Properties Of Alloys Research Articles

Discovering Pyramidal Treasures: Multi-Scale Design of High Strength-Ductility Titanium Alloys.

Mechanical properties of titanium alloys, one of humankind's most essential structural materials, suffer from the lack of 〈c + a〉 dislocations on pyramidal slip planes, failing homogeneous plastic strain accommodation. This mechanical treasure is not easily accessible in titanium alloys because of the required excessively high stress levels. The present work demonstrates that such a dilemma may be overcome by meticulously tuning the c/a ratio, the simplest crystallographic parameter of the hexagonal close-packed lattice, through Sn alloying. Combining this lattice-scale design concept with a cross-rolling based polycrystal-scale design solution, this study showcases a facile route to bimodal (α + β) titanium alloys with exceptional strength-ductility synergy.

Research on the Influence of Cold Drawing and Aging Heat Treatment on the Structure and Mechanical Properties of GH3625 Alloy.

With the development of the petroleum industry, the demand for materials for oilfield equipment is becoming increasingly stringent. The strength increase brought about by time strengthening is limited in meeting the needs of equipment development. The GH3625 alloy with different strength levels can be obtained through cold deformation and heat treatment processes. A study should be carried out to further develop the potential mechanical properties of GH3625. In this study, the GH3625 alloy was cold drawn with different reductions in area (0-30%) and heat treated, and its mechanical properties were tested. The microstructure of the alloy during deformation and heat treatment was characterized by methods such as optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) based on the principles of physical metallurgy. The strength increase caused by dislocation strengthening was calculated from the dislocation density, tested by X-ray diffraction (XRD). The calculated value was compared to the measured value, elucidating the strengthening effect of cold deformation and heat treatment. The results showed that the yield strength and yield ratio of the cold-drawn alloy significantly reduced after aging at 650 °C and 760 °C. Heat treatment can make a cold-deformed material recover, ablate dislocations, and greatly reduce the dislocation density in the microstructure of the GH3625 alloy, which was the main factor in the decrease in yield strength. The work-hardening gradient of the cold-drawn material varied greatly with different reductions in area. When the reduction in area was small (10%), the hardness gradient was obvious. When it increased to 30%, the alloy was uniformly strengthened as the deformation was transmitted to the axis. This study can provide more mechanical performance options for GH3625 alloy structural components in the petrochemical industry.

Morphology and properties of non-ferrous alloys in the zones of laser thermal deformation processing

Morphology and properties of non-ferrous alloys in the zones of laser thermal deformation processing

Influence of Mg and Cu on precipitation behaviors and mechanical properties of Al–Si alloys

Al–8Si-0.5 Mg, Al–8Si–2Cu, and Al–8Si–2Cu-0.5 Mg alloys have been designed in this study, aiming to reveal the influence of Mg and/or Cu additions on microstructures and mechanical properties of Al–Si alloys. Transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Kampman-Wagner Numerical (KWN) model have been used to investigate age-hardening behaviors as well as their relation to mechanical properties. Microstructure analysis suggest that β'', θ′ and QP precipitates have formed in peak-aged Al–8Si-0.5 Mg, Al–8Si–2Cu and Al–8Si–2Cu-0.5 Mg alloys, respectively. Notably, the Al–8Si–2Cu-0.5 Mg alloy exhibits faster precipitation kinetics, larger age-hardening response and remarkable thermal stability compared to the other two alloys. Theoretical calculations indicate that the nucleation of QP precipitates is easier than β'' and θ′ precipitates, but the slower diffusivity of Cu limits the growth rate of QP precipitates during the growth stage. Furthermore, the contribution of β'', θ′ and QP precipitates to yield strength of peak-aged Al–Si alloys has been quantified, which shows a significant variation. β'' precipitates in the Al–8Si-0.5 Mg alloy exhibit the highest strengthening effect (∼186.4 MPa), followed by QP precipitates in Al–8Si–2Cu-0.5 Mg (∼160.2 MPa) and θ′ precipitates in the Al–8Si–2Cu alloy (∼13.4 MPa). This work provides valuable insights into the influence of Mg and/or Cu additions on the aging response and mechanical properties of Al–Si alloys, offering a reference for further enhancing the performance of Al–Si alloys.

