Scandium Addition Research Articles

Drilling performance of Al-Ni eutectic alloy with scandium addition

Al-Ni eutectic alloys are an alternative alloy for high-temperature applications because of their excellent thermal stability of the Al3Ni eutectic fibers. Since the matrix of eutectic Al-Ni is weak, adding Sc to the alloy (Al-6Ni-0.4Sc) is able to increase its strength and hardness. This study is to investigate the machinability of Al-6Ni-0.4Sc alloy compared to Al-6Ni alloy through a drilling process. The results revealed that the Al-6Ni-0.4Sc alloy required less power, torque, and thrust force in the drilling process than Al-6Ni, despite having higher strength and hardness. The average specific energy for the drilling of Al-6Ni-0.4Sc alloy was 1.011 W s/mm3. This was 12.77% less than the value for Al-6Ni alloy. The chip velocity in the drilling of the alloy with Sc addition was twice that of the alloy without Sc, implying low heat accumulation in the cutting tool, less tendency for built-up edge formation, and a low wear rate on the drill’s rake face when drilling Al-6Ni-0.4Sc alloy.

Role of scandium addition to microstructure, corrosion resistance, and mechanical properties of AA7085/ZrB2+Al2O3 composites

The effect of varying amounts of scandium (Sc) on the mechanical performance and corrosion resistance of aluminum alloy (AA7085) composites reinforced with Zirconium diboride (ZrB2) and Aluminum oxide (Al2O3) nanoparticles was investigated. The specimens were made using an in-situ process with varying amounts of Sc up to 0.5 wt%, and their microstructural behavior, corrosion, and mechanical properties were explored in detail. Phase structural analysis revealed the successful incorporation of ZrB2 and Al2O3 into the matrix through in-situ synthesis, ranging from 30 to 61.7 nm. In addition, HRTEM and XRD analysis displays the Al3Zr prominence observed with 0.1 wt% Sc content, transforming to Al3(Sc, Zr) in the 0.3 wt% Sc composite, and finally becoming Al3Sc with 0.5 wt% Sc. Corrosion analysis revealed that the 0.3 wt% Sc composite exhibited fine Al3(Sc, Zr) precipitate phases that enhanced corrosion properties. The Sc addition leads to a significant improvement in the mechanical properties of AA7085/ZrB2+Al2O3 composites. The ultimate tensile strength of 678 ± 5 MPa for 0.5 wt% Sc under the hot rolled and T6 aged condition was achieved. The optimum content of Sc in AA7085/ZrB2+Al2O3 composites has identified both corrosion and mechanical properties enhancement at 0.3 wt% and 0.5 wt%, respectively.

Ageing Characteristics of Stir Cast AZ 61 Alloy with Minor Additions

Background: Knowing that magnesium (Mg) alloys and its composites bear the potential of being used simultaneously for light structural as well as biomedical applications, it appears prudent to look for developing a novel Mg alloy; the concurrent demand is to monitor recent trend in development of functional Mg-alloy and its composite materials through extensive patent search. Review of recent patents in the related field makes it relevant to investigate this aspect. Objective: The authors aim to study the evolution of structure and properties in stir cast of AZ- 61 alloy with minor additions of scandium, calcium and manganese. This paper reports the results of this investigation. Methods: The castings are prepared by stirring the molten alloy at 600 rpm for 10 minutes, followed by pouring into a preheated metal mould. The solidified alloys are homogenized at 550°C for 12 hours. The homogenized alloys are then subjected to solutionising treatment at 500°C for 5 hours; subsequently, the alloys are quenched in iced water. The quenched alloys are subjected to ageing treatment at different temperatures between 100°C to 400°C at an interval of 100°C. Similar experiments are conducted with its statically cast counterparts. The structure and properties of all the samples have been characterized by optical and scanning electron microscopy, and XRD analysis; DSC heating run is conducted to study the kinetics of phase transformation. Mechanical behaviour of castings is studied with the aid of tensile testing and fractography. Moreover, tribological behaviour of alloys is assessed by wear testing with the help of pin on disc method. Results: The results show that the stir cast alloy produces a homogeneous structure with significant improvement in properties. The precipitates of Mg17Al12, Al Mn, Mg Zn2, Al2 Ca and Mg2 Ca are formed due to the ageing of both stir cast and statically cast alloy. It is found that the diffusion of Al in magnesium controls the precipitation process. The tribological properties are found to be satisfactory for the stir cast alloy. Conclusion: The modified AZ61 alloy with minor additives, achieves excellent structural homogeneity and mechanical properties after stir casting followed by quench ageing.

