Solution Treatment Aging Research Articles

Microstructures and Mechanical Properties of SUS 630 Stainless Steel: Effects of Age Hardening in a Tin Bath and Atmospheric Environments

This study investigates the solution-aging treatment of precipitation-hardening SUS 630 stainless steel, alongside an analysis of the carbon emissions generated by the energy consumed during aging treatments. By employing atmospheric and liquid tin as aging media, the research comprehensively explores the effects of aging treatments on the characteristics of 630 stainless steel. The maximum hardness value for the 630 stainless steel was observed after atmospheric aging at 500 °C for 1 h. The given 630 stainless steel obtained its maximum hardness value after atmospheric aging at 500 °C for 1 h, indicating that the formation of secondary precipitates strengthens the steel’s performance. By leveraging the intrinsic characteristics of liquid tin, using it as an aging medium (Sn bath aging) significantly improves the efficiency of the aging process, achieving mechanical properties comparable to those of atmosphere-aged steel. The 630 stainless steel aged in a Sn bath exhibited a refined martensitic matrix with substantial precipitate formation, contributing to superior impact toughness and dynamic fatigue resistance. With an equivalent mass and performance, Sn bath aging notably reduced the duration of the treatment compared to atmospheric aging, leading to substantial energy savings and reduced carbon emissions. The Sn bath treatment, recognized in metallurgical science and heat treatment for its excellent thermal conductivity and recyclability, shows potential to enhance process efficiency and enable low carbon emissions in the heat treatment industry. By highlighting the differences between aging methods, this study provides solutions for optimizing heat treatment processes and thereby achieving industrial advancement and sustainability goals.

Effect of solution-aging treatment on microstructure and high temperature fracture toughness of Ti60 alloy rolled sheet

Effect of solution-aging treatment on microstructure and high temperature fracture toughness of Ti60 alloy rolled sheet

Effect of solution aging treatment on corrosion resistance and erosion resistance of laser metal deposition 17-4PHss

Slurry erosion and cavitation erosion are the primary causes of failure in pass flow components, and preventive maintenance can effectively extend their service life. In this paper, 17-4PH stainless steel was prepared using laser metal deposition (LMD) technology and aged to investigate the effect of solution treatment on its microstructural transformations. The microhardness, electrochemical corrosion behavior, slurry erosion resistance, and cavitation erosion behavior of the as-built and solution-treated, aged samples were analyzed, with traditional forged specimens used as controls. During heat treatment, the microstructure fully transformed to martensite, and NbC precipitated as a second phase. Solution treatment led to microstructural coarsening, while aging significantly refined the microstructure and produced partial reverted austenite. Microhardness analysis showed that the microhardness of the solution-treated and aged samples increased to 465.5 ± 8.6 HV0.2 due to the combined effects of finer and more uniformly distributed NbC precipitation and grain refinement. The solution aging samples exhibited the lowest corrosion current density and the highest corrosion potential, influenced by the presence of reverted austenite. Slurry erosion results indicated that the corrosive environment accelerated mass loss due to the synergistic effects of mechanical abrasion from gravel and brine corrosion. Meanwhile, the solution aging samples demonstrated superior resistance to slurry erosion, with mass losses in clear water and brine slurry of only 69 % and 63 % of those observed in the traditional forged samples. In the cavitation erosion experiment, the solution aging sample showed the lowest cumulative mass loss (3.54 ± 0.18 mg), and the work-hardening of the reverted austenite further enhanced the cavitation erosion resistance of the solution aging sample.

Effect of Heat Treatment on Fatigue Life of Ti‐6Al‐4V Alloy With Two‐Layered Structure of Additively Manufactured and Conventional Wrought Parts

ABSTRACTTo investigate fatigue life of the two‐layered Ti‐6Al‐4V alloys with additively manufactured layer and conventional wrought layer, fatigue tests were conducted under constant amplitude loading. The effect of post heat treatment on fatigue life was also examined. Three types of specimens were used as test materials: specimens without heat treatment (As‐built material), specimens with solution aging treatment (STA), and specimens with heat treatment (1100AC). Compared at the same stress amplitude, there was a tendency that STA material has a longer fatigue life because of the lower initial stress of STA specimens at the attachment of the fatigue testing machine. However, As‐built material had the longest and 1100AC material had the shortest fatigue lives compared at the same σswt. And a comparison of the fatigue limits showed that As‐built and STA materials have almost the same values.