Structural, Mechanical and Tribological Properties of Hydroxiapatite Reinforced Ti13Nb13Zr/HA Composite Produced by Friction Stir Process (FSP)

AbstractMany modification methods are applied to produce Ti-based biomedical materials. In this study, the structural, mechanical and tribological properties of unreinforced Ti13Nb13Zr alloy and Ti13Nb13Zr/HA composites with different contents of hydroxyapatite (HA) reinforcement were investigated by friction stir processing (FSP) to Ti13Nb13Zr alloy. SEM, FTIR and EDS analyzes were performed to determine the structural properties. Surface roughness values were determined using a 3D optical microscope. Surface wettability properties were investigated with a contact angle. Microhardness and wear test devices were used to determine the mechanical and tribological properties, respectively. Wear tests were carried out in a dry environment and phosphate buffered saline solution (PBS). The wear tracks were analyzed by SEM and 3D optical microscope. As a result of FTIR analysis, HA has PO43−, HPO42−, CO32− and OH− bonds. All samples exhibited hydrophilic surfaces suitable for cell adhesion. The FSP process increased the hardness and wear resistance of the Ti13Nb13Zr alloy in both atmospheres. In addition, Ti13Nb13Zr/HA composites significantly increased the hardness and wear resistance of Ti13Nb13Zr alloy and Ti13Nb13Zr alloy modified by FSP.

Effect of Shot Peening Duration on Microstructure and Mechanical Properties of GH4169 Alloy Prepared by 3D Printing

Effect of Shot Peening Duration on Microstructure and Mechanical Properties of GH4169 Alloy Prepared by 3D Printing

Wear resistance and antibacterial properties of 3D-printed Ti6Al4V alloy after gas nitriding

This research focused on tribological and antibacterial studies of 3D-printed Ti6Al4V alloys based on the selective laser melting method vs conventional technology after gas nitriding for biomedical applications. Gas nitriding reduced friction and wear in the following order: 3D-printed AM Ti6Al4V > wrought CM Ti6Al4V > CP-Ti. The best tribological performance was demonstrated on nitrided Ti6Al4V alloy using 3D printing. The antibacterial activity of the samples was estimated for the Gram-positive Staphylococcus aureus and the Gram-negative bacteria Escherichia coli. AM Ti6Al4V showed a positive antibacterial effect of nitriding against S. aureus bacteria by up to 30 %. Gas nitriding of 3D-printed Ti6Al4V alloys suggests an effective strategy to improve the antibacterial activity and mechanical resistance of biomedical implants.

Tailoring the Microstructure and Mechanical Properties of Ta-Alloyed AlCoCrFeNi High-Entropy Alloys

Tailoring the Microstructure and Mechanical Properties of Ta-Alloyed AlCoCrFeNi High-Entropy Alloys

Effects of PVD CrAlN/(CrAlB)N/CrAlN Coating on Pin–Disc Friction Properties of Ti2AlNb Alloys Compared to WC/Co Carbide at Evaluated Temperatures

Physical vapor deposition (PVD) coatings could affect the friction performance at the contact interface between Ti2AlNb alloy parts and tool couples. Suitable coating types could improve the friction properties of Ti2AlNb alloy while in contact with WC/Co carbide. In this study, the linear reciprocating pin–disc friction tests between the Ti2AlNb alloy and the WC/Co carbide tool couple, with the sole variation of the PVD CrAlN/(CrAlB)N/CrAlN coating were conducted within the temperature range of 25–600 °C. The antifriction properties of the Ti2AlNb alloy were estimated using the time-varied friction coefficients, the alloy wear rate, worn surface topography, worn surface element, and wear mechanism analysis. The results showed that the PVD CrAlN/(CrAlB)N/CrAlN coating could decrease the average friction coefficient and alloy wear rate compared to the uncoated WC/Co carbide couple. The apparent adhesive wear and abrasive wear of the Ti2AlNb alloy could be improved due to the PVD coating at evaluated temperatures. The PVD CrAlN/(CrAlB)N/CrAlN coating could be utilized to improve the antifriction properties of the Ti2AlNb alloy, which may be deposited on the cutting tool to improve the machining performance of Ti2AlNb alloys in future aerospace machining industry.

