Solution Treatment Research Articles

Regulation of reinforced phases and its influence on the properties of (Ni2B+C)/Cu composite by heat and mechanical treatments

In this paper, (Ni2B+C)/Cu composites were prepared by hot pressing sintering (HP), and then heat treatment (HT) and multidirectional forging (MDF) were carried out to regulate the amount, size and distribution of reinforced phases. The evolution behavior of local structure and its effect on properties during heat treatment and multidirectional forging were studied. Results show that the Vickers hardness and electrical conductivity of (Ni2B+C)/Cu composite after solid solution, multidirectional forging, and aging treatment can reach 171.1 HV and 46.5 %IACS, respectively, which are increased by 55.3 % and 69.1 % compared with the as-sintered. The tensile strength can reach 355.1 MPa, and the facture elongation is increased to 5.2 % compared with the as-sintered (0.3 %), achieving a transition from brittle fracture to plastic fracture. In addition, the dry friction and wear mechanism of the composite is mainly abrasive wear, while the current-carrying friction and wear mechanism changes from abrasive wear to a coexistence of abrasive wear and oxidation wear. This work provides a new way to improve the properties of (Ni2B+C)/Cu composites.

Regulating microstructure and mechanical properties of the as-cast Mg-4Zn-0.5Y-0.5Nd alloy by heat treatment

The Mg-4Zn-0.5Y-0.5Nd alloy was designed and fabricated by conventional casting with subsequent heat treatment to regulate the microstructure and mechanical properties. The microstructure, secondary phase, mechanical properties, and fracture behavior were analyzed to elucidate the influencing mechanism. The results reveal that the as-cast alloy is composed of equiaxed grains with large sizes and discontinuously distributed secondary phases. Moreover, the secondary phase is mainly W-Mg3Zn3Y2, which partly forms the eutectic structure. The solid solution treatment coarsens the equiaxed grains and transforms the secondary phase into near continuous distribution. The Mg41Nd5 phase appears and volume fraction of secondary phase decreases a little. The combining of solid solution and aging treatment increases grain size and volume fraction of secondary phase more or less. Furthermore, the Mg24Y5 phase appears and secondary phases have been changed into semi-continuous distribution. After heat treatment, the average grain size reaches its maximum value of 107.18 μm, and the volume fraction of secondary phase climbs up to 2.73 %. Moreover, the solid solution treatment weakens the crystallographic orientation preference along {0001} but induces diversified crystallographic orientation preference. The heat treatment increases microhardness from 57.2 HV0.1 of the as-cast state to 70.5 HV0.1 of the heat-treated state. Comparatively, the solid solution treatment decreases mechanical properties, while the solid solution and aging treatment increase strength and ductility simultaneously. Especially for the ductility, it has been improved by more than 80 %, which is beneficial to the subsequent thermalmechanical processing greatly.

Evolution of microstructure and properties of CuCr50 alloy prepared by liquid phase sintering coupled with complementary copper infiltration

CuCr alloy has become the preferred contact material in the field of environmental protection vacuum switches because of its good mechanical and electrical properties, and the development of preparation technology of highly dense and homogeneous CuCr alloy has become one of its research directions. In this paper, the concepts of liquid phase sintering and complementary copper infiltration are coupled to prepare CuCr50 alloys, which are subjected to secondary treatment using solid solution as well as aging heat treatments, to observe the evolution of the microstructure and properties of CuCr50 alloys. It is found that CuCr50 alloy can be prepared stably by liquid phase sintering coupled with complementary copper infiltration. The average particle size of the Cr-rich phase in CuCr50 alloy is 48.9 μm after liquid phase sintering, solid solution treatment and aging treatment, and the uniformity of the distribution of the Cr-rich phase is improved compared with the billet and sintered state. At this time, the density of the CuCr50 alloy is 7.94 g·cm−3, the electrical conductivity is 22.77 MS·m−1, and the hardness reaches 113.2 HB. Compared with the requirements in the national standard GB/T 26867-2011, the density, conductivity, and hardness are increased by 0.51%, 42.3%, and 41.5%, respectively. The peak of the density of states at energies around −5 eV on the total density of states diagram is contributed by the superposition of the 3d orbitals of Cu and the 3d orbitals of Cr, which is a reason for the stable existence of the CuCr50 alloy.

