformation. This will allow to obtain with high accuracy the important characteristics of the technological heredity of the products that they acquire as a result of their plastic processing. The first and important step in the calculations of the stress-strain state is to obtain the kinematic characteristics of the plastic flow of metal in the form of analytical dependences, which will formulate the patterns of deformation in the technological processes of metal forming. The article considers the possibility of applying the method of current functions to determine the components of the strain rate tensor in established stationary processes of plastic deformation. It is assumed that in the case of axisymmetric plastic deformation of a metal in a channel with curvilinear boundaries, the kinematics of the process is similar to a plane flow. In obtaining the equations, the differential equation of current lines taking into account the incompressibility condition was used to determine the components of the strain rate tensor. To explain the physical meaning of the current functions, two infinitely close current lines were considered in the flow plane, and an expression was obtained for the flow through a finite transverse current tube. In the absence of radial velocity components at the boundaries, constraints are obtained that are imposed on derivatives of current functions at these boundaries. The developed method of calculating the kinematic characteristics of plastic deformation for established axisymmetric stationary processes will simplify the mathematical processing of the obtained results and increase the reliability of the determination of the stress-strain state.

ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ ВОЛОЧЕНИЯ СТАЛЬНОЙ ПРОВОЛОКИ

Using the ANSYS program, the stress-strain state of steel wire in the drawing process is investigated by the finite element method. The problem of plastic flow of metal in a conical matrix-fiber is solved. The problem statement is axisymmetric for different positions of the wire relative to the matrix. The fields of radial stresses, axial stresses and equivalent plastic deformations are obtained. The results allow us to proceed to the study of the influence of various drawing parameters on the stress state of the wire. This will make it possible to optimize the drawing process and offer new drawing designs and lubrication methods that reduce wear and increase the service life of this tool.

Material flow behavior and microstructural evolution during refill friction stir spot welding of alclad 2A12-T4 aluminum alloy

In this study, we used the stop-action technique to experimentally investigate the material flow and microstructural evolution of al-clad 2A12-T4 aluminum alloy during refill friction stir spot welding. There are two material flow components, i.e., the inward- or outward-directed spiral flow on the horizontal plane and the upward- or downward-directed flow on the vertical plane. In the plunge stage, the flow of plasticized metal into the cavity is similar to that of a stack, whereby the upper layer is pushed upward by the lower layer. In the refill stage, this is process reversed. As such, there is no obvious vertical plasticized metal flow between adjacent layers. Welding leads to the coarsening of S (Al2CuMg) in the thermo-mechanically affected zone and the diminishing of S in the stir zone. Continuous dynamic recrystallization results in the formation of fine equiaxed grains in the stir zone, but this process becomes difficult in the thermo-mechanically affected zone due to the lower deformation rate and the pinning action of S precipitates on the dislocations and sub-grain boundaries, which leads to a high fraction of low-angle grain boundaries in this zone.

Metal structure prediction in cross-wedge rolling processes

A method of computer prediction of the size of metal grains, their disorientation, grain boundaries and dislocation density, depending on the modes of cross-wedge rolling, is considered. The regularities of the formation of the parameters of the metal structure depending on the stress state are revealed by methods of computer simulation. The stress state is described by two parameters: the average stress and the parameter of the third invariant of the stress deviator. The effect of the stress state in the deformation zone on the metal structure parameters was determined for the first time. The new method allows improvement of the quality of products by computer optimization of rolling modes. The results of determining the metal structure and parameters of the stress-strain state in the deformation zone during hot rolling of the water pump shaft of steel 45 are presented. The verification and analysis of the data of virtual experiments on the formation of the structure of structural steels in the processes of cross-wedge rolling are carried out. To analyze the output data of the simulation, the parameters for predicting the calculation of grain boundaries and grain size were used. The created computer model for predicting the characteristics of metal structures, depending on the modes of plastic deformation, provides, at minimal cost and without carrying out field experiments, finding the optimal thermodynamic and stress-strain modes of plastic flow of metal, which guarantee the highest operational properties of the products obtained.

Organic monolayers disrupt plastic flow in metals.

