Effect of heat treatment on the relaxation resistance of the KhN77TYu alloy

Conclusions Double heat treatment consisting of quenching from 1050–1080°C in air and tempering for 16 h in air at 750°C provides the highest resistance to relaxation in the KhN77TYu alloy.Central Scientific Research Institute of Ferrous Metallurgy Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 60–63, January, 1966     

Thermally Stable Aluminum-Lithium Alloy 1424 for Application in Welded Fuselage

Sheets of Al – Li alloy 1424 have high fracture toughness and diminished rate of fatigue crack growth, high corrosion resistance, and excellent weldability. The chemical composition and the regime of the hardening heat treatment of alloy 1424 are shown to provide good thermal stability of the sheets with respect to fracture toughness (K _c ^f) and growth rate of fatigue cracks (GRFC) after a hold of up to 3000 h at 85°C. These characteristics decrease only after a hold of 4000 h and only in the L – T direction. The suggested process for manufacturing sheets diminishes the anisotropy of the strength characteristics and the elongation due to the formation of a partially recrystallized structure.     

Isothermal treatment of alloy KhN35VT

Conclusions Isothermal treatment of alloy KhN35VT results in a long-term strength and, particularly, long-term plasticity at 650°C that are higher than after standard heat treatment, and short-term characteristics that are somewhat lower.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 35–37, July, 1971.     

Effect of heat treatment on the properties of deformed alloy 36N

Iron-nickel alloy 36N (Invar) is widely used in industry as a material having an anomalously low and almost constant thermal coefficient of linear expansion (TCLE) in the temperature range of 20 – 100°C. This value of the coefficient is attained after heat treatment of the deformed semifinished product by the regime of quenching from 830°C in water, tempering at 315°C for I h, and aging at 95°C for 48 h. The minimum value of the TCLE is provided by the quenching operation, whereas the tempering and aging prevent growth of the TCLE during long-term operation of Invar. The use of such heat treatment for rods and wire of alloy 36N guarantees a TCLE of at most 1.5 × 10^–6 °C^–1. It is known that the value of the TCLE and the level of the mechanical properties of Invar can be changed by changing the temperature and deformation regime of its treatment. The aim of the present work is to determine an optimum regime of heat treatment of the alloy after drawing that would ensure, without a finishing treatment, a TCLE not exceeding 1.0 × 10^–6 °C^–1 in the temperature range 20 – 100°C.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 31 – 32, April, 1996.     

Improvement of the technological plasticity of KhN56VMTYu-VD alloy

Conclusions The maximum technological plasticity of the KhN56VMTYu-VD alloy in the two-phase state is achieved after heat treatment by the following method: hardening at 1120°C (2 h) in air+aging at 975°C (2 h) with cooling in water.Kulebaksk S. M. Kirov Metallurgical Plant. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 40–42, March, 1981.     

Effect of TiN/Ti composite coating and shot peening on fretting fatigue behavior of TC17 alloy at 350 °C

A TiN/Ti composite coating has been prepared on a TC17 titanium alloy substrate by an ion-assisted arc deposition (IAAD) technique with a view to improving the fretting fatigue resistance of the titanium alloy at 350 °C. The composition distribution, bonding strength, micro-hardness, ductility, tribological properties, and fretting fatigue resistance at elevated temperature of the coating have been investigated. The results indicate that the IAAD technique can be used to prepare a TiN/Ti composite coating with high hardness, good ductility, excellent bonding strength, and high load-bearing capability. The TiN/Ti composite coatings can improve the resistance to wear and fretting fatigue of the Ti alloy, as manifested in its excellent tribological behavior at 350 °C. However, the fretting fatigue resistance of the titanium alloy treated by shot peening (SP) combined with IAAD TiN/Ti coating post-treatment was lower than that by IAAD TiN/Ti coating or SP alone, because the compressive residual stress induced by SP was significantly relaxed during coating process and the coating easily cracked and broke off.     

