Increase In Solution Treatment Temperature Research Articles

Study on the role of solution treatment on corrosion behavior of duplex lightweight steel in different environments

Diverse microstructure and complex application environments increases the uncertainty of the corrosion resistance of lightweight steels. The effect of solution treatment on the corrosion behavior of Fe–16Mn–10Al–1.5C–0.1Ti lightweight steel in Cl−, HSO3− and Cl−–HSO3− environments was investigated using electrochemical measurement, scanning electron microscope (SEM) and X–ray photoelectron spectroscopy (XPS). The lightweight steels are dominated by austenite and contain a small amount of ferrite. The increase in solution treatment temperature leads to more ferrite formation, but it has less effect on grain size. The decrease in austenite content results in more corrosion microcells and a porous oxide film; therefore, the corrosion resistance of the steel deteriorates with increasing temperature. In addition, in the Cl−–HSO3− environment, the synergistic effect of Cl− and HSO3− leads to the formation of a weak protective oxide film, resulting in a significant increase in corrosion rate compared to the Cl−and HSO3− environment.

Effects of solution treatment on microstructure and mechanical properties of (SiC+TiB2)/Al–Zn–Mg–Cu composite fabricated by laser powder bed fusion

This study investigated the effects of solution treatment (ST) on the microstructure and mechanical properties of (SiC+TiB2)/Al–Zn–Mg–Cu composite produced using laser powder bed fusion (LPBF). Microstructural analysis reveals that the grid-like distribution of eutectic precipitates within the as-printed composite disappeared, giving way to the formation of uniformly distributed precipitates. As the ST temperature increased, the content of spherical Si particles decreased, while the content of elongated Al4SiC4 precipitates increased. Matrix grains recrystallization occurred, resulting in a gradual increase in the average grain size from 3.79 μm to 5.23 μm. The preferred crystallographic orientation features along the printing direction, <001> {001} plate texture, were weakened, gradually exhibiting a more disordered growth. The microhardness and tensile strength of the composites exhibited a slight decrease and exhibited a trend of initially increasing and then decreasing with increasing ST temperature. Additionally, the heterogeneity in microhardness along different directions has been reduced. When the ST temperature was 460 °C, the elongation of the composite experienced a significant increase, escalating from 6.12 ± 0.36% to 10.3 ± 0.25%. However, with the increase in ST temperature, it displayed an obvious downward trend. The maximum tensile strength was 449 ± 8 MPa, and the elongation was 9.6 ± 0.4% with the ST temperature of 500 °C. The variations in mechanical properties were primarily attributed to the elimination of grid-like substructure, the uniform distribution of precipitates, and the gradual coarsening of grains. This research was expected to contribute to developing advanced lightweight materials with improved performance, opening up new opportunities for their application in various industries.

Effect of solution treatments on microstructure and mechanical properties of Ti–6Al–4V alloy hot rolled sheet

The solution and aging treatment were carried out with the hot rolled sheet Ti–6Al–4V alloy sheet, and the effects of solution treatments on the microstructure and mechanical properties were mainly studied. In the solution treatment process, α→β→βt transformation occurred. With the increase of solution treatment temperature and time, the α phase gradually changed from long strip to equiaxed morphology, and the fraction of equiaxed α and β phases gradually increased. The bimodal microstructure of αp and βt was obtained during the solution treatments. Among them, βt is mainly composed of high-density nano-needle αs with different orientations, which has a significant contribution to the strength of Ti–6Al–4V alloy. The strength of bimodal microstructure increases with the increase of βt content, but its influence on ductility is complicated. When βt content exceeds a certain amount, it is easy to lead to brittleness. It is found that when the specimens are treated at 930 °C for 60min or 960 °C for 30min, the best strength-ductility matching can be obtained. In this case, the volume fractions of αp and βt are almost equal, and the PSE of Ti–6Al–4V alloy reaches more than 14500 MPa⋅%.

