Aging Heat Treatment Research Articles

Effect of Solution Aging Heat Treatment on Tribological Properties of Selective Laser Melted WC/18Ni300 Composite

Different contents of WC particle‐reinforced 18Ni300 composites are prepared by selective laser melting method, and the tribological properties are comparatively studied before and after solution aging heat treatment. The results show that a part of WC particles are dissolved, and no obvious pore defects appear. With the increase of WC content, the microstructure gradually transforms from cellular and fine columnar α‐Fe martensite to γ‐Fe austenite. After solution aging heat treatment, the phase is transformed into acicular martensite. The grain size significantly decreases, and the Vickers hardness increases. The grain size decreases and the hardness increases with increasing WC contents. For the as‐built composite, the friction coefficient first decreases and then increases, and the wear rate first increases and then decreases with the increase of WC content. With WC content increasing, the wear rate first decreases and then increases. After heat treatment, the tribological properties are improved. The groove of the specimens before heat treatment is deep with large delaminated craters, and the wear mechanism is dominated by adhesive and abrasive wear. The grooves become shallower, and the adhesive trace becomes lighter after heat treatment. The wear mechanism is mainly adhesive wear and abrasive wear, accompanying with oxidative wear.

Influence of aging heat treatment on the microstructure and mechanical properties of Co29Cr31Cu4Mn15Ni21 high-entropy alloys strengthened by nano-precipitates

Influence of aging heat treatment on the microstructure and mechanical properties of Co29Cr31Cu4Mn15Ni21 high-entropy alloys strengthened by nano-precipitates

Thermal Cycling Behavior of Aged FeNiCoAlTiNb Cold-Rolled Shape Memory Alloys

Fe–Ni–Co–Al-based systems have attracted a lot of interest due to their large recoverable strain. In this study, the microstructure and thermal cycling behaviors of Fe41Ni28Co17Al11.5Ti1.25Nb1.25 (at.%) 98.5% cold-rolled alloys after annealing treatment at 1277 °C for 1 h, followed by aging for 48 h at 600 °C, were investigated. From the electron backscatter diffraction results, we see that the texture intensity increased from 9.4 to 16.5 mud and the average grain size increased from 300 to 400 μm as the annealing time increased from 0.5 h to 1 h. The hardness results for different aging heat treatment conditions show the maximum value was reached for samples aged at 600 °C for 48 h (peak aging condition). The orientation distribution functions (ODFs) displayed by Goss, brass, and copper were the main textural features in the FeNiCoAlTiNb cold-rolled alloy. After annealing, strong Goss and brass textures were formed. The transmission electron microscopy (TEM) results show that the precipitate size was ~10 nm. The X-ray diffraction (XRD) results show a strong peak in the (111) and (200) planes of the austenite (⁠⁠γ, FCC) structure for the annealed sample. After aging, a new peak in the (111) plane of the precipitate (⁠⁠γ′, L12) structure emerged, and the peak intensity of austenite (⁠⁠γ, FCC) decreased. The magnetization–temperature curves of the aged sample show that both the magnetization and transformation temperature increased with the increasing magnetic fields. The shape memory properties show a fully recoverable strain of up to 2% at 400 MPa stress produced in the three-point bending test. However, the experimental recoverable strain values were lower than the theoretical values, possibly due to the fact that the volume fraction of the low-angle grain boundary (LABs) was small compared to the reported values (60%), and it was insufficient to suppress the beta phases. The beta phases made the grain boundaries brittle and deteriorated the ductility. On the fracture surface of samples after the three-point bending test, the fracture spread along the grain boundary, and the cross-section microstructural results show that the faces of the grain boundary were smooth, indicating that the grain boundary was brittle with an intergranular fracture.

