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The softening of aluminum alloy is an important factor affecting its service life. In the present work, the softening characteristics and mechanism in the friction pull plug welding (FPPW) joint of AA2219-T87 plate with a nominal thickness of 18 mm were studied, and an effective measure to mitigate the softening issue was proposed. The softening zone in the thick-plate FPPW joint is located in thermo-mechanically affect zone near the bonding interface and is 6–12 mm away from the top surface of the plate. The disappearance of the strengthening transition phase θ′ is the main cause for the softening; the degree of dynamic recrystallization, which influences the grain size and the work hardening, also affects the softening; but solid solution of Cu atoms in α-Al has little effect on the hardness change in the softening zone. After optimizing the geometric structure of joint and FPPW process parameters, the softening zone was still the weakest point of the joint. After solution and aging treatment on the above-mentioned optimized joint, the minimum hardness in the softening zone increased from 76 HV1 to 95 HV1, the tensile strength increased from 318 to 355 MPa, and the fracture position shifted from the softening zone to the plug. [ABSTRACT FROM AUTHOR]

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

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⋅%.

In this study, TA15 titanium alloys were successfully prepared using selective laser melting (SLM). The results show that the microstructure of each TA15 specimen is composed of a large number of acicular α' martensite crystals accompanied by a lot of dislocations and twin structures in the martensite due to non-equilibrium heating and cooling via SLM. After solution treatment and aging treatment, the martensite structure is successfully transformed into a typical duplex structure and an equiaxial structure. When there is an increase in the solution temperature, the size of the equiaxed primary α phase and the elongation of the specimen gradually increases, while the thickness of the layered secondary α phase and the tensile strength of the specimen decreases accordingly. After solution treatment at 1000 °C, the specimens show the best comprehensive mechanical properties, i.e., a high-temperature tensile strength of 715 MPa and a corresponding elongation of 24.5%. Subsequently, an appropriate solution–aging treatment is proposed to improve the high-temperature mechanical properties of SLMed TA15 titanium alloys in aerospace. [ABSTRACT FROM AUTHOR]

An AlZn4SiPb/steel clad composite was prepared via roll bonding at room temperature. The influence of solution and aging treatment on the structure and performance of the clad composite was investigated. The results show that the Al/steel clad composites exhibited satisfactory interfacial adhesion. Pb of the aged Al matrix was spheroidized and uniformly dispersed. An uneven interfacial transition area with a thickness of 30–150 nm was observed for the aged sample. Some rod-shaped nanoscale β' phases occurred in the aged Al matrix. After the solution and aging treatment, the steel layer recovered, and the γ-fibre texture increased. The tensile strength for individual Al alloy layer improved. The yield ratio of the aged clad sheet was lower than that of the initial sample. The tensile strength values of the composites were consistent with the computed values from the rule of mixture. The interfacial bonding strength of the initial sample was 70 MPa; the aged sample greatly improved and reached 130 MPa in strength. [ABSTRACT FROM AUTHOR]

Based on the first principles and d electronic alloy design theory, the metastable β type titanium alloy Ti28Nb5.8Mo14.6Zr alloy was designed. After being prepared in a vacuum non-consumable electric arc furnace, it was subjected to solution aging heat treatment. The microstructure and phase were investigated by SEM, TEM, XRD of the alloy, and the mechanical properties of the alloy was test by universal press and micro Vickers hardness tester, the influence of different aging time and aging temperature on alloy structure and mechanical properties were studied. The research results indicate the Ti28Nb5.8Mo14.6Zr alloy after solution treatment consisits of β phase and has relatively lower elastic modulus and tensile strength, while foe the alloy after aging treatment, it contains β and α phases exhibits significantly higher elastic modulus and compressive strength, when aging is carried out at 450°C, the elastic modulus, compressive strength and hardness of the alloy gradually increase with the extension of the aging time. Among them, the alloy's elastic modulus, compressive strength and hardness gradually increase after aging at 450°C for 60 min are 33.59 GPa, 1275 MPa and 380.07 HV, respectively. The comprehensive mechanical properties are the best, and its various mechanical properties meet the requirements of human implant materials. [ABSTRACT FROM AUTHOR]

The nickel-based superalloys processed by additive manufacturing are very promising structural materials in aircraft engines as high-pressure turbine discs. In this work, a nickel-based superalloy with good mechanical performance and few defects was manufactured by optimized selective laser melting (SLM) processing. We then investigated the influences of post heat treatments on its microstructural characteristics and mechanical performance. The results indicated that a fine grain size with uniform grain orientation was presented in the as-printed nickel-based superalloy sample. After heat treatments, the grains were slightly grown and grain orientation was also changed. Under transmission electron microscopy, fine subgrains with an approximate size of 0.5 μm were found in the as-printed sample which accompanied massive dislocations and discontinuous Laves phases. After the post heat treatments, fine subgrains and less dislocations were retained. On the other hand, massive γ′ and γ″ precipitates with an orientation relationship of (001)[100]γ′//(100)[001]γ or (001)[100]γ″//(100)[001]γ were formed. As a result, the yield stress and tensile strength increased to 1362 and 1410 MPa, respectively, in a heat-treated sample, which retained the identical elongation of the as-printed specimen. [ABSTRACT FROM AUTHOR]

