Solution Treatment Research Articles

Effect of Carbide Precipitation on Hardness and Wear Resistance of H13 Steel

The carbide precipitation of H13 steel and its effect on hardness and friction and wear resistance are investigated by microstructure observation, phase analysis, and mechanical property test. Results show that the tempering hardness is mainly related to the content of secondary carbides. After solution treatment in the temperature range of 1040–1070 °C, quenching and tempering, with the increase of the solution temperature, the content of secondary carbides and hardness of H13 steel in the tempering microstructure increase first and then decrease, and both reach the maximum value when the solution temperature is 1060 °C. The change of hardness is consistent with that of the content of secondary carbides. When the solution temperature is 1040 °C, the wear mass loss of the tempered H13 steel is the least, which is 4.63 mg, indicating that its wear resistance is the best, and this is caused by the presence of more undissolved carbides in the tempering microstructure. With the increase of the solution temperature, the wear mass loss increases gradually, and the wear resistance decreases, which is mainly related to the content decrease of undissolved and secondary carbides and the content increase of residual austenite.

Dissolution Behavior of Laves Phase and Hardness Evolution for Direct Energy Deposited Inconel 718 Alloy with δ Aging and Solution Treatment

Dissolution Behavior of Laves Phase and Hardness Evolution for Direct Energy Deposited Inconel 718 Alloy with δ Aging and Solution Treatment

On the precipitation and transformation kinetics of precipitation-hardening steel X5CrNiCuNb16-4 in a wide range of heating and cooling rates

In this work, the transformation and dissolution/precipitation behaviour of the soft martensitic, precipitation-hardening steel X5CrNiCuNb16-4 (often referred to as 17–4 PH or AISI 630) has been investigated by various analytical in situ techniques. First, austenite formation during the heating stage of a solution treatment (or austenitization) is examined. Subsequently, a major part of this work evaluates precipitation during cooling from the solution treatment (i.e., the quench-induced precipitation of Cu-rich particles). The following analytical in situ techniques were utilised: synchrotron high-energy X-ray diffraction, synchrotron small-angle X-ray scattering, differential scanning calorimetry, and dilatometry. These were complemented by ex situ high-angle annular dark-field scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy on as-quenched samples after various cooling rates. The continuous heating transformation and continuous cooling transformation diagrams have been updated. Contrary to previous reports, X5CrNiCuNb16-4 is rather quench sensitive and the final properties after ageing degrade if cooling is done slower than a certain critical cooling rate. Quench-induced Cu-rich precipitation happens in two reactions: a larger, nearly pure Cu face-centred cubic phase forms at higher temperatures, while at medium temperatures, spherical Cu-rich nanoparticles form, which are found to be body-centred cubic at room temperature. The dimensions of the quench-induced particles range from several µm after cooling at 0.0001 K s-1 down to just a few nm after cooling at 1 K s-1. The maximum age hardening potential of X5CrNiCuNb16-4 can be exploited if a fully supersaturated solid solution is reached at cooling rates above the critical cooling rate of about 10 K s-1.

PEDOT:PSS Films With Very High Thermoelectric Properties Through Water‐Swollen Assisted Reduction With a Tetrakis(dimethylamino)ethylene Solution

AbstractThermoelectric (TE) materials have attracted significant attention because they can be used to directly harvest waste heat into electricity. Organic TE materials like poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) have advantages including high mechanical flexibility, low cost, and low intrinsic thermal conductivity. However, their TE properties are notably inferior to their inorganic counterparts. Here, PEDOT:PSS films with very high thermoelectric properties through the sequential treatments with H2SO4, water, and ethanol solution of tetrakis(dimethylamino)ethylene (TDAE) are reported for the first time. The PEDOT:PSS films can exhibit a Seebeck coefficient of 58.2 µV K−1 and electrical conductivity of 1552 S cm−1, and the corresponding power factor is 526 µW m−1 K−2. The water treatment prior to the TDAE solution treatment is crucial for the high TE properties of PEDOT:PSS films. Without the water treatment, the control PEDOT:PSS films exhibit a Seebeck coefficient of only 32.4 µV K−1 and electrical conductivity of 1124 S cm−1, and the corresponding power factor is only 118 µW m−1 K−2. The effect of the water treatment on the Seebeck coefficient is attributed to the swelling of PEDOT:PSS films, which facilitates the penetration of TDAE from solution into the polymer films and thus the reduction of PEDOT:PSS.