Investigation of the Solid Solution Hardening Mechanism of Low-Alloyed Copper–Scandium Alloys

The addition of alloying elements is a crucial factor in improving the mechanical properties of pure copper, particularly in terms of enhancing its yield strength and hardness. This study examines the influence of scandium additions (up to 0.27 wt.%) on low-alloyed copper. Following the casting and solution-annealing processes, the alloys were quenched in water to maintain a supersaturated state. The mechanical properties were evaluated by tensile tests to measure the yield strength and the dynamic resonance method to determine the modulus of rigidity. Additionally, X-ray diffraction was utilized to analyze changes in lattice parameters, elucidating the structural modifications induced by scandium. This study dissects the parelastic and dielastic effects underlying the solid solution hardening mechanism, providing insights into how scandium alters copper’s mechanical properties. The findings align with the solid solution hardening theories proposed by Fleischer and Labusch, providing a comprehensive understanding of the observed phenomena.

Characterisation of a New Generation of AlMgZr and AlMgSc Filler Materials for Welding Metal–Ceramic Composites

When manufacturing the welded joints of components made of metal–ceramic composites of the Al-Si/SiC type, we encounter significant difficulties. This is related to the presence of a ceramic phase in the aluminium alloy matrix. The interaction between the molten metal matrix and the ceramic particles in the weld pool influences a complex of physicochemical phenomena resulting in, among other things, the structure of the welded joint. This is particularly true of the effect of the distribution of ceramic particles and their influence on the crystallisation process in the weld pool. An important issue is the influence of the reinforcing particles on the susceptibility of the aluminium matrix to both hot and cold cracking. The scope of the research included the development of the chemical composition of an additive material for the TIG welding of aluminium–ceramic composites. This material was made in the form of so-called sticks, cast from alloys containing elements such as magnesium, scandium or zirconium in addition to aluminium. The appropriate composition of the mass content of the individual components was intended to change the crystallisation mode of the weld pool and to obtain strengthening precipitates. The most favourable structure was obtained in the case of a modification of the AlMg5 alloy by the addition of scandium. Minor dispersions of Al3Sc became the nucleation pads of fine grains, which improved the mechanical properties of the alloy. Also, in the case of the addition of zirconium, the crystallisation shifted from dendritic to fine-grain growth. In this paper, the basic strength properties of the developed materials were tested and the most favourable chemical compositions of the filling materials were selected.

Enhancing electrochemical corrosion resistance in Al–6Ni alloys through trace Sc additions

Al–Ni-Sc alloys exhibit superior mechanical properties at both room and elevated temperatures, owing to the high thermal and chemical stability of Al3Ni microfibers, and Al3Sc nanoprecipitates. This study explores the impact of scandium additions (0.2 and 0.4 wt%) in eutectic Al–6Ni casting alloys and the influence of aging treatment on electrochemical corrosion behavior in a 0.05 M NaCl solution. Scandium addition did not alter the polarization curve direction but reduced the anodic current density, slowing corrosion. Scandium strengthened the passive film, evident in Electrochemical Impedance Spectroscopy (EIS) with higher Rp values. Sc addition influences the susceptibility to localized corrosion in Al–Ni alloys by promoting the coherence of passive films through the formation of Al3Sc nanoprecipitates and affecting the distribution of Al3Ni. XPS results show that as-aged Sc-containing increases the density of coherent Al3Sc nanoprecipitates, which could result in the formation of Sc2O3 film along with films like Ni2O3 and Al2O3. These synergistic effects contribute to improving the overall corrosion resistance with Sc additions subjected to aging treatment. The microgalvanic effects between the matrix and reinforcement phases, as a result of the formation of nobler Al3Ni and Al3Sc that serve as cathodes within anode Al matrix, cause severe pitting. Nevertheless, after aged treatment, the corrosion resistance dramatically drops for alloys with 0.2 wt% Sc and remains unchanged for 0.4 wt% Sc, due to higher density of nobler Al3Sc nanoprecipitates phase that can counteract the microgalvanic effects and lead to less extensive pitting than as-aged Al–6Ni-0.2Sc.