In this study, TA15 titanium alloys were successfully prepared using selective laser melting (SLM). The results show that the microstructure of each TA15 specimen is composed of a large number of acicular α’ martensite crystals accompanied by a lot of dislocations and twin structures in the martensite due to non-equilibrium heating and cooling via SLM. After solution treatment and aging treatment, the martensite structure is successfully transformed into a typical duplex structure and an equiaxial structure. When there is an increase in the solution temperature, the size of the equiaxed primary α phase and the elongation of the specimen gradually increases, while the thickness of the layered secondary α phase and the tensile strength of the specimen decreases accordingly. After solution treatment at 1000 °C, the specimens show the best comprehensive mechanical properties, i.e., a high-temperature tensile strength of 715 MPa and a corresponding elongation of 24.5%. Subsequently, an appropriate solution–aging treatment is proposed to improve the high-temperature mechanical properties of SLMed TA15 titanium alloys in aerospace.

An AlZn4SiPb/steel clad composite was prepared via roll bonding at room temperature. The influence of solution and aging treatment on the structure and performance of the clad composite was investigated. The results show that the Al/steel clad composites exhibited satisfactory interfacial adhesion. Pb of the aged Al matrix was spheroidized and uniformly dispersed. An uneven interfacial transition area with a thickness of 30–150 nm was observed for the aged sample. Some rod-shaped nanoscale β’ phases occurred in the aged Al matrix. After the solution and aging treatment, the steel layer recovered, and the γ-fibre texture increased. The tensile strength for individual Al alloy layer improved. The yield ratio of the aged clad sheet was lower than that of the initial sample. The tensile strength values of the composites were consistent with the computed values from the rule of mixture. The interfacial bonding strength of the initial sample was 70 MPa; the aged sample greatly improved and reached 130 MPa in strength.

Addition of rare earth elements for improving the tensile properties of aluminum alloys has attracted great attention. In this study, a systematic analysis on the microstructure and tensile properties of A356–0.13Ti alloys with different contents of scandium (Sc) and scandium/zirconium (Sc/Zr) after solution and aging treatment process was carried out. The addition of Sc/Zr into A356–0.13Ti alloys can greatly refine the grain size and modify the deleterious coarse eutectic Si structure and harmful acicular iron-containing phase morphology. As a result, the maximum value of strength (298 MPa) and ductility (elongation of 8.4%) are acquired by co-addition of Sc/Zr after solution and aging treatment process, which indicates that the tensile properties of A356 alloy are greatly enhanced by the synergistic effect of co-addition of Sc/Zr. [ABSTRACT FROM AUTHOR]

The nickel-based superalloys processed by additive manufacturing are very promising structural materials in aircraft engines as high-pressure turbine discs. In this work, a nickel-based superalloy with good mechanical performance and few defects was manufactured by optimized selective laser melting (SLM) processing. We then investigated the influences of post heat treatments on its microstructural characteristics and mechanical performance. The results indicated that a fine grain size with uniform grain orientation was presented in the as-printed nickel-based superalloy sample. After heat treatments, the grains were slightly grown and grain orientation was also changed. Under transmission electron microscopy, fine subgrains with an approximate size of 0.5 μm were found in the as-printed sample which accompanied massive dislocations and discontinuous Laves phases. After the post heat treatments, fine subgrains and less dislocations were retained. On the other hand, massive γ′ and γ″ precipitates with an orientation relationship of (001)[100]γ′//(100)[001]γ or (001)[100]γ″//(100)[001]γ were formed. As a result, the yield stress and tensile strength increased to 1362 and 1410 MPa, respectively, in a heat-treated sample, which retained the identical elongation of the as-printed specimen.

This work mainly studies on Sc microalloying in Al-7075 alloys. The microstructure characteristics and mechanical properties of the Sc-contained Al-7075 alloys were investigated after homogenization at 460 ℃ for 10 h. The corrosion behavior of the 7075 alloys after aging was examined using a three-electrode system. The results showed that significant reduction in grain sizes from 129.92 μ m without Sc alloy to 32.17 μ m with 0.6% Sc. The microhardness increased with the increase of Sc content in the alloy from 71.7 ± 1.3 HV without Sc alloy to 89.2 ± 4.7 HV. The tensile strength also increased from 151.82 ± 1.07 MPa to 212.85 ± 7.35 MPa. The results also revealed that the addition of Sc element in 7075 aluminum alloys not only reduced the corrosion current density of the alloy, but also increased the corrosion resistance of the alloy in the corrosive environment.