Influence of Solution Treatment Temperatures on LPBF-Produced Inconel 939 Alloy on Mechanical Performance

This study investigates the influence of solution treatment temperatures on the microstructure and mechanical properties of LPBF (Laser Powder Bed Fusion)-manufactured Inconel 939 alloy. The primary objectives are to assess the impact of sub-recrystallization (below recrystallization temperature) and recrystallization temperatures during solution treatment on mechanical performance under different conditions. This study validates the hypothesis concerning carbide redistribution and mechanical performance in LPBF-produced Inconel 939 parts through comprehensive analysis, including microstructure studies and tensile tests. The results indicate that higher heat treatment temperatures lead to significant changes in carbide redistribution and mechanical performance. For instance, at room temperature, the specimen with sub-recrystallization solution treatment temperature exhibited superior mechanical properties compared to both the as-built and recrystallization-temperature solution treatment specimens. However, at elevated temperatures (700 °C), a reversal in mechanical anisotropy was observed, with the vertical axis demonstrating higher tensile strength compared to the horizontal axis for all material states. Furthermore, a microstructural analysis revealed distinct changes in grain structure and precipitate distribution, particularly the migration of carbides from grain boundaries to intragranular regions. These findings underscore the importance of precise control over heat treatment parameters to achieve optimal mechanical behavior. This research provides valuable insights into optimizing LPBF processes for the Inconel 939 alloy, highlighting the need for a meticulous control of the solution treatment parameters to ensure mechanical integrity. The findings contribute to a broader understanding of material-specific responses in additive manufacturing, with significant implications for aerospace applications.

Improving strength-conductivity synergy of Al-Cu-(Sn/Er) alloy with nanoscale substructure

As a conductive material for power transmission, Al-Cu alloy is widely used in power engineering, microelectronics and other fields. In view of the contradiction between the conductivity and strength of aluminum alloy, Sn and Er elements were selected to micro-alloy Al-Cu alloy. Al-Cu, Al-Cu-Sn and Al-Cu-Sn-Er alloys were prepared by near-liquidus casting. After solution treatment, it was subjected to three-stage alternating process of rolling and aging. The effects of micro-alloying and alternating process on the microstructure and properties of Al-Cu alloy were studied. The results show that the precipitated phase Al2Cu of Al-1.12 Cu alloy is rod-shaped after the first-stage process, and the average size is about 278±87 nm. The precipitated phases in the Al-Cu-Sn alloy are Al2Cu (average size of about 206±79 nm) and nano-sized β-Sn particles. The fine β-Sn nanoparticles in the Al-Cu-Sn-Er alloy heterogeneously nucleated on Al8Cu4Er (average size of about 167±45 nm), making Al8Cu4Er grow into particles. After secondary processing, stacking faults (SFs) appeared in the substructures of the three alloys, and the precipitated phases were further refined. The size of most precipitated phases in Al-1.13Cu-0.12Sn and Al-1.01Cu-0.15Sn-0.22Er alloys is reduced to nanometer level. After the three-stage process, some of the Al2Cu precipitates in the Al-Cu alloy are also refined to the nanometer level, and the precipitates in the other two alloys are all refined to the nanometer level. Nanotwins also appear in Al-1.01Cu-0.15Sn-0.22Er alloy. The tensile strength of Al-1.13Cu-0.12Sn and Al-1.01Cu-0.15Sn-0.22Er alloys after three-stage alternating process is 303 MPa and 327 MPa, respectively. The elongations are 21.6 % and 23.3 %, respectively. The relative conductivity was 61.7 %IACS and 59.8 %IACS, respectively. The synergistic effect of microalloying of Sn and Er elements and three-stage alternating processing technology not only reduces the size of precipitates and twins in the alloy to the nanometer level, but also adjusts the distribution of dislocation tangles and stacking faults (SFs), improves the substructure configuration, and improves the mechanical and electrical properties of conductive aluminum alloys.

Effects of Alkaline Solutions on the Structure and Function of Influenza A Virus

Influenza A virus (IAV) infection contributes to high annual morbidity and mortality, thus necessitating measures aimed at protecting against the disease. Alcohol-based disinfectants are commonly used to inactivate IAV, but they have several undesirable properties. In search of other means which would inactivate IAV, we focused on the effect of alkaline solutions on IAV. We found the viral infectivity remarkably decreased with treatment of an alkaline solution at pH 12.0 for 1 min, where destruction of the viral spikes was observed using an electron microscope. A more detailed examination revealed that the infectivity of IAV was remarkedly reduced by brief treatment with the alkaline solution at pH 11.75 or above, most likely due to the degradation of viral hemagglutinin protein. These results show that at a high pH, the haemagglutinin protein is degraded, resulting in very rapid inactivation of IAV.