Effect of heat treatment on phase transformation behavior, tensile fracture mechanism and spring application characteristics of 631 stainless steel

This study focuses on enhancing the mechanical properties of 631 stainless steel through heat treatment for spring applications. 631 stainless steel (17–7PH), can achieve increased hardness and mechanical properties, offering high strength and hardness suitable for use in aerospace, chemical, and automotive industries. Heat treatment was recommended as one of the best ways in this regard; hence, the effects of temperature and time on the microstructure, mechanical, and corrosion properties of 631 stainless steel have been studied. This research conducted a series of heat treatments on 631 stainless steel, included solid-solution treatment, CH900, RH950, and TH1050 processes to modify the temperature holding period and the degree of undercooling of phase transformations. The study explored the microstructure and mechanical properties of each heat treatment, including spring tests. The results indicate that solid-solution treatment has no significant contribution to hot-rolled 631 stainless steel, whereas two-stage aging is able to conspicuously improves material hardness and mechanical performance. Quenching in 0°C ice water (increasing the degree of undercooling) can elevate hardness to approximately HRC40. After a two-stage aging heat treatment, 631 stainless steel possesses excellent strength and corrosion resistance. Spring test results show a K value of 1.1 kg/ mm, indicating its potential application.

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.

The evaluation of the aging process in 15-5 PH materials in terms of formability and microstructure

In this study, the effects of aging heat treatment of 15-5 PH stainless steel material on the mechanical properties, microstructure, and formability were investigated. Instead of cooling in air, cooling in the oven spontaneously was applied in the oven for the first time. Experimental studies show that aging heat treatment was applied for H900, H1025, and H1150 conditions at temperatures of 482 °C, 552 °C, and 621 °C, respectively, and 60 min for H900 and 240 min for H1025 and H1150. It has been observed that controlled cooling in the oven increases the mechanical values of the material obtained by cooling in the air by 8%–10%. The microstructures of the conditions after heat treatment were also examined, and it was observed that the cooling aging heat treatment in the oven caused precipitation hardening in the microstructure of the material. In addition, when evaluating the formability of the results using V-bending, it was observed that materials which could not withstand bending beyond 75° in Condition A (Con A), the initial state of the material, were smoothly shaped in all conditions and at all angles as a result of the cooling process in the oven. A decrease in spring-back angles has been detected due to the decrease in mechanical properties caused by increasing aging temperature. The highest spring-back value was also observed on a 75° bending die with 10.948° in the H900 condition which has the highest mechanical properties.

Development of a 7000 series aluminium alloy suitable for laser-based Additive Manufacturing

High strength aluminium alloys are of significant interest for laser-based Additive Manufacturing as they can provide a high specific strength but have limited assembly possibilities due to poor weldability and the presence of large intermetallic particles challenging the conventional manufacturing route. Increasing the geometrical freedom by enabling their use with laser-based Additive Manufacturing would create new possibilities. This study investigates the possibilities of using an aluminium 7000 series alloy with Laser Powder Bed Fusion (L-PBF) and secondly for comparison with Direct Energy Deposition (DED). The chemical composition targets 5.1–6.1 wt% Zn and 2.1–3.9 wt% Mg. The level of Zn and Mg in the powder was increased to 10 wt% Zn and 3 wt% Mg to compensate for the expected evaporation during the laser-based AM process and guarantee a sufficient Zn and Mg content for precipitation strengthening. Solidification cracking in the initial alloy composition was resolved by the addition of 1 wt% Zr and 1 wt% V. For L-PBF, a study of the impact of the laser spot size showed a larger spot size is beneficial to improve the process stability. A study of the capability of preheating and of slowing down the process showed both further improve the process stability as well which is required to manufacture successfully larger parts to characterise the quasi-static tensile properties. For optimal process parameters for a fast process, meaning a scan speed of 700 mm/s, a yield stress of 425 ± 7 MPa and an ultimate tensile strength of 442 ± 5 MPa was obtained after a homogenisation and ageing heat treatment. In the as built state, the strength was significantly lower. For optimal process parameters for a slow process, meaning a scan speed of 250 mm/s, a yield stress of 398 ± 11 MPa and an ultimate tensile strength of 440 ± 16 MPa were obtained in as built state. For DED the mechanical properties of the alloy showed to be significantly dependent on process parameters. An excessive energy input results in more Zn and Mg evaporation and decreased cooling rates. Such parameters also impact the process stability of DED throughout the build cycle. Limiting the energy input resulted in dense samples and stable build cycles which after a heat treatment to peak ageing reached a yield stress of around 400 MPa and an ultimate tensile stress of around 440 MPa in the X- and Z-direction.