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.

Laser powder bed fusion of GH4099 Ni-based superalloy under a static magnetic field with tailored microstructure and enhanced mechanical performance

ABSTRACT In the present work, the static magnetic field (SMF) was applied in the L-PBF process of a typical γʹ strengthening Ni-based superalloy of GH4099 concerning the as-built and heat-treated conditions. The SMF during the L-PBF process can effectively refine the cellular str ucture, refine the grain size, promote the columnar to equiaxed transition (CET), and reduce the dislocation density. After the solution-aging procedure, the SMF samples exhibited a refined grain structure, suggesting that the tailored microstructure is inherited after the solution-aging treatment. The tensile test results show that by applying the SMF during the L-PBF process, the ductility can be notably improved on both building planes under the as-built and heat-treatment conditions, and the anisotropy along different directions can be reduced. It reveals that the SMF in L-PBF can be an effective method to modulate the microstructure and improve the comprehensive mechanical properties for γʹ strengthening Ni-based superalloys.

Enhancing Wear Resistance and Erosion Wear Performance of Laser Additive Manufactured 17-4PHss through Solution Aging Treatment

Enhancing Wear Resistance and Erosion Wear Performance of Laser Additive Manufactured 17-4PHss through Solution Aging Treatment

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.

The effect of direct aging treatment on microstructure and mechanical properties of the GH4099 superalloys produced by selective laser melting

The effect of direct aging (DA) treatment on microstructure and mechanical properties of the GH4099 superalloys produced by selective laser melting (SLM) was investigated by the microhardness tests, room- (RT) and high-temperature (HT) tensile tests, field emission scanning electron microscopy (FE-SEM), and electron backscattered diffraction (EBSD) in this study. Both microhardness and RT tensile results show that DA treatment improves mechanical properties more than solution-aging (SA) treatment. By analyzing the effect of the microstructural features on the yield strength, we found that the dominant strengthening mechanisms responsible for higher yield strength of the DA specimens are the grain size hardening of fine γ matrix, high-density dislocation strengthening, Orowan dislocation bypass strengthening of smaller but dense M23C6-type carbides, and chemical strengthening of smaller but dense γ΄ nanoprecipitates. Furthermore, a transgranular fracture is a dominant fracture type for RT tensile specimens produced by DA treatment. Conversely, the failure type of SA tensile specimens is a typical intergranular fracture mechanism. The underlying mechanism for the above phenomenon is attributed to the effects of transgranular and intergranular M23C6-type carbides.

Microstructure, mechanical properties and deformation behavior of laser additively repaired 5083 and 6061 Al alloys utilizing AlMgScZr powders

Laser additive repair (LAR), as an efficient repair method, lacks specialized repair materials for Al alloys. In this work, the high-strength AlMgScZr powder was employed to address the scarcity of specialized materials and the issue of inadequate performance in LAR of 5083-H112/6061-T6 Al alloy. The microstructure, mechanical properties and deformation behavior of repaired specimens were studied. The repair zone (RZ) had high strength and high density, and the porosity was as low as 0.12 %. There was good compatibility between the repair material and the base metal (BM), and good metallurgical bonding was achieved at the fusion line. The microstructure and strengthening phase (T-phase) in the heat affected zone (HAZ) of the 5083 repaired parts exhibited negligible changes, there was no deterioration in mechanical properties. The yield strength was 162 MPa, tensile strength was 291 MPa, and elongation was 16.2 %, reaching 94 %, 104 %, and 70 % of the BM, respectively. The mechanical properties are superior in the current research on LAR of Al alloys. The LAR technique showcases its versatility in repairing aging non-strengthening Al alloys. The transition of β′′→β′ (or with B′/U1/U2)→β of the nano-reinforced phase resulted in deteriorative mechanical properties of HAZ in the 6061 repair part, consequently, the tensile strength of 6061 repair part was only 63.8 % of the strength of BM. After solution aging treatment, the β′′ phase in HAZ re-precipitated, effectively restoring the strength of 6061 repaired parts. The tensile strength of the repaired parts was increased to 95.2 % of the strength of BM. The present study elucidates the evolution of microstructure and mechanical properties during LAR process of Al alloys, offering valuable insights for future applications of this technology on Al alloys.