Изучение влияния содержания гафния и эрбия на формирование микроструктуры при литье алюминиевого сплава 1590 в медный кокиль

Introduction. High-magnesium aluminum alloys are widely used in the automotive, building and aerospace industries due to its low specific gravity and high strength. The characteristics of such alloys can be improved by small additions of scandium and zirconium. However, scandium is very expensive, so in new generation alloys its amount is tended to be reduced. In the recently developed 1590 aluminum alloy, this was achieved by addition of erbium and hafnium. The objective of the paper is to study the effect of erbium and hafnium concentrations on the modification of the cast structure in 1590 aluminum alloy at high solidification rates. Research Methods. The paper investigates the microstructure, chemical composition and size of intermetallic compounds in specimens from ten alloy 1590 modifications with different hafnium and erbium contents cast into a copper chill mold with a solidification rate of 10 °C/sec. The grain structure was studied using an optical microscope. The chemical composition and size of the intermetallic phases were studied using a Tescan Vega 3 scanning electron microscope. Results and discussion. It is established that as the amount of hafnium and erbium increases, the cast structure is modified. In general, grain refinement with the addition of hafnium and erbium can be explained by a higher degree of supercooling between the solid and liquid phases. At a hafnium content of 0.16 %, the dendritic structure begins to transform into an equiaxed grain structure. This transformation can be explained by the appearance of primary intermetallic compounds of the Al3Sc type in the liquid phase. Such intermetallic compounds are identified at a concentration of erbium and hafnium equal to 0.16 %. Moreover, in all alloys eutectic intermetallic compounds are identified that contained manganese and iron and had no effect on the cast structure. Comparison with previously obtained results on the grain size of specimens cast into a steel mold shows that with higher solidification rate, the structure modification in 1590 alloy is getting less efficient. This is explained by an increase in the concentration of transition elements in the solid solution, primarily scandium, necessary for the formation of primary intermetallic particles.

Improving thermal stability and creep resistance by Sc addition in near-α high-temperature titanium alloy

High-temperature titanium alloys’ thermal stability and creep resistance are significant during service in high temperatures. This study systematically investigated the thermal stability and mechanical properties of Ti-6.5A1–2.5Sn-9Zr-0.5Mo-1Nb-1W-0.3Si-xSc (x, 0–0.5 wt.%) at 650 °C. The lamellar secondary α phase is refined and the formation of Sc2O3 is increased with the increasing scandium (Sc) additions, which improves the strength of the alloy, while excessive Sc2O3 becomes the crack source and deteriorates the plasticity. The oxygen content in the matrix is reduced by the interaction between Sc and oxygen, inhibiting the growth of the Ti3Al phase and improving the thermal stability of the alloy. Meanwhile, Sc accelerates the dissolution of the residual β phase and precipitation of fine, diffusely distributed ellipsoidal silicides, which strongly prevents dislocation movement. The enhancement of creep resistance for the Sc-containing alloy is attributed to the refined lamellar secondary α phases, Sc2O3 particles, Ti3Al phase, and silicides, especially the precipitated silicides. Eventually, the 0.3Sc alloy shows optimal thermal stability (the plasticity loss rate 17.3%) and creep resistance (steady-state creep rate 4.4 × 10–7 s–1). The investigation results provide new insights into the mechanism and thermal stability improvement in high-temperature titanium alloys modified by rare earth (RE).

Examining the influence of Scandium interlayer and parameters on the mechanical behaviour in FSW of AA 5754-H111 plate through response surface approach

Friction stir welding (FSW) was conducted on 5754-H111 aluminium alloy using a response surface methodology to examine the impact of process parameters on the efficiency of the weld. The key FSW parameters were the percentage of scandium inclusion in the interlayer, tool rotational speed, and tool travel speed. The significant responses were identified as the tensile strength of the weld and the hardness in the weld zone. An Al-Mg-Sc alloy was employed as an interlayer material between the 5754 plates to enhance the strength in the weld zone. The addition of Scandium had a more pronounced effect on the hardness of the stir zone. The tensile strength was increased by raising the tool’s rotational speed. The results showed that the maximum tensile strength of the joints was 225 MPa and the hardness was highest at 118 HV1 in the weld stir zone. The introduction of Scandium improved the joint strength by producing fine grains and Al3Sc precipitates. The welding speed had the least impact on the tensile properties of the joint among all the variables investigated.

