Transformation of austenite in Fe-Cu alloys. I: Kinetics of the transformation

The kinetics of autstenite decomposition in a hypereutectoid Fe-5.5% Cu alloy has been studied. Unusually large n values in the Avrami equation have been noted when using it for the approximation of experimental dependences. An explanation of this feature is given based on the hypothesis of a two-stage decomposition of the γ phase. An accelerating effect of hot plastic deformation on the austenite decomposition has been demonstrated.     

Transformation of austenite in Fe-Cu alloys. II: Kinetics of a two-stage transformation of austenite in the Fe-5.5% Cu alloy

The decomposition of austenite in the hypereutectoid Fe-5.5% Cu alloy has been considered as a complex process that includes the precipitation of ε-phase particles and a eutectoid transformation, during which particles of a granular pearlite are nucleated. The theory of the growth of particles has been considered, and the kinetic equations for each stage of the austenite transformation have been introduced.     

Transformation of supercooled austenite in now-alloy steel 16GFR during continuous cooling

Conclusions A C–C–T diagram was plotted for steel 16GFR, which makes it possible to predict with adequate reliability the character of the structure formed during cooling of pipe at given rates under plant conditions and thus to correct the heat-treatment process for pipe made of steel 16GFR with strength _b=720 MPa and guarantee the mechanical properties and cold resistance required.Institute of Ferrous Metallurgy, Dnepropetrovsk. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 54–56, July, 1981.     

高性能桥梁钢Q370qE-HPS过冷奥氏体连续冷却相变行为

利用Gleeble 1500D型数控动态热-力学物理模拟试验机,针对新近研发的Q370q E-HPS高性能桥梁钢进行了过冷奥氏体连续冷却相变行为研究。结果表明,当冷却速度小于5℃/s时,形成铁素体+珠光体组织,当冷却速度在8℃/s~15℃/s时,形成针状铁素体+贝氏体组织。Q370q E-HPS高性能桥梁钢铁素体转变温度区间为700~800℃,贝氏体转变温度区间为550~700℃,与传统正火工艺桥梁钢Q370q E相比较,Q370q E-HPS钢转变开始温度高。Q370q E-HPS钢两阶段变形后的冷速≤5℃/s时形成均匀细小的铁素体+珠光体组织,可作为控冷阶段的参考冷速。     

Isothermal decomposition of the austenite of P/M steels alloyed with chromium and molybdenum

Perm' Polytechnic Institute, The Republic Engineering and Technical Center for Powder Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 28–33, August, 1992.     

Thermal stability of retained austenite in TRIP steels studied by synchrotron X-ray diffraction during cooling

We have performed in situ X-ray diffraction measurements at a synchrotron source in order to study the thermal stability of the retained austenite phase in transformation induced plasticity steels during cooling from room temperature to 100 K. A powder analysis of the diffraction data reveals a martensitic transformation of part of the retained austenite during cooling. The fraction of austenite that transforms during cooling is found to depend strongly on the bainitic holding time and the composition of the steel. It is shown that that austenite grains with a lower average carbon concentration have a lower stability during cooling.     

0.6Ni中碳合金钢的奥氏体连续冷却转变行为

通过热模拟试验、光学和扫描电镜(SEM)观察以及维氏硬度测试,研究了0.6Ni中碳合金钢的动态和静态奥氏体连续冷却转变规律,分析了变形以及合金元素Ni对中碳合金钢奥氏体转变行为的影响。结果表明:奥氏体变形有效抑制了0.6Ni中碳合金钢连续冷却后铁素体和珠光体的形成,大幅促进了贝氏体和马氏体相变,将全马氏体临界冷速由5 ℃/s降低到3 ℃/s。试验钢在动态连续冷却条件下,冷速为3 ℃/s时,全马氏体组织显微硬度为810 HV0.1;而静态连续冷却条件下,冷速为5 ℃/s时,全马氏体组织显微硬度为689 HV0.1。奥氏体变形的再结晶细化作用可以明显细化冷却后的马氏体组织,进而提高马氏体的硬度。在奥氏体静态连续冷却条件下,中碳合金钢中0.6Ni元素的加入,抑制了铁素体和珠光体相变,大幅促进贝氏体和马氏体相变,提高了奥氏体的稳定性,将Ms点从329 ℃降低到304 ℃,马氏体临界冷速从0.5 ℃/s降低到0.3 ℃/s;相对于约0.4Mn元素的加入,0.6Ni元素的加入可以大幅抑制铁素体和珠光体相变,可以将Ms点从320 ℃降低到304 ℃,同时可以有效细化奥氏体冷却后的显微组织。