Reducing directionally arranged substructure induced anisotropic mechanical properties of Hastelloy X superalloy fabricated by laser directed energy deposition

In this study, the effects of solution treatment (ST) on the microstructure and anisotropic mechanical properties of Hastelloy X fabricated by laser directed energy deposition (L-DED) were investigated. The microstructure of the as-deposited (AD) sample presented coarse granular grains aligned with the deposition direction. Due to the segregation of Mo and Cr elements, a special cellular-structure was formed in the inter-dendritic region, along with the strip-like carbides consisting of both M23C6 and M6C carbides. The cellular-structure homogenized rapidly after the ST. In detail, as the ST temperature increased, recrystallization generally occurred. Meanwhile, the strip carbides began to gradually dissolve and dissociate into dispersed particles which led to a drop in microhardness from 220 HV to 161 HV. The room temperature tensile results showed that the yield strength in the transversal direction (TD) and longitudinal direction (LD) decreased with the increase of ST temperature, reaching a minimum value of 285 MPa after the ST at 1175 °C. In addition, the ultimate tensile strength of the LD and TD samples reached maximum values of 693 MPa and 703 MPa at 1150 °C, respectively. It should be noted that the elongation of the low ductile TD sample can be improved significantly from 30% to 75% after the ST at 1175 °C. Therefore, it can be concluded that the anisotropy within the TD and LD samples can be effectively eliminated by controlling the cellular-structure, grain-structure, and carbide morphology during ST.

Effect of Solution Treatment Temperature on Microstructures and Mechanical Properties of (35.5-x)Ti-49.5Ni-15Hf-xNb (x = 3, 10) (at. %) High Temperature Shape Memory Alloys

In this study, the effects of solution treatment temperature on the microstructures and mechanical properties of (35.5-x)Ti-49.5Ni-15Hf-xNb (x = 3, 10) (at.%) high-temperature shape memory alloys were studied by means of scanning electron microscopy, differential scanning calorimetry, and tensile tests. The microstructures of the solution treated with a 1123 K Ti-49.5Ni-15Hf-3Nb alloy consisted of (Ti, Hf, Nb)2Ni and Nb-rich phases and a B19′ martensite matrix. The solution treated at 1123 K Ti-49.5Ni-15Hf-10Nb alloy consisted of the B19′ martensite matrix and Nb-rich, Hf-rich, and Ni-rich phases. The Ni-rich phases were eliminated by increasing the solution treatment temperature. When the solution treatment temperature was increased from 1123 K to 1273 K, the fracture strain increased from 8.4% to 10.4% and from 11.2% to 22.1% for the Ti-49.5Ni-15Hf-3Nb and Ti-49.5Ni-15Hf-10Nb alloys, respectively, which was ascribed to the elimination of the Ni-rich phase. Ms (B2-B19′ transformation start temperature) also increased from 421.3 K to 439.7 K and from 192.6 K to 299.2 K for the 3Nb and 10Nb alloys, respectively. Superelastic recovery ratios of 62.7% and 78.7% were observed in the 3Nb and 10Nb alloy solutions treated at 1123 K, respectively. The superelastic recovery ratio increased with an increase in solution treatment temperature from 1123 K to 1273 K for both the 3Nb and 10Nb alloys.

Effect of Solid Solution Treatment on Corrosion Resistance of Al-Cu-Mg-Ag Alloy

In this experiment, Al-Cu-Mg-Ag alloy was used as material and solution temperature was used as variable to investigate its effect on the corrosion properties of the alloy and Hardness test, metallographic observation, electrochemical test, intergranular corrosion and exfoliation corrosion test were carried out on three groups of samples. The results show that the intergranular corrosion resistance of the alloy decreases with the increase of solution treatment temperature, and the sample treated at 505 °C has the best performance. This is mainly because grain boundary structure plays a role in increasing PFZ and expanding corrosion channels. The exfoliation corrosion resistance of Al-Cu-Mg-Ag alloy increases first and then decreases, and the sample treated at 515 °C has the best performance. This is due to the dual effects of grain boundary structure and grain morphology. On the one hand, the solution treatment temperature increases, which widens the precipitation-free zone and reduces the electrochemical corrosion resistance of the alloy. On the other hand, the increase of recrystallized grains decreases the cohesion of corrosion products and enhances the electrochemical corrosion resistance of the alloy.

