Material Properties Of Alloys Research Articles

Theoretical Study of the Competition Mechanism of Alloying Elements in L12-(Nix1Crx2Cox3)3Al Precipitates

The impact of variations in the content of single alloying element on the properties of alloy materials has been extensively discussed, but the influence of this change on the content of multiple alloying elements in the alloy materials has been disregarded, as the performances of alloy materials should be determined by the collective influence of multiple alloying elements. To address the aforementioned issue, the present study conducted a comprehensive investigation into the impact of variations in the content of alloying elements, namely Ni, Cr, and Co, on the structural and mechanical properties of L12-(Nix1Crx2Cox3)3Al precipitates using the high-throughput first-principles calculations and the partial least squares (PLS) regression, and the competitive mechanism among these three elements was elucidated. The findings demonstrate that the same alloying element may exhibit opposite effects in both single element analysis and comprehensive multi-element analysis, for example, the effect of Ni element on elastic constant C11, and the influence of Cr element on Vickers hardness and yield strength. The reason for this is that the impact of the content of other two alloying elements is ignored in the single element analysis. Meanwhile, the Co element demonstrates a significant competitive advantage in the comparative analysis of three alloying elements for different physical properties. Therefore, the methodology proposed in this study will facilitate the elucidation of competition mechanisms among different alloy elements and offer a more robust guidance for experimental preparation.

Effect of Multistage Solution Aging Heat Treatment on Mechanical Properties and Precipitated Phase Characteristics of High-Strength Toughened 7055 Alloy.

In this paper, a one-step hot extrusion dual-stage solution treatment method is employed to fabricate high-strength and tough T-shaped complex cross-section 7055 (Al-Zn-Mg-Cu-Zr) alloy profiles, and a detailed investigation is conducted on the microstructure and mechanical properties. The results indicate that the comprehensive mechanical properties of the 7055 aluminum extruded alloy using the two-stage solution aging treatment are excellent. This is particularly evident in the balance between strength and ductility, where outstanding strength is accompanied by a plasticity that is maintained at 13.2%. During the extrusion process, the deformation textures are mainly composed of brass and copper, forming a 15.1% recrystallization texture Cube. In addition, the equilibrium phase η(MgZn2) precipitated in the grain is the main strengthening phase, and there are large discontinuous grain boundary precipitates at the grain boundary, which hinders the grain boundary dislocation movement and has great influence on the mechanical properties of alloy materials.

Numerical and parametric study on fracture behaviour and effect of friction on resistance of aluminium alloy shear connections

Fastener pre-tension is commonly used in the practical cases of aluminium alloy bearing-type connections with friction provided by treated surfaces. However, research on the effect of friction on the ultimate resistance is currently limited. In this paper, a numerical investigation on the structural performance and design of aluminium alloy double shear connections fastened by preloaded stainless steel swage-locking pins is presented. Finite element (FE) models were developed using Abaqus explicit dynamic packages and validated against the tests conducted previously. Prior to the numerical modelling of shear connections, the framework of aluminium alloy material properties has been studied. In order to simulate the full-range stress–strain relations and the failure of the tested aluminium alloys, two damage models were evaluated. The adopted model was then used to simulate the fracture occurred at the peak load or the post-peak stage in the double shear connection tests, and investigate their failure mechanism of bearing, shear-out and end-splitting. Upon validation, an extensive parametric study of 330 shear connections was conducted to investigate the effect of friction and pin configuration on the structural performance of shear connections made of different aluminium alloy grades. The values of the friction and pin hole resistance at the ultimate loads were comprehensively discussed. The numerically derived ultimate resistances were also compared with the current design equations, which were shown to provide conservative and scattered results due to the lack of consideration of the friction effect. A new design method was proposed with the friction effect incorporated, resulting in accurate predictions of ultimate resistance for aluminium alloy shear connections with preloaded stainless steel swage-locking pins.

Numerical Investigation Into the Influence of Alloy Type and Thermo-Mechanics on Void Formation in Friction Stir Welding of Aluminum Alloys

Abstract This study employs a high-fidelity numerical framework to determine the plastic material flow patterns and temperature distributions that lead to void formation during friction stir welding (FSW), and to relate the void morphologies to the underlying alloy material properties and process conditions. Three aluminum alloys, viz., 6061-T6, 7075-T6, and 5053-H18, were investigated under varying traverse speeds. The choice of aluminum alloys enables the investigation of a wide range of thermal and mechanical properties. The numerical simulations were validated using experimental observations of void morphologies in these three alloys. Temperatures, plastic strain rates, and material flow patterns are considered. The key results from this study are as follows: (1) the predicted stir zone and void morphology are in good agreement with the experimental observations, (2) the temperature and plastic strain rate maps in the steady-state process conditions show a strong dependency on the alloy type and traverse speeds, (3) the material velocity contours provide a good insight into the material flow in the stir zone for the FSW process conditions that result in voids as well as those that do not result in voids. The numerical model and the ensuing parametric studies presented in this study provide a framework for understanding material flow under different process conditions in aluminum alloys and potentially in other alloys. Furthermore, the utility of the numerical model for making quantitative predictions and investigating different process parameters to reduce void formation is demonstrated.