Effect of heat treatment on tensile and fatigue deformation behavior of extruded Al-12 wt%Si alloy

This study investigated the effect of heat treatment on tensile and high-cycle fatigue deformation behavior of extruded Al-12 wt%Si alloy. The material used in this study was extruded at a ratio of 17.7: 1 through extrusion process. To identify the effects of heat treatment, T6 heat treatment (515 °C/1 h, water quenching, and then 175 °C/10 h) was performed. Microstructural observation identified Si phases aligned in the extrusion direction in both extruded alloy (F) and heat treated alloy (T6). The average grain size of F alloy was 8.15 °C, and that of T6 alloy was 8.22 °C. Both alloys were composed of Al matrix, Si, Al₂Cu, Al₃Ni and AlFeSi phases. As T6 heat treatment was applied, Al₂Cu phases became more finely and evenly distributed. Tensile results confirmed that yield strength increased from 119.0 MPa to 329.0 MPa, ultimate tensile strength increased from 226.8 MPa to 391.4 MPa, and the elongation decreased from 16.1% to 5.0% as T6 heat treatment was applied. High-cycle fatigue results represented F alloy’s fatigue limit as 185 MPa and T6 alloy’s fatigue limit as 275 MPa, indicating that high-cycle fatigue properties increased significantly as heat treatment was conducted. Through tensile and fatigue fracture surface analysis, this study considered the deformation behaviors of extruded and heat treated Al-Si alloys in relation to their microstructures.     

Heat treatment of large forgings of titanium alloy VT3-1

Conclusion The optimal heat treatment for large forgings of alloy VT3-1 consists of heating at 870° for 2 h, air cooling, heating at 650° for 2 h, and air cooling.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 65–66, June, 1977.     

Effect of heat treatments on the tensile strength and SCC-resistance of AA7050 in an alkaline saline solution

Effect of heat treatments (namely T6, T73, RRA, OP1 and OP2) on the tensile strength (TS) and stress corrosion cracking (SCC) resistance of aluminum alloy 7050 in 3.5% NaCl solution at pH 12 has been investigated using constant extension rate tester (CERT). T6 increases the TS but decreases the SCC-resistance. To the opposite, T73 (i.e., T6 + 160 °C/30 h) increases the SCC-resistance but decreases the TS. Retrogression and re-aging (RRA, i.e., T6 + 200 °C/10 min + water quench + 120 °C/24 h) increases both TS and SCC-resistance but this treatment confines only to thin and small specimens. Step-quench aging (SQA, i.e., 470 °C/1 h + step-quench to 200 °C/1 min + water quench/or air cooling + natural aging at room temperature/1 week + 120 °C/24 h) provides a relatively practical treatment to enhance both the TS and SCC-resistance even the specimen either having quenched in water (OP1) or cooled in the air (OP2) in the process. Through electrochemical testing and micro-structural examination, we found that both the TS and SCC-resistance of AA7050 is governed by the microstructures that depend on heat treatments.     

Mechanical properties and thermal stability of Ti−Zr−Al alloys with an elevated oxygen content

Conclusions Alloy AK3 of the optimal composition has high thermal stability and ductility. The strength at 500°C is comparable with the long-term strength of mass-produced titanium alloys. The fatigue strength of the alloy is fairly high despite the elevated oxygen content.A. A. Baikov Institute of Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 9–10, October, 1973.     

Heat treatment of cast aluminum alloys obtained by application of regulated pressure during crystallization

conclusion For castings of AK8 alloy obtained by application of regulated pressure during crystallization, we recommend the following heat treatment conditions: homogenization at 460–470°C for 8 h, quenching from 505–510°C, aging at 150–170°C for 3.5–4h. After treatment according to this procedure, a hardness of 72–74 HRB is achieved for the alloy.Vladimir Polytechnical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 36–39, October 1992.     