Effects of solution treatment on microstructure and tensile properties of as-cast alloy 625

Effects of solution treatment between 1050 and 1250 °C on microstructure and tensile properties of as-cast alloy 625 were investigated. The microstructure and solidification characteristics of the alloy were studied by SEM, EDS, EPMA and DTA. The results showed that the solidification sequence of the alloy should be written as L → L + γ → L + γ +MC→ L + γ +MC+ γ /Laves→ γ +MC+ γ /Laves. After solution treatment at 1225 and 1250 °C, incipient melting of Laves phase was observed. The ultimate tensile strength decreased monotonically with the increase of solution treatment temperature, and the yield strength had no significant variation. The elongation increased slightly at first and then reached a minimum value at 1250 °C. The fracture mechanism changed from transgranular mode to intergranular mode after solution at 1250 °C for the reason that numerous Laves phases melted at grain boundaries and microcracks nucleated in the molten pool. The suitable solution treatment temperature of this alloy was 1200 °C.

Microstructural evolution of a Y2O3 network reinforced Ni–Co based superalloy fabricated by spark plasma sintering

A Y2O3 network reinforced Ni–Co based superalloy was prepared by ball milling and spark plasma sintering (SPS). Ball milling time and solution treatment temperature were studied to obtain the best microstructure. Optical microscope (OM), scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA) were used to observe the microstructure evolution of as-sintered and solution-treated samples. Hardness also was conducted to analysis the variations of properties with the increase of solution-treatment temperature. The results revealed that the ball milling was beneficial to sintering activity of Ni–Co based superalloy powders. The Y-containing oxides in as-sintered alloys exhibited a network distribution. Master alloy with low C content made the microstructure more uniform during the sintering. After solution treatment at 1250 °C, the precipitations in the Y2O3 network reinforced Ni–Co based superalloy with low C content were fine nano tertiary γ′ phase with the size of ~30 nm. In the Vickers hardness test, Y-containing oxides provided additional hardness for the alloy. The appropriate solution treatment temperature and master alloy with low C content were beneficial to obtain better microstructure and properties of the alloy.

Study on microstructure and properties of high frequency induction cladding TiC/Ni coating after solution treatment

To improve the performance of the 35CrMo sucker rod during operation, the microstructure, microhardness and wear properties of the TiC/Ni-based composite coating prepared by induction high frequency cladding at different solution treatment temperatures were investigated. The results show that the coating consists mainly of γ-Ni, Ni3Fe, Cr23C6, CrB, TiC, SiB6, NiCr2O4 and Fe2O3 phases after solution treatment. The average microhardness of the coating increased from 835.7 HV0.2 before the heat treatment to a maximum of 890.3 HV0.2, an increase of 6.5%. The wear resistance of the coating increases first and then decreases with the increase of solution treatment temperature. When the solution temperature is 950 °C, the wear resistance is best. The wear mechanism of the coating and friction pair is mainly adhesive wear and abrasive wear, and accompanied by brittle fracture.

Effect of Solid Solution Temperature on Microstructure and Corrosion Resistance of CoNiCrMo Alloy

Influence of solid solution temperature on microstructures and corrosion properties of CoNiCrMo alloy were investigated by means of optical microscopy (OM), scanning electron microscope (SEM) and electronic differential system. The corrosion resistance of CoNiCrMo alloy in 0.9%NaCl aqueous solution was also investigated. The results indicated that with the increase of solution treatment temperature, the dendrites of CoNiCrMo alloy gradually disappeared. Thus, the corrosion resistance of the alloy decreased. When the solution temperature is 1200oC, the dendrites almost disappeared and most carbide dissolved, and begins to spheroidization. The corrosion resistance of CoNiCrMo alloy treated at 1000oC for 1h is the highest than the one at 1100 oC and 1200oC. Its self-corrosion potential is -424mV and self-corrosion current density is 1.02×10-8A/cm2.