Wear and corrosion resistance of Al1.2CoCrFeNiScx high entropy alloys with scandium addition

The present study focuses on investigating the microstructure, hardness, wear, and corrosion resistance of Al1.2CoCrFeNiScx high entropy alloys, where the Sc content (x) varies between 0, 0.1, 0.2, and 0.3. The results indicate that the addition of Sc promotes the formation of the FCC phase and improves the hardness and wear resistance, but reduces the corrosion resistance of the alloy. The alloy's evolution can be observed as a transition from a single BCC phase to a combination of Fe, Cr-rich BCC phase, Al, Co, Ni-rich BCC phase, and Ni, Sc-rich FCC phase. As the Sc content increases from 0 to 0.3, the hardness increases from 438 HV to 581 HV, representing a 32.6 % increment. This increase can be mainly attributed to grain size strengthening and solid solution strengthening. Additionally, the average friction coefficient experiences a notable reduction from 0.999 to 0.574, indicating a 42.5 % decrease. With respect to wear resistance, the Al1.2CoCrFeNiSc0.3 alloy exhibits superior performance, demonstrated by its lower friction coefficient, reduced wear rate, and smaller volume, width and depth of wear marks. Furthermore, the addition of Sc to the Al1.2CoCrFeNiScx alloys leads to an overall decrease in corrosion potential, accompanied by an increase in corrosion current density, suggesting that Sc has a detrimental effect on the corrosion resistance of the alloy. Moreover, the Al1.2CoCrFeNi alloy displays pitting corrosion, while the Al1.2CoCrFeNiScx alloys demonstrate intercrystalline corrosion, which preferentially occurs on the Ni, Sc-rich phase due to the high electrochemical activity and low equivalent chemical potential.

Investigating the Effect of Heat Treatment on the Microstructure and Hardness of Aluminum-Lithium Alloys.

In this study, the effects of heat treatment on the microstructure and strength (micro-hardness) of an aluminum-lithium (Al-Li) base alloy containing copper (Cu) and scandium (Sc) were investigated, with a view to enhancing the alloy performance for aerospace applications. The heat treatment conditions were investigated to understand the precipitation behavior and the mechanisms involved in strengthening. Aging was carried out at temperatures of 130 °C and 150 °C for aging times of 1 h, 2.5 h, 5 h, 10 h, 15 h, 25 h, 35 h, and 45 h at each temperature for Al-Li alloy and at 160 °C, 180 °C, and 200 °C for aging times of 5 h, 10 h, 15 h, 20 h, 25 h, and 30 h at each temperature for Al-Li-Cu and Al-Li-Cu-Sc alloys. The investigation revealed that both solution heat treatment and artificial aging had a notable impact on strengthening the hardness of the alloy. This effect was attributed to the characteristics of the precipitates, including their type, size, number density, and distribution. The addition of copper (Cu) and scandium (Sc) was observed to have an impact on grain size refinement, while Cu addition specifically affected the precipitation behavior of the alloy. It led to remarkable changes in the number density, size, and distribution of T1 (Al2CuLi) and θ' (Al2Cu) phases. As a result, the hardness of the alloy was significantly improved after the addition of Cu and Sc, in comparison with the base Al-Li alloy. The best heat treatment process was determined as: 580 °C/1 h solution treatment +150 °C/45 h artificial aging for Al-Li alloy and 505 °C/5 h solution treatment +180 °C/20 h artificial aging for Al-Li-Cu and Al-Li-Cu-Sc alloys.

Effect of scandium on grain refinement mechanism and mechanical properties of Al–7Si–0.6 Mg alloy at different cooling rates

The effects of scandium (Sc) additions on the solidification microstructure and mechanical properties of Al–7Si–0.6Mg-0.25Ti alloy at different cooling rates have been systematically studied by thermal analysis and detailed SEM and TEM microstructure characterization of the castings. It is found that the addition of Sc has significant effects of refining the grain structure and modifying the Al–Si eutectics into fibrous structure. As a result, substantially improved strength and ductility in the as-cast state have been achieved in the Sc-added alloy. More importantly, the addition of Sc reduces the sensitivity of the alloy's strength and ductility to local cooling rates in the castings. The underlying mechanisms on the grain refinement, modification of Al–Si eutectics and strengthening by Sc addition have been studied. A new phase, DO22 structured (Al, Si)3(Ti, Sc), has been found to form in the liquid aluminium, acting as high potency nucleation sites of Al grains, which overcomes the Si poisoning effect on grain refinement for Al–Ti–B grain refiners.