A thermo-elastic-hydrodynamic model for air foil thrust bearings considering thermal seizure and failure analyses

This study aims to investigate the thermo-elastic performance of an air-lubricated thrust bearing under the thermal failure effect. A thermo-elastic-hydrodynamic model was established using temperature-dependent alloy material properties. The thermo-elastic deformation characteristics were analyzed based on the fluid-thermal-structure interaction approach. The mechanisms of bearing thermal seizures and failure behavior were studied. The results show that the rotor thermal warping deformation at low rotating speed plays a leading role in the increase of the film thickness. The rotor-foil thermal seizure occurs in a high rotating speed. The additional forced cooling conditions effectively reduce the risk of thermal failure.

Surface finish, microhardness and microstructure of laser metal deposited 17-4PH stainless steel

Laser metal deposition is a metal-based additive manufacturing technology. It is a very sensitive and complex process because of the different process parameters involved and the interrelations between these parameters. A thorough understanding of the underlying physics of the process is essential in developing a comprehensive database of the properties of materials processed with this technology. The main objective of this study was to investigate the effect of laser power on a laser-deposited 17-4 precipitation hardenable stainless steel alloy. The as-built microstructure, phase composition, microhardness and surface finish were analysed. The results show that a defect-free sample with good metallurgical bonding and minimal dilution can be produced using high laser power in the range 1400–2600 W and a scanning speed of 0.6 m/s. The microstructure in the clad layer was dominated by martensite and an improvement in surface finish and maximum hardness was observed with increased laser power. Significance: To fully benefit from the additive manufacturing technology, a comprehensive database of the material properties of alloys produced with this technology is required. This study expands on the body of knowledge related to the additive manufacturing of a 17-4PH stainless steel alloy, particularly highlighting the possibility of producing fully dense parts using higher laser power and scanning speed. These two parameters could significantly reduce the build time.

Wear Resistance Mechanism of Sub-Nano Cu3P Phase Enhanced the Cu-Pb-Sn Alloy

High Cu-Pb-Sn, as the material for bimetallic cylinder block, is widely used in the selection of wear-resistant parts due to its excellent wear reduction, thermal conductivity, fatigue resistance, and strong bearing capacity, such as bearings and bearing bushes, aerospace pump rotor, turbine and guide plate, etc. However, because its wear resistance is not enough to meet the harsh conditions of high temperature, high speed, and heavy load, the research on high wear resistance Cu-Pb-Sn materials has important theoretical significance and application value for the application of bimetallic materials. ZCuPb20Sn5 alloy was taken as the research object to analyze the influence mechanism of its different microstructure and mechanical properties on the friction and wear properties of alloy materials. Friction experiments under two conditions of oil lubrication and dry friction were carried out on the MMW-1A pin-on-disc friction and wear testing machine. The wear resistance and wear mechanism of ZCuPb20Sn5alloy under the action of Cu3P were discussed, and a high wear-resistant Cu-Pb-Sn alloy for bimetal cylinder block was prepared. The results show that with the increase of P content, both the friction coefficient and wear rate decrease, and the wear reduction of ZCuPb20Sn5 alloy increases. Under oil lubrication conditions, the friction coefficient decreases by 21.4% and the wear rate decreases by 85.5% compared with that without adding P. The friction-reducing and wear-resistant properties of ZCuPb20Sn5 alloy materials are increased. In dry friction and oil lubrication, the mass wear amount of ZCuPb20Sn5 alloy material decreases with the increase of P element addition, and the change rule of alloy wear amount is consistent under the two methods. In the process of friction and wear, adhesive wear occurs, and the wear amount of the alloy material increases. With the increase of P content, the lead particles are refined and evenly distributed, which promotes the formation of a uniform self-lubricating lead film during the friction process and reduces the degree of adhesive wear. The appearance of Cu3P reduces the contact area of the friction surface and weakens the adhesive wear, so the wear rate is reduced.