Effect of Heat Treatment on Microstructure and Stress Rupture Properties of a Ni–Mo–Cr–Fe Base Corrosion-Resistant Superalloy

The influences of heat treatment and test condition on the microstructure and stress rupture properties of a Ni–Mo–Cr–Fe base corrosion-resistant superalloy have been investigated in this paper. Optical microscope and scanning electron microscope were employed for the microstructure observation, and X-ray diffraction, electron probe micro-analyzer, and transmission electron microscope were used for phase determination. It was found that the grain size increased and the volume fractions of initial M6C carbides decreased along with the increase in solution treatment temperature. When tested at 650 °C/320 MPa, the stress rupture lives decreased with the increase in solution treatment temperature, but the stress rupture lives increased slightly at first and then decreased for the samples solution heat treated at 1220 °C when tested at 700 °C/240 MPa. The elongations showed the descendent trends under these two conditions. The stress rupture life and elongation for the aged samples all showed a noticeable improvement at 650 °C/320 MPa, but there was no noticeable improvement at 700 °C/240 MPa. The reasons can be attributed to the grain size, test conditions, and the initial and secondary carbides.

Effect of Solution Treatment Temperature on the Grain Growth Behavior of Fine Grained FGH96 Superalloy

The effect of solution treatment temperature on the grain growth behavior of fine grained nickel-base superalloy FGH96 has been investigated. The results showed that with the increase of solution treatment temperature, the grain growth of fine grained FGH96 alloy (&lt;5μm) experienced 3 stages, the slow growth stage below 1120°C, the steady grain size stage from 1120°Cto 1250°C, which revealed the fine grained FGH96 alloy with wide solution treatment window compared to coarse grain, and the exponential growth stage. At the same time, the primary γ′ and MC carbides on impeding grain boundary migration to limit grain growth was demonstrated. The grain growth model has been established, and the activation energy of grain growth was calculated to be 288 KJ/mol through linear fitting.

Effect of Cooling Medium on Solution Treatment Response of Titanium Alloy Ti-5Al-5V-2Mo

Titanium alloys are widely used in aerospace industry in the areas of pressure vessels, airframe structures, landing gears, aeroengine compressor blades etc. The principal qualities of titanium alloys required for these applications are high specific strength, low density and high specific modulus. Among the families of Ti alloys, high strength titanium alloys come under martensitic α + β and metastable β alloys. Titanium alloy Ti-5Al-5V-2Mo (BT-23) is an important example of martensitic α + β alloy similar to the work horse Ti6Al4V alloy which exhibits good combination of strength and ductility in solution treated and aged conditions. But due to quenching from solution treatment temperature, the alloy tends to retain good amount of residual stresses. The severity of residual stress increases with increase in solution treatment temperature as well as severity of quench. An attempt has been made to study the effect of air cooling subsequent to solution treatment to compare the strength of the alloy vis-à-vis that achievable during water quenching. An attempt has also been made to correlate the microstructure evolution, hardness with variation in solution treatment temperature and quench severity in titanium alloy Ti-5Al-2Mo-5V. Samples subjected to air cooling subsequent to solution treatment exhibited higher microhardness when compared to water quenched samples. It is proposed that dynamic aging and/ or stress relieving occurs during air cooling from solution treatment temperature down to room temperature. Also the fine α precipitates formed during air cooling may be resulting in higher hardness compared to the α’’/α’ formed during water quenching. The same has been supported by thermal analysis of air cooling and water quenching processes employed subsequent to solution treatment.

