Mechanical Properties Of Alloys Research Articles

Effect of Solution Treatment and Aging Treatment on Mechanical Properties of 2060 Al-Li Alloy and Process Multi-Objective Optimization

Solution and aging heat treatment are effective means to improve the mechanical properties of Al-Li alloys. The solution treatment and aging treatment tests of 2060 Al-Li alloy were carried out. The yield strength, tensile strength, elongation, Vickers hardness, and microstructure of specimens after heat treatment were obtained by the tensile test at room temperature, Vickers hardness test, SEM analysis, TEM analysis, and EDS analysis. The effects of solution and aging heat treatment parameters on mechanical properties of 2060 Al-Li alloy were analyzed by response surface model and test results. The results show that sufficient solution can make the Cu-rich second phase of the alloy continuously dissolves into the aluminum matrix, and consequently obtain the supersaturated solid solution, the insoluble second phase is mainly θ’ (Al2Cu) phase, T(Al2Cu2Mg3) phase, and S’ (Al2CuMg) phase. The strength and hardness of the alloy are improved, but the ductility worsens with the degree of solution treatment enhances. With the increase of aging temperature and aging time, the strength and hardness of the alloy increase, but the elongation decreases. Taking tensile strength, elongation, and Vickers hardness of the alloy as the optimization objectives, the NSGA-II multi-objective optimization algorithm was used to optimize the process parameters of solution and aging heat treatment, and the heat treatment experiment was carried out. The optimization results show that the best mechanical properties of the alloy with matching strength and toughness can be obtained under the solution treatment at 466 °C/60 min and aging treatment at 185 °C/13 h.

ДОСЛІДЖЕННЯ СТРУКТУРИ ТА ВЛАСТИВОСТЕЙ АЛЮМІНІЄВИХ СПЛАВІВ, МОДИФІКОВАНИХ ДИСПЕРСНИМИ КОМПОЗИЦІЯМИ

The effect of modifying dispersed compositions on the grain structure and mechanical properties of industrial aluminum alloys is studied. Aluminum alloys of the Al-Mg, Al-Mg-Sc systems were modified with dispersed SiC powder with a particle size of up to 200 nm. Calculated the amount of modifier to enter into the melt. The physicochemical properties of dispersed SiC were studied. The melting of alloys AL4S, 1570, 2219, AK9ch in the initial state and with the processing of SiC melts was carried out. The dependences of the particle size and amount of the modifier on the mechanical properties of the alloys are established. The mechanism of interaction of the modifier with the aluminum melt during crystallization is established. In industrial experiments, the most effective particle size of SiC was found to increase the σт of the AK9ch alloy from 115 to 260 MPa in the cast state. The optimal SiC content (0,10%) was determined to increase the σt of aluminum alloys.

Compound Structure-Composition Control on the Mechanical Properties of Selective Laser-Melted Titanium Alloys.

In the performance optimization of the additive manufacturing of Ti6Al4V components, conventional control methods have difficulty taking into account the requirements of quality and mechanical properties of components, resulting in insufficient mechanical properties and a small control range. Therefore, combining the advantages of porous structure and alloy composition control, this paper proposed a structure–composition composite control method for selective laser-fused titanium alloy components by coupling the effects of porous structure parameters and boron content on the properties of Ti6Al4V components. Based on the Gibson–Ashby formula, the compression test of porous Ti6Al4V alloy and the tensile test of boron-containing Ti6Al4V alloy were carried out by SLM forming technology. The parameters C and n related to the pore parameters of porous structure were solved by the experimental data, and the analytical relationship between the pore parameters and the mechanical properties of Ti6Al4V alloy was established. The analytical relationship between boron content (t wt%) and mechanical properties of the alloy was established by tensile test. Finally, the Gibson–Ashby formula was used to combine the above analytical relationship, and a composite regulation model of compressive strength was obtained. The results show that the control range of the composite model ranges from 19.46–416.47 MPa, which was 45.53% higher than that obtained by controlling only pore parameters, and performance improved by 42.49%. The mechanical properties of the model are verified and the deviation between calculated values and experimental values was less than 1.3%. Taking aviation rocker arm as an example, the optimized design can improve the strength and reduce the mass of rocker arm by 51.94%. This method provides a theoretical basis for expanding the application of Ti6Al4V additive manufacturing components in aerospace and other fields.

