Mechanical Properties Of Alloys Research Articles

Microstructure evolution and strengthening mechanism of rolled Mo-ZrO2 alloy plates after high temperature annealing

Molybdenum alloy plates with different ZrO2 volume contents were prepared by liquid-liquid doping. The microstructures were characterized by scanning electron microscope and transmission electron microscope. The mechanical properties of the alloy were tested by microhardness tester and a precision universal testing machine. The addition of sub-micron ZrO2 can significantly reduce the grain size of Mo alloys. For the rolled Mo-0.4% ZrO2 alloy plate, the grain size is 5.8 μm in comparison with 11.2 μm of pure Mo. After vacuum annealing at 1200 °C, the grain size of Mo-0.4% ZrO2 alloy has not obvious change although pure Mo grain size is sharply increased to 30.3 μm. The addition of ZrO2 can increase the recrystallization temperature and improve mechanical properties of Mo alloy. The recrystallization temperature of Mo-0.4% ZrO2 is increased by 200–300 °C as analyzed by microscopic morphology and EBSD results. The elongation of Mo-0.4% ZrO2 annealed at 1200 °C reached 49% and the strength remained at 482 MPa, which were 120% and 35 MPa higher than that of pure Mo, respectively. The addition of ZrO2 can change the slip system of Mo alloy from {110}〈111〉 to {123} 〈111〉, which increases the number of slip systems in the Mo alloy and thus increases the elongation of the Mo alloy. The strengthening model was built and strengthening mechanism clarified.

Study of mechanical characteristics and strengthening mechanism of AA5154 during cryogenic rolling

Cryogenic rolling (CR) and room-temperature rolling (RTR) process of AA5154 were studied for their effects on the strengthening mechanisms underlying the alloy's mechanical properties. The results indicate that following Cryogenic processing, the AA 5154 dislocation density increases while the particle size of the sub-grains as well as second-phase particles greatly decreases. The AA 5154 benefits greatly from CR processing, as compared to RTR processing, in terms of yield strength, ultimate tensile strength, and elongation. This can be explained by the combined impacts of a higher quality grain structure and a strengthening of the material due to dislocations.

Solute-solute interactions and their impacts on solute co-segregation and interfacial cohesion of {101¯2} twin boundary in zinc

• Zn-based biodegradable alloys are receiving increasing attention in recent years. Alloying is an effective approach to increase mechanical properties of such alloys for load bearing biodegradable applications, but it is unclear how solute atoms of the added alloying elements interact with each other and how these solute-solute interactions affect the mechanical properties of these alloys. In this work, the interactions between solutes (Li, Mg, Mn, Cu, and Ag) commonly used in biodegradable Zn alloys are investigated using first-principles calculations. The segregation ability of these solutes and the effects of the segregations of these solutes on { 10 1 ¯ 2 } twin boundary cohesion are also examined. This work uncovers the effect of solute-solute interactions on solute co-segregation and interfacial cohesion of twin boundaries along which fracture occurs. The findings of the present work are extendable to other hexagonal alloys such as Mg that often contain multiple alloying elements. Interactions of solute atoms in biodegradable zinc alloys and their effect on alloy mechanical properties have been less investigated. In this work, the interactions between the common solutes (Li, Mg, Mn, Cu, and Ag) used in the biodegradable Zn alloys, including a solute-solute pair with the same element or with two different elements, are investigated based on first-principles calculations. It is found that the energetically favorable configuration is the third nearest-neighboring for most solute-solute pairs in the bulk lattice because of the relatively strong electronic interaction between solute and Zn atoms or the relatively small local elastic deformation associated with the configuration. Considering that interfacial cleavage is a key fracture mode of zinc, the segregation ability of these solutes and their effect on the { 10 1 ¯ 2 } twin boundary cohesion are also examined. The result shows that Li tends to fully occupy its preferred site in the twin boundary, while Mg, Mn, Cu, or Ag has a concentration limitation in the twin boundary. The twin boundary cohesion can be significantly enhanced by the segregation of Mn, followed by Cu and Ag, because of the contribution of their d states close to the Fermi level. Furthermore, the co-segregation ability of two solute atoms in the twin boundary increases with increasing the binding tendency of these two solute atoms in the boundary. Mn and Li or Mg show a relatively strong co-segregation ability in the twin boundary. Adding Mn to Zn-Li or Zn-Mg alloys can significantly enhance the resistance to fracture of twin boundaries.