Polycrystal plasticity with grain boundary evolution: a numerically efficient dislocation-based diffuse-interface model

Grain structure plays a key role in the mechanical properties of alloy materials. Engineering the grain structure requires a comprehensive understanding of the evolution of grain boundaries (GBs) when a material is subjected to various manufacturing processes. To this end, we present a computationally efficient framework to describe the co-evolution of bulk plasticity and GBs. We represent GBs as diffused geometrically necessary dislocations, whose evolution describes GB plasticity. Under this representation, the evolution of GBs and bulk plasticity is described in unison using the evolution equation for the plastic deformation gradient, an equation central to classical crystal plasticity theories. To reduce the number of degrees of freedom, we present a procedure which combines the governing equations for each slip rates into a set of governing equations for the plastic deformation gradient. Finally, we outline a method to introduce a synthetic potential to drive migration of a flat GB. Three numerical examples are presented to demonstrate the model. First, a scaling test is used to demonstrate the computational efficiency of our framework. Second, we study the evolution of a tricrystal, formed by embedding a circular grain into a bicrystal, and demonstrate qualitative agreement between the predictions of our model and those of molecular dynamics simulations by Trautt and Mishin (2014 Acta Mater. 65 19–31). Finally, we demonstrate the effect of applied loading in texture evolution by simulating the evolution of a synthetic polycrystal under applied displacements.

Dynamic Response Analysis of Frontal Crash on Vehicle Against Lighting Column Using FEM

Acollision between a car and a rigid object on the street, such as an electrical pole or lighting column, may pose a major risk to the the car driver and passengers. It is critical to investigate the collision of a vehicle with a rigid body, particularly the deformation of the vehicle's frontal region against a lighting column at various speeds. In this study, the deformation and dynamic response of the vehicle's frontal area are calculated and analyzed using the ANSYS finite element approach. According to the numerical analysis of frontal impact, a speed of 80 km/h results in a total deformation of 0.0713 m, while a velocity of 120 km/h results in a total deformation of 0.10218 m. When the vehicle is traveling at a higher speed, the lighting column causes additional deformation to the frontal region of the vehicle. Because of the significant internal energy generated during a collision, the car absorbs more impact energy than the lighting column due to the aluminium alloy's material properties.

Effects of residual stress and surface roughness on the fatigue life of nickel aluminium bronze alloy under laser shock peening

The surface properties of alloy materials have a significant influence on the overall strength and fatigue properties of the materials. In this study, the effects of laser shock peening (LSP) on the residual stress distribution and variation in surface roughness and its correlation to the resulting high-cycle fatigue properties of a treated nickel aluminium bronze (NAB) alloy were investigated. The residual stress, surface roughness, and microhardness of NAB specimens subjected to various laser pulse energies were tested and analysed. In addition, the fatigue stress concentration factor considering the combined effect of the residual compressive stress and surface roughness induced by LSP was derived to explain the fatigue characteristics gain mechanism of the treated NAB alloy. Furthermore, axial tension–tension fatigue tests on the NAB specimens were conducted and the fatigue fracture morphologies were analysed in detail to establish the response mechanism between the LSP process parameters and the resulting fatigue life. The results indicated that the high-cycle fatigue life variation trend of the NAB specimens under different laser pulse energies agreed well with the fatigue stress concentration factor, and the beneficial surface roughness and compressive residual stress induced by LSP were considered the main factors that contributed to the improvement of the fatigue properties.

Numerical investigation of mechanical properties of aluminum-copper alloys at nanoscale

Nanoindentation is a powerful tool capable of providing fundamental insights of material elastic and plastic response at the nanoscale. Alloys at nanoscale are particularly interesting as the local heterogeneity and deformation mechanism revealed by atomistic study offers a better way to understand hardening mechanism to build a stronger material. In this work, nanoindentation in Al-Cu alloys are studied using atomistic simulations to investigate the effects of loading direction, alloying percentages of Cu via dislocation-driven mechanisms. Also, a low-fidelity finite element (FE) model has been developed for nanoindentation simulations where nanoscale materials properties are used from atomistic simulations. Material properties, such as hardness and reduced modulus, are computed from both the FE and MD simulations and then compared. Considering the fundamental difference between these two numerical approaches, the FE results obtained from the present study conform fairly with those from MD simulations. This paves a way into finding material properties of alloys with reduced simulation time and cost by using FE where high-fidelity results are not required. The results have been presented as load-displacement analysis, dislocation density, dislocation loops nucleation and propagation, von-Mises stress distribution and surface imprints. The techniques adopted in this paper to incorporate atomistic data into FE simulations can be further extended for finding other mechanical and fracture properties for complex alloy materials.