Linear friction welded joints of Ti 2 AlNb-based alloy were subjected to different solution and aging treatments. Relationships among solution and aging conditions, microstructural evolution and mechanical properties were investigated. The results indicate that the microstructures are very sensitive to solution conditions. In weld zone, the lath O precipitates at the grain boundaries when the joint is solution treated in O+B2 phase region, while the formation of lath α 2 phase occurs in α 2 +B2+O phase region. In thermo-mechanically affected zone (TMAZ), aggregation of O phase and rim O phase resulted from further decomposition of α 2 phase can be found during solution treatment. And after aging treatment, both weld zone and TMAZ are comprised of secondary acicular O phase within B2 grains. Solution and aging treatments have significantly enhanced the microhardness of weld zone due to the precipitation hardening of O phase and refined grain strengthening. After aging treatment, the tensile strength of the joints is further improved because of precipitation of secondary O phase, whereas, elongation is reduced due to the suppression of the hard deformation modes in fine acicular microstructures. [ABSTRACT FROM AUTHOR]

The microstructure evolution of Mg–6 wt% Gd–2 wt% Y alloy (denoted as GW62) during solid solution and aging process were investigated by optical microscope, scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction and high resolution transmission electron microscopy. The microstructure of as-cast GW62 alloy is comprised of isometric α(Mg) crystals, equilibrium phase Mg 5 (Gd,Y), and non-equilibrium phase Mg 2 (Gd,Y). With the increase of solution treatment time, the sizes of the semicontinuous Mg 5 (Gd,Y) phases gradually decrease until dissolved. Rare-earth-rich phases (Mg(Gd,Y) 2 ) with fcc structures a =0.56 nm were newly generated in the alloy at grain boundaries and inside grains after solution treatment, which could hinder the growth of isometric α(Mg) crystals in the solution process. The maximum hardness of the GW62 alloy is significantly different for different aging temperatures. The age-hardening effect is most apparent at 175 °C. The microstructural evolution of the alloy after aging at 175 °C was as follows: the β″ phase precipitated from α(Mg) during the under-aging stage (4–32 h); next, the β′ phase precipitated from α(Mg) up until peak aging was reached (32–100 h); as aging time progressed, the hardening reached its maximum at 100 h. At this stage, the precipitated phases were the β′ and β″ phases; finally, during over-aging (>100 h), the size of β′ phase continually increased while transforming into the β 1 and β phases. [ABSTRACT FROM AUTHOR]

In order to investigate interfacial oxide evolution of 7050 aluminum alloy clad plates during the subsequent heat treatment and the effect on mechanical properties, the clad plates were subjected to solution and aging treatment. The results indicated that the solution treatment had little effect on the evolution of Al 2 O 3 film at the interface, and the shear properties at the interface with different reductions at 10−2 Pa were significantly improved after solution process, reaching the matrix level. However, Al 2 O 3 film at the interface primarily evolved to MgO and became an interface inclusion during the aging process, which significantly reduced the interfacial bonding effect at rolling reductions of 60% and 70% and the vacuum degree of 105 Pa and 10 Pa. When the rolling reduction was 80% and the vacuum degree was 10−2 Pa, the bonding interface disappeared completely without any impurity element aggregation as well as defects. And the shear properties at the aged interface could be entirely restored to the matrix level. Therefore, increasing the rolling reduction and the vacuum degree contributed to eliminate the negative effect of evolution products during solution and aging process on the healing of the interface. [ABSTRACT FROM AUTHOR]

As a commonly used engineering material, the mechanical properties of titanium alloy under dynamic loads are closely related to their microstructure. In this work, the effects of solution treatment (ST) and solution and aging treatment (SAT) on the microstructure and dynamic compressive properties of Ti–6Al–4V alloy manufactured by selective laser melting were studied. The results showed that the microstructure of selective laser melted Ti–6Al–4V consisted of nearly full acicular α′ martensite, then the acicular α′ martensite was decomposed into α+β phase with basket-weave morphology with solution treatment. Clusters of α 2 particles with size of several hundred nanometers were precipitated in the α plates further with solution and aging treatment. The ultimate compressive strength (UCS) of selective laser melted TC4 alloy was increased with the increasing strain rate, showing strong strain rate hardening effect. Stress collapse happened once the strain exceeded 1500/s, which is the dominant failure model of selective laser melted TC4 under impacting load. As expected, the UCS of the ST sample decreased, but the ductility increased compared with the as-built sample; however, both the UCS and ductility of the SAT samples were enhanced synergistically due to the widely distributed α 2 precipitates. Besides, the SAT samples had the highest energy absorption compared with the as-built and ST counterparts under the same conditions, indicating that the SAT samples had better load-bearing capacities. • Clusters of α 2 particles with size of several hundred nanometers were precipitated with solution and aging treatment. • Compressive testing with different strain rates were carried out on the SLMed TC4 alloy. • Both the compressive strength and ductility were increased with the increasing strain rate. • Compressive strength and ductility of the SAT samples were enhanced synergistically compared with the as-built sample. [ABSTRACT FROM AUTHOR]