Effect of Heat Treatment on the Electrochemical Behavior of AA2055 and AA2024 Alloys for Aeronautical Applications

Since their development, third-generation aluminum–lithium alloys have been used in aeronautical and other applications due to their good properties, replacing conventional Al-Cu and Al-Zn alloys and resulting in an increase in payload and fuel efficiency. The aim of this work was to investigate the influence of different heat treatments on the electrochemical corrosion behavior of the alloys AA2055 and AA2024 in the presence of three different electrolytes at room temperature, using an electrochemical noise (EN) technique in accordance with the ASTM-G199 standard. In the time domain, the polynomial method was employed to obtain the noise resistance (Rn), the localization index (IL), skewness, and kurtosis, and in the frequency domain, employing power spectral density analysis (PSD). The microstructure and mechanical properties of the alloys were characterized using scanning electron microscopy (SEM) and the Vickers microhardness test (HV). The results demonstrated better mechanical properties of the AA2055 alloy, which had a Vickers hardness of 77, 174, and 199 in the heat treatments T0, T6, and T8, respectively. An electrochemical noise resistance (Rn) of 2.72 × 105 Ω·cm2 was obtained in the AA2055 T8 alloy evaluated in a NaCl solution, while the lowest Rn resistance of 2.87 × 101 Ω·cm2 occurred in the AA2024 T8 alloy, which was evaluated in a HCl solution. The highest electrochemical noise resistance (Rn) was obtained in the AA2055 alloys, which had received the T6 and T8 heat treatments in the three solutions.

Microstructures and mechanical properties of the precipitation strengthened Al0.4Cr0.7FexNi2V0.2 high entropy alloys

In this study, a series of Al0.4Cr0.7FexNi2V0.2 (x: molar ratio, x = 0.5, 1, 2) high entropy alloys were cold-rolled and annealed. The microstructures and mechanical properties of the alloys were systematically investigated. The results revealed that all the solution-treated alloys with different Fe contents exhibited solo FCC phase. After annealing, the coherent L12 phases and hard BCC phases were formed in the Fe0.5 and Fe1 alloys, while the Fe2 alloy only contained the L12 phases. The precipitation of L12 and BCC phases increased the hardness of the alloys. The volume fraction of BCC phase was found to decrease as the Fe content increased, the excessive BCC phases led to the decrease of plasticity. The mechanical properties of alloys were mostly determined by the degree of recrystallization and the amount and type of precipitates. The precipitation of the second phase was regulated by tailoring the alloy composition, so that the AN Fe1 alloy can obtain excellent mechanical properties.

Exploring the Microstructural and Mechanical Properties of Next-Generation Super Alloys

The utilisation of next-generation superalloys is of utmost significance in the progression of contemporary engineering applications that necessitate extraordinary mechanical strength, stability at elevated temperatures, and resistance to corrosion. The present work aims to conduct a thorough investigation of the microstructural and mechanical properties of these advanced materials, providing insights into their distinct features and possible areas of application. The examination of microstructure involves the utilisation of several methodologies, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The present study comprehensively examines the complicated grain structures, phase compositions, and distribution of strengthening precipitates inside the superalloys using various methodologies. The correlation between processing factors and resultant microstructures is established, facilitating a more profound comprehension of the influence of microstructure on the mechanical properties of the alloy. The knowledge acquired from this investigation into the microstructural and mechanical characteristics of next-generation superalloys provides useful insights for engineers, researchers, and designers engaged in materials development and component design. Through the use of a comprehensive comprehension of the distinctive properties of these alloys, it becomes feasible to expand the limits of performance in exceedingly challenging conditions, so influencing the trajectory of high-temperature engineering applications in the future.