Effect of HIP on Creep Properties in the Single Crystal Superalloy

The Rene N5 is a second-generation single crystal superalloy containing 3wt% Re, commonly used in gas turbine blades for power generation at temperatures up to 1600°C due to its excellent creep life. Generally, single crystal (SX) and directionally solidified (DS) blades are not applied to hot isostatic pressing (HIP) because their porosities are lower than conventionally cast (CC) blades, and it causes recrystallization issue. However, in this study, HIP was chosen as a candidate to improve the mechanical properties of the second-generation single crystal superalloy Rene N5. HIP followed by ultra-rapid cooling rate of 660K/minute was applied in an attempt to address this issue. This approach was expected to enhance creep rupture properties through pore reduction and microstructural homogenization. Furthermore, by setting the HIP temperature and time identical to the solution treatment condition, the possibility of replacing solution treatment with HIP was discussed. As results of creep rupture tests, the rupture life was excellent in the order of specimens treated with HIP + solution + aging, solution + aging, and HIP + aging treatments. It is interesting that this is found to be primarily influenced by the size and shape of carbides and γ’ phases, with the effects of crystallographic orientation, shrinkage porosity, and eutectic phase being negligible.

The evolution and toughening mechanism of austenite in high Co–Ni ultrahigh strength steel

The austenite, as a “soft” phase, has a significant impact on the mechanical properties in ultrahigh strength steel. The morphology, size, and distribution of austenite play a critical role in toughness of steel. This study concentrates on morphology, size, and distribution of austenite subjected to solid solution, cryogenic, and aging treatments and explores its evolution characterized by transmission electron microscopy, scanning electron microscopy, electron backscatter diffraction and x-ray diffraction. The toughening mechanism of austenite with different characterization was investigated through charpy impact testing and fracture morphology analysis. The results indicate that filmy and blocky austenite existed at the lath boundary of martensite. Blocky austenite and some filmy austenite were eliminated after cryogenic treatment, while approximately less than 15 nm filmy reverted austenite was formed after aging treatment. Filmy reverted austenite at the boundary of martensite laths can enhance toughness. Retained austenite without cryogenic treatment can induce the formation of larger blocky austenite, which decreased toughness.

Effect of recrystallization annealing, solid solution and pre-aging intermediate treatment on microstructure and mechanical properties of Al-Mg-Si rolled sheet

The intermediate heat treatment plays an important role in the severe deformation processing of aluminum alloys. In this study, the effects of recrystallization annealing, solid solution and pre-aging intermediate treatments on the microstructure and mechanical properties of Al-Mg-Si sheet were analyzed, and the strengthening ability of grain boundary, residual dislocation and precipitation was explored. The tensile results show that the pre-aging treatment can significantly improve the mechanical properties, increasing the yield strength, ultimate tensile strength and elongation by 22.9 %, 19.9 % and 10.9 %, respectively, compared with the alloy without intermediate treatment. Further studies present that the recrystallization annealed alloys are mainly composed of elongated recrystallized tissue and isometric crystals, and the strength enhancement is mainly attributed to precipitation strengthening. Solid solution treated alloys are composed entirely of fine equiaxed crystals with a higher density of residual dislocations, showing significant grain boundary strengthening and improving the plasticity. Pre-aging treatment obtains the benefits of solid solution treatment, while also forming a large number of GP zones and quasi-β'' phases, which impede the dislocation movement during cold rolling and then increase the effective nucleation sites of precipitation during T6 treatment. This promotes the generation of the strengthening β'' phase, and enhances the precipitation strengthening effect of the alloy from 165.7 MPa in solid solution treatment to 195.6 MPa in pre-aging treatment.