The role of Sc on the microstructures and mechanical properties of the Ni-rich NiTi alloy

The microstructure and mechanical properties of Ni-rich alloys with the addition of Sc range from 0.15 at% to 0.5 at% were investigated by X-ray diffractometer(XRD), electro-probe microanalyzer(EPMA), transmission electron microscopy(TEM), microhardness, room-temperature tensile properties, and room-temperature fracture toughness in this paper. The as-cast binary alloy and Sc modified ternary alloy are mainly composed of NiTi matrix phase, Ni4Ti3, and Ni3Ti2 phases. After solution treatment, the Ni3Ti2 phase is dissolved back into the matrix, and the alloy mainly consists of NiTi matrix phase and nanoscale Ni4Ti3 phases. The addition of Sc inhibits the precipitation of brittle Ti2Ni phases because O is prone to combine with Sc to form Sc2O3. Trace Sc addition has a weak effect on the microhardness, and it can improve the room-temperature tensile properties and fracture toughness of the alloy. Trace Sc addition moderately reduce the size of the Ni4Ti3 phases and change the aspect ratio of the Ni4Ti3 phases. The reduced precipitate size is responsible for the improvement of alloy mechanical properties.

Experimental research on machinability characteristics of Al-9Si alloy: Effect of Sr and Mg additives

In this study, the effects of strontium (Sr) and magnesium (Mg) elements in certain rates added to Al-9Si alloy manufactured using permanent mold casting technique on the structural, mechanical, and machinability properties of these alloys were investigated. While microstructural images of the alloys were obtained with an optical microscope, hardness, tensile strength, and elongation to fracture were determined by conventional methods. The resultant cutting force ( F) and average surface roughness ( Ra) were measured as experimental outputs in the turning process. It was observed that Al-9Si alloy comprised of α-Al, eutectic Al-Si, β, and primary Si phases. The addition of Sr to the Al-9Si alloy led to the formation of the Al4Sr phase and the transformation of the β phase into the δ phase. The addition of Mg to Al-9Si-0.1Sr alloy caused the δ phase to transform into the π phase. The hardness of the tested alloy increased significantly with the Mg addition. The yield strength and tensile strength of them increased with both Sr and Mg additions. On the other hand, elongation to fracture value of the Al-9Si alloy increased with Sr addition while it decreased with the Mg addition. The F and Ra values obtained from the Al-9Si alloy increased with Sr addition in the turning process while decreased with Mg addition. The results obtained from turning tests were discussed based on the mechanical properties of alloys.

EFFECT OF COOLING RATE ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF SOLUTION-TREATED Mg-9Gd-4Y-2Zn-0.5Zr ALLOY

Different cooling rates, such as room temperature water cooling (WQ), furnace cooling (FC), and water cooling + furnace cooling (FC +WQ), were introduced to study the effect on the solution-treated Mg-9Gd-4Y-2Zn-0.5Zr (w/%) alloy microstructure and mechanical properties. The grain size decreases as the cooling rate increases. With the lengthening of the cooling process time, the LPSO phase had enough time to nucleate and diffuse, the LPSO (long-period stacking order) phase filled the whole matrix crystal grains at the same time. In the process of furnace cooling and water cooling, the brightness of the LPSO phase was different, so it could be seen that the cooling rate would affect the contrast and morphology of the LPSO phase. The tensile yield strengths of the samples cooled with the furnace were better than those of the water-cooled samples, but their ultimate tensile strength and elongation to failure were poor. The fracture modes of the samples under different cooling rates were all subject to cleavage fracture, and the number and area of the cleavage planes and cleavage steps increased with the decrease of cooling speed, and the tearing area decreased, resulting in poor ultimate tensile strength and stretchability.

