Single Aging Treatment Research Articles

Influence of Single Aging Treatment on the Mechanical Properties of Additively Manufactured Ultra-Thin 18Ni-300 Maraging Steel

Influence of Single Aging Treatment on the Mechanical Properties of Additively Manufactured Ultra-Thin 18Ni-300 Maraging Steel

Precipitation behaviour of single and duplex aged metastable β-Ti alloy, Ti–5Al–5Mo–5V–3Cr

This work presents the influence of single-aging and duplex-aging treatments on microstructure evolution and the associated properties of Ti-5553 β-Ti alloy. We found that single-aged samples with a slow heating rate and duplex-aged samples produced approximately the same microstructures and microhardness at all aging conditions. This can be attributed to the same precipitation mechanism in both cases as observed via in situ electrical resistivity measurements. The slowly heated and duplex-aged samples generally produced higher microhardness in comparison to fast-heated samples; however, the difference in the microhardness tended to decrease with aging time at higher temperatures. A correlation () between the microhardness values and the width of α-phase (d) was established for all the aged samples. Highlights Duplex aging and slow heating yield similar microstructure and microhardness. Duplex aging and slow heating showed similar precipitation mechanism. Duplex aging and slow heating generally produced higher hardness than fast heating. The gap in hardness for different aged conditions decreased at higher temperatures. The microhardness values showed a good correlation with the width of α-phase.

Microstructural evolution and properties of electromagnetic cast-rolled novel Al–Li alloy under different heat treatment procedures

A large number of dislocations and dislocation tangles are induced in the Al–Li alloy after 5% pre-stretching deformation before aging treatment, which increases the density of the defects in α(Al) matrix and affects the competitive precipitation relationship and precipitation behavior of δ′ (Al3Li), S′ (Al2CuMg) and T1 (Al2CuLi) precipitates during the aging process. The increase of crystal defects such as dislocations provides superior nucleation sites for the heterogeneous nucleation and promotes the precipitation of T1 phase, greatly improving the mechanical properties of the alloy. The uniform and dense precipitation of T1 phase in the grain reduces the potential difference between the grains and the grain boundaries. Therefore, not only does it reduce the driving force of intergranular corrosion (IGC), but also decreases the difference of the corrosion rate between the grain boundary and intragranular. These are beneficial to slow down the corrosion process and promote uniform corrosion. The intermittently distributed grain boundary precipitates (GBPs) in the T8 treated alloy cut off the continuous corrosion channel at grain boundaries and hinder the IGC process. Furthermore, the width of the precipitation free zones (PFZs) in the T8 treated alloy is narrow. Hence, the alloy exhibits excellent IGC resistance and superior corrosion protection performance under T8 single aging treatment. The pre-aging process in low temperature before T8 single aging treatment greatly enhances the precipitation driving force of T1 phase and effectively promotes the precipitation of T1 phase in the subsequent high-temperature aging process, which further increases the strength and improves the IGC resistance of the alloy.

Microstructural evolution and mechanical properties of 2219 aluminum alloy from different aging treatments to subsequent electromagnetic forming

The manufacturing process of 2219 aluminum alloy (AA2219) thin-walled parts nowadays exhibits challenging to meet the service requirements of the high performance and lightweight new-generation launch vehicle. This work employs different aging treatments and subsequent electromagnetic forming to investigate the microstructure evolution and mechanical properties of AA2219. The results show that the optimal single aging treatment is 180 °C for 6 h, and the optimal double aging treatment through L 16 (4 4 ) orthogonal experimental is 140 °C for 2 h + 180 °C for 6 h. Meanwhile, the precipitated phase of single aging is mainly θ″ phase with a three-layer Cu atomic structure while double aging is mainly θ″ phase with a two-layer Cu atomic structure and GP zones. The average thickness and size of θ″ phase and GP zones in the double aged sample are smaller than that of θ″ phase in the single aged sample. However, it has a higher number density and more concentrated size distribution. The plasticity of aged AA2219 improved obviously under the electromagnetic forming. Besides, the forming performance of double aged sample is better with the tensile strength after electromagnetic forming is 424.0 MPa, and the total strain is 25.75%. Electromagnetic forming has negligible effects on the morphology, size, and distribution of precipitated phase. Nevertheless, some dislocations sheared θ″ phase along the {111}<110> slip system under tensile loading. The interaction mechanism of dislocation with different precipitated phases during electromagnetic forming was depicted. This work provides guidance for the strengthening treatment and forming process of AA2219 high-performance parts. • The morphology, size, and distribution of the precipitated phase were investigated. • The plasticity of aged 2219 aluminum alloy improved obviously under the electromagnetic forming. • The interaction mechanisms of dislocation with precipitated phase were depicted.