Effect of Cryogenic Treatment on Residual Stress and Microstructure of 6061 Aluminum Alloy and Optimization of Parameters.

Residual stress induced by solution treatment in 6061 aluminum alloy can lead to workpiece deformation, or even premature failure. The efficiency of traditional heat treatment for relieving residual stress is relatively low. Therefore, this study introduces a novel cryogenic treatment technique to reduce residual stress. The optimal cryogenic process parameters were achieved by orthogonal experiments: cryogenic temperature of 113 K, holding time of 24 h, 1 cryogenic cycle, and a cooling rate of 3 K·min-1, and the residual stress of aluminum alloy was measured by the blind hole method. The microstructural evolutions in 6061 aluminum alloy were tested by OM, SEM, and TEM. The results show that the introduction of cryogenic treatment can reduce residual stress in 6061 aluminum alloy by 64%, mainly due to the reduction of dislocations and the uniform distribution of β'' phase.

The Dissolution Behaviors of Carbides During Solution Treatment for AMSC‐DB Ni‐Based Superalloys Fabricated by Laser‐Directed Energy Deposition and Forging

The Dissolution Behaviors of Carbides During Solution Treatment for AMSC‐DB Ni‐Based Superalloys Fabricated by Laser‐Directed Energy Deposition and Forging

A novel integrated hot forming with in-situ stress relaxation-aging for titanium alloy thin-walled components

The simultaneous achievement of high strength and precision in the fabrication of titanium alloy thin-walled components is a long-standing issue. This work proposes a novel integrated forming process, named Hot Forming with In-situ Stress Relaxation-Aging (short for HF-ISRA) to solve the special issue. In contrast to usual isothermal forming, the forming temperature in the proposed process is raised to the solution treatment temperature. Dies at a lower temperature realize in-situ stress relaxation-aging after hot forming. The role of the dies, in addition to forming, is also achieved post-forming heat treatment. This novel process comprises three main steps: solution heat treatment, rapid forming at solution temperature, and in-situ stress relaxation-aging. An experimental prototype of HF-ISRA was developed for V-bending test, in which a sheet blank was rapidly heated using electric current and the forming die was heated using heating rods. The process window of the proposed HF-ISRA was established based on the V-bending and uniaxial tensile tests of the TA15 titanium alloy. The results showed that compared with cold forming, the springback angle obtained using the optimized HF-ISRA decreased by 97.8 %, from 9°06′ to only 12′. The tensile strength at room temperature and 500 °C was improved by 4.4 % and 10.9 % compared with the as-received material, respectively. The relaxation mechanisms of αs were the precipitation, growth, and then globularization. The relaxation mechanism of αp was dislocation movements. The strength improvement in HF-ISRA was due to the formation of αs and dislocations strengthening. The stress-induced twinning in αs was also a contributor. The proposed novel process provides a new route for the fabrication of titanium alloy thin-walled components with high precision and strength.

Effect of age hardening precipitates on the corrosion performance of laser Powder-Directed energy deposited CuNi2SiCr

This study explores Laser Powder − Direct Energy Deposition (LP-DED) processing of CuNi2SiCr and the effect of heat treatment on corrosion behavior. The findings pave the way to increasing the life of the components and the possibility of refabrication upon failure. LP-DED manufactured CuNi2SiCr was subjected to solution treatment followed by age-hardening at 500℃ for 1,3,5 and 7 h. The microstructure analysis showed the formation of Cr3Ni precipitates due to a higher cooling rate in the LP-DED process. Upon aging, Ni3Si, Ni2Si, and CrSi2 precipitates evolved. Due to the Orowan phenomenon, microhardness increases with the aging time as the number of precipitates along the grain boundary increases with the aging time. The 5-hour aged sample exhibited the best corrosion resistance due to precipitation coherency in the matrix and the medium-sized precipitates with uniform precipitation-free zones (PFZ) in the grain boundary.

