9Cr2Mo钢中贝氏体的组织形貌

采用光学显微镜和扫描电子显微镜等技术手段观察了经1100℃奥氏体化的9Cr2Mo钢在不同温度的盐浴中等温淬火后贝氏体的组织形貌。结果表明：9Cr2Mo钢1100℃奥氏体化后,在410℃的硝盐浴中等温得到羽毛状的经典上贝氏体组织,在350℃的硝盐浴中等温得到针状（或片状）的下贝氏体组织;上贝氏体铁素体铁素体是在奥氏体晶界处形核并向晶内生长,碳化物在铁素体条间分布;下贝氏体是在奥氏体晶内形核,碳化物分布在铁素体片中间,碳化物大多数与片条的主轴方向交角排列,但角度不等。     

0Cr20Ni12Mn5Mo2NbN钢循环应力应变本构关系

针对奥氏体0Cr20Ni12Mn5Mo2Nb N钢开展了系列应变幅的循环加载试验,分析了其循环应力应变特性,结果表明,循环全过程中真应力和真应变呈指数关系,基于该指数关系提出了描述循环应力应变关系的本构模型:σ=σ0+α·exp(β·ε)。     

7Cr7Mo3V2Si钢加热相变研究

利用Ｆｏｒｍａｓｔｏｒ全自动相变测定仪研究了７Ｃｒ７Ｍｏ３Ｖ２Ｓｉ钢在连续加热条件下的相变规律及特点；测定了能反映其相变规律与特点的奥氏体形成图。结果表明，钢中球状珠光体向奥氏体的转变是在较宽的温度区间（Ａｃ１ｂ－Ａｃ１ｅ）内完成的；钢中大量合金碳化物的溶解、按其难易程度不同分别与ｎ个溶解温度相对应；连续加热条件下，奥氏体难以实现均匀化。     

9Cr2Mo钢转向辊调质开裂原因分析

通过化学成分分析、宏观和微观检验对9Cr2Mo钢辊身近端部纵向开裂的原因进行了分析。结果表明：材料化学成分超标、内裂纹的存在、原始组织晶粒粗细差异都对裂纹的形成产生了直接影响。最后根据分析结果制订了改进措施。     

34Mn2V钢在正火条件下钒碳化物的析出机理及其对力学性能的影响

利用TEM分析研究了34Mn2V钢在不同正火工艺下钒的碳化物的析出机理及其对力学性能的影响.     

热处理工艺对Y1Cr17Mo钢组织和性能的影响

Y1Cr17Mo钢属于铁素体-马氏体钢的范畴,其显微组织随热处理保温时间和温度的不同而发生变化,显然这也将影响到材料的力学性能。主要介绍了热处理工艺对Y1Cr17Mo钢显微组织的影响,摸索淬火温度、保温时间与显微组织、硬度之间的关系,以便为实际生产提供科学指导,从而得到所需的力学性能。     

60Mn钢高温力学性能研究

在Gleeble-2000动态热/力模拟实验机上,采用凝固法对60Mn钢的高温力学性能进行了研究。测定了零塑性温度和零强度温度,在4×10-4/s应变速率下,所测钢种在熔点至750℃之间存在两个脆性温度区域,即熔点至1 250℃的第Ⅰ脆性温度区域和925~750℃的第Ⅲ脆性温度区域。在第Ⅲ脆性温度区域,γ单相区的铝、钛、铌以AlN和NbN等氮化物及γ+α两相区先共析α相呈网膜状在γ晶界的析出是造成钢脆化的主要原因。通过控制钢中氮、铝含量,采用合理的二冷方式,提高钢种的内在质量。     

Cr9Mo铸钢组织和性能的研究

研究了Cr9Mo铸钢组织和性能之间的关系。依据试验结果,指出了热处理工艺变化对其组织、性能的影响,并与Cr5Mo铸钢作比较。     

正火40MnMoV钎钢的贝氏体组织

用ＴＥＭ研究了新型钎钢４０ＭｎＭｏＶ的正火组织，发现它与Ｓｉ－Ｍｎ－Ｍｏ系的另一种钎钢５５ＳｉＭｎＭｏ相似，由无碳化物上，下贝氏体Ｂｕ、Ｂｌ、以孪晶马氏体为主的“块状组织”和约１５％残余奥氏体Ａｒ组成，但４０ＭｎＭｏＶ的Ｂｕ，Ｂｌ较多，Ａｒ和Ｌ则较少；Ｂｕ板条较粗大，其间分布着不连续的Ａ小片条；Ｂｌ片中有渗碳体与粤氏体Ａ共存；Ｌ的尺寸较小，硬度较低，讨论了该钢正火时贝氏体（Ｂ）相变的原因及影响贝氏     

Corrosion behavior of 5Cr0.5Mo steel in sulfur‐bearing solution at high temperature

Corrosion behavior of 5Cr0.5Mo steel in sulfur‐bearing solutions as a function of temperature, test time, and sulfur content was investigated by weight loss measurements in this study. The results indicate that the corrosion rate of the steel increases with increasing test temperature. Besides, the corrosion rate increases during the initial test time and then decreases with longer test duration. Moreover, the corrosion rate rises with a higher amount of sulfur in the solution, and consequently a lower amount of sulfur leads to a decreased corrosion rate. In addition, the effect of Cr and Mo elements has been discussed.     

高强钢TRB高温下热流变特性

为了准确仿真高强钢板热冲压成形过程,获得高强钢高温下的材料本构关系模型,利用Gleeble3500热模拟试验机在不同温度和应变速率下对不同厚度的高强钢B1500HS钢板进行了单向拉伸试验,获得各种工艺条件下的应力-应变曲线,并基于变形抗力数学模型,引入板材厚度参数,通过最小二乘法进行数据拟合获得高强钢TRB高温下的材料本构关系.利用试验结果对本构关系模型进行的拟合验证表明,拟合程度较好,说明建立的材料本构关系能很好地描述高强钢TRB在高温下的应力-应变关系.     