Effect of Zn addition and natural aging on the microstructure and mechanical properties of secondary AlSi7Cu2 alloys

The effect of different Zn contents on the microstructure of a secondary AlSi7Cu2 alloy has been studied. The mechanical properties of the alloy during natural aging has been investigated too. The Zn additions range from 0.7 to 8 wt.%, and the tensile testing has been carried out at the as-cast condition and after 3, 7, 12 and 21 days of natural aging. Metallographic and image analysis techniques have been used to characterize the microstructural changes of the alloy. The results indicate that the alloy is strengthened as a function of the aging time and Zn addition. Both yield stress and elongation to fracture tend to stabilize over long aging times, independently of Zn level. The steady-state tensile properties are achieved earlier by increasing the Zn content. Furthermore, high Zn contents promote the formation of eutectic structure and the precipitation of needle-like Fe-rich compounds, which decrease the ductility of the material.

The effect of lithium on the mechanical properties of alloys in the Al-Li system

The article considers the dependence of wear resistance and hardness on each other on the mechanical properties of alloys in the aluminum-lithium system. In experiments, lithium fluorine compound from A K7 and D16 aluminum alloys was added as alloying elements to obtain an aluminum-lithium sample. Based on the mechanical properties of the samples, the hardness was changed in accordance with the Rockwell method and the abrasiveness was investigated.The samples were poured into a heat-resistant furnace at a temperature of 750 °C.The lithium fluoride compound was introduced into the charge in three different masses. Lithium compound with fluorine was added in an amount of 5%, 10% and up to 15% of the total weight of the charge. Based on the conducted experiments, a graph of the dependence of the hardness of the samples and the wear resistance was compiled.

Development of an accurate “composition-process-properties” dataset for SLMed Al-Si-(Mg) alloys and its application in alloy design

Al-Si-Mg series alloys are the most common alloys available for additive manufacturing forming with low cracking tendency. However, there is no systematic study on the computational design of SLMed Al-Si-(Mg) alloys due to the huge parameter space of composition and processes. In this paper, a high-quality dataset of SLMed Al-Si-(Mg) alloys containing 176 pieces of data from 50 publications was first established, which recorded the information, including alloy compositions, process parameters, test conditions, and mechanical properties. A threshold value of 35 J/mm3 for energy density (Ed) was then proposed as a criterion to clean the data points with lower ultimate tensile strength (UTS) and elongation (EL). The cleaned dataset consists of a first training/testing dataset with 142 data for model construction and a second testing dataset with 9 data for model verification. After that, four machine learning models were applied to establish the quantitative relation of “composition-processes-properties” in SLMed Al-Si-(Mg) alloys. The MLPReg model was chosen as the optimal one considering its best performance and subsequently utilized to design novel compositions and process parameters for SLMed Al-Si-(Mg) alloys. The UTS and EL of the designed alloy with a maximum comprehensive mechanical property are 549 MPa and 16%, both of which are higher than all the available experimental data. It is anticipated that the present design strategy based on the machine learning method should generally be applicable to other SLMed alloy systems.

Finite Element Analysis: Connector Designs and Pontic Stress Distribution of Fixed Partial Denture Implant-Supported Metal Framework.

This virtual study was designed to evaluate the stress-deformation of a metal fixed partial dentures (FPDs) pontic under different loads using two different connectors. The STL file was generated for a RPD of two implant-supported restorations. The Co-Cr metal substructure was designed with two types of connector design. The pontic is connected to implant-supported crowns with square and round shape connectors. This study was designed for a cementless-retained implant-supported FPD. Finite element modeling (FEM) is used to assess the stress and deformation of the pontic within a metal substructure as the FEM might provide virtual values that could have laboratory and clinical relevance. The Co-Cr alloy mechanical properties like the Poisson ratio and modulus of elasticity were based on the parameters of the three-dimensional structure additive method. Nonparametric analyses (Mann-Whitney U test) was used. The use of square or round connectors often resulted in non-significant changes in stress, and deformation under either three or each loaded point on the occlusal surface of a pontic (P > 0.05). However, the deformation revealed distinct variations between loads of the three points compared to each loaded point (P ≤ 0.05). According to this study data, the pontic occlusal surface appears to be the same in stress and deformation under different loads depending on whether square or round connectors are used. While at the same connector designs, the pontic occlusal surface deformed significantly at three loaded points than it did at each point.