Influence of thermo-mechanical treatment on the tensile properties of a modified 14Cr–15Ni stainless steel

The titanium modified 14Cr–15Ni austenitic stainless steel is used as clad and wrapper material for fast breeder nuclear reactor. Thermo-mechanical treatments consisting of solution annealing at two different temperatures of 1273 and 1373K followed by cold-work and thermal ageing have been imparted to the steel to tailor its microstructure for enhancing strength. Tensile tests have been carried out on the thermo-mechanically treated steel at nominal strain rate of 1.6×10−4s−1 over a temperature range of 298–1073K. The yield stress and the ultimate tensile strength of the steel increased with increase in solution treatment temperature and this has been attributed to the fine and higher density of Ti(C,N) precipitate. Tensile flow behaviour of the steel has been analysed using Ludwigson and Voce constitutive equations. The steel heat treated at higher solution temperature exhibited earlier onset of cross slip during tensile deformation. The rate of recovery at higher test temperatures was also influenced by variations in solution heat treatment temperature. In addition, dynamic recrystallization during tensile deformation at higher temperatures was profound for steel solution heat-treated at lower temperature. The differences in flow behaviour and softening mechanisms during tensile testing of the steel after different heat treated conditions have been attributed to the nature of Ti(C,N) precipitation.

English

Aging treatment was conducted on Fe-Ni-Cr superalloy to observe its effect on the microstructures and hardness of the material. Solution treatments were carried out at 900oC, 975oC, 1050oC, and 1125oC followed by water quenching. The samples were further treated with a double aging treatment at 720oC and 650oC for 4 hours and 12 hours respectively. Materials characterization techniques such as SEM, XRD, and optical microscopy were used to analyze the heat-treated samples. The Fe-Ni-Cr superalloy formed mainly a dendritic austenitic structure with Cr23C6 precipitated along the grain boundaries. Increase in solution treatment temperature results in dissolution of chromium carbide, coarser grain, and lower hardness for non-aged samples. Double aging treatment produced more chromium carbide, higher hardness, but no apparent change in grain size. Neither quenching nor aging treatments caused any phase transformation. The highest hardness value of 220.4 Hv was recorded for the sample solution treated at 1125oC for 2 hours and water quenched, followed by 2-step aging at temperature 720oC and 650oC for 4 hours and 12 hours respectively, and air cooled.

Formation of L10-type ordered β′ phase in as-solutionized dental Ag–Pd–Au–Cu alloys and hardening behavior

The relationship between the microstrucutural changes of L10-type ordered β′ phase and hardening behavior in as-solutionized dental Ag–Pd–Au–Cu alloys was investigated by changing the cooling rate and the solution treatment temperature. Additionally, the formation process of the β′ phase in as-solutionized Ag–Pd–Au–Cu alloy was attempted to clarify. The microstructural changes were observed by X-ray diffraction (XRD) method and transmission electron microscopy (TEM). The hardness was evaluated using a Vickers microhardness tester. The β′ phase is precipitated regardless of the cooling rate, after solution treatment at 1123K. TEM dark field images show that the size of the β′ phase decreases and the number of β′ phase increases with an increase in the cooling rate. The Vickers hardness value increases with an increase in cooling rate. TEM dark field images show that the microstructure of β′ phase is similar when the solution treatment temperature increases from 1123K to 1173K. However, the Vickers hardness increases with an increase of solution treatment temperature. It is of great significance to reveal that the β′ phase precipitated in as-solutionized Ag–Pd–Au–Cu alloy is formed during cooling after high-temperature solution treatment and that the growth of the β′ phase is diffusion controlled.

Fabrication of Ti-Ni-Zr Shape Memory Alloy by P/M Process

This work focuses on the fabrication of Ti-Ni-Zr high-temperature shape memory alloy by powder metallurgy (P/M) process. The effects of fabrication conditions on the microstructure and shape memory characteristics of Ti-50.2 mol%Ni-5 mol%Zr alloy were investigated. In this research, elemental Ti, Ni and Zr powders were used. These powders were mixed by a planetary ball mill at a rotational speed of 500 rpm for milling times of 0.6 ks (mixed powder) and 720 ks (MAed powder). The mixtures were sintered by a pulse-current pressure sintering equipment at 1153 K for sintering times of 1.8 ks and 1.2 ks. The solution treatment was carried out at various temperatures between 1073 K and 1273 K to homogenize the microstructure of the as-sintered alloy. The microstructure of the alloy became more homogeneous with an increase in solution-treatment temperature. In the case of the mixed powder, however, Zr-rich phases were observed in the microstructure of the solution-treated alloy. The alloy solution-treated at 1173 K showed a yielding behavior in the stress-strain curve, and the tensile strength and elongation of the alloy were more than 350 MPa and 2.5%, respectively. On the other hand, in the case of the MAed powder, the microstructure of the as-sintered alloy was homogeneous. The P/M alloy showed higher transformation temperatures than those of the wrought alloy. But, the alloy showed no shape memory effect and poor tensile property due to contamination of the MAed powder.