An SMA-based compliant adjustable constant force gripper for micro-assembly

Ensuring precise and consistent force regulation in a confined workspace is critical for high-quality micro-assembly operations. To enhance structural efficiency and reduce system complexity, this study leverages the variable stiffness properties of the shape memory alloy (SMA) and presents a novel compliant adjustable constant force microgripper. In this work, a passive variable stiffness chained pseudo-rigid-body model is established to address the coupling analysis problem arising from the mechanical and SMA’s in-homogeneous phase transformation properties, thereby facilitating the integrated design of the SMA and the mechanism. Exploiting the variable stiffness property of SMA, an improved stiffness-tunable two-beam-binding constant force mechanism is proposed for the gripper jaws, which makes adjustable constant force operation via current control can be achieved straightforwardly. Further, inspired by differential actuation mode, a compact SMA-based actuator comprising two parallel guide mechanisms and SMA drivers is developed to meet the requirement for the large working stroke of the gripper. Numerical simulations and experimental studies validate the design model’s efficiency and the proposed structures’ capabilities, and also prove the gripper’s constant operation force value can be regulated in the range of 0.152 to 0.381 N. With dimensions of 35×56.5×7 mm3 and a maximum stroke of 2.077mm, the gripper demonstrates fine compactness and potential for continuous, cross-scale micro-assembly.

Understanding the effect of refractory metal chemistry on the stacking fault energy and mechanical property of Cantor-based multi-principal element alloys

Multi-principal-element alloys (MPEAs) based on 3d-transition metals show remarkable mechanical properties. The stacking fault energy (SFE) in face-centered cubic (fcc) alloys is a critical property that controls underlying deformation mechanisms and mechanical response. Here, we present an exhaustive density-functional theory study on refractory- and copper-reinforced Cantor-based systems to ascertain the effects of refractory metal chemistry on SFE. We find that even a small percent change in refractory metal composition significantly changes SFEs, which correlates favorably with features like electronegativity variance, size effect, and heat of fusion. For fcc MPEAs, we also detail the changes in mechanical properties, such as bulk, Young's, and shear moduli, as well as yield strength. A Labusch-type solute-solution-strengthening model was used to evaluate the temperature-dependent yield strength, which, combined with SFE, provides a design guide for high-performance alloys. We also analyzed the electronic structures of two down-selected alloys to reveal the underlying origin of optimal SFE and strength range in refractory-reinforced fcc MPEAs. These new insights on tuning SFEs and modifying composition-structure-property correlation in refractory- and copper-reinforced MPEAs by chemical disorder, provide a chemical route to tune twinning- and transformation-induced plasticity behavior in fcc MPEAs.

Enhancing mechanical properties of high Cr dual-phase FeCrNi medium-entropy alloy through mutual phase transformation and grain refinement

A high Cr Fe40Cr40Ni20 (at.%) medium-entropy alloy was prepared through vacuum arc melting. The alloy exhibited a dual-phase structure comprising face-centered-cubic (FCC) and body-centered-cubic (BCC) phases in a solid solution state. After annealing and cold rolling, two different heterogeneous structures emerged from the original FCC and BCC phases through mutual phase transformation. Moreover, the alloy exhibited a yield strength, ultimate tensile strength, and total elongation of 1.18 GPa, 1.25 GPa, and 13 %, respectively. The high strength of the alloy was mainly attributed to boundary strengthening and heterogeneous deformation-induced (HDI) strengthening within the two heterogeneous structures. Notably, the effectiveness of HDI strengthening was enhanced owing to the complete encapsulation and constraint of soft zones by hard zones in the heterogeneous structure originating from the BCC phase. Additionally, the deformation ability of the alloy mainly depended on dislocation slips and deformation twinning in recrystallized FCC grains and FCC strip phases, thereby ensuring satisfactory ductility.