Микроструктура и свойства сплава Zn–1%Li–2%Mg, подвергнутого интенсивной пластической деформации

In this paper, the authors consider the mechanisms of formation of high-strength states in the Zn–1%Li–2%Mg alloy as a result of its processing by the high pressure torsion (HPT) method. For the first time, the study showed that using HPT treatment, as a result of varying the degree of deformation at room temperature, it is possible to increase the ultimate strength of a zinc alloy from 155 to 383 MPa (with an increase in the yield stress from 149 to 306 MPa) without losing its ductility. To explain the reasons for the increase in the zinc alloy mechanical properties, its microstructure was analyzed by scanning electron microscopy (SEM), X-ray phase analysis (XPA), X-ray diffraction analysis (XRD), and small-angle X-ray scattering (SAXS). Using XPA, the authors established for the first time that Zn(eutectic)+β-LiZn4(eutectic)→~LiZn3+Zn(phase)+Zn(precipitation) and MgZn2→Mg2Zn11 phase transformations occur in the zinc alloy during HPT treatment. SEM analysis showed that at the initial stages of HPT treatment, cylindrical Zn particles with a diameter of 330 nm and a length of up to 950 nm precipitate in β-LiZn3 phase. At the same time, the SAXS method showed that needle-like LiZn4 particles with a diameter of 9 nm and a length of 28 nm precipitate in the Zn phase. The study established that, only spherical Zn and LiZn4 particles precipitate at high degrees of HPT treatment. Precision analysis of the zinc alloy microstructure showed that HPT treatment leads to grain refinement, an increase in the magnitude of crystal lattice microdistortion, a growth of the density of dislocations, which are predominantly of the edge type. As a result of the analysis of hardening mechanisms, the authors concluded that the increase in the zinc alloy strength characteristics mainly occurs due to grain-boundary, dislocation, and dispersion hardening.

Uncovering the roles of laser action modes in surface mechanical properties of 2024 aluminum alloy

The surface state/performance after laser action is as essential as the interplay mechanism between laser and material. Through the designed experiments, the effect of distinct laser action modes on the evolution mechanism of aluminum alloy surface's microstructure and mechanical property was discussed. Under laser-induced thermal effect, the procedure of “vaporization - plasma plume - recoil effect - solidification” occurred. The grains grew longitudinally with an average size of 13.49 μm, which is smaller than that of substrate. Under the thermal oxidation, new oxides were formed. However, laser-induced force effect did not purpose a change in the composition. Importantly, force effect refined the grains to an average grain size as low as 6.21 μm. Notably, an anomaly was discovered. The thermal effect produced stress concentration that increases the residual stress by 64.7%, which caused the hardness to rebound. Additionally, surface composition and microstructure evolution led to the first decrease and then increase of friction coefficient. Due to grain refinement and residual stress induced by force effect, the hardness improved continuously and the friction coefficient decreased continuously. Understanding the influence mechanism of laser action modes on surface structure/property can furnish theoretical guidance for development of laser processing technology in the industrial field.

Characterization and strengthening effect of precipitate microstructure in Mg-3Nd-3Gd-0.2Zn-0.5Zr alloy aged at 225 °C

In this study, a high-performance Mg-3Nd-3Gd-0.2Zn-0.5Zr alloy is prepared. The precipitate microstructures of the studied alloy during isothermal aging at 225 °C are characterized by HAADF-STEM observations, and the corresponding mechanical properties are also investigated. It is noted that the evolution of the precipitate microstructure is mainly divided into three stages: the precipitation and growth of β″, the transition from β″ to β1, and the ripening of β1. There are apparent differences in the mechanical properties of alloy in these three stages. At the beginning of aging treatment, due to the precipitation and growth of β″, the yield strength of alloy increases rapidly while the elongation decreases. Afterwards, the transition of precipitates from β″ to β1 leads to the simultaneous increment in the yield strength and elongation of the alloy. Finally, as the β1 precipitates ripen, the yield strength of the alloy decreases while its elongation shows a trend of increment owing to the significantly improved dimensions and reduced number density.

