A principle for producing metastable austenite and controlling its amount and stability in the development of rationally alloyed alloys and strengthening treatments

It is known that martensite can form from austenite in deformation. This has been widely used in strengthening treatment of austenitic steels in the stage of preparing final products. Alhough many publications are devoted to the investigation of metastable austenite, they concern mostly the improvement of the properties of metastable austenitic steels. This article shows the possibility of improving the properties of steels and cast irons of other structural classes by forming a structure of metastable austenite in them. A principle is suggested for the development of new steels on the basis of metastable austenite.     

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 austenitizing temperature on the mechanical properties of steel after standard and thermomechanical treatments

Conclusions An increase of the austenitizing temperature with TMT of secondary-hardening steel 40Kh5MVFS, as in the case of SHT, increases the strength up to a certain limit. The negative influence of the increase in the austenite grain size on the ductility of the steel is smaller in the case of TMT than in SHT.Central Scientific-Research Institute of Ferrous Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 24–27, December, 1969.     

分级时效对Al-Cu-Li-Mg-Mn-Zr合金微观组织与性能的影响

通过合金室温力学性能测试及时效组织的透射电镜分析,研究了分级时效对Al-Cu-Li-Mg-Mn-Zr合金显微组织与性能的影响.结果表明,经过先低温后高温的三级时效可使合金获得比T6处理更高的强度,且随着第二级时效时间的延长,合金抗拉强度和屈服强度逐渐提高.采用先高温后低温二级时效,可获得较先低温后高温三级时效更高的力学性能,且其强度随第一级高温时效时间的延长而增加,达到T8峰时效的强度水平.合金在先低温后高温时效时,在100℃低温预时效形成GP区,在140℃析出弥散细小的δ'、θ'和T1相并稳定下来,然后在175℃进一步析出长大,从而提高了合金强度.当合金在先高温后低温二次时效时,高温欠时效析出δ'和T1等强化相,然后在140℃较低温度二次析出大量细小弥散的δ'相,产生二次强化效果.     

Thermal stability and mechanical properties of Gd-Co-A1 bulk glass alloys

The glass forming ability of Gd-Co-A1 ternary alloy systems with a composition ranging from 50% to 70% （molar fraction） for Gd and from 5% to 40% （molar fraction） for AI were investigated by copper mold casting and Gd60Co25Al15 bulk glass alloy cylinders with the maximum diameter of 5 mm were obtained. The reduced glass transformation temperature （TG/Tm） and the distance of supercooling region ATx are 0.616 and 45 K, respectively for this Gd-Co-A1 alloy. The compressive fracture strength （σf） and elastic modulus （E） of Gd-Co-A1 glassy alloys are 1 170-1 380 MPa and 59-70 GPa, respectively. The Gd-AI-Co bulk glassy alloys with high glass forming ability and good mechanical properties are promising for the future development as a new type function materials.     

Microstructure and mechanical properties of Fe3Al-based alloys with strengthening boride precipitates

Five quaternary Fe–Al–B–M (M = Ti, Hf, Zr, V, W) alloys based on Fe₃Al with strengthening boride precipitates were produced by vacuum induction melting. The alloys were investigated with respect to their microstructure and mechanical behaviour up to 1000 °C. The mechanical properties were determined by tensile tests, 4-point-bending tests, high-temperature compression tests up to 1000 °C as well as creep tests at 650 and 750 °C. Microstructural and phase analysis were carried out by light optical microscopy, scanning electron microscopy, X-ray diffraction analysis and differential thermal analysis. The alloys were tested in the as-cast state, after homogenisation at 1200 °C for 48 h and after annealing at 800 °C for 624 h. Compared to a corresponding binary alloy the examined alloys exhibit significantly improved mechanical high-temperature properties as well as stable microstructures without considerable loss of ductility.     

Si对超高强钢残留奥氏体回火稳定性与力学性能的影响

采用XRD、TEM等实验方法研究了Si含量对超高强钢回火过程残留奥氏体稳定性及其力学性能的影响.结果表明,Si对抑制回火脆性和提高回火抗力具有有益作用;Si抑制残留奥氏体的分解,随Si含量提高,回火过程逐渐出现逆转奥氏体;Si对提高碳分配作用显著,可增强残留奥氏体的稳定性.马氏体板条内部,Si与C原子相互排斥;而奥氏体内Si与C相互吸引.发现1.8%Si钢250℃回火后出现ε-碳化物;400℃回火后ε-碳化物明显粗化,导致回火脆性.对0.4%Si钢而言,导致回火脆性的是回火后出现的大量针状或长条状碳化物,确定这类碳化物为非ε-碳化物.探讨了Si对回火过程残留奥氏体分解及逆转奥氏体形成的作用机理.     

Effects of Ti addition and heat treatments on mechanical and electrical properties of Cu-Ni-Si alloys

The mechanical and electrical properties of Cu-5.98Ni-1.43Si and Cu-5.98Ni-1.29Si-0.24Ti alloys under heat treatment at 400 and 500 °C after hot- and cold-rolling were investigated, and a microstructural analysis using transmission electron microscopy was performed. Cu-5.98Ni-1.29Si-0.24Ti alloy displayed the combined Vickers hardness/electrical conductivity value of 315.9 Hv/57.1%IACS. This was attributed to a decrease of the solution solubility of Ni and Si in the Cu matrix by the formation of smaller and denser δ-Ni₂Si precipitates. Meanwhile, the alloyed Ti was detected in the coarse Ni-Si-Ti phase particles, along with other large Ni-Si phase particles, in Cu-5.98Ni-1.29Si-0.24Ti.