Influence of scandium addition on microstructure and mechanical properties in nickel-based superalloys: An integrated multiscale modeling and experimental approach

Microalloying has long been recognized as an effective method for improving the mechanical properties of metallic materials and developing new ones. In this study, we comprehensively investigate the effects of Sc addition on the microstructural evolution and mechanical performance of nickel-based superalloys using a combination approach of the experiment, first-principles calculation, and multiscale modeling. The results show that Sc addition simultaneously improves the yield strength increasing from 1068 MPa to 1172 MPa (9.7%) and elongation increasing from 13.4% to 19.7% (47%). The microstructural characterizations reveal that Sc addition refines the grain size, increases the volume fraction of primary precipitate, induces the coarsening of secondary precipitates, and produces a new type of Sc-rich particle. First-principles calculations from the atom probe tomography experiment show that the anti-phase boundary energy of secondary precipitate is significantly increased in Sc-containing superalloys. A modified alloying-dependent yield strength model is developed by considering the multimodal precipitate size distribution and microstructure evolution obtained from experiments and atomic simulations. The increased yield strength originates from not only the Sc addition induced increased volume fraction of primary precipitate at grain boundary to enhance grain boundary strengthening, but also Sc addition induced increased anti-phase boundary energy of secondary precipitate to improve the precipitate strengthening. The increased elongation depends on the fact that the Sc element has a good affinity to deleterious elements and forms Sc-rich particle and oxygen-rich precipitate to enhance grain boundary strength. This work integrating multiscale modeling and experiment can be denoted as a universal framework to study the influence of alloy element on the microstructure and properties, which gives guiding significance to screen and design high-performance superalloys.

Effect of a Small Addition of Scandium on the Phase Composition and Properties of Wrought Al–Cu–Er–Mg–Mn–Zr Alloy

Effect of a Small Addition of Scandium on the Phase Composition and Properties of Wrought Al–Cu–Er–Mg–Mn–Zr Alloy

The Structure and Mechanical Properties of Rolled Sheets of the Multicomponent Al–2.5Ca–2.5Mg Alloy Doped with Scandium and Zirconium

Using the Al–2.5% Mg–1% Mn–0.4% Fe base alloy (wt %) as an example, the effects of calcium, scandium, and zirconium additives (at about 2.5, 0.1, and 0.2 wt %, respectively) on the strength of rolled sheets has been studied. Ingots of the alloy of the chosen composition and the hot and cold rolled sheets obtained from them were used as objects for the experimental study. Based on microstructural studies, it isshown that calcium binds iron into compact inclusions (presumably, into the Al10CaFe2 phases), which has a positive effect on the mechanical properties of the alloy, as well as on the technological plasticity during therolling operation. Zirconium and scandium additives make it possible to form thermally stable nanoparticles of the Al3(Zr, Sc)–L12 phase, which is favorable for maintaining a partially unrecrystallized structure in coldrolled sheets during annealing at least up to 400°C. Using the alloy of the selected composition as an example, the fundamental possibility for producing sheet products from cast (unhomogenized) ingots with the properties of thermally hardenable alloys of the AlSiMgMn and AlZn4.5Mg1.5Mn types without using quenching has been demonstrated.

Investigation on the Microstructure and Mechanical Properties of Ni-Based Superalloy with Scandium

In this work, a method concerning thermal consolidation is proposed to simulate the traditional powder metallurgy process and accomplish the composition screening of powder metallurgy Ni-based superalloys U720Li and RR1000 with rare metal scandium, and superalloys with zero scandium addition, medium scandium addition and high scandium addition are selected. Then effects of scandium on the microstructure and mechanical properties of superalloys are further investigated through fast hot pressed sintering. The results indicate that scandium doping can effectively refine the grain through modifying the size and volume fraction of primary γ’ precipitates at the grain boundary. Meanwhile, scandium can promote the growth and precipitation of secondary γ’ precipitates to some extent. Due to the comprehensive effects of γ’ precipitate modification and grain boundary strengthening, as-sintered U720Li with 0.043 wt.% scandium presents an excellent combination of tensile strength and ductility at ambient and elevated temperature while as-sintered RR1000 with 0.064 wt.% scandium has a good performance at elevated temperature.