Influence of aging heat treatment on microstructure and mechanical properties of a novel polycrystalline Ni3Al-based intermetallic alloy

A novel polycrystalline Ni3Al-based intermetallic alloy was prepared using the vacuum induction melting process. Subsequently, the alloy was subjected to the solution-treatment underwent two different aging processes: 870 °C for 24 h in air cooling, referred to as AT 1, and 1060 °C for 4 h in air cooling followed by 870 °C for 24 h in air cooling, referred to as AT 2. The effects of different aging processes on the microstructure and mechanical properties of the polycrystalline Ni3Al-based intermetallic alloys were analyzed. Results indicated the cubicity of the primary γ′ phase within the dendritic γ+γ′ structure of the AT 2 sample was significantly enhanced, yielding the best overall mechanical properties for the alloy. The percentage elongation increased from less than 3 % for the AT 1 sample to about 4.5 %, highlighting a notable enhancement in room temperature tensile plasticity. The creep rupture time at 1100 °C/30 MPa reached 113 h. The α-Cr particles in the As-cast and solid solution alloy gradually transformed into Cr23C6 during the aging process, exhibiting the orientation relationships of (020)Cr23C6||(010)γ' and [103]Cr23C6||[103]γ'. High-temperature aging treatments resulted in Cr23C6 particles that provided enhanced precipitation strengthening effects, thereby improving the creep rupture performance of the Ni3Al-based intermetallic alloys. Following high-temperature aging, a four-layer interface structure formed around the blocky γ′ matrix phase, which altered the alloy's fracture mechanism from a brittle intergranular fracture to a ductile transgranular fracture.

Superior strain-hardening and strength-ductility synergy by hierarchical L12 phases in a highly (Al, Ti)-added medium-entropy alloy

A novel precipitate-strengthened Co–Cr–Ni medium-entropy alloy with a pure “FCC + L12” dual-phase structure is developed by adding a high concentration (6 at.%) of Al and Ti elements. After aging heat treatment at 700 °C for 4 h, the hierarchical L12 phases, composed of primary large-sized L12 phases (∼70 nm) and secondary L12 particles (∼14 nm), are achieved. The designed alloy featuring hierarchical L12 phases exhibits excellent strength-ductility combinations and strain-hardening ability, properties that are much improved over their counterparts with homogeneous dispersed L12 phases (∼13 nm) and without L12 phases. Especially, the yield strength (1320 MPa), ultimate tensile strength (1886 MPa), and average strain-hardening rate (5.15 GPa) are obtained in the alloy with hierarchical L12 precipitates deformed at cryogenic temperature. The Orowan bypass mechanism of the primary L12 phases, along with the shearing mechanism of the secondary L12 phases, collectively contributes to the exceptional strength of the alloy with hierarchical L12 precipitates. The penetration of dislocations and stacking faults (SFs) in the primary L12 phases, combined with hetero-deformation-induced (HDI) hardening attributed to these hierarchical L12 precipitates, may be a key factor in improving strain-hardening properties of the alloy.

Effect of aging temperature on the redrawn cup wall of a novel Cu-0.5Cr-0.05Zr-0.05Ti (wt.%) alloy sheet: Analyses on microstructure evolution, mechanical properties and strengthening mechanism