First-principles calculation of the effect of Mn element on the solid solubility of C in α-Fe

The mechanical and chemical properties of alloy materials strongly depend on their chemical composition. Among them, Mn is an essential alloying element. After adding Mn to the α-Fe matrix, Mn will substitute the position of Fe. In the Fe-C-Mn system, Mn atoms will interact with C atoms in their neighbouring positions, thereby affecting C atoms’ concentration distribution around them in equilibrium. Based on the first principles method, the interaction between the Mn and C atoms in α-Fe and its effect on C atoms’ solid solubility are calculated and analyzed. The results show an attractive force between the Mn atom and C atom at its nearest position. The interaction energy of the two gradually tends to 0 as the distance increases, especially when the distance exceeds 1.5×aα-Fe. The Mn element increases the solid solubility of the C element in the α-Fe matrix.

Investigation of microstructure and electrochemical hydrogen storage thermodynamic and kinetic properties of ball-milled CeMg12-type composite materials

The ball milling method was used to prepare CeMg12/Ni composite hydrogen storage materials with nanocrystalline and amorphous structure in order to improve the electrochemical hydrogen storage and kinetic properties of alloy materials. The phase composition and crystalline structure were characterized by X-ray diffraction (XRD) and high resolution transmission electronic microscopy (HRTEM). The electrochemical discharging performances were measured though discharge capacity and cycling stability. High rate dischargeability (HRD), electrochemical impedance spectroscopy (EIS) and hydrogen diffusion behavior were utilized for studying the change of electrochemical kinetics. Results indicate that adding Ni significantly strengthens the glass forming ability of alloy samples in the process of ball milling. The maximum discharging capacity of the ball-milled composites monotonously goes upward from 46.7 to 1061.2 mAh/g with an increment in Ni content from 50 to 200 wt%. The increasing Ni content results in an obvious reduction in thermodynamic parameters (including enthalpy change ΔH and entropy change ΔS) of ball-milled composites. Besides, the addition of Ni speeds up the hydrogen diffusion rate inside the alloy. Meantime, the addition of Ni can also diminish the activation energy, which is helpful for ameliorating the electrochemical reaction kinetics on the surface of alloy.

The efficiency analysis of grain refinement in high-zinc aluminium alloys with Ti-containing master alloy

ABSTRACTThe paper concerns double high-zinc aluminium alloys inoculated with master alloys containing titan and comprises research on the influence of inoculation on grain refinement. Most aluminium alloys before being cast have relatively low strength properties and therefore a series of treatments are applied in order to improve these properties. One of the treatments is the grain fragmentation process, called grain refinement treatment that allows to improve material properties of alloy, improve the feeding properties during the casting solidification, as well as to obtain more robust machinability of casting. Al alloy with 20wt% Zn (AlZn20) was tested, inoculated with the addition of traditional master alloy AlTi3C0.15 before casting to the sand mould.The results obtained during the studies show nucleating activity of the master alloy, proved by reduced overcooling and recalescence on cooling curves. Additionally, the role of titanium in this process is explained.

Second nearest-neighbor modified embedded-atom method interatomic potentials for the Pt-M (M = Al, Co, Cu, Mo, Ni, Ti, V) binary systems

Interatomic potentials for Pt-M (M = Al, Co, Cu, Mo, Ni, Ti, V) binary systems have been developed on the basis of the second nearest-neighbor modified embedded-atom method (2NN MEAM) formalism. The parameters of pure Mo have also been newly developed to solve a problem in the previous 2NN MEAM potential in which the sigma and α-Mn structures become more stable than the bcc structure. The potentials reproduce various materials properties of alloys (structural, thermodynamic and order-disorder transition temperature) in reasonable agreements with relevant experimental data and other calculations. The applicability of the developed potentials to atomistic investigations for the shape and atomic configuration of Pt bimetallic nanoparticles is demonstrated.

Investigations on mechanical and tribological properties of Al-Si10-Mg alloy/sugarcane bagasse ash particulate composites

ABSTRACTAluminum metal matrix composites are a new generation of metal matrix composites that have the potential of sustaining the emerging demand for advanced engineering applications. These demands were satisfied due to massive mechanical and tribological properties of the aluminum hybrid composite material. In this work, abundantly available agricultural waste product (i.e., sugarcane bagasse ash) was used as a reinforcement material in AlSi10Mg alloy to enhance the alloy material properties for their better accomplishment in industrial applications. Initially, the chemical composition of the sugarcane bagasse ash particles was analyzed using Energy Dispersive X-ray Spectroscopy test, which revealed the presence of rich Silica content in the ash particles. Sugarcane bagasse ash particles of three different weight percentages (i.e., 6, 9, and 12%) are reinforced with aluminum alloy (AlSi10Mg) using stir casting process. The wear mechanisms and fractured morphology of the tensile tested specimen were analyzed with the aid of scanning electron microscopy. The result shows that the tensile, hardness, and impact strength were increased with increase in the weight percentage of sugarcane bagasse ash particles but ductility decreased when increasing the weight percentage. Further, dry sliding wear behavior of the fabricated composites was tested using Pin-on-Disc for three different loads (10 N, 20 N, 30 N). The wear rate and coefficient of friction for the hybrid matrix composites were found to be decreased while increasing the weight percentage of ash content, but they increase while increasing the applied load.