Control of microstructure and shape memory properties of a Fe-Mn-Si-based shape memory alloy during laser powder bed fusion

• Microstructure modification by varying the laser scan velocity is demonstrated for a Fe-Mn-Si based shape memory alloy fabricated by laser powder bed fusion. • Pronounced Mn evaporation affects the primary solidification phase and, thus, the phase fraction in the samples. • Phase-transformation bcc-δ → fcc-γ induced by the intrinsic heat treatment refines the microstructure and reduces the crystallographic texture. • Microstructural changes result in variation of the alloy's shape memory and mechanical properties. Fe-Mn-Si shape memory alloys are materials, whose functional properties strongly depend on microstructural factors such as grain size and orientation, phase fraction and chemical composition. The present study demonstrates the possibility of microstructure modification via process parameter variation on a Fe-Mn-Si based shape memory alloy fabricated by laser powder bed fusion. By varying the scan speed, samples characterized by coarse elongated grains with strong <001> orientation along the build direction or by finer equiaxed grains without preferential orientation can be fabricated. Changes in the volume phase fraction of bcc-δ ferrite and fcc-γ austenite are also introduced by selective Mn evaporation. A direct correlation between the generated microstructure and achieved mechanical and shape memory properties is found.

Mechanical Properties of Ti-Nb-Cu Alloys for Dental Machining Applications.

Titanium has excellent biocompatibility and good corrosion resistance and is extensively used in dental implants and denture bases. However, pure titanium lacks the strength for use in dental prostheses that require relatively high strength. We developed 15 different types of Ti-Nb-Cu alloys and investigated their alloy phases and mechanical properties, including tensile and yield strength, elongation after fracture, and Vickers hardness. The alloy phases of Ti-8%Nb-2%Cu and Ti-13%Nb-2%Cu were α + β, while those of Ti-5%Nb-5%Cu and Ti-10%Nb-5%Cu were α + Ti2Cu. The tensile strength and hardness of these alloys were significantly higher than those of titanium; however, their elongation was less. In particular, the yield strength of these alloys was more than twice that of titanium. These differences in mechanical properties are attributable to solid-solution strengthening and precipitation strengthening. Other compositions with an alloy phase of α + β + Ti2Cu or β + Ti2Cu had high hardness but not high strength. These results suggest that the Ti-8%Nb-2%Cu, Ti-5%Nb-5%Cu, Ti-13%Nb-2%Cu, and Ti-10%Nb-5%Cu alloys can be applied to dental prostheses, which are subject to very high forces from accessories such as long-span bridges, clasps, implant-retained superstructures, and narrow-diameter implants.

Direct Metal Laser Sintering of the Ti6Al4V Alloy from a Powder Blend.

Additively manufactured Ti6Al4V parts have only seen major application in industries such as the aerospace and medical industries, mainly due to the high cost of production of the feedstock powder. In this article, the feasibility of in situ alloying a powder blend of elemental Ti and an Al-V master alloy to produce the Ti6Al4V alloy through direct metal laser sintering is presented and discussed. In a previous study, single track formation from this powder blend was studied and analyzed to determine the optimum principal process parameters suitable for this powder blend. These process parameters were employed in this study to produce single and double layers where the effects of varied hatch distance and the employment of a rescanning strategy on the surface morphology and alloy homogeneity were investigated. Lastly, in the current study, three-dimensional specimens were produced and analyzed to determine the alloy microstructure, homogeneity, part porosity and mechanical properties. The analyses revealed that a Ti6Al4V alloy with a density of up to 99.9% and corresponding tensile strength and ductility values of up to 942.9 MPa and 17% was produced. Furthermore, a minimum Al evaporation value of 7.2% was recorded. Therefore, in situ alloying can indeed be employed to produce high-quality Ti6Al4V parts from an elemental Ti and an Al-V master alloy powder blend.

