Effect of combined treatment on the stability of austenite and the mechanical properties of chromium-manganese steels

The phase composition, the stablity of austenite with respect to the γ→α′ transformation under a load, and the mechanical properties in torsion of Cr−Mn steels 17Kh13G7S, 20Kh14G7, and 40Kh14G7 with metastable austenite after straining and heat treatment by various regimes are investigated. Methods for a combined treatment of Cr−Mn steels are suggested in order to provide a high level of their strength and ductility properties. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 18–21, January, 1997.     

Effect of the austenite stability on the fracture mode and mechanical properties of aging nonmagnetic alloys after different strengthening treatments

Aging austenitic alloys with a stable (N26Kh5T3; M _s < −196°C) and metastable (N25Kh2T3; M _s = −130°C) austenite have been investigated after employing different methods of heat and thermomechanical treatments, namely, (1) aging at a temperature T _a = 600°C (A); (2) strengthening using phase-transformation-induced hardening (“phase naklep” (PN)) and subsequent aging at T _a = 600°C (PN + A); (3) deformation to 30% (D) at T _d = 600°C after preliminary aging at the same temperature (A + D); and (4) PN + A + D. In this case, the alloy with stable austenite has not been strengthened by phase naklep. Structure, fracture mode, ultimate strength, yield strength, relative reduction of area, and relative elongation have been studied depending on the duration of aging τ_a upon these strengthening treatments. It has been established that the physicomechanical properties of the alloys depend not only on τ_a, but also on the testing temperature. It is shown that all above physicomechanical characteristics of the alloys under consideration are affected substantially by the austenite stability.     

Effect of residual austenite on properties of tool steel following shortened treatments in lower bainitic phase

Abstract

Recent investigations show the possibility of shortened low-cost treatment of chromium alloyed tool steels in the lower bainitic state. But with these treatments just above the martensite start temperature remains still an amount of residual austenite. For better understanding of the reactions due to the transformation of austenite into lower bainite metallographic, studies completed by dilatometric tests have been carried out. Structural characteristics due to applied heat treatment processes are discussed and special changes of specific properties are discussed by example of the steel 100Cr6 (SAE 52100).     

Increasing the stability of austenite by programmed loading

Conclusion The stability of austenite under strain can be increased by programmed loading in the temperature range where the stability of heated austenite is highest and the diffusion mobility of lattice defects is adequate. For some parts of austenitic steels (of the Kh18NI0T type) operating at low temperatures under stress, programmed loading can be used as the final treatment.Physicotechnical Institute of the Academy of Sciences, Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 71–72, June, 1970.     

逆转变奥氏体稳定性对中锰钢强韧性的影响

对淬火态中锰钢进行了不同温度的回火试验,研究了不同回火温度下逆转变奥氏体的含量和稳定性,及其对中锰钢强韧性能的影响.结果表明:当回火温度由630℃升高至670℃时,中锰钢室温组织中逆转变奥氏体体积分数由19％增加至42％,逆转变奥氏体稳定性不断降低;中锰钢的屈服强度由750 MPa降低至565 MPa,抗拉强度由845...     

临界退火冷却方式对含铌中锰钢奥氏体稳定性和力学性能的影响

针对含铌中锰钢进行了不同退火温度(700、750和800 ℃)和不同冷却方式(空冷、水冷)下的临界退火试验。结果表明,随着临界退火温度的升高,强塑积和残留奥氏体含量呈现先升高再降低的趋势。在750 ℃临界退火水冷后,试验钢的力学性能最佳,屈服强度达到750 MPa,抗拉强度为1820 MPa,断后伸长率为13.9%。随着临界退火温度升高,试验钢中渗碳体逐渐溶解,基体中C和Mn含量增多,在保温过程中配分进入奥氏体的C和Mn含量增多,导致奥氏体更稳定,残留奥氏体含量增多。当临界退火温度进一步升高,保温时奥氏体含量的增多导致配分进入奥氏体的C和Mn浓度降低,导致奥氏体稳定性降低,在冷却过程中形成大量马氏体。马氏体的增多和大尺寸团簇状(Nb,Mo)C的析出导致800 ℃临界退火后试验钢的高强度和低塑性。在相同临界退火温度下,水冷和空冷后试验钢的相组成相同。在800 ℃临界退火时,两种冷却方式对残留奥氏体含量和力学性能引起的差异最为明显,这与空冷过程中C和Mn向奥氏体配分更充分有关。     

Effect of austenite stability on the pitting corrosion resistance of cold worked stainless steels

The influence of cold rolling on the pitting resistance of stainless steels is investigated with respect to the austenite stability. A maximum in pitting initiation frequency for 20% reduction is confirmed whatever the austenite stability, but the value of this maximum fairly correlates to the amount of deformation-induced martensite. A direct influence of dislocations piling-up and an indirect role of martensite as a pile-up stabilizer is postulated. In the potentiostatic regime, cold work is shown to lower the repassivation ability and to increase the number of stable pits. Then, addition of alloying elements (such as copper) affects the pitting resistance not only for chemical but also for mechanical reasons (such as their effect on the staking fault energy and austenite stability), confirming the decisive role of microstructure in pitting corrosion of industrial alloys.     

Effect of the electrodeposition conditions on the morphology,composition and physicomechanical properties of Co-Mo-P alloys

By means of electron microscopy, EDX analysis, and tribotesting, there is found a correlation between the composition, morphology, and properties of Co-Mo-P alloy coatings deposited at direct current from a citrate electrolyte containing ammonium hypophosphite in a current density range of 1–15 A/dm², at temperatures of 28 and 60°C, and pH of 4–6. It is shown that the electrolyte pH increase from 4 to 6 leads to a decrease in the phosphorus content and to an increase in the molybdenum concentration in the electrodeposits. A direct correlation between the microhardness and the wear resistance of electrodeposits and the phosphorus content in coatings is shown.