Functional dependences between indicators of mechanical properties and tin-aluminum bronze chemical composition

Problem statement. Statistically significant relationships establishing between cast tin-aluminum bronze properties, as well as between bronze properties and its chemical composition will predict the level of its mechanical properties when poured into dry sand-sodium-silicate mold. Purpose. Functional relationships determination between mechanical properties of tin-aluminum bronze with tin and aluminum content of up to 6% each. Material and methods. Alloys for investigation have been prepared by melting of technical purity primary charge materials in crucible induction furnace using graphite crucible and charcoal as coating material. Studied alloys mechanical proper-ties have been calculated based on experimental samples tests results during their static expansion and impact bending at room temperature in accordance with actual stand-ards. Alloys chemical composition control has been carried out using precision analyzer EXPERT 4L on samples cut from club-shaped samples. Relationships between mechani-cal properties indicators, as well as mechanical properties and alloys chemical compo-sition have been built using EXEL computer program. Results and discussion. According to Cu-Sn-Al alloys examination results, functional dependences between mechanical properties and Sn and Al content from 1 to 6% by weight of each have been established. This makes it possible to predict mechanical properties level according to chemical composition of such bronze during casting. Conclusions. For the first time, relationships between cast tin-aluminum bronze mechanical properties have been established. This is at the stage of Cu-Sn-Al system bronze designing, with tin and aluminum up to 6% each content, allows predicting its mechanical properties level when pouring bronze in dry sand-sodium-silicate mold.

Evolution of the microstructure and mechanical properties of as-cast Al0.3CoCrFeNi high entropy alloys by adding Si content

In this paper, a set of as-cast Al0.3CoCrFeNiSix (values of x is 0, 0.1, 0.2, 0.3, 0.4, 0.5) HEAs were fabricated by arc vacuum melting. The evolutions of microstructure and mechanical properties of alloys were systematically investigated. The results revealed that addition of Si could promote formation of (Al, Ni, Si)-rich phase with B2 structure (BCC1 phase) and (Fe, Cr)3Si phase with L21 structure (BCC2 phase). The microstructure of alloys changed from a single FCC phase to mixed FCC plus BCC1/BCC2 phases with a typical dendritic structure with increasing Si content. Meanwhile, addition of Si could improve the hardness and strength of alloys, the hardness and yield strength of alloys increased from 141 ± 2.0 to 445 ± 6.6 HV and 167 ± 4.3 to 713 ± 5.7 MPa with increasing Si content. According to the relationship between microstructure and mechanical properties, the strengthening mechanisms of current HEAs were evaluated, demonstrating that precipitation strengthening of ordered BCC phase is the dominant strength mechanism.

A critical review on the effects of process-induced porosity on the mechanical properties of alloys fabricated by laser powder bed fusion

Laser powder bed fusion (LPBF) is an emerging additive manufacturing technique that is currently adopted by a number of industries for its ability to directly fabricate complex near-net-shaped components with minimal material wastage. Two major limitations of LPBF, however, are that the process inherently produces components containing some amount of porosity and that fabricated components tend to suffer from poor repeatability. While recent advances have allowed the porosity level to be reduced to a minimum, consistent porosity-free fabrication remains elusive. Therefore, it is important to understand how porosity affects mechanical properties in alloys fabricated this way in order to inform the safe design and application of components. To this aim, this article will review recent literature on the effects of porosity on tensile properties, fatigue life, impact and fracture toughness, creep response, and wear behavior. As the number of alloys that can be fabricated by this technology continues to grow, this overview will mainly focus on four alloys that are commonly fabricated by LPBF—Ti-6Al-4 V, Inconel 718, AISI 316L, and AlSi10Mg.

The Effect of Heat Treatment on Damping Capacity and Mechanical Properties of CuAlNi Shape Memory Alloy

This paper discusses the effect of different heat treatment procedures on the microstructural characteristics, damping capacities, and mechanical properties of CuAlNi shape memory alloys (SMA). The investigation was performed on samples in the as-cast state and heat treated states (solution annealing at 885 °C/60′/H2O and after tempering at 300 °C/60′/H2O). The microstructure of the samples was examined by light microscopy (LM) and scanning electron microscopy (SEM) equipped with a device for energy dispersive spectrometry (EDS) analysis. Light and scanning electron microscopy showed martensitic microstructure in all investigated samples. However, the changes in microstructure due to heat treatment by the presence of two types of martensite phases (β1′ and γ1′) influenced alloy damping and mechanical properties by enhancing alloy damping characteristics. Heat treatment procedure reduced the alloys’ mechanical properties and increased hardness of the alloy. Fractographic analysis of the alloy showed a transgranular type of fracture in samples after casting. After solution annealing, two types of fracture mechanisms can be noticed, transgranular and intergranular, while in tempered samples, mostly an intergranular type of fracture exists.