A solution-treated Cu-0.5Cr-0.05Zr-0.05Ti (wt.%) alloy was drawn into a large-depth cup implementing a two-stage deformation process in the present study, firstly using a ∅50 mm cylindrical punch and subsequently redrawn by a ∅34 mm punch. The redrawn cup wall was subjected to aging heat treatment up to 400 °C, 500 °C, and 600 °C for 2 h followed by water quenching to understand the microstructural evolution and its correlation with mechanical properties. These aging temperatures were adopted to simulate a similar environmental condition in which the inner liner of the thrust chamber of cryogenic and semi-cryogenic engines was exposed during satellite launching. It was identified that the above aging temperatures influenced the grain characteristics, recrystallization, and annealing twin formation significantly. The redrawn cup wall possessed semi-coherent bcc spherical Cr-rich precipitates with an average size of 1.8 ± 0.1 nm, which progressively increased to 5.5 ± 0.3 nm at 600 °C, while the precipitate volume fraction increased to a maximum of 1.2% at 500 °C. The precipitation mostly influenced the strength, while the recrystallization and twin formation governed the ductility during the aging. After an initial decrement at 400 °C, the yield strength of the aged specimen was increased to a maximum of 193 MPa with a concurrent increase in ductility to 24% upon the optimal aging at 500 °C. However, a higher increment in the strength than the ductility indicated the dominance of the precipitation. Further increase in the temperature to 600 °C reduced the strength while considerably enhancing the ductility. This was attributed to the highest recrystallization and twin fraction, as well as precipitate coarsening with reduced volume fraction. Moreover, precipitation strengthening prevailed in the aged specimens, unlike dislocation strengthening in the redrawn condition. The contribution from the former was maximum at 500 °C with a 52% share of the total estimated strength, whereas it was only 31% in the redrawn specimen.

Simulation of Quench Rate by Jominy End Quench Test for 6082 Aluminium Alloys

In the present study, it is aimed to investigate the influence of quench rate on the hardness and electrical conductivity that obtained after artificial aging by using Jominy End Quench test method. The Jominy End Quench test bars were solution heat treated at 560°C for 3 hours. After solution heat treatment, water, spray, and air quenching medias were used in order to obtain different quench rates. After the quench, quench rate determination, hardness and electrical conductivity measurements were performed for three different quenching medias. Then, artificial aging heat treatment were applied to all samples at 180°C for 8 hours to understand the effect of quench rate on aging process. The relationship between quench rate, hardness and electrical conductivity have presented.

The Effect of Heat Treatment on the Plasma Nitriding of Hot-rolled 17–7 PH Stainless Steel

17–7 PH stainless steel is a highly versatile material with a multitude of applications in a diverse range of fields, including aerospace, chemistry and petrochemistry, and medicine. The material’s exceptional mechanical properties and corrosion resistance render it the optimal selection for numerous components and instruments. Nevertheless, the surface properties of 17–7 PH stainless steel are inadequate for applications requiring high hardness and wear resistance in certain extreme environments. Due to its excellent mechanical properties and corrosion resistance, it can be utilized in the manufacturing of pharmaceutical equipment components. However, certain specialized environments still require surface nitriding treatment. Considering the complex heat treatment process required for this material, this paper reports a detailed study of the surface performance changes of 17–7 PH steel before and after ion nitriding following aging heat treatment. The study employs rolled 17–7 PH stainless steel as the subject material. The impact of heat treatment on plasma nitriding of stainless steel is investigated by comparing and analyzing the influence of martensite content and dislocation density within the martensite of the material prior to and following heat treatment on the hardness, thickness, and corrosion resistance of the nitrided layer on the surface of the steel after nitriding. The results demonstrate that 17–7 PH stainless steel, which does not undergo heat treatment, exhibits a high internal dislocation density, a high nitriding efficiency, and consequently, a high surface hardness. Following the application of a heat treatment, there is an increase in the martensite content of 17–7 PH stainless steel, a decrease in the dislocation content, and an increase in the matrix hardness.

Research on the microstructure and mechanical properties of functional gradient materials of TC4/TC11 titanium alloys for wire arc additive manufacturing with different transitional forms