Optimization of microstructure and high-temperature mechanical properties of Ti4822/Ti2AlC composites through multiple solution-aging treatments

In this paper, a Ti-48Al-2Cr-2Nb (Ti4822, at%) based composite with uniformly distributed Ti2AlC nano-micro precipitates was prepared by powder metallurgy followed by a multiple solution-aging treatment. Multiple solution treatments eliminated the equiaxial γ grains in the sintered composites and refined the coarse-grained primary Ti2AlC phases, resulting in a fully lamellar microstructure with fine Ti2AlC precipitates embedded between the α2/γ lamellae. The high-temperature ultimate tensile strength of the heat-treated Ti4822/Ti2AlC composites reached 543 MPa at 800 ℃, and the elongation was 7.7 %, increased by 9.7 % and 0.8 % correspondingly compared to that of the sintered composite. The enhancement of the properties of Ti4822/Ti2AlC composite in the heat-treated state was due to the elimination of γ grains in the microstructure to transform the full lamellar microstructure on the one hand, and the refinement and dispersion of agglomerated Ti2AlC precipitates on the other hand. This study provided a valuable reference for the refinement and dispersion of the second phase in TiAl composites.

Improving the electrochemical performance of lithium-rich manganese-based cathode materials by Na₂S₂O₈ surface treatment

Lithium-rich manganese-based cathode materials are well-regarded for their high specific capacity and notable voltage thresholds, making them attractive for advanced energy storage applications. However, their widespread commercialization is hindered by challenges in cycle performance, including suboptimal initial Coulombic efficiency, inadequate cycle stability, and constrained rate capability. To address these issues, this paper introduces a novel modification strategy using Na₂S₂O₈ to chemically delithiate the surface of the materials. This modification strategy dramatically enhances the initial Coulombic efficiency. The results demonstrate that the initial Coulombic efficiency of the two pre-activated samples improved to 84.6 % and 102.2 %, respectively. At the same time, the Na₂S₂O₈-treated samples exhibit a higher maximum discharge capacity at a 0.2 C rate, reaching 211.1 mAh g⁻¹ and 201.3 mAh g⁻¹, which notably surpasses the untreated sample's capacity of 188.7 mAh g⁻¹. Additionally, the treated samples exhibit improved cycling and rate performance, with capacity retention of 81.2 % and 63.5 %, respectively. After 60 cycles, these figures continue to be superior to those of the untreated material, which stands at 57.3 %. The results demonstrate that Na₂S₂O₈ treatment leads to the in situ formation of spinel phases on the material surface, thereby enhances the cycling stability and rate capability of the cathode material. Compared to traditional surface treatment methods, Na₂S₂O₈ solution treatment can induce more profound structural evolution without necessitating high-temperature calcination, thus reducing the demands on process conditions and equipment and offering greater process controllability. Moreover, this surface modification strategy paves the way for applying spinel coatings on other substrates with similar structures.

Optimization of high-temperature mechanical properties of aluminum alloys through exclusive precipitation of T-phase

An aluminum alloy with an actual composition of Al - 5.4 wt%Cu- 1 wt%Mn was cast and subjected to solution heat treatment for 1 h, 2 h, 4 h, 8 h, and 16 h to make the T-phase the sole strengthening phase. The microstructural evolution of the samples, especially the T-phase microstructure, was studied using transmission electron microscope (TEM) and scanning electron microscope (SEM) with electron backscatter diffraction (EBSD) attachment. The ImageJ software was utilized to statistically analyze T-phase content. Tensile tests were conducted to obtain mechanical property data, and high-temperature tensile tests were performed at 200 °C, 300 °C, and 400 °C to assess the high-temperature performance. Subsequently, the strengthening effect of the T-phase on the room-temperature and high-temperature mechanical properties of the aluminum alloy was quantitatively evaluated. The sample subjected to an 8 h solution treatment exhibited optimal strength and toughness. The yield strength was 147 MPa, and the tensile strength was 300 MPa. The yield strength contributed by the T-phase was 73 MPa. The tensile strength of the sample at 400 °C remained at 91 MPa. The T-phase contributes significantly to the mechanical properties of the aluminum alloy both at room temperature and at high temperatures.