Investigation on the lattice vibration, mechanical properties, stress-strain behavior and electronic properties of FeTiSi, CoTiSi and NiTiSi intermetallics from a first-principles calculations

In the present work, we have investigated the structural, electronic, elastic and thermodynamic properties of titanium alloy (XTiSi) (X = Fe, Co, Ni) by using the first-principles calculations. The results showed that XTiSi are dynamically and thermodynamically stable. And the sequence of phase stability is CoTiSi > FeTiSi > NiTiSi. According to the mechanical parameters, three XTiSi ternary alloys exhibit mechanical stability based on the Born stability criteria. FeTiSi exhibits the strongest compression resistance, shear resistance and elastic hardness. The ductility of three alloys is ranked in the order NiTiSi > CoTiSi > FeTiSi. Stress-strain curves are considered by stretching along two directions [100] and [001] directions for three XTiSi alloys. The three-dimensional constructions and two-dimensional projection of elastic moduli were calculated to visually display the anisotropy of three XTiSi alloys. The Debye temperature show that the FeTiSi has good thermal conductivity and chemical bond strength. The electronic structures were used to discussed the magnetic properties, mechanical properties and bonds properties.

Influence of Ni on the Organization and Properties of AlCoCrFeMn High-Entropy Alloys by Laser-Sintering Technique

In order to investigate the effect of the Ni element on the properties of AlCoCrFeMn HEAs, this experiment prepared AlCoCrFeMn and AlCoCrFeNiMn HEAs by using a laser-ignition self-propagation sintering technique with an equal molar ratio. And analyzed the effect of the Ni element on the microstructure of AlCoCrFeMn HEAs by using a metallurgical optical microscope (OM), scanning electron microscope (SEM), energy spectroscopic analysis (EDS), X-ray diffraction (XRD), and other experiments. Characterization equipment was used to analyze the effect of the Ni element on the microstructure, physical phase structure, wear resistance, compressive properties, and corrosion resistance of AlCoCrFeMn HEA materials. The results show that after the addition of the Ni element, the AlCoCrFeNiMn HEA changes from a single BCC phase to one consisting of BCC and a small amount of an FCC phase, with an equiaxial organization, and the yield strength reaches 780 MPa and the compressive strength is 3920 MPa. The corrosion rate is 2.08 × 10−3 mm/a, and the corrosion resistance and mechanical properties are greatly increased.

A review on manufacturing processes of cobalt-chromium alloy implants and its impact on corrosion resistance and biocompatibility.

Cobalt-Chromium (CoCr) alloys are currently used for various cardiovascular, orthopedic, fracture fixation, and dental implants. A variety of processes such as casting, forging, wrought processing, hot isostatic pressing, metal injection molding, milling, selective laser melting, and electron beam melting are used in the manufacture of CoCr alloy implants. The microstructure and precipitates (carbides, nitrides, carbonitrides, and intermetallic compounds) formed within the alloy are primarily determined by the type of manufacturing process employed. Although the effects of microstructure and precipitates on the physical and mechanical properties of CoCr alloys are well reviewed and documented in the literature, the effects on corrosion resistance and biocompatibility are not comprehensively reviewed. This article reviews the various processes used to manufacture CoCr alloy implants and discusses the effects of manufacturing processes on corrosion resistance and biocompatibility. This review concludes that the microstructure and precipitates formed in the alloy are unique to the manufacturing process employed and have a significant impact on the corrosion resistance and biocompatibility of CoCr alloys. Additionally, a historical and scientific overview of corrosion and biocompatibility for metallic implants is included in this review. Specifically, the failure of CoCr alloys when used in metal-on-metal bearing surfaces of total hip replacements is highlighted. It is recommended that the type of implant/application (orthopedic, dental, cardiovascular, etc.) should be the first and foremost factor to be considered when selecting biomaterials for medical device development.