3D fluid-structure interaction (FSI) simulation of new type vortex generators in smooth wavy fin-and-elliptical tube heat exchanger

PurposeThe purpose of this paper is to investigate the numerical fluid-structure interaction (FSI) framework for the simulations of mechanical behavior of new vortex generators (VGs) in smooth wavy fin-and-elliptical tube (SWFET) heat exchanger using the ANSYS MFX Multi-field® solver.Design/methodology/approachA three-dimensional FSI approach is proposed in this paper to provide better understanding of the performance of the VG structures in SWFET heat exchangers associated with the alloy material properties and geometric factors. The Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are applied for modeling of the turbulent flow in SWFET heat exchanger and the linear elastic Cauchy-Navier model is solved for the structural von Mises stress and elastic strain analysis in the VGs region.FindingsParametric studies conducted in the course of this research successfully identified illustrate that the maximum magnitude of von Mises stress and elastic strain occurs at the root of the VGs and depends on geometrical parameters and material types. These results reveal that the titanium alloy VGs shows a slightly higher strength and lower elastic strain compared to the aluminum alloy VGs.Originality/valueThis paper is one of the first in the literature that provides original information mechanical behavior of a SWFET heat exchanger model with new VGs in the field of FSI coupling technique.

마그네슘을 적용한 자동차 시트 쿠션 패널 비등온 성형해석

Mg alloy sheet exhibits significant differences in tensile and compressive yield stress depending on the temperature, as well as variations in its hardening behavior. Such unusual behavior makes it difficult to simulate the forming process of Mg alloy sheets. Results of analysis tend to deviate significantly from the experimental data because commercial software do not completely implement the unusual hardening behavior, yield asymmetry and temperature dependent changes in the Mg alloy's material properties. In the previous study, an in-plane tension-compression cyclic tester was developed to predict the cyclic behavior of Mg alloy sheets at an elevated temperature of up to <TEX>$250^{\circ}C$</TEX>. A new constitutive equation was suggested to analyze the unusual behavior, and was implemented in the commercial software in the form of user subroutine. In this paper, a stamping process of Mg seat cushion panel for automotive parts was simulated using the experimental data and user subroutine. Based on the analysis, an optimal temperature condition was determined and a stamping die shape at each step was suggested in the non-isothermal stamping of Mg alloy sheets.

Mechanical Properties, Microstructure and Crystallographic Texture of Magnesium AZ91-D Alloy Welded by Friction Stir Welding (FSW)

The objective of the study was to characterize the properties of a magnesium alloy welded by friction stir welding (FSW). The results led to a better understanding of the relationship between this process and the microstructure and anisotropic properties of alloy materials. Welding principally leads to a large reduction in grain size in welded zones due to the phenomenon of dynamic recrystallization. The most remarkable observation was that crystallographic textures appeared from a base metal without texture in two zones: the thermo-mechanically affected and stir welded zones. The latter zone has the peculiarity of possessing a marked texture with two components on the basal plane and the pyramidal plane. These characteristics disappeared in the TMAZ, which had only one component following the basal plane. These modifications have been explained by the nature of the plastic deformation in these zones, which occurs at a moderate temperature in the TMAZ and high temperature in the SWZ.

Shape-dependent magnetism of bimetallic FeNi nanosystems

Shape-dependent magnetic properties of a bimetallic system have been studied for FeNi nanoparticles with well-defined concave cubic and octahedron shapes. The alloy composition was chosen to be close to that of an Invar FeNi alloy (with 35% Ni content) but with the coexistence of both bcc and fcc phases, in order to investigate the role of phase combinations in controlling the magnetic properties for the first time. Different saturation magnetization and coercivities were observed for the resulting FeNi alloy nanoparticles, and these differences have been correlated with surface anisotropy and formation of different two-phase combinations. The role of two-phase combinations in governing the magnetic properties has also been studied for both bulk and nanoalloys by large-scale Density Function Theory (DFT) calculations using VASP, which provides a new complementary approach to understanding the magnetic properties of alloy materials.