Comparisons of Age Hardening and Precipitation Behavior in 7075 Alloy Under Single and Double-Stage Aging Treatments

Various sets of heat treatments are applied on 7075 alloy in this study in order to reduce the treatment time and yet still achieve the similar mechanical property as the traditional T6 tempered alloy. The main parameters like solid solution treatment time, single aging temperature, as well as first aging duration in double aging treatment, first aging temperature and second aging temperature are studied and valued by hardness test. The double aging treatment at 125 °C for 60 min and then at 165 °C for 130 min is compared with traditional single aging treatment by using advanced Cs-corrected high-angle annular dark field scanning-transmission electron microscopy (HAADF-STEM). The precipitates and dispersoids found in those two corresponding samples are mainly Cr-containing large dispersoids, a few η particles and large quantity of fine precipitates like η′. The similarity of precipitates in them can well support the approximate hardness level of the double aged and single aged samples.

Precipitation and coarsening behavior of γ′ phase in CoNi-base superalloy under different aging treatments

In order to investigate the influence of aging regimes on the coarsening behavior of γ′ precipitates in CoNi-base superalloy, single and double aging treatments were performed, respectively. For the superalloy after experiencing single aging treatment, the typical γ/γ′ microstructure with coherent γ′ embedded in the matrix is obtained and the coarsening kinetics of γ′ precipitates is in accordance with the Lifshitz-Slyozov-Wagner (LSW) theory. The corresponding coarsening rate increases owing to the addition of γ′ forming elements (Ti and Ni) and the calculated activation energy suggests that coarsening kinetics of γ′ is controlled by diffusion of Ni and Ti in the matrix for the investigated CoNi-base superalloy. Whereas for the superalloy after experiencing the double aging treatment, bimodal size distributions of γ′ precipitates are recognized and a decelerated coarsening of secondary γ′ precipitates in coarsening zone is found as compared with the one after experiencing the single aging treatment, which could be attributed to the effect of primary γ′ precipitates.

Fine Precipitates in Nickel Base Superalloys

Presence of fine, secondary/tertiary precipitates in superalloys improves especially the creep-fatigue properties of these alloys. It is conveniently accepted that the fine precipitates form non-isothermally, for example, during cooling from an aging temperature or isothermally during a secondary, lower temperature aging. In the current study, several single-aging treatments were conducted to assess the formation of the fine precipitates in the polycrystalline, nickel-base superalloy IN738LC. The agings were carried out stress-free at 950oC, 1050oC, 1120oC, and 1140oC for various times. Stressed agings at 950oC and 1050oC were also conducted. A time-dependent isothermal formation of the fine precipitates was observed. The formation time decreased as the aging temperature increased. It is suggested that dissolution of some coarse precipitates, evolution of the precipitate-matrix interface toward a fully faceted one, and increased matrix channel width saturate the channels and control the formation of the fine precipitates.