Hydrogen-induced cracking behaviors of Ni–Cr–Mo-based superalloy fabricated by wire arc additive manufacturing under different solution temperature

The hydrogen embrittlement behavior of Ni–Cr–Mo-based superalloy fabricated by wire arc additive manufacturing (WAAM) with or without solution treatment was investigated by electrochemical hydrogen charging. The results show that the dissolution of the Laves phase promotes the precipitation of the δ phase in the matrix of WAAM superalloy after solution treatment at 980 °C. When the solution temperature goes up to 1080 °C, the large Laves phase disappears and only MC exists in the matrix. The interfaces between the Laves phase/δ phase and matrix generally could act as hydrogen traps, which would reduce the motion of hydrogen and lead to high hydrogen embrittlement resistance of the WAAM and ST-980 °C samples. However, hydrogen mainly accumulates on grain boundaries in the ST-1080 °C due to the disappearance of the Laves phase and δ phase. Hydrogen-induced intergranular brittle fracture occurs during the slow strain rate tensile test and the ST-1080 °C samples exhibit higher hydrogen embrittlement susceptibility than that of the WAAM and ST-980 °C samples.

A quasi-in-situ EBSD study on abnormal grain growth in 2219 aluminum alloy friction stir welded joints during post-weld heat treatment

Abnormal grain growth occurs in the friction stir welds of 2219 aluminum alloy during the solution treatment. To further investigate abnormal grain growth, the quasi-in-situ electron backscatter diffraction (EBSD) experiment, including the EBSD testing and heating by thermal simulation testing machine, was proposed to observe the grain growth process in the weld. The results show that the abnormal grain growth behavior in the stir zone and the thermo-mechanically affected zone is different, and different microstructures at different positions in the weld promote the growth of abnormal grains. In the stir zone, the modified Humphreys’ model is used to analyze the abnormal grain growth behavior. The grains with an advantage size and low strain are more likely to grow abnormally. The non-uniform pinning caused by the dissolution of second-phase particles further promotes abnormal grain growth. In the thermo-mechanically affected zone, the abnormal grains are formed by unstrained equiaxed grains near the stir zone or recrystallized sub-grains. The growth of abnormal grains in the thermo-mechanically affected zone is a strain-induced grain boundary migration process. The research is helpful to understand the abnormal grain growth in friction-stir welds during post-weld heat treatment.

Synergistic strengthening effects of precipitation and work hardening in cold-rolled Cu-0.4 wt%Cr alloy

Given the limitation of the precipitation strengthening effect in high strength and high conductivity Cu-Cr alloy, work hardening emerges as a practical and effective means to further enhance its strength. The Cu-0.4 wt%Cr alloy underwent varying degrees of cold rolling between the solution and aging treatments. The results of TEM characterization indicate that plastic deformation enhances precipitation, which occurs earlier than recrystallization in the deformed Cu-0.4 wt%Cr alloy. Thermodynamic calculations indicate that the driving force for precipitation is several orders of magnitude higher than that for recrystallization, while the nucleation barrier for precipitation is several orders of magnitude lower than that for recrystallization. Thus, the delayed recrystallization relative to precipitation theoretically allows for the coexistence of precipitates and deformed microstructures. In the peak aging state, despite the presence of numerous deformed microstructures, conductivity is almost fully restored. After aging for 1 h, the synergistic strengthening effects of precipitation and work hardening result in the yield strength and tensile strength of the sample cold rolled 64 % reaching 384.6 MPa and 422.0 MPa, respectively.

Innovative D-process MIG welding for enhanced performance of thick sections of MDN 250 in aerospace applications

Maraging steel, known for its exceptional strength, toughness and ductility, is widely used in aerospace and hypersonic missile manufacturing. The present study investigates the feasibility of joining 12 mm thick sections of maraging steel using advanced D-Process MIG welding technology. The D-Process integrates different welding modes such as MIG, Single Pulse-MIG and Double Pulse-MIG to optimize welding parameters, minimizing heat input. Additionally, the research investigates the influence of various post-weld heat treatments (PWHTs) on the performance of welded joints. The PWHTs included in the study are Ageing Treatment (AT), Solution Treatment + Ageing Treatment (SAT) and Homogenizing Treatment + Solution Treatment + Ageing Treatment (HSAT). Metallographic and mechanical tests were conducted on as-welded (AW) and PWHT conditions. Results showed the HSAT condition yielded superior properties with an average UTS of 1771 MPa, YS of 1734 MPa, and an average fracture toughness (FT) of 88 MPa√m. This underscores the efficacy of D-Process welding in meeting stringent requirements for maraging steel in aerospace and high-performance applications.