Mg-Sc-Nd-xZn series alloys with medium strength and high plasticity

Different application scenarios put forward diverse requirements of mechanical properties for magnesium alloys. In this study, the extruded Mg-Sc-Nd-Zn alloy series with high plasticity and medium strength was developed. The uniformly distributed Mg3Nd (β1) phase, high-density twins, and the activated non-basal dislocation slips contribute to the high plasticity of Mg-Sc-Nd alloy. With the addition of Zn element, the appearance of coarse ScZn phases, which prevents the activation of {10 2} tensile twins, leads to an increase in strength but a simultaneous decrease in the plasticity of the extruded alloys. Adjusting the Zn content in the Mg-Sc-Nd-xZn allows a series of alloys with various strengths and plasticity matching. The results obtained in this work are of great importance for developing a regulatable magnesium alloy series that aims at different application scenarios.

The Effect of Heat Treatment on the Microstructure and Mechanical Properties of Powder Metallurgy Ti-48Al Alloy

Heat treatment is the critical step in achieving a refined microstructure and enhanced mechanical properties of TiAl-based alloys. This study investigated the influence of heat treatment temperature, cooling method, and heat treatment time on the microstructure and mechanical properties of an extruded powder metallurgy Ti-48Al alloy, and achieved the control of fully lamellar fine microstructures and the enhancement of performance through a simple heat treatment, rather than the traditional approach of homogenization followed by heat treatment. The results indicate that the heat treatment temperature determines the type of microstructure, while the cooling rate dictates the lamellar width. As the heat treatment temperature was increased from the two-phase region to the α single-phase region, the microstructure transitioned from duplex to near lamellar, and the alloy strength initially increased and then decreased, influenced by both the lamellar colony ratio and grain size. A rapid cooling rate (water quenching) induces a non-diffusive massive phase transformation, whereas a slow cooling rate (air cooling) gradually forms α2/γ lamellar colonies. Therefore, a suitable heat treatment regime for the powder metallurgy Ti-48Al alloy was determined to be 1340 °C/5 min/air cooling. The microstructure of the alloy was near lamellar, consisting of lamellar colonies approximately 50 μm and a small number of γ equiaxed grains of about 10 μm. Subsequently, the alloy exhibited a room temperature tensile strength of 784 MPa and a yield strength of 763 MPa, representing improvements of 17.0% and 38.7% over the extruded alloy, respectively. This research provides a reference for establishing a heat treatment process for powder metallurgy TiAl alloys.

Applications of unified phase-field methods to designing microstructures and mechanical properties of alloys

Applications of unified phase-field methods to designing microstructures and mechanical properties of alloys

Microstructure and Mechanical Properties of the Ti62Nb12Mo12Ta12W2 Refractory High Entropy Alloy Prepared through Spark Plasma Sintering

Microstructure and Mechanical Properties of the Ti62Nb12Mo12Ta12W2 Refractory High Entropy Alloy Prepared through Spark Plasma Sintering

Investigation on the electrical and thermal properties of Cr-doped FeSe2 alloys

FeSe2 is a p-type semiconductor with a narrow band gap, which can be considered a potential thermoelectric material. Herin, the electrical and thermal properties of Cr-doped FeSe2, Fe1-xCrxSe2 (x = 0, 0.03, 0.06, and 0.09), polycrystalline alloys are investigated. All compositions show single-phase marcasite structures of FeSe2 with gradual decreases in lattice parameters with Cr doping x. With increasing x, the electrical conductivity gradually increases from 13 (x = 0) to 46 S/cm (x = 0.09), owing to a large increase in carrier concentration originated from the substitution of Cr2+ and Cr3+ at the Fe site. However, the magnitude of Seebeck coefficient decreases considerably at 300 K, resulting in decrease in power factor. In addition, the density-of-state effective mass decreases significantly from 6.0 m0–1.04 m0. At 700 K, the decrease in Seebeck coefficient is less severe. Although the total and lattice thermal conductivity decrease at all temperatures owing to additional phonon scattering of the extrinsic Cr ions, a thermoelectric figure of merit, zT, generally decreases compared to that of the pristine sample due to power factor decrease at 300 K. Meanwhile, a slight increase of zT to 0.11 is observed for x = 0.06 at 700 K.