Performance evaluation of GH3536/GH4169 functionally graded materials with linear gradient changes fabricated through direct energy deposition

This study employs the direct energy deposition method to fabricate functionally graded materials (FGMs) using GH3536 and GH4169 alloys. The approach achieves a seamless linear gradient transition in the FGMs, progressing from GH3536 alloy to GH4169 alloy. Additionally, the impact of a solid solution twin-aging process on the properties of the FGMs was investigated. The findings reveal that variations in the powder content of GH3536/GH4169 alloy exhibit minimal impact on the microstructure of the deposited FGMs, with columnar crystals predominantly growing along the <001> direction. The direct energy deposition process induces an exceptionally high temperature gradient and cooling rate, preventing the timely precipitation of the second strengthening phase (γ", γ', δ), as well as M6C and M23C6 in the FGMs. Furthermore, the formation of the Laves phase (Ni2Nb, Cr2Mo) diminishes the overall performance of the FGMs. In correspondence with the linear variation of GH3536/GH4169 alloy powder content, the hardness of each layer within the deposited FGMs exhibits an initial increase followed by a subsequent decrease. Following the solution aging treatment, complete dissolution of the Laves phase and δ phase occurs, leading to the formation of a secondary chain phase (M23C6) along the grain boundaries. Simultaneously, needle and granular δ phases disperse within the grain structure, contributing to enhanced performance in the FGMs and ensuring uniform hardness throughout.

Effects of solution aging treatments on microstructure features, tensile properties and low-cycle fatigue behavior of Ti-6.2Al-4.26Mo-1.33Mn alloy

High-performance titanium alloy fasteners play an important role in the aerospace industry as important general basic parts. This work developed a high-elastic-modulus Ti-6.2Al-4.26Mo-1.33Mn alloy with good balance of strength and plasticity through regulating its primary equiaxed α (αp) phase with solution aging treatment. The influence of αp on the tensile properties and low-cycle fatigue (LCF) behavior of the alloy was investigated systematically, and the crack propagation mechanism of fatigue fracture of titanium alloy was revealed. The results show that with increasing solution temperature, the content of αp phase decreases from 43.6 % to 15.1 % in the range of 825 °C–925 °C, and the LCF life is increased by almost 2 times. However, the size of αp phase is almost unchanged with a diameter of about 2.3 μm. With the increase in solution temperature, the tensile strength of the alloy is improved, while the plasticity decreases gradually. At the solution temperature of 875 °C, the ultimate tensile strength (UTS) of the alloy is 1350 MPa, which is 18.6 % higher than the as-forged alloy, with an elongation (El) of >7 %. Moreover, the fatigue performance is also significantly improved, which is associated with the reduced αp phase that was characterized to act as crack initiations and crack propagation path.