Functional gradient materials (FGMs) have garnered increasing interest for their potential in material and structural design. Additive manufacturing, as a kind of free manufacturing and near-net shaping technology with in-situ controllability of materials, is the dominant technology for fabricating FGMs. While numerous studies have been conducted on titanium alloy FGMs, there is still a lack of research on the structure and properties of the material with the number of transitional layers. This study employs double-wire arc additive manufacturing to fabricate FGMs composed of TC4 and TC11 alloys. The study examines the utilization of direct and continuous transition forms in conjunction with stress relieving and solution aging heat treatment processes. The composition, grain morphology, microstructure, and mechanical properties of FGMs are analyzed. Results indicate that in samples employing direct transition, higher heat treatment temperatures and durations lead to a more uniform composition and microstructure. Additionally, the interface morphology becomes increasingly indistinct, and transversal elongation at the interface is enhanced by the strain compensation of the two materials. In continuous transitional samples, an increase in the number of transitional layers results in a more uniform microstructure near the interface, leading to a reduction in interface morphology and an enhancement of mechanical properties. The fracture position tends to shift closer to the TC4 side, with both process forms exhibiting ductile fractures. The plasticity of the TC4 part is superior, and the ductile fracture morphology is more pronounced. This study offers a valuable experimental foundation for investigating the direct and continuous transition of titanium alloy FGMs.

Influence of post heat treatment on tribological and microstructural properties of plasma wire arc additive manufactured maraging steels

Abstract Metallic alloys are increasingly being produced using wired arc additive manufacturing (WAAM). In this study, 18Ni300 defect-free maraging steels were produced using the WAAM technique. A traditional solution treatment, direct aging, and cryogenic heat treatment processes were applied to the WAAM produced maraging steels. The influence of conventional and novel cryogenic heat treatments on microstructural, mechanical, and tribological properties were examined. The microstructure of the as-built materials obtained by WAAM thermal cycling has mainly been homogenized through the solution, direct-aging, and cryogenic heat treatments. As a result, homogeneously distributed precipitate phases were obtained and the hardness increased by 30 % with a combination different post heat treatments. The cryogenic heat treatment improved the martensitic transformation and facilitated the formation of various Fe–Ni–Mo–Ti-containing intermetallic precipitates. Similarly, because of the different heat treatments, the wear resistance improved by a factor of 2–5.5 relative to the as-built material. Adding the cryogenic heat treatment to the traditional heat treatment procedure improves wear resistance by a factor of 1.2–2.9.

Mechanical and metallurgical properties of a glass fiber-reinforced Al7075 hybrid composite produced by infiltration and after aging and abrasion

Abstract Within the scope of this study, composite structures were produced by reinforcing Al7075 with 6 mm size glass fiber (GF) scrap at different weight rates (2–3 %) using the infiltration method. Mechanical and metallurgical examination of unreinforced Al7075 samples and reinforced Al7075 composite samples were carried out. After the aging heat treatment of the samples, pin-on-disc wear and hardness tests were performed. FESEM and EDS analyses were conducted to examine the hardness and microstructural changes caused by the applied processes on the samples. It was observed that GF reinforcement increased the hardness of the material and there was full wettability between Al 7075 and GF. Thus, wear resistance increased. The highest hardness and wear resistance were obtained in the 6 h aged 2 wt.% GF-reinforced Al 7075 matrix hybrid composite sample. In addition, it was observed that the distribution of GF scrap added as reinforcement at a rate of 2 wt.% in Al 7075 was homogeneous, and the hardness measurements taken from different areas were similar.

Corrosion of aluminium alloy AA2024-Τ3 specimens subjected to different artificial ageing heat treatments

The effect of artificial-ageing on corrosion behaviour of aluminium alloy (AA)2024-T3 was investigated. The natural ageing which takes place during the aircraft's lifespan was simulated with isothermal heat-treatments at 190 °C. Electrochemical impedance spectroscopy measurements were performed in different heat-treated specimens to examine the prevailing corrosion mechanisms. Additionally, pre-corroded tensile specimens from different heat-treatment conditions were mechanically tested to assess the corrosion-induced degradation. Different forms of corrosion were revealed in the investigated ageing tempers; intense localized attack was noticed in the initial (T3) and under-aged (UA) tempers. UA condition exhibited the highest susceptibility to corrosion propagation followed by T3, according to the charge transfer resistance RCT and degradation rate of tensile elongation at fracture Af ( ≈ 0.118) and ( ≈ 0.103), respectively. Corrosion-induced degradation rates for the peak-aged (PA) and over-aged (OA) tempers ( ≈ 0.042 and 0.054, respectively) were almost one third of UA, attributed to volume fraction and size of the precipitated second-phase particles.