Investigating Metal Solidification with X-ray Imaging

In the last two decades, X-ray imaging techniques have been used increasingly to study metal solidification in real-time as, thanks to advances in X-ray sources (synchrotron and laboratory-based) and detector technology, images can now be obtained with spatio-temporal resolutions sufficient to record key phenomena and extract quantitative information, primarily relating to crystal growth. This paper presents an overview of the research conducted at the University of Oxford over the last 6 years as a partner in the UK’s Future Liquid Metal Engineering (LiME) Manufacturing Hub. The focus is on in situ X-ray radiography to investigate the solidification of Al alloys, including the formation of primary α-Al crystals, and the formation and growth of secondary intermetallic phases. Technologically, the thrust is to understand how to control as-cast phases, structures and element distributions, particularly elements associated with recycling, as a means to facilitate greater recirculation of aluminium alloys. We first present studies on refinement of primary α-Al, including extrinsic grain refinement using inoculation and intrinsic refinement based on dendrite fragmentation. Second, we describe studies on intermetallic phase formation and growth, because intermetallic fraction, morphology and distribution are frequently a limiting factor of alloy mechanical properties and recyclability. Then we present some of the latest progress in studying liquid flow during solidification and associated hot tear formation. Finally, future research directions are described.

Modification mechanism and tensile property of Al-9Si-0.4Mg-0.1Cu alloy

In this work, eutectic Si modification grade formula was established and effect of Sr element on modification level and mechanical properties of Al-9Si-0.4Mg-0.1Cu alloy was studied. Thermal analysis, SEM, EPMA and TEM were applied to analyze cooling curves, microstructure and Si twinning of the alloys. The results showed that precision and accuracy of eutectic Si modification grade formula were significantly improved and quantitative evaluation modification level of eutectic Si could be achieved. Modification level of eutectic Si increased first and then decreased with Sr content increasing. Though twin plane re-entrant edge (TPRE) mechanism and impurity induced twinning (IIT) mechanism were effective under certain conditions, they cannot fully explain the modification mechanism of eutectic Si in Al-9Si-0.4Mg-0.1Cu alloy. Sr element caused constitutional undercooling at the front of solid-liquid interface, promoted the formation of fine Al 2 Si 2 Sr phases and nano-precipitates, resulting in the changes of size and morphology of eutectic Si. With the improvement of eutectic Si modification level, the UTS and El of the alloys increased. While, adding excessive Sr led to the formation of coarse Al 2 Si 2 Sr, which was detrimental to the improvement of modification level and mechanical properties of alloy. • Modification level function suitable for quantitatively evaluate modification grade of eutectic Si was established. • Fine Al 2 Si 2 Sr phases and nano-precipitates change the size and morphology of eutectic Si. • Coarse Al 2 Si 2 Sr reduces the modification level of eutectic Si and the mechanical properties of alloy.

Precipitation kinetics and crystal plasticity modeling of artificially aged AA6061

An artificially aged AA6061 alloy was investigated at multiple heat treatment conditions with monotonic tensile and cyclic shear testing to characterize the effect of precipitation on the alloy's mechanical properties. The microstructure was first measured with scanning electron microscopy, which was observed to remain fairly constant throughout all aging conditions. Mechanical testing showed that artificial aging reduced the initial work hardening rate without affecting dynamic recovery. The alloy also exhibited a reduction in plastic anisotropy and an increase in kinematic hardening with increased aging time. Afterwards, a numerical through-process framework was introduced to predict both the precipitation kinetics and mechanical behavior of AA6000-series materials. The kinetics model was calibrated and validated with transmission electron microscopy measurements on several Al-Mg-Si alloys. The mechanical model uses the simulated precipitate distribution in a modified crystal plasticity framework to calculate the alloy's constitutive response. The framework was able to simulate the yield strength, work hardening, plastic anisotropy and Bauschinger behavior of AA6061 with reasonable accuracy. Plastic anisotropy and kinematic hardening was specifically captured with an inclusion-based method of modeling the precipitates. The model was later used to simulate precipitation hardening in individual single crystals. It was observed that the effect of artificial aging is minor compared to the overall effect of texture on the material.