Effect of heat treatment on microstructure and mechanical properties of 18Ni-350 maraging steel fabricated by Wire and Arc Additive Manufacturing

An 18Ni-350 maraging steel single wall structure was fabricated using Wire Arc Additive Manufacturing (WAAM). Due to the rapid cooling and cyclic heating, elements such as Ni, Ti, and Mo were segregated within the single wall, resulting in a microstructure characterized by coarse primary dendrites and secondary dendrites. Various heat treatment were devised for the samples, encompassing Solution Treatment (ST), Solution + Aging Treatment (SAT), and Direct Aging Treatment (DAT). The findings revealed that elemental segregation persisted when the ST temperature was below 1050 °C, but disappeared when it exceeded 1150 °C, withthe microstructure transitioning from dendritic to equiaxed grains. ST resulted in the decrease of microhardness and tensile strength, but an enhancement in elongation. The effect of DAT was unsatisfactory for the improvement of mechanical properties while SAT could significantly improve them. Transmission Electron Microscope (TEM) analysis showed that a uniform distribution of Ni3Ti and Ni3Mo strengthening phases was formed in the martensitic matrix after SAT. The ultimate tensile strength of the sample reached 2163 ± 42 MPa under the optimal heat treatment condition (SAT 1150 °C-1 h + 480 °C-6 h).

High-Performance 2319 Aluminum Alloy via CMT-WAAM: Microstructure, Porosity, and Mechanical Properties

The process of cold metal transfer (CMT) wire arc additive manufacturing (WAAM) for 2319 aluminum alloy was studied. The research investigated the coarse and fine equiaxed grain bands and porosity of the 2319 alloy after solution aging treatment, with a focus on the mechanical properties and deformation behavior of the aluminum alloy at different positions and orientations. Pores and coarse second phases mainly appeared at grain boundaries but were also observed within coarse equiaxed grains. The yield strength of the top horizontal samples reached 325.5 MPa, one of the highest yield strengths reported for 2319 aluminum alloy in the literature. The coarse brittle second phases at grain boundaries were the main crack sources during the failure process of the samples. In the fine equiaxed grain layer, cracks propagated along the grain boundaries connected to the second phases, and the presence of pores accelerated crack propagation; in the coarse equiaxed grain layer, cracks directly penetrated through the grains.

Improving the strength and maintaining good ductility of as-forged Ti6Al4V alloy by regulating the microstructural defects

Solution-aging treatment is a conventional method for enhancing the strength of titanium alloys contributed by the decomposition of metastable phases, like martensite. The traditional viewpoint suggests that the martensite transformation occurring after water quenching does not significantly contribute to the strengthening of titanium alloy and this perspective actually overlooks the high strength resulting from the high-density defects formed in the martensite microstructure due to rapid cooling. So, previous studies have not fully taken advantages of the excellent strengthening capability of martensite. This study adopted a technique which combined solid solution and incomplete aging treatment to control the decomposition behavior of martensite and as a result, the strength of the as-forged Ti-6Al-4V (TC4) alloy had been obviously improved and good ductility had been maintained. Furthermore, the changes of phase structure and microstructural defects in TC4 titanium alloy during solution and aging process have been detailly studied by XRD refinement, EBSD, and TEM. Specifically, the highest tensile strength increased by 28.8 % which could reach 1224 MPa, and the elongation at fracture could still remain at 13 %. The reason is as follows. The formation of martensite after water quenching led to a substantial increase in internal microstructural defects, which were partly retained during the subsequent aging process because of lower temperature and short aging time, and the remaining martensite and microstructural defects can help maintain high strength. What's more, a small part of defects disappeared during this incomplete aging process due to martensite decomposition and recovery, which was beneficial to ductility.

Influence of various heat treatment processes behavior of a novel maraging steel coating process on the microstructure, nanoindentation pattern, and wear