Effects of solution treatment on microstructure and properties of Ti-5.7Al-3.9Sn-0.91Mo-3.4Zr-0.40Si-0.38Nb-0.95Ta titanium alloy

This study investigated the effects of solution treatments under various conditions on the matrix and silicides microstructure and their impact on the mechanical properties of high-temperature Ti60 (Ti-5.7Al-3.9Sn-0.91Mo-3.4Zr-0.40Si-0.38Nb-0.95Ta) titanium alloy. The microstructure evolution during solution treatments was characterized, and the tensile properties at 600 °C and room temperature (RT) were investigated. The results show that the fraction and grain size of martensite and silicides can be tailored through solution treatments. With increasing solution temperature, the fraction of primary α (αp) phase and silicides decreases, while that of the transformed β (βt) microstructure increases. After solution treatment at 1025 °C, the yield strength (YS) and ultimate tensile strength (UTS) reach 685.0 MPa and 900.8 MPa, respectively, at 600 °C, increasing by 18.0% and 27.0%, respectively, compared to the initial state. The elongation (EL) remains at 16.2%. The strengthening mechanisms of Ti60 alloy include grain boundary strengthening of the αp phase and martensite formed during rapid cooling, as well as precipitation strengthening of the silicides. With increasing solution temperature from 950 °C to 1025 °C, the fraction of martensite strengthening increases from 38.4% to 89.3%, while the fraction of precipitation strengthening of silicides decreases from 3.63% to 1.17%.

Microstructure and properties of a HIP manufactured B4Cp reinforced highly alloyed Al-Zn-Mg-Cu-Zr aluminum matrix composite

In this study, an aluminum matrix composite with good mechanical property and excellent corrosion resistance, B4C particles (B4Cp) reinforced highly alloyed Al-Zn-Mg-Cu-Zr matrix composite, was successfully fabricated through ball-milling, cold isostatic pressing, vacuum degassing, hot isostatic pressing (HIP), homogenization, hot extrusion, solution treatment, and aging treatment. It was found that the B4C/MgAl2O4/Al was the dominant interface structure, which was coherent and enhanced the bonding between the particles and the matrix considerably, while the B4C/Al2O3/Al was the minor interface structure. The grain boundary was very clean in both T4 and T6 aging states, without aging precipitates and O element segregation. In T4 aging state, the composite exhibited superior properties, with the mass density of 2.84 g·cm-3, the elastic modulus of 119.18 GPa, the yield strength of 576.08 MPa, the ultimate tensile strength of 655.27 MPa, the tensile elongation of 1.48%, and the very low electrochemical corrosion current density of 4.4581×10-8 A·cm-2 in 3.5 wt.% NaCl water solution. The MgAl2O4 and BO3-rich interface phases, the strengthening mechanisms and the anti-corrosion mechanisms of the composite were discussed in detail.

Temperature-dependent deformation behavior of Hastelloy X Ni-based superalloy fabricated via laser powder bed fusion