Machine learning prediction of the mechanical properties of refractory multicomponent alloys based on a dataset of phase and first principles simulation

In this work, a dataset including structural and mechanical properties of refractory multicomponent alloys was developed by fusing computations of phase diagram (CALPHAD) and density functional theory (DFT). The refractory multicomponent alloys, also named refractory complex concentrated alloys (CCAs) which contain 2–5 types of refractory elements were constructed based on Special Quasi-random Structure (SQS). The phase of alloys was predicted using CALPHAD and the mechanical property of alloys with stable and single body-centered cubic (BCC) at high temperature (over 1,500°C) was investigated using DFT-based simulation. As a result, a dataset with 393 refractory alloys and 12 features, including volume, melting temperature, density, energy, elastic constants, mechanical moduli, and hardness, were produced. To test the capability of the dataset on supporting machine learning (ML) study to investigate the property of CCAs, CALPHAD, and DFT calculations were compared with principal components analysis (PCA) technique and rule of mixture (ROM), respectively. It is demonstrated that the CALPHAD and DFT results are more in line with experimental observations for the alloy phase, structural and mechanical properties. Furthermore, the data were utilized to train a verity of ML models to predict the performance of certain CCAs with advanced mechanical properties, highlighting the usefulness of the dataset for ML technique on CCA property prediction.

Heterogeneous-structured Ti-6Al-4V with enhanced mechanical properties in monotonic and cyclic deformation modes

This study aimed to develop heterogeneous-structured (HS) Ti-6Al-4V composed of coarse and fine grains to enhance the alloy's mechanical properties. This microstructure was induced by selective activation of dynamic globularization by using water-quenching and subsequent rolling below the β-transus temperature. Microstructures and mechanical properties of the HS alloy in monotonic and cyclic deformation modes were compared with those of coarse-grained (CG) and ultrafine-grained (UFG) counterparts. HS Ti-6Al-4V had a higher mechanical strength and better resistance to low-cycle fatigue (LCF) fracture without the loss of ductility compared with commercial mill-annealed CG alloy, and HS alloy had an engineering advantage of low-cost mass production in contrast to UFG counterpart, despite their similar mechanical properties under both monotonic and cyclic deformations. The enhanced mechanical properties of HS alloy were attributed to the presence of UFG region and the partial transformation of transverse to basal texture with a high intensity. Such conditions gave rise to an active slip transfer, low internal stress, and high strain compatibility, thereby leading to the high LCF resistance.

Post-processing influence on additively produced Ti–6Al–4V alloy structure and mechanical properties

This article studies the formation of microstructure and mechanical properties of Ti–6Al–4V alloy manufactured by direct laser deposition (DLD) as a result of post-processing. Heat treatment, hot rolling and hot isostatic pressing (HIP) of additively produced material as well as different combinations of these methods were carried out as part of the investigation. It was determined that material density increased as an average of 0.05% as a result of post-processing. Specimen’s microstructure changed subtly upon post-processing, however, HIP of specimens caused widmanstatten structure decomposition and resulted in the most intense material strength deterioration. Post-processing including plastic deformation causes a decrease in material tensile strength at an average of 3% and an increase in elongation by almost 2 times.

Investigation of Microstructure and Mechanical Properties of SLM-Fabricated AlSi10Mg Alloy Post-Processed Using Equal Channel Angular Pressing (ECAP).

With the aim of improving the excellent mechanical properties of the SLM-produced AlSi10Mg alloy, this research focuses on post-processing using ECAP (Equal Channel Angular Pressing). In our article, two different post-processing strategies were investigated: (1) low-temperature annealing (LTA) and subsequent ECAP processing at 150 °C; (2) no heat treatment and subsequent ECAP processing at 350 °C, 400 °C and 450 °C. The microstructure and mechanical properties of this alloy were analyzed at each stage of post-treatment. Metallographic observations, combined with SEM and EBSD studies, showed that the alloys produced by SLM have a unique cellular microstructure consisting of Si networks surrounding the Al-based matrix phase. Low-temperature annealing (LTA), followed by ECAP treatment, facilitated the microstructural evolution of the alloy with partial breakup of the Si network and observed nucleation of β-Si precipitates throughout the Al matrix. This resulted in a Vickers microhardness of 153 HV and a yield strength of 415 MPa. The main results show that post-processing of SLM-produced AlSi10Mg alloys using ECAP significantly affects the microstructural evolution and mechanical properties of the alloy.