Single and double aging treatments on Mg97Zn1Y2 alloy

The development of magnesium alloys was limited due to the low absolute strength and poor corrosion resistance. It was found that the optimal performance could not be achieved in some alloys by a single quenching and aging treatment, but could be achieved after a graded aging or multiple-stage aging heat treatment. The Mg97Zn1Y2 alloy was prepared and subjected to single and double aging treatments. Single aging was carried out at 250 oC for 6 to 15 h. For double aging, the first step was performed the same as the single aging. The second step was performed at 350 oC for 12 h. The microstructure and properties of the alloy with single and double aging were analyzed by means of hardness measurement, optical microscopy, scanning electron microscopy, X-ray diffraction, and polarization curve measurements. Results show that the precipitated nanoscale phases are formed during aging, and evenly distributed in the matrix. Compared with the single aging treatment, the hardness and corrosion resistance of the alloy are further improved due to the double aging treatment.

Ambient and elevated temperature mechanical behavior of Mg-Gd-Cu-Zr alloy

The Mg-6.0Gd-1.2Cu-1.2Zr (wt%) alloy was designed, then processed by solution treatment, as well as the following single-aging and double-aging treatments respectively. The mechanical behavior of the alloys at ambient temperature and 150 °C was evaluated. The results indicate that the ambient temperature yield strength of the alloy is slightly reduced after solution treatment but is enhanced after following single-aging and double-aging treatments. At 150 °C, the yield strength of the as-cast alloy decreases by 18.0%, and those of the heat-treated alloys are reduced from 1.2% to 17.7% as compared to those at ambient temperature. Aging treatment results in higher yield strength decrease at elevated temperature than solution treatment.

Effect of aging treatment on microstructures, tensile properties and intergranular corrosion behavior of Al–Cu–Li alloy

The influence of aging treatment on microstructures, tensile properties and corrosion properties of Al–Cu–Li alloy was investigated. The results show that the T8 duplex aging treatment was more effective than T6 and T8 single aging treatment in enhancing the tensile properties and improving the intergranular corrosion (IGC) resistance. Based on the microstructure observation, tensile test, electrochemical experiment and IGC measurement, the factors which affect the microstructures, tensile properties and IGC behavior changing of Al–Cu–Li alloy during aging treatments were discussed in detail.

Effects of different aging treatments on microstructures and mechanical properties of Al-Cu-Li alloy joints welded by electron beam welding

Post-weld single aging treatment (solution treatment at 510°C for 1h, water quenching, and aging at 155°C for 16h) and post-weld double aging treatment (solution treatment at 510°C for 1h, water quenching, aging at 155°C for 16h, and aging at 130°C for 12h) are carried out on Al-Cu-Li alloy joints by electron beam welding (EBW) respectively. The effects of aging treatments on microstructures and mechanical properties of welded joints are investigated. Results show that the mechanical properties of welded joints are obviously improved after both aging treatments. The strength coefficient of joints is increased from 0.64 in an as-welded condition (AW) to 0.90 after post-weld double aging treatment. Microstructure analysis shows that the precipitates of the fusion zone within grains and grain boundaries are less in the AW condition. After post-weld heat treatment (PWHT), a lot of fine needle-like phases T1 (Al2CuLi) precipitate in grain boundaries of the fusion zone, and more horseshoe-shaped β′ (Al3Zr) particles precipitate within grains. In addition, grains of the fusion zone are refined after post-weld double aging treatment, which leads to an effect of grain refinement strengthening. Consequently, the mechanical properties of welded joints are greatly improved.

Effects of Cu addition on the microstructure and mechanical properties of as-cast and heat treated Mg-6Zn-4Al magnesium alloy

The microstructure and mechanical properties of as-cast and heat treated Mg-6Zn-4Al-xCu (x=0, 0.5, 1.0 and 1.5wt%) alloys were investigated in this work. The results show that the grain sizes of the alloys decrease considerably with increasing Cu addition, and the eutectics are refined with 0.5% Cu addition. The icosahedral quasi-crystalline phase is observed in Mg-6Zn-4Al and Cu-containing alloys，and the MgAlCu phase forms in the Cu-containing alloys because of Cu addition. Compared with Mg-6Zn-4Al alloy, the Cu-containing alloys exhibit improved age-hardening response during single-aging treatment. In addition, high-density fine precipitates are formed in the matrix during double-aging treatment, resulting in remarkable improvement of the tensile strength. The double aged Mg-6Zn-4Al-0.5Cu alloy shows the relatively optimal tensile properties. The yield strength, ultimate tensile strength and elongation are 202MPa, 312MPa and 7%, respectively, which is attributed to the combined effects of fine grains and the uniform distribution of high-density fine precipitates. It is noticed that the ductility of as-aged Cu-containing alloys is lower than that of the as-aged Mg-6Zn-4Al alloy due to the stress concentration during the tensile stress caused by the residual phases distributed along the grain boundaries after solution treatment.