Process Recycling and Environmental Treatment

A useful coating technology for electroless Ni-1.5wt%P has been developed. The bath can work normally for more than 5 turnovers with a plating rate of 20 μm/h. In the as-deposited condition, Ni-1.5wt%P deposit is a supersaturated solid solution of P dissolved in a nanocrystalline Ni matrix with a grain size of several nanometers. The microstructure transformed into a larger grain size Ni matrix with dispersive Ni₃P precipitates with increasing the heat treatment temperature. Ni-1.5wt%P deposit possesses as-deposited hardness and wear resistance superior to Ni-10.5wt%P deposit. The microhardness and wear resistance can be further improved by proper heat treatment. The optimum wear resistance of Ni-1.5wt%P deposit corresponds to its peak hardness (annealing at 375°C for 1 h), whereas for Ni-10.5wt%P deposit the optimum wear resistance is obtained after annealing at 650°C for 1 h. Ni-1.5wt%Ppossesses a corrosion resistance in NaOH solution superior to conventional medium and high phosphorus deposits, which have much better corrosion resistance in NaCl and HCl solution. The rotating fatigue results indicate that electroless nickel deposits cause a decrease in the fatigue strength of 30CrMo steel, and increase the fatigue strength of LY12 alloy. Ni-1.5wt%P deposit demonstrates higher fatigue resistance than Ni-10.5wt%P deposit.     

Effects of heat treatments on microstructure and mechanical properties of Mg-11Y-5Gd-2Zn-0.5Zr (wt.%) alloy

The microstructure and mechanical properties of Mg-11Y-5Gd-2Zn-0.5Zr (wt.%) (WGZ1152) alloy during different heat treatments were investigated. Almost all the Mg₂₄(GdYZn)₅ eutectic phases dissolved into the α-Mg matrix after solution treatment at 535 °C for 20 h. After ageing at 225 °C for 24 h (T6 state), a great amount of fine β′ precipitates formed. Both the 18R-type long period stacking ordered (LPSO) Mg₁₂YZn phase and 6H′-type LPSO phase exhibit good thermal stability during the high-temperature heat treatments process. The 18R-type LPSO Mg₁₂YZn phases are much harder than α-Mg matrix and have a volume fraction of ∼16%. The ultimate tensile strength at the room temperature of the peak-aged alloy (T6 state) is 307 ± 6 MPa and elongation is 1.4 ± 0.3%. The alloy in T6 state shows anomalous positive temperature dependence of the strength from room temperature to 250 °C, and maintains a strength of more than 260 MPa up to 300 °C (0.64T_m). The excellent strength of the WGZ1152 alloy at both room and elevated temperatures is mainly attributed to the solid solution strengthening, β′ precipitates strengthening and LPSO strengthening. Slip line observations suggest a transition from basal to non-basal slip with increasing temperature.     

Effect of boron on microstructure and mechanical properties of thermomechanically processed near alpha titanium alloy Ti-1100

The effect of 0.2 wt.% of boron on the mechanical properties of Ti-1100, a near α titanium alloy, was evaluated at room temperature and at 600 °C in the as cast and thermomechanically processed (α-β rolled) condition after subjecting it to different heat treatments. Boron addition in Ti-1100 significantly refined the microstructure in the as cast condition but the mechanical properties did not show any improvement. However, in the thermomechanically processed (α-β rolled) and standard heat treatment condition, the yield strength (YS) and ultimate tensile strength (UTS) of the boron containing alloy increased significantly without any drop in elongation-to-failure as compared to the base alloy at both room temperature and 600 °C. No discernible trend was seen in YS and UTS in boron containing alloy with change in solution treatment temperature either at room temperature or at 600 °C.     

Roles of temperature and humidity in the oxidation of sputter-deposited Cu-Ta alloys in air

Oxidation behavior of a series of Cu-Ta alloys prepared by co-deposition of RF sputtered pure copper and tantalum was studied in air. Alloy composition, oxidation temperature and relative humidity (RH) ranges examined were 5-69 at.% Ta (alloys with 22-69 at.% Ta were amorphous), 40-85°C and 20-70%, respectively. Although Cu-58at.%Ta alloy showed no apparent change, some of the alloys exposed to an air at 70°C and RH=70% for 60 h showed change in color. The Cu-5at.%Ta alloy showed bright blue, and alloys with 10-30 at.% Ta were all turned to reddish color by oxidation. Among the alloys examined, Cu-24at.%Ta alloy showed the highest oxidation rate under the above condition. The in-depth profiles of Cu-24at.%Ta alloy specimens oxidized for 6-60 h in the air of 70°C and RH=70% indicated existence of metallic Cu-layer on the top of Ta-rich oxide layer and Cu-enriched alloy layer under the oxide film. The metallic copper layer must be caused by diffusion of metallic copper from the Cu-enriched alloy layer to the top of the surface similarly to the oxidation of Cu-Zr alloys at room temperature in a laboratory air. Even Cu-Ta alloys which show very high corrosion resistance in HCl solutions does not always have high corrosion resistance to oxidation in air because of difference in surface film formation process and the resulting compositions and film structure.     