Understanding the deformation behavior of additive manufacturing components across a wide spectrum of operating temperatures is crucial from an application standpoint. This study investigated the tensile deformation behavior of Hastelloy X (HX), fabricated via laser powder bed fusion (LPBF), over a temperature range of -50 °C to 900 °C through uniaxial tensile tests. The focus was on the temperature-dependent tensile properties and deformation mechanisms of HX in a fully heat-treated condition, involving initial hot isostatic pressing followed by solution treatment. The results indicate that as the temperature increases, the ultimate tensile strength decreases sharply from approximately 790 MPa at -50 °C to 610 MPa at 200 °C, then gradually declines to 530 MPa at 600 °C, and finally drops to 230 MPa at 900 °C. Meanwhile, the yield strength falls rapidly from 345 MPa at -50 °C to 230 MPa at 200 °C, then slowly reduces to 170 MPa at 600 °C, stabilizing up to 900 °C. Electron back scattered diffraction analysis revealed that with rising temperature, the predominant plastic deformation mechanism transitions from deformation twinning to slip bands and eventually to dynamic recrystallization. Remarkably, the strain hardening capacity increases with rising temperature below 600 °C, attributed to the beneficial effects of deformation twins and subsequent slip bands. Furthermore, dynamic strain aging takes place between 300 °C and 600 °C, slightly limiting the improvement of plasticity within this intermediate temperature range. Understanding these temperature-dependent deformation mechanisms in heat-treated LPBF HX would provide valuable insights into its performance over a wide range of service temperatures.

Impact of Weld Time and Solution Treatment on the Performance of IN625 Spot Joints: An Experimental Study

Impact of Weld Time and Solution Treatment on the Performance of IN625 Spot Joints: An Experimental Study

Effect of solution and cooling methods on the high-temperature mechanical behavior of Ti60 alloy

The influence of solution treatment temperature and cooling rate on the mechanical behavior of Ti60 alloy at 600℃ was investigated. Five different solution treatment temperatures and five different cooling methods were used for the Ti60 alloy. The study revealed that, at the same solution treatment temperature the ultimate tensile strength (UTS) and elongation (Z%) of the water-quenched (WQ) microstructure were 32 % and 61 % higher, respectively, compared to the furnace-cooled (FC) microstructure. The WQ microstructure exhibited significantly superior strength and ductility. This phenomenon was primarily attributed to the differences in microstructural morphology caused by varying cooling methods. The effects of different cooling methods on high-temperature tensile behavior were discussed in terms of fracture morphology, high-angle grain boundaries, and void distribution. On the other hand, the UTS of the air-cooled (AC) microstructure initially increased and then decreased with decreasing solution treatment temperature, while the UTS of the FC microstructure decreased with decreasing solution treatment temperature. This phenomenon was mainly due to the competing effects of effective slip length (colony size) and elemental distribution. The correlation between solution treatment temperature and cooling rate parameters and high-temperature mechanical properties was established using the response surface methodology (RSM). The optimized solution cooling scheme was determined to be at 1012℃ with a cooling rate of 4238℃/min.

Impacts of T6 heat treatment on the microstructural, mechanical, and corrosion properties of thixoformed AA7075 alloy produced by cooling slope casting

Abstract Research into semi-solid metal forming techniques has been ongoing for an extended period with the aim of producing near-net shape products from aluminum alloys. The primary focus has traditionally been on casting alloys seeking to offer an alternative to the other processes such as high pressure die casting. Over the past twenty years, wrought aluminum alloys have also been explored for thixoforming operations as an alternative to traditional plastic deformation techniques. This research investigated the impacts of T6 heat treatment on the microstructural, mechanical, and corrosion properties of AA7075 alloy samples produced through cooling slope casting and subsequent thixoforming with different reheating durations. The selected alloy was chosen due to its widespread use in various industries, attributed to its excellent strength-to-density ratio achieved after T6 heat treatment. Building on optimized cooling slope casting parameters from a prior study, the standard solution treatment procedure following thixoforming with extended reheating times was found to be inadequate. Hardness and tensile tests revealed that specimens reheated for 120 min exhibited significantly reduced response to T6 treatment. Despite achieving the targeted hardness value of 154 HB with samples reheated for 20 min prior to thixoforming and T6 heat treatment, especially the elongation at break values were unsatisfactory. Potentiodynamic polarization tests indicated that corrosion primarily involved grain dissolution, with longer reheating times decreasing corrosion resistance due to increased amount of secondary phases and grain isolation. These findings highlight that while AA7075 alloy can be processed into semi-solid formable materials via cooling slope casting, issues such as hot tearing, micro-shrinkage, and physical defects post-thixoforming hinder the achievement of desired tensile properties.