Effects of extrusion and heat treatments on microstructure and mechanical properties of Mg–8Zn–1Al–0.5Cu–0.5Mn alloy

The effects of extrusion and heat treatments on the microstructure and mechanical properties of Mg–8Zn–1Al–0.5Cu– 0.5Mn magnesium alloy were investigated. Bimodal microstructure is formed in this alloy when it is extruded at 230 and 260 °C, and complete DRX occurs at the extruding temperature of 290 °C. The basal texture of as-extruded alloys is reduced gradually with increasing extrusion temperature due to the larger volume fraction of recrystallized structure at higher temperatures. For the alloy extruded at 290 °C, four different heat treatments routes were investigated. After solution + aging treatments, the grains sizes become larger. Finer and far more densely dispersed precipitates are found in the alloy with solution + double-aging treatments compared with alloy with solution + single-aging treatment. Tensile properties are enhanced remarkably by solution + double-aging treatment with the yield strength, tensile strength and elongation being 298 MPa, 348 MPa and 18%, respectively. This is attributed to the combined effects of fine dynamically recrystallized grains and the uniformly distributed finer precipitates.

Effect of ω-assisted precipitation on β→α transformation and tensile properties of Ti–15Mo–2.7Nb–3Al–0.2Si alloy

Microstructure and tensile properties of Ti–15Mo–2.7Nb–3Al–0.2Si alloy subjected to single and duplex aging treatments were investigated. The single aging treatment was carried out at 500°C for 8h. The duplex aging treatments was performed at 320°C for 2h for the first step, and the second step was carried out as the single treatment. As for microstructure, researches indicated that the precipitation formed during aging treatments was affected by phase transformation courses. Different from the needle-like α precipitates of β matrix during the single aging treatment, the finer shuttle-like α precipitates during the duplex aging treatment was obtained due to the assistance of ω phase formed in the first step aging. EBSD analysis showed that the orientation of precipitation was similar no matter with the single aging or the duplex aging treatment. The higher ultimate tensile strength value of 1437MPa was obtained through strengthening of shuttle-like α phase with a length of 0.5μm in the duplex aging treatment, with an acceptable elongation of 10.6%. The tensile fracture of those aging treatments illustrated that deep dimples in the duplex aging sample were beneficial for the higher strength.

Effect of Double Aging on the Toughness and Precipitation Behavior of a Novel Aluminum-Lithium Alloy

Precipitation behavior and mechanical properties of a novel aluminum-lithium alloy were investigated during a double-aging treatment to obtain superior combination of strength and plasticity. The double-aging process, involving subsequent high to low temperature treatments, was applied to strengthen the alloy. Transmission electron microscopy was used to characterize the precipitation behavior of the alloy, while tensile and tear tests were performed to evaluate the mechanical properties. The results indicated that the samples double aged at (165 °C, 10 h) + (140 °C, 35 h) possessed a desired combination of strength, plasticity, and toughness. T 1 phases were observed to nucleate preferentially at the defects during the first (primary) aging step. During the second (secondary) step of aging, these phases grew further and promoted the formation of new precipitates. Compared to the single-aging treatment, the double-aging treatment effectively prevents coarsening of T 1, which is beneficial in improving the plasticity and toughness of the alloy.