Microstructure Control for Enhancing the Combination of Strength and Elongation in Ti-6Al-4V through Heat Treatment

For the application of Ti-6Al-4V alloys in urban air mobility, safety is very important, so achieving excellent strength and toughness is essential to prevent fractures. Regarding toughness, which is a combination of strength and ductility, it is necessary to derive the optimal heat treatment conditions for this combination of Ti-6Al-4V alloy and further understand its microstructure and fracture characteristics. For this purpose, this study investigated the microstructure in terms of grain size, plate thickness, and element distribution, as well as mechanical properties, including phase hardness and tensile properties, of Ti-6Al-4V alloy subjected to solution treatment and aging (STA) heat treatment under various aging conditions. As a result, this study suggests that solution treatment followed by aging at 630 °C for 480 min can achieve approximately 26% higher toughness than the just-solution treatment process. This is because there is little difference in hardness between the equiaxed α and basketweave structures, and β plates, which contain an excessive V between α plates, function like fibers and delay fracture.

The Effect of Aging Heat Treatments on Room and High-Temperature Wear Performance of the Inconel 718™ Manufactured by Laser Powder Bed Fusion

The Effect of Aging Heat Treatments on Room and High-Temperature Wear Performance of the Inconel 718™ Manufactured by Laser Powder Bed Fusion

Effect of Solution and Aging Heat Treatment on the Microstructure and Mechanical Properties of Inconel 625 Deposited Metal

Inconel 625 deposited metal was prepared by gas metal arc welding. The solid solution treatment temperature was set at 1140 °C for 4 h using the DSC test method, followed by secondary aging at 750 °C/4 h and 650 °C/24 h. The specimens in the prepared state and after heat treatment were subjected to high temperature tensile at 600 °C, respectively. The fracture morphology, thermal deformation behavior, and strengthening mechanism of the samples in different states were analyzed. The results showed that the stress–strain curves of the deposited metals exhibited obvious work-hardening behavior at 600 °C. The solid solution and aging heat-treated samples have higher tensile and yield strength, but the plasticity is obviously lower than that of the deposited metal. It was also found that the γ″ phase and M23C6 carbides, as well as the continuous stacking faults in the alloy, were the main reasons for the increase in tensile strength of the solution and aging heat-treated sample.

Effect of Direct Aging Heat Treatment on Microstructure and Mechanical Properties of Laser Powder Bed Fused Maraging Steel 300-Grade Alloy

Abstract This paper investigates the effects of a 6-hour direct aging heat treatment at 490 °C on the mechanical, tribological, and microstructure characteristics of laser powder bed fused maraging 300 steels, which is produced at various laser energy densities. After direct aging heat treatment, the grain boundaries become irregular and vague due to the residual stress releasing, squeezing of precipitates into the grain boundaries, and phase transformations. The XRD analysis reveals the reverted austenite (γ′) phase forms during aging treatment due to the inevitable reversion of metastable martensite to the stable reverted γ′ phase. The heat-treated samples' microhardness rises with rising the laser energy density (LED) from 61.41 to 92.10 J/mm3 due to a decrease in the reversed austenite phase and a further rise in LED decreases the microhardness of heat-treated samples due to a rise in the reversed austenite phase after heat treatment. The heat-treated sample produced at LED of 92.10 J/mm3 shows maximum yield, ultimate tensile strengths, and minimum elongation percentage due to its high microhardness, and the fractography results show the failure mode as a mixed brittle and ductile fracture. The wear-rate of the heat-treated additively manufactured maraging 300 steel decreases as the LED increases from 61.41 to 92.1 J/mm3 and a further rise in LED from 92.10 J/mm3 to 166.66 J/mm3, the wear-rate increases. The wear-rate rises with a rise in sliding velocity from 1.5–3.5 m/s. The dominant wear mechanism was observed as abrasion with small grooves and saplings.