The Three-Level Elastoviscoplastic Model and Its Application to Describing Complex Cyclic Loading of Materials with Different Stacking Fault Energies.

The development of new technologies for thethermomechanical processing of metals and the improvement of the existing ones would be unattainable without the use of mathematical models. The physical and mechanical properties of alloys and the performance characteristics of the products made of these alloys are generally determined by the microstructure of materials. In real manufacturing processes, the deformation of metals and alloys occurs when they undergo complex (non-proportional) loading. Under these conditions, the formation of defect substructures, which do not happen at simple (proportional) loading, can take place. This is due to the occurrence of a great number of slip systems activated under loading along complex strain paths, which leads, for instance, to the more intense formation of barriers of different types, including barriers on split dislocations. In these processes, the formation and annihilation of dislocations proceed actively. In this paper, we present a three-level mathematical model that is based on an explicit description of the evolution dislocations density and the formation of dislocations barriers. The model is intended for the description of arbitrary complex loads with an emphasis on complex cyclic deformation.The model is composed of macrolevel (a representative macrovolume of the material that can be considered as an integration point in the finite-element modeling of real constructions), and mesolevel-1 (description of the mechanical response of a crystallite) and mesolevel-2 (description of the defect structure evolution in a crystallite) submodels. Using the model, we have performed a series of numerical experiments on simple and complex, monotonic and cyclic deformations of materials with different stacking fault energies, analyzed the evolution of defect densities, and analyzed the challenges of a relationship between the complexity of loading processes at a macrolevel and the activation of slip systems at low scale levels.

Sintering behavior, microstructure and mechanical properties of NbC-Ni alloys with different carbon contents

This work aims to study the influence of the carbon content in a (NbC-3vol%Mo2C)-12vol%Ni-0.5vol%WC alloy on the sintering process, and its resulting effect on the microstructure and mechanical properties. NbC cemented carbides with additions of Mo or C were sintered at 1450 °C for 1 h in the vacuum furnace of a dilatometer and of a TGA (Thermogravimetric Analysis) device. Liquid phase sintering temperature is decreased with addition of Mo or C, leading to an early densification which limits nickel evaporation. Swelling occurs during heating in the 3 phase (NbC + Ni + liquid) domain for the high carbon content alloys. A graphite phase is observed for largest carbon contents. The C/Mo ratio also affects the phase composition and lattice parameters. The lattice parameter variation of the carbide and Ni rich-binder is explained by the variation of the metallic solute contents as a function of the overall composition. Grain growth is globally enhanced by increasing the carbon content. A significant effect of C/Mo ratio on the mechanical properties of the alloy is also observed. The Vickers hardness (HV30) decreases while the toughness (KIc) exhibits a maximum value as the carbon content increases.

Изменение структурно-фазового состояния и механических свойств сплава ВТ35 после интенсивной пластической деформации и последующих отжигов

The influence of severe plastic deformation and subsequent pre-recrystallization annealings on the structural-phase state and mechanical properties of the VT35 titanium alloy has been studied. It is shown that the formation of an ultrafine-grained structure leads to an increase in the mechanical properties of this alloy at room temperature by 65-75% compared to the initial coarse-grained state. It has been established that a significant scatter in the mechanical properties of the alloy after such treatment is due to the inhomogeneity of the distribution of α and β phases in the bulk of the workpieces. Subsequent pre-recrystallization annealings of the VT35 ultrafine-grained alloy at temperatures of 723 and 773 K lead to an additional increase in its mechanical properties (the yield strength and ultimate strength values can exceed 1700 MPa). Using the example of alloy samples after annealing at 723 K for 0.5 h, it is shown that the increase in mechanical properties is due to an increase in the volume fraction of the α-phase due to the β→α phase transformation occurring inside the β phase regions and, as a result, a more uniform distribution of α and β phases.