Relaxation mechanisms of near – α titanium alloy during stress relaxation with synchronous aging

Stress relaxation with synchronous aging (SRSA) could not only reduce springback but as well improve the performance of titanium alloy components. To reveal the relaxation mechanisms during SRSA, solution treatments of Ti-6.5Al–2Zr–1Mo–1V alloy under different temperatures were carried out to obtain diverse initial microstructures. The evolutions of microstructure including phase transformation, dislocation movement and stress-induced twinning were meticulously characterized. The progress of activation energy was analyzed quantitatively by the Kohlrausch-Williams-Watts equation. Results show that SRSA under all different conditions exhibits a rapid stress decline initially followed by a quasi-static stage, due to a shift in the driving force from stress-driven to thermally activated driven. The activation energy changes from a quasi-static state to a rapid rise with relaxation time. After two-phase solution treatment, the primary α (αp) dominant mechanism is the dislocation movement, including dislocation tangles and then recovery. The relaxation mechanism of the supersaturated metastable β phase is phase transformation (precipitation and growth of secondary α (αs)) and stress-induced twinning, and the αs realizes stress release through the globularization in the later stage. The full martensite microstructure was obtained by solution treatment in a single-phase region, and the main relaxation mechanism involves stacking faults, stress-induced twinning and then globularization. The enhancement in strength following SRSA is primarily attributed to the formation of αs, dislocation strengthening, and stress-induced twinning.

Polypropylene Packaged Ten Days Cold Stored Rose Cut Flowers cv. Bordeaux Influenced by Different Pulsing Solution

The study included different pulsing solution viz., water, HQC 200mg/l, sucrose 50g/l + HQC 200 mg/l, citric acid 200mg/l, α-lipoic acid 200mg/l, GA3 100 mg/l and BA 100mg/l to study the effect on flower quality and vase life of PP (polypropylene) packaged cold storage (at 2°C) rose cv. Bordeaux, for the period of 10 days. Pre-storage pulsing of GA3 100mg/l solution treatment showed highly promising results in extending flowers vase life along with maintained flower quality just after storage and at 4th DAS in vase life. Further, GA3 100mg/l solution treatment recorded significantly higher water up take (175.65 ml), change in fresh weight (10.50%) at 4th DAS, total dissolve solids (8.85 °brix, 8.05 °brix and 6.75 °brix) and membrane stability index (81.97 %, 65.97 % and 37.88 %) at 2nd, 4th and 6th DAS. Moreover, it was evident from the results that same treatment recoded significantly higher total soluble sugar (59.65 mg/g fresh weight), Estimated protein (18.79 mg/g fresh weight), catalase activity (20.42 µ mol H2O2 min-1 g-1 protein), peroxidation activity (40.30 µ mol H2O2 min-1 g-1 protein), pigment content (15.82 mg/g fresh weight) anthocyanin content in the petals at 4th DAS. Whereas, GA3 100 mg/l pulsing solution treated PP packaged cold stored rose cut flowers cv. Bordeaux recorded significantly higher vase life (6.88 days) which was at par with treatment P2 (Sucrose 50 g/l + HQC 200 mg/l).

Precipitation Refinement via Aging Time Modification for Enhancing Wear Resistance in Ti–V–Nb Microalloyed High‐Manganese Steels

It is imperative to ensure an even distribution of refined precipitates to enhance wear resistance. Herein, different heat treatments are to control the size and distribution of precipitates. The treatments include water quenching at 1100 °C followed by aging at 400 °C for 24, 60, and 84 h, designated as AT24, AT60, and AT84, respectively. The microstructure, mechanical properties, and impact wear properties of high‐manganese steel are investigated under solution and aging conditions using scanning electron microscopy, field‐emission scanning electron microscopy, tensile testing, and impact abrasive wear testing. Notably, the absence of nanoscale precipitates largely accounts for the poor wear resistance of as‐casting steel, whereas the strengthening effect of larger micrometer‐sized precipitates is insufficient. After the solution and aging treatment, nanosized precipitates continuously form within the matrix, conducive to the formation of the deeper work‐hardening layer, thereby improving the wear resistance. The fine micrometer‐sized precipitates and evenly distributed nanoscale precipitates in AT60 actively contribute to toughness. Additionally, these precipitates interact with slip dislocations, providing stronger strengthening via the Orowan looping mechanism. The wear mechanisms of steel can be transformed from wide, deep pits to shallow grooves and microcutting by extending the aging time.