Experimental study on the characteristic of grain-boundary segregation of phosphorus in Ni-base superalloy

In virtue of Auger electron spectroscopy, the levels of grain-boundary segregation of phosphorus in Ni-based superalloy after solution-treated at 1200 °C for 9.8 h and at 1020 °C for 68.5 h and then aged at 720 °C all for 2 h are measured. It is found that the levels increase with the increase in solution treatment temperature. The measurement result is analysed with the laws of equilibrium segregation and non-equilibrium segregation. Based on the analysis, the characteristic of non-equilibrium grain-boundary segregation of phosphorus in the superalloy is confirmed for the first time.

Effect of solution treatment temperature on microstructure and mechanical properties of hot isostatically pressed superalloy Inconel* 718

Hot isostatically pressed superalloy Inconel 718 heat treated as per the standard schedule of aerospace material specification (AMS) 5662 (solution treatment at 980°C/1 h/water quenching followed by two step aging at 720°C/8 h/ furnace cooling to 620°C/8 h/air cooling to room temperature) has shown yield strength (YS) and ultimate tensile strength (UTS) comparable to that of wrought heat treated alloy, but it had poor ductility and inferior stress rupture properties. To find an appropriate heat treatment to improve these properties, the influence of solution treatment temperature on the structure and properties of the alloy has been studied. The results show that although YS and UTS decrease with increasing solution treatment temperature, considerable improvement occurs in the ductility of the unaged alloy. For the aged alloy, an increase in solution treatment temperature resulted in only a marginal improvement in strength, but the 650°C ductility and stress rupture life were improved significantly. This has been attributed to the dissolution of MC carbides and disruption of prior particle boundaries (PPBs) at higher solution treatment temperatures that had led to enhanced bonding between the particles. Fractography studies revealed a transgranular ductile mode of fracture for the unaged condition for all solution treatment temperatures. In contrast, aged alloys subjected to lower solution treatment temperatures have shown decohesion of particle boundaries leading to an intergranular mode of fracture, while alloys solution treated at temperatures greater than 1250°C revealed a transgranular ductile mode of fracture suggestive of improved ductility. The improvement of high temperature properties obtained by higher solution treatment temperature makes it possible to explore the near net shape capability of HIP technology to its maximum potential, when adopted for producing alloy 718 components.

Effects of solution treatment temperature on grain growth and mechanical properties of high strength 18%Ni cobalt free maraging steel

The effects of solution treatment (ST) temperature (1073–1473 K) on the prior austenite grain size, microstructure, and mechanical properties of a 2000 MPa grade 18%Ni Co free maraging steel have been investigated. The results show that prior austenite grain size normally increases with increase of ST temperature. Strength and ductility in the solution treated condition are independent of both ST temperature and prior austenite grain size due to constant martensite lath spacing and dislocation tangles. In the solution treated + aged condition, the relationship between yield strength and prior austenite grain size follows the Hall- Petch equation, and ductility improves until the ST temperature used is >1373 K. Accordingly, the fracture mode transforms from intergranular to transgranular at a critical prior austenite grain size of ~ 150 μ m, because of severe segregation of Ni3(Mo,Ti) and reverted austenite at prior austenite grain boundaries and martensite lath boundaries. The variation of Charpy V notch impact energy with increase of ST temperature in both the solution treated and solution treated + aged conditions is similar to that of the tensile ductility. The fracture toughness KIC, however, increases with increase of ST temperature. No thermal embrittlement resulted from the Ti(C,N,S) inclusion segregation at prior austenite grain boundaries and martensite lath boundaries in the high temperature solution treatment.