Adsorbed films often influence mechanical behavior of surfaces, leading to well-known mechanochemical phenomena such as liquid metal embrittlement and environment-assisted cracking. Here, we demonstrate a mechanochemical phenomenon wherein adsorbed long-chain organic monolayers disrupt large-strain plastic deformation in metals. Using high-speed in situ imaging and post facto analysis, we show that the monolayers induce a ductile-to-brittle transition. Sinuous flow, characteristic of ductile metals, gives way to quasi-periodic fracture, typical of brittle materials, with 85% reduction in deformation forces. By independently varying surface energy and molecule chain length via molecular self-assembly, we argue that this "embrittlement" is driven by adsorbate-induced surface stress, as against surface energy reduction. Our observations, backed by modeling and molecular simulations, could provide a basis for explaining diverse mechanochemical phenomena in solids. The results also have implications for manufacturing processes such as machining and comminution, and wear.

Calculation of the Plastic Metal Flow in the Cold Extrusion Technology by Finite Volume Method

This paper presents an application of the finite volume method to ideal plastic metal flow in extrusion technology. Governing equations for the mass and momentum balance are used in an integral form. Solution domains in the cases considered are discretized with a Cartesian numerical mesh with computational points placed at the center of each control volume. After discretization of the governing equations, the resulting system of nonlinear algebraic equations is solved by an iterative procedure, using a segregated algorithm approach. Resulting stress fields are obtained from the Levy-Mises equations. The experimental results and numerical calculations are in good agreement.

Анализ механизмов наследования в живой природе и технике

The evolution of ideas on inheritance is analyzed and basic types of inheritance in animate nature are presented. Reasoning from the analysis of terms adopted in genetics and engineering technique there is carried out the analysis of inheritance mechanisms at machining and machinery operation. There is shown the evolution of ideas on hereditary information: first the part manufactured the accuracy dimensions of which were “copied” (inherited) in the course of engineering procedure; further – a thin surface layer formed during the engineering process and within the frames of the scientific investigation carried out – material of the deformation source where a plastic metal flow takes place. An analysis is carried out and the directions of the development of scientific investigations in the field of technological inheritance are presented.

Effect of Radial Forging on the Microstructure and Mechanical Properties of Ti-Based Alloys

Radial forging is a reliable way to produce Ti alloy rods without preliminary mechanical processing of their surface, which is in turn a mandatory procedure during almost each stage of the existing technology. In the present research, hot pressing and radial forging (RF) of the titanium-based Ti-3.3Al-5Mo-5V alloy were carried out to study the specifics of plasticized metal flow and microstructural evolution in different sections of the rods. The structural analysis of these rods was performed using metallography and X-ray diffraction techniques. The X-ray diffraction reveals the two-phase state of the alloy. The phase content in the alloy was shown to vary upon radial forging. Finally, radial forging was found to be a reliable method to achieve the uniform fine-grained structure and high quality of the rod surface.

Quasi-Particle Approach to the Autowave Physics of Metal Plasticity

This paper is the first attempt to use the quasi-particle representations in plasticity physics. The de Broglie equation is applied to the analysis of autowave processes of localized plastic flow in various metals. The possibilities and perspectives of such approach are discussed. It is found that the localization of plastic deformation can be conveniently addressed by invoking a hypothetical quasi-particle conjugated with the autowave process of flow localization. The mass of the quasi-particle and the area of its localization have been defined. The probable properties of the quasi-particle have been estimated. Taking the quasi-particle approach, the characteristics of the plastic flow localization process are considered herein.

Plasticity of Metals and Mendeleev’s Periodic Law

The laws of localized plastic flow in various metals are considered. The relations between the plasticity characteristics of a metal and its position in the periodic table and its lattice characteristics are found. A model is proposed to explain the nature of these laws using the concepts of dislocation drag by an electron gas.

Relation of the Lattice and Deformation Characteristics at Plastic Flow of Metals

A new approach is suggested for explanation of autowave processes during plastic deformation of metals. It is based on the postulate that a quasiparticle corresponds to a localized flow autowave. Characteristics of the quasiparticle are determined, and a number of consequences from the postulate are considered. The relations have been established for the processes on micro- and macro-level in the course of plastic deformation.