Research on the microstructure, mechanical and fatigue performance of 7075/6061 dissimilar aluminum alloy fusion welding joint treated by nanoparticle and post-weld heat treatment

The microstructure and mechanical properties of 7075/6061 high-strength dissimilar aluminum alloy fusion welds, after TiC nanoparticle-assisted welding and heat treatment, were discussed, and their fatigue performance was analyzed. The results indicate that the significant increase in hardness at the weld zone with T6 treatment compared to T5 is due to the solution treatment providing supersaturated solid solution for subsequent aging precipitation. T5 treatment causes the precipitation in the heat affected zones, thereby increasing the hardness of these regions. The joints exhibit excellent yield strength and tensile strength after heat treatment, with the elongation performance being optimal in T6 state. The fatigue performance of dissimilar aluminum alloy joints treated with nanoparticle and heat treatment is superior to the joints with single riveting. Porosity defects and microcracks generated during welding are prone to stress concentration, with interconnected pores and easily propagating cracks forming fatigue sources for pores and cracks. The crack propagation behavior is influenced by the pinning effect of TiC nanoparticles at the grain boundaries, and the second phase particles hinder crack propagation along the grain boundaries, forcing cracks to extend towards the 6061 side or the HAZ of the lower strength 6061 matrix. It demonstrates that the method of combining nanoparticle-assisted melt inert-gas welding and T6 heat treatment improves the fatigue life of 7075/6061 dissimilar aluminum alloy joints.

Influence of layer thickness and heat treatment on microstructure and properties of selective laser melted maraging stainless steel

As one of the main parameters of selective laser melting (SLM) process, layer thickness has a significant impact on the forming performance and efficiency of printed parts. Based on microstructure analysis and properties testing, the metallurgical mechanism, phase composition and mechanical behavior of SLM-formed Corrax stainless steel with different layer thicknesses were discussed. The influence of heat treatment process on the properties was comparatively investigated. The results indicated that at smaller or larger layer thicknesses, the increase in melt dynamic instability and spheroidisation feature easily induced the formation of unfused pore defects, which in turn led to lower relative density and mechanical properties. At the appropriate layer thickness, the suitable melt flow behaviour promoted the formation of good metallurgical bonding between adjacent melt channels. The maximum tensile strength, yield strength and hardness of the samples prepared at a layer thickness of 60 μm were 1224 MPa, 948 MPa and 39.2 HRC, respectively. The microstructure of the as-built samples was martensite and a small amount of austenite. With increasing layer thickness, the cooling rate of the molten pool decreased and the austenite content increased. After solution treatment, the alloying elements dissolved in the martensitic matrix resulted in lower mechanical properties. After aging and solution aging treatment, the mechanical properties were significantly improved due to precipitation strengthening of NiAl nanoparticles and dislocation strengthening. The corresponding tensile strengths were 1655 MPa and 1796 MPa, the yield strengths were 1328 MPa and 1573 MPa, and the hardnesses were 45.7 HRC and 50.2 HRC, respectively.

The Application of Ultrasound Pre-Treatment in Low-Temperature Synthesis of Zinc Oxide Nanorods