Effect of aging on the mechanical properties and corrosion susceptibility of an Al-Cu-Li-Zr alloy containing Sc

The effects of aging on the microstructure, mechanical properties, intergranular corrosion, and exfoliation corrosion of an Al-3.5Cu-1.5Li-0.22(Sc+Zr) alloy have been investigated. The results show that the alloy has the character of age hardening, and the major phase of precipitation and strengthening is the T 1 phase. The aging temperature and aging time have a significant effect on the amount and distribution of the T 1 phase. The proper artificial single-aging treatment of the alloy is at 160r°C for 40 h. The intergranular corrosion and exfoliation corrosion of the alloy are caused by the anodic dissolution of the T 1 phase and the precipitate-free zone (PFZ). With increasing the aging time to overaged, the T 1 phase coarsens, and the PFZ widens, leading to an increase in the susceptibility to intergranular corrosion and exfoliation corrosion.

Single-aging characteristics of 7055 aluminum alloy

The microstructures and properties of 7055 aluminum alloy were studied at different single-aging for up to 48 h using hardness test, tensile test, electrical conductivity measurement, XRD and TEM microstructure analysis. The results show that at the early stage of aging, the hardness and strength of the alloy increase rapidly, the peak hardness and strength are approached after 120 °C aging for 4 h, then maintained at a high level for a long time. The suitable single-aging treatment of 7055 alloy is 480 °C. 1 h solution treatment and water quenching, then aging at 120 °C for 24 h. Under those condition, the tensile strength, yield strength, elongation and electrical conductivity of the studied alloy are 513 MPa, 462 MPa, 9.5% and 29%(IACS), respectively. During aging, the solid solution decomposes and precipitation occurs. At the early aging stage of 120 °C, GP zones form and then grow up gradually with increasing ageing time. η' phase forms after ageing for 4 h and η phase starts to occur after 24 h aging.

Microstructure and corrosion behavior of Mg–Zn–Ag alloys

The majority of Mg components currently in use in the automotive and electronic industries are produced by conventional casting processes. However, there is a strong need to develop new high strength wrought alloys for wide-spread application of Mg alloys in near future. In the present study, new Mg–Zn–Ag alloys were developed and characterized. In order to evaluate the effects of Ag addition on the mechanical properties of the extruded Mg–Zn alloys, the age hardening response and mechanical properties were examined with different amounts of alloying element. The microstructures of the specimens were examined with optical microscopy and transmission electron microscopy. The grain sizes of the alloys in as-extruded condition were markedly reduced with the addition of Ag. The hardness was found to increase more rapidly in the alloys with double aging treatment compared to those with single aging treatment. The peak hardness was also found to be higher in the alloys with double aging treatment. In all heat treatment conditions, the hardnesses of the Mg–Zn–Ag alloys were found to be higher than those of the Mg–Zn alloys. Moreover, the addition of Ag to the Mg–Zn alloys increased the corrosion rate measured by immersion test.

Structure and strength of an Al-Zn-Mg alloy after duplex aging treatment

Multiple aging has been applied to an Al-7.5 wt.% Zn-2.5 wt.% Mg alloy with a view to producing a duplex distribution of precipitate particles. A combination of a coarse distribution of η phase, together with finer η′ and GP zones, has been obtained. Transmission electron microscopy shows that coarse, well-defined slip bands occur on deformation of the alloy after a single aging treatment to peak hardness. A more homogeneous dislocation distribution is observed in the material after double aging treatment because of the presence of the incoherent phase in the alloy. Tensile tests indicate that no improvement in ductility occurs with duplex aging, but this may be owing to the larger grain boundary PFZ present.

CARPENTER CUSTOM 455

Abstract Carpenter Custom 455 is a low-carbon martensitic stainless steel that responds to precipitation-hardening. The single aging treatment produces exceptionally high yield strength with good ductility and toughness. It is suitable for applications requiring high strength and corrosion resistance at temperatures up to 800 F. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness and fatigue. It also includes information on forming, heat treating, machining, joining, and surface treatment. Filing Code: SS-193. Producer or source: Carpenter.