Analysis of the Thinning Mechanism of an Aluminum Alloy in Friction Stir Welding Based on the Indirect Extrusion–Vortex Flow Filling Model

Different morphology and thinning cases of the weld zone of a 7022 aluminum alloy in friction stir welding were analyzed. Metal plastic flow processes in the contact zone for an aerospace friction stir-joint 7022 aluminum alloy were evaluated. The cross section of the contact zon was analyzed by metallographic and tool microscopes. Then, the plastic flow law of the contact zone was established. Theoretical analysis confirmed the validity of the metal plastic flow law and corresponding thinning model of the weld zone. The thinning model for filling due to indirect extrusion–vortex flow can adequately characterize the plastic flow of metals and formation process of thinning in the weld zone.

Microstructural Analysis of Friction Stir Butt Welded Al-Mg-Sc-Zr Alloy Heavy Gauge Sheets

Friction stir welding (FSW) on a heavy gauge sheet of a hereditary fine-grained Al-Mg-Sc-Zr alloy was carried out to study the specifics of plasticized metal flow and microstructural evolution in different sections and zones of the joint. It was found that the stir zone (SZ) macrostructure may contain either a single or many nugget zones depending on the metal sheet thickness and the seam length. The effect of grain kinking in a thermomechanically affected zone (TMAZ) under pressure from the stir zone metal was discovered. The stir zone metal was fine-grained but had a microhardness lower than that of the base metal, which may be explained by the overaging effect of FSW on the Al3Sc precipitates. The tensile strength of the joint was almost equal to that of the base metal (BM). The grain size distributions were obtained in different sections below the sheet surface and away from the exit hole, which allowed us to suggest the specific adhesion-assisted layer-by layer metal transfer mechanism in FSW.

Effects of traverse speed on weld formation, microstructure and mechanical properties of ZK60 Mg alloy joint by bobbin tool friction stir welding

ZK60B (Mg-6% Zn-0.6% Zr) alloy joints fabricated by bobbin tool friction stir welding (BTFSW) with various traverse speeds were investigated. The sound joint fabricated by the BTFSW was possible under the appropriate welding parameters. The severe plastic deformation during BTFSW resulted in dispersion and segregation of the Zr-rich particles within the stirred zone (SZ) followed by evolution of a bimodal grain structure with distributed bands of 0.8–1.7 μm ultrafine grains and 4.1–7.1 μm equiaxed grains. Micro-hardness of SZ is substantially reduced in contrast to that of parent metal (PM) in spite of the finer grain size owing to dissolution of Mg-Zn based precipitates having hardening effects on alpha-Mg matrix. With the decrease in traverse speed, randomization degree of the plasticized metal flow increases, which is evidenced by the randomized arc line pattern at the low traverse speed. Among all defect-free joints, the 200 mm/min joint exhibits the weakest isotropy of texture within SZ and the best tensile properties, which has reduced ultimate tensile strength and yield strength by 5.4% and by 22.2%, respectively, as compared to the PM. The randomized texture hinders the joint fracturing within SZ at low elongation. Therefore, a relatively high elongation of 10.8% was achieved, which corresponded to 72% of the PM value.

Macrostructure, microstructure and mechanical properties of bobbin tool friction stir welded ZK60 Mg alloy joints

Friction stir welding based on bobbin tool was studied for the joining of ZK60 Mg alloy. Sound joints with the ultimate tensile strength reaching 91.0–94.9% of that of the parent metal can be obtained under the appropriate welding parameters. The welding causes dynamic segregation of Zr-rich precipitates in the stirred zone followed by development of a bimodal recrystallized grain structure with distributed bands of 0.6–1.5 μm ultra-fine grains and 4.4–9.5 μm coarser equiaxed grains. Extensive softening occurred in the stirred zone owing to dissolution of the Mg-Zn based precipitate particles. With the increase in tool rotational speed, the average grain size in the stirred zone increases while the tensile properties are not declined as the enhanced complicated type of plasticized metal flow at the high tool rotational speed produces relatively randomized {0001} textures. The joint produced at the 600 rpm tool rotational speed exhibits the weakest isotropy of {0001} texture and the best combination of strength and ductility. The randomized {0001} textures alleviated the inhomogeneity of plastic deformation during the tensile test, which hindered the joint fracturing with low elongation.