Zinc oxide, due to its unique physicochemical properties, including dual piezoelectric and semiconductive ones, demonstrates a high application potential in various fields, with a particular focus on nanotechnology. Among ZnO nanoforms, nanorods are gaining particular interest. Due to their ability to efficiently transport charge carriers and photoelectric properties, they demonstrate significant potential in energy storage and conversion, as well as photovoltaics. They can be prepared via various methods; however, most of them require large energy inputs, long reaction times, or high-cost equipment. Hence, new methods of ZnO nanorod fabrication are currently being sought out. In this paper, an ultrasound-supported synthesis of ZnO nanorods with zinc acetate as a zinc precursor has been described. The fabrication of nanorods included the treatment of the precursor solution with ultrasounds, wherein various sonication times were employed to verify the impact of the sonication process on the effectiveness of ZnO nanorod synthesis and the sizes of the obtained nanostructures. The morphology of the obtained ZnO nanorods was imaged via a scanning electron microscope (SEM) analysis, while the particle size distribution within the precursor suspensions was determined by means of dynamic light scattering (DLS). Additionally, the dynamic viscosity of precursor suspensions was also verified. It was demonstrated that ultrasounds positively affect ZnO nanorod synthesis, yielding longer nanostructures through even reactant distribution. Longer nanorods were obtained as a result of short sonication (1–3 min), wherein prolonged treatment with ultrasounds (4–5 min) resulted in obtaining shorter nanorods. Importantly, the application of ultrasounds increased particle homogeneity within the precursor suspension by disintegrating particle agglomerates. Moreover, it was demonstrated that ultrasonic treatment reduces the dynamic viscosity of precursor suspension, facilitating faster particle diffusion and promoting a more uniform growth of longer ZnO nanorods. Hence, it can be concluded that ultrasounds constitute a promising solution in obtaining homogeneous ZnO nanorods, which is in line with the principles of green chemistry.

Effect of Ca addition on structure, phase composition and hardness of Al–6 %Cu–2 %Mn sheet alloy

The Al–Cu–Mn–Ca system was proposed as a bases for the design of new group of heat-resistant alloys which can be used for high-temperature applications instead of the 2219 types industrial alloys. Unlike the latter ones, the new alloys also do not require a full cycle of strengthening heat treatment including solid solution treatment, quenching and aging. The effect of calcium addition in the 1–4 wt% range on the structure, phase composition and hardness after high temperature annealing of the Al–6 %Cu–2 %Mn base sheet alloy has been studied. It has been shown that calcium addition leads to the formation of high-temperature eutectics (614–617 °С) with the participation of the Al27Ca3Cu7 and (Al,Cu)4Ca phases that are capable of spheroidization at high temperature annealing. The ingots of Ca-containing alloys do not require homogenization but have sufficient deformation plasticity at both hot and cold rolling. The structure of the previously unstudied quaternary Al–Cu–Mn–Ca phase diagram in the region of the aluminum corner has been also proposed, according to which it can contain 5 four-phase fields in the solid state with the participation of (Al), binary (Al2Cu, Al4Ca, Al6Mn) and ternary (Al8CaCu4, Al27Ca3Cu7, Al10CaMn2 and Al20Cu2Mn3) phases. Based on the obtained data, the composition Al–6 %Cu–2 %Mn–1 %Ca has been proposed as a basis for the development of a new heat-resistant alloy. It is shown that this alloy superior to industrial 2219 alloy in terms of heat resistance, especially after annealing at 400 °C, when the difference in hardness reaches 32 HV. The high heat resistance of the new wrought alloy originates from the formation of a specific microstructure consisting of fine Ca-containing eutectic inclusions and Al20Cu2Mn3 phase dispersoids with a size of about 100 nm which prevent recrystallization and allow maintaining the fine sub-grained structure.

Effect of heat treatment on the microstructure and mechanical properties of AZ91D magnesium alloy fabricated via GTA wire arc additive manufacturing

This study aims to address elemental segregation and poor mechanical properties in as-deposited AZ91D magnesium alloy fabricated via wire arc additive manufacturing through heat treatment. Three distinct heat treatments are investigated: solution treatment (T4), artificial aging treatment (T5), and a combination of solution and aging treatment (T6). Microstructural analysis reveals equiaxed grains in all samples. In the T4 state, the eutectic phase along grain boundaries dissolvs into the matrix, reducing elemental segregation but increasing grain size. In the T5 state, elemental segregation is further reduced; however, due to the relatively low aging temperature, the microstructural features of the as-deposited state are largely retained. In the T6 state, solution treatment increases grain sizes, and the uneven distribution of the reprecipitated β phase leads variations in mechanical properties between vertical and horizontal directions. Compared to the as-deposited state, the T6 treatment achieves a synergistic improvement in both strength and ductility. The ultimate tensile strength increases to 262.3 MPa, and the elongation rises to 13.8%, representing improvements of 12.5% and 32.7%, respectively, compared to the as-deposited values of 233.2 MPa and 10.4%.

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