Effective subsequent heat treatment is essential for achieving excellent performance in maraging steel. This paper presents the preparation of a maraging steel coating with a high content of Mo and Co elements using laser cladding technology. The study investigates the effects of direct aging treatment and solid solution-aging treatment on the microstructure, elemental distribution, crystallographic features, nanoindentation characteristics, and wear behavior of the coatings. The results indicate that all three coatings consist primarily of α-Fe with a small amount of γ-Fe, and solid solution-aging treatment effectively inhibits the martensite-to-austenite transformation. Following both heat treatments, a significant number of nanoscale precipitated phases were observed within the martensitic matrix, proving pivotal in enhancing the coatings' hardness. Notably, the solid solution-aging-treated coating exhibits excellent nanomechanical properties, with a hardness of approximately 8.39 ± 0.19 GPa, representing a remarkable 75 % improvement compared to the untreated coating. Second-phase strengthening and dislocation strengthening are identified as the primary mechanisms responsible for enhancing the solid solution-aging coating. Furthermore, solid solution-aging treatment significantly enhances the wear performance of the coatings, as evidenced by a dry sliding average friction coefficient of 0.578 and a wear volume of (3.18 ± 0.97) × 106 μm3, surpassing those of the original coatings. The observed wear mechanisms include abrasive wear, oxidative wear, and slight adhesive wear, with the precipitation of nanoscale precipitated phases playing a key role in enhancing wear resistance.

Tailoring microstructure and mechanical anisotropy of laser-MIG hybrid additive manufacturing TC11 titanium alloy through solution aging treatment

Tailoring microstructure and mechanical anisotropy of laser-MIG hybrid additive manufacturing TC11 titanium alloy through solution aging treatment

Development of highly corrosion-resistant Mg-Al-Y extruded alloy via regulating the Mg17Al12 phase

A highly corrosion-resistant AW90 extruded alloy (Mg-9Al-0.2Y wt %) was developed via alloying and solution-aging treatment (PW = 0.14 mm/y). The solution-treated AW90 alloy exhibits the most severe localized corrosion due to the strong micro-galvanic acceleration effects. The finely dispersed Mg17Al12 phase promotes the strong quasi-passive behavior and uniform corrosion of the aged AW90 alloy due to the formation of a dense and uniform corrosion product film. The high corrosion resistance of the aged AW90 alloy is attributed to the formation of a Mg-Al layered double hydroxide film, which has stronger resistance to chloride ions.

In-situ reinforced Ti6Al4V-TiB2 titanium matrix composite fabricated by selective laser melting: Microstructure, mechanical properties and heat treatment

Ti6Al4V-x wt%TiB2 titanium matrix composites (x = 0, 0.01, 1, 3.4, 4.8) were prepared by selective laser melting (SLM), followed by solution-aging treatment. The microstructure and mechanical properties of the SLM-formed samples and the heat-treated ones were systematically investigated. In the SLM-formed samples, in-situ TiB whiskers clustered around the original position of the TiB2 particles, which reacted with the matrix through dynamic dissolution. The phase transformation of α' → α + β and the coarsening of TiB whiskers occurred during solution-aging treatment. The microhardness of the samples was enhanced with the increase of TiB2, while the heat treatment was harmful to microhardness. The fine grain strengthening and the dispersion strengthening caused by TiB whiskers enhanced the quasi-static compressive strength of the samples. The samples were modified successfully by solution-aging, and the compressive strength and strain of the Ti6Al4V-0.01wt.%TiB2 composite reached 1957 MPa and 23.7% respectively. The samples had higher ductility but lower strength under dynamic load, and the heat treatment had little effect on the dynamic properties.

Grain size control method for enhancing high-temperature durability of Al–Cu–Mg–Ag alloy

Reducing the grain boundary density (obtaining larger grain size) is beneficial for improving high-temperature durability of the heat-resistant aluminum alloys, and thus for extending their service life. In this paper, a grain size control method was proposed to enhance high-temperature durability of an Al–Cu–Mg–Ag alloy. A relationship formula between grain size, holding time, and annealing temperature was obtained through theoretical analysis. The recrystallization curve of a deformed Al–Cu–Mg–Ag alloy under different heating rates was determined through three-point bending thermal relaxation experiments. Based on the above relationship formula, the recrystallization kinetics parameters were obtained. Subsequently, based on actual processing conditions, the annealing temperature with the maximum grain size under a given annealing time was calculated. After the annealed sample underwent solution-aging (T6) treatment, the grain size increased by more than 60% compared with that of the directly solution-aging treated sample. This method can increase the duration by more than 60% at conditions of 210 °C/190 MPa without significantly reducing the room-temperature mechanical properties.