Effects of heating temperature and duration on the microstructure and properties of the self-healing coatings

The present work investigates how the heating temperature and duration affect the properties of the self-healing coating on martensitic steels. The coating composed of TiC + mixture (TiC/Al₂O₃) + Al₂O₃ is fabricated by means of air plasma spraying. The thermal shock test is performed at 600 °C, 700 °C and 800 °C, respectively, to evaluate the thermal-mechanical stability of the coating. The cross-section morphology of the samples after 1 h, 9 h, 18 h and 30 h of heat treatment shows that the porosity of the coating decreases with the increase of heating duration. The evaluation of electrochemical performance by electrochemical impedance spectroscopy shows that the corrosion resistance of the coating after being heated for 18 h is much better than the other samples due to the process of the inner layer being compacted in the coating. The adhesive tensile strength test between coating and substrate shows that the adhesive strength of the coatings is higher than 9 MPa within 40 h of heat treatment at 600 °C. The residual stress reaches a minimum value after the coating was heated for 9 h at 600 °C, then increases with the heating duration after 9 h. Energy dispersive X-ray analysis at the Vickers indentation indicates that the oxygen content at the crack position increases significantly after being heated for 30 h at 600 °C. These experimental results suggest that this coating can meet the requirement of application under the actual temperature conditions.     

Oxidation kinetics of an Fe-31.8Mn-6.09Al-1.60Si-0.40C alloy at temperatures from 600 to 900 °C

An Fe-31.8Mn-6.09Al-1.60Si-0.40C alloy was subjected to thermogravimetric tests, in atmospheres of pure oxygen and synthetic air. The alloy showed good oxidation resistance, especially at 600 and 700 °C in air and at 600 °C in oxygen. Owing to autocorrelation identified in the results, kinetic data were analyzed by the statistical method of Cochrane and Orcutt. Parabolic kinetic behaviour was observed for the Fe-Mn-Al-Si-C alloy oxidation process in air at 600, 700 and 800 °C and in pure oxygen at 900 °C.     

Corrosion behaviour of garnet particulate reinforced LM13 Al alloy MMCs

This paper describes a study of the corrosion characteristics of LM13 Al alloy-based composites reinforced with various amounts of garnet particulates. The weight loss method was used and the corrodent was 1 M HCl solution at room temperature. The durations of the tests ranged from 24 to 96 h. Corrosion tests were performed on the unreinforced matrix alloy as well as on the various composites in both heat-treated and as-cast conditions. In each test, the corrosion rates of the unreinforced matrix alloy and the composites were found to decrease with duration of exposure to the corrodent. Solution heat treatment at 525°C followed by artificial aging at 175°C was found to improve the corrosion resistance of every specimen tested. Corrosion resistance was also found to improve with increase in garnet content. An attempt is made in the paper to explain these phenomena.     

热加工和后处理对Ti-6Al-4V合金显微组织和拉伸性能的影响

研究了热压缩、热轧制和后续轧制退火处理对Ti-6Al-4V合金显微组织和拉伸性能的影响。热压缩实验在温度800~1075°C和应变速率0.001~1s-1下进行,得到了流变曲线与加工过程参数之间的关系。然后,样品在温度800~1070°C和恒应变速率2s-1下进行2道次热轧制,总变形量为75%。热轧后,样品分别在870°C和920°C下保温热处理2h,随后空冷。在β相区的热轧导致粗大的β相冷却时转变为马氏体相,而在α/β两相区的热轧会导致生成部分球化的α相组织。后续的热轧处理能使在两相区部分球化的α相得以完成球化,然而,在β相区轧制的样品会导致马氏体结构被破坏。拉伸实验表明,随着轧制温度从两相区升高到单相区,合金的强度及伸长率会显著降低。升高热处理温度会降低两相区轧制合金的强度性能,而在β相区轧制合金的强度会得到提高。