Effect of sintering temperature on microstructures and mechanical properties of ZK60 magnesium alloys

In this study, ZK60 Mg alloys were prepared via hot-press sintering under a constant pressure of 30 MPa as well as Ar atmosphere. The sintering temperature was determined to be in the range of 450 °C–600 °C with an interval of 50 °C. The effect of sintering temperature on the microstructures and mechanical properties of the alloys was investigated. All the four sintered alloys mainly exhibited an α-Mg-phase structure and equiaxed grain microstructure. However, a specific amount of melt, enriched in Zn element, formed when the sintering temperature reached 500 °C. Thus, only the alloy sintered at 450 °C maintained the nominal composition of the alloy powder, and exhibited the favorable yield strength and hardness, which was 135.1 MPa and 57 HV, respectively. The alloys sintered at 550 °C and 600 °C exhibited a reduced yield strength and hardness due to the loss of Zn element.

Evaluation of mechanical properties of aluminium alloy (AA 6082) reinforced with Rice husk ash (RHA) and Boron carbide (B4C) hybrid metal matrix composites using stir casting method

Aluminum alloys are commonly employed in shipbuilding and automotive manufacturing units. The mechanical properties of alloys, such as strength and hardness, can be improved by adding reinforcement to the matrix material. Stir casting is an improved method for uniform dispersion of particles over conventional casting methods. Therefore, an effort is made to fabricate aluminium alloy (AA 6082) composites with different ratios of hybrid reinforcement of Rice Husk Ash (RHA) and Boron Carbide (B4C) reinforcements.The mechanical properties of composites such as tensile strength, hardness, flexural strength, and impact strength were evaluated. The microstructural properties of composites were evaluated using a scanning electron microscope to determine the dispersion of particles in the matrix material. It is found that tensile strength, hardness were improved by 20% as well as the uniform distribution of reinforcement particles in composites.

Hybrid Heat Treatment for Conventionally Treatable Steel Powder Reinforced Age Hardenable Aluminium Alloy Matrix Composites and Mechanical Property Evaluation

The present work is associated with research concentrating on the innovation and use of hybrid heat treatment for eutectoid steel powder (0.8 wt%) reinforced Al-Zn-Mg (Al 7075) alloy composites. Due to high hardness, wear resistance, tensile strength and flexibility modifying heat treatment, heat treatable aluminium metal matrix composites reinforced with heat treatable hard steel particles may be the choice to explore. In this work, an attempt is made to increase hardness and tensile properties to higher levels through hybrid heat treatment, comprising simultaneous treatment to matrix and reinforcement in 3 different routes (Pearlite, Bainite and Martensite) compared to conventional age hardening treatment. SEM images and microhardness distribution witnessed the phase transformation in both matrix and reinforcement. Aging kinetics in conventional age hardening and hybrid treatments is accelerated by the increase in the quantity of reinforcement and increase in aging temperature. The improvement in hardness and tensile strength obtained by conventional age hardening path is further improved by the hybridisation path. Hybridisation route with martensite reinforcement phase shows excellent result in hardness, strength followed by bainite and pearlite path respectively in the decreasing order. In all heat treatment cycles, lower aging temperature marks greater property enhancement compared to higher temperature. Al 7075 with 6 wt% steel powder reinforced (martensite form) composite showed excellent peak age hardness, tensile strength compared to lesser quantity reinforced composites.

The influence of cryogenic treatment on titanium alloys mechanical properties

One of the most promising applications of cryogenic therapy is its ability to transform a wide range of materials. In this study, Titanium alloy (Ti6Al4V) was subjected to both deep and shallow cryogenic treatment. In addition to the anti-aging treatment, a deep cryogenic treatment was administered to the patient. Tensile tests were used to examine how cryogenic treatment affected the mechanical characteristics and ductility of Ti6Al4 alloy. According to this studies, cryogenic treatment expands flexibility of Ti6Al4V alloy. After 24 and 36 h, the deep cryo-treated samples had Uniform Plastic Deformation Region (UPDR) that were 5.3% and 8.3% greater than the untreated ones. However, after 36 h of cryogenic treatment, the yield strength of the material decreased by 2%. When subjected to a 36-hour period of severe cryogenic treatment, the alloy's phase ratio decreased from 8.1% to 5.6%, resulting in structural changes within the material. The unstable a phase gave rise to both stable and unstable phases. Experiments have shown that cryogenic treatment raises the flexibility and durability of Ti6AI4V alloy while also controlling the microstructure and lowering residual stress when performed at room temperature.