The effect of minor scandium addition on microstructure evolution and mechanical properties of spray formed Al-Zn-Mg-Cu alloy

In this investigation, both Scandium (Sc)-added and Sc-free Al-Zn-Mg-Cu aluminum alloys were prepared by spray forming. The as-deposited alloys were hot extruded and then subjected to solid solution and aging treatment at different temperatures. The effect of minor scandium addition on microstructure evolution and mechanical properties were studied. The results revealed that, with Sc added spray formed alloy (7055Sc alloy), Sc element was mainly observed in the primary Al3(Sc,Zr) phase, the secondary Al3(Sc,Zr) phase and the W(AlCuSc) phase in the alloy. Compared to the alloy without Sc addition (7055 alloy), the effects of fine grain strengthening, dislocation strengthening and precipitation strengthening of Al3(Sc,Zr) phase were enhanced. At low aging temperature, the precipitation of MgZn2 phase was inhibited and the size of this phase was found large in the 7055Sc alloy. Therefore, after 120 °C for 24 h aging, the yield strength of 7055Sc alloy was tested as 603.4 MPa, which was 46.9 MPa lower than that of 7055 alloy at the same aging temperature. After 160 °C for 24 h aging, in the 7055Sc alloy the quantity and density of MgZn2 phase increased and the size of the phase was smaller. As a result, the yield strength of the 7055Sc alloy was 576.9 MPa, which was 31.6 MPa higher than that of the 7055 alloy. The effects of Sc on the aging precipitation of spray formed 7055Sc alloy at different aging temperatures were explained by the vacancy mechanism of diffusion.

Study on microstructure and mechanical properties of RSW joints of 7075T-6 containing Sc

Currently, resistance spot welding (RSW) is a common welding method used in automobile and other industries, and 7000 series aluminum (Al) alloys have become a very common industrial material because of their high strength and easy machinability. Scandium (Sc) is often used for alloy strengthening; however, there are few studies on the RSW joints of aluminum alloys containing scandium. Here, 7075-T6 alloys containing a small amount of scandium were obtained to investigate the joint of resistance spot weldability. The simulation shows that the effective contact area between the aluminum sheet surface is about 19.5%, which is an important factor in nucleation. It was found that the average grain size of the nugget decreased from 51.51 ± 5.74 to 8.15 ± 1.09 μm when scandium was added from 0 to 0.4 wt%, which is mainly due to Al3Sc particles acting as a heterogeneous nucleus in the melt. The test results show that the tensile shear strength of welded joints with 0.4 wt% scandium addition is 29.2% higher than that of the joints without scandium because of grain refinement strengthening.

Effects of Sc and Zr Addition on the Mechanical Properties of 7000 Series Aluminum Alloys

Scandium addition to aluminum alloys has been evaluated at various research institutions, and it is known that the Al3Sc precipitates effectively increase their strengths. In this study, the effect of Sc addition on the strengths of two types of 7000 series aluminum alloys was investigated. As a result, the strength increased by the Sc addition to both types of alloys, but the increased amounts were limited to 10–40 MPa. It was considered that because the strengthening effect by the η′ phase was sufficiently high, the precipitation strengthening by the dispersion of Al3(Sc1−xZrx) particles was relatively low in these alloys.

Thermal treatment effect on the mechanical properties of 1570, 1580 and 1590 aluminum alloys

The study addresses the effect of thermal treatment on the mechanical properties and grain size of magnesium rich alloys with small scandium additions 1570, 1580 and 1590. The effect of preheat temperature (within 260440 С range) and soaking time (within 2 100 hours range) on yield strength, tensile strength and relative elongation of the alloys under investigation was analyzed. Mechanical properties were determined using uniaxial tensile tests in accordance with ISO 6892-1. In addition, for some modes the microstructure was studied for Al3Mg2 -phase presence and distribution by optical metallography methods depending on thermal treatment conditions. The studies demonstrated that supersaturated solid solution in the 1570 alloy decomposes faster in the entire studied temperature range, and after 48 hours soaking, its strength properties start degrading. At the same time, the 1580 and 1590 alloys are much more thermally stable, with slightly lower yield strength after long soaking time, while tensile strength remains unchanged. The conditions of 260 C annealing temperature are not favorable for plastic properties, severely degrading (due to -phase formation) in the 1570 and 1580 alloys. Plastic properties degradation is not so evident at higher soaking temperature, however, the 1590 alloy maintains the highest plasticity indices.