Fe-Cr合金钢高温性能研究

本文试验研制了四种Fe-Cr合金材料,其在900 ℃时的热膨胀率在10～11×10-3范围内,其中FeCr-4合金的热膨胀率为10.27×10-3,与钇稳定氧化锆(YSZ)相比,热膨胀率逐渐接近;与传统合金材料相比,热膨胀率之差均有了明显下降,因而降低了界面热应力,有效改善层间的热失配现象.随着温度的升高,各合金试样的电阻率呈平缓增大的趋势.在850℃时,四种合金试样的电阻率在0.95～1.17×10-3 Ω·cm范围内,其中Fe-Cr-4试样的电阻率较低,为1.17×10-3 Ω·cm,满足用作SOFC连接体材料导电性能的要求.Fe-Cr -1、4两种合金试样的抗氧化性能较好,随着氧化时间的延长,试样表面形成稳定的3Cr2 O3 Fe2 O3氧化层,氧化增重逐渐趋于稳定.累计氧化455 h后,Fe-Cr-1、4两种试样对应的氧化增重在0.0002 g/g左右;而Fe-Cr-2、3两种试样仍在0.0004 g/g以上.     

高温快速退火对电子束物理气相沉积制备高硅硅钢片的影响

对电子束物理气相沉积高硅硅钢片进行了高温快速退火处理.用SEM,EDS,XRD对制备态硅钢片和热处理态组织,成分,物相进行了表征,并测试了其电阻率和磁滞回线.结果表面:高温快速退火使高硅硅钢片硅成分变均匀,靠近基板侧的相由Fe3Si变成DO3;硅钢片中孔长大,电阻率从90μΩ·m增大到160μΩ·m,矫顽力减小,磁感应强度减小.     

New insight to the oxidation kinetics of silicon-containing steel at high temperature

This study investigated the oxidation kinetics of silicon-containing steel at 1150–1300 °C using a Simultaneous Thermal Analyzer under atmospheric conditions similar to that of an industry reheating furnace. There is a critical time point for the oxidation kinetics at an oxygen concentration of 4·0 vol.-%., following which the oxidation rate constant increases with the increasing oxidation temperature. The model coefficient A in the kinetic oxidation equation was found to be constant. However, before the critical time point, the oxidation rate constant remained unchanged; the model coefficient A decreased with the increasing temperature. Therefore, the kinetic model of silicon-containing steel for isothermal oxidation was observed to be a modified one on the basis of the experimental data. In addition, the critical time point was prolonged with the increasing isothermal oxidation temperature. Moreover, the oxidation activation energy of the tested silicon-containing steel was 366·16 kJ mol^?1.     

Constitutive modelling for high temperature behavior of 1Cr12Ni3Mo2VNbN martensitic steel

The deformation behavior of 1Cr12Ni3Mo2VNbN martensitic steel in the temperature range of 1253 and 1453 K and the strain rate range of 0.01 and 10 s⁻¹ are investigated by isothermal compression tests on a Gleeble 1500 thermal-mechanics simulator. Most of the stress-strain curves exhibit a single peak stress, after which the stress gradually decreases until a steady state stress occurs, indicating a typical dynamic recrystallization (DRX) behavior of the steel under the deformation conditions. The experimental data are employed to develop constitutive equations on the basis of the Arrhenius-type equation. In the constitutive equations, the effect of the strain on the deformation behavior is incorporated and the effects of the deformation temperature and strain rate are represented by the Zener-Holloman parameter. The flow stress predicted by the constitutive equations shows good agreement with the experimental stress, which validates the efficiency of the constitutive equations in describing the deformation behavior of the material.     

CO2 capture at high temperature using calcium-based sorbents

Calcium-based sorbents synthesized from CaO, CaCO₃, and Ca(OH)₂ precursors were demonstrated as high-temperature CO₂ capture materials. The effect on CO₂ capture capability of calcium-based sorbents receiving different activations was also investigated. After proper activation, the best carbon capturing material is CaO that captured 75% of available CO₂ in nine cyclic tests and captured 61% even after 40 cyclic experiments. The correlation of the structural difference in the three activated sorbents and CO₂ conversion has been discussed. The sintering effect is presumably a major cause for activity decline of calcium-based sorbents… after cyclic carbonation/decarbonation runs.     

Mn-Cr齿轮钢动态再结晶行为及组织演变

采用Gleeble 1500热模拟试验机研究了一Mn-Cr齿轮钢在变形速率为0.1～1 s-1、变形温度为900～1150℃、原始奥氏体晶粒尺寸为70～150 μm条件下的动态再结晶行为及再结晶奥氏体晶粒尺寸的变化规律.实验结果表明,Mn-Cr齿轮钢在温度较高,应变速率较低及原始奥氏体晶粒较细的情况下变形时,表现出典型的动态再结晶行为.再结晶发生的条件为Zener-Hollomon参数小于某一临界值(Zc).再结晶晶粒按晶界突出机制形核.通过回归分析,确定该齿轮钢的再结晶激活能为378.6 kJ/mol,应力指数为5.8.Z参数控制形变储存能,因而唯一地决定动态再结晶晶粒尺寸Ds,二者符合关系式Ds=1.3×105Z-0.25.     

High temperature cross-weld characterisation of steel weldments by microtensile testing

Abstract

Study of local material properties and damage mechanisms are undertaken in order to characterise weldments that show significant variation of properties across weldments. One of the methods to characterise the local variation of properties is microtensile (MT) testing of specimens machined out of specific narrow zones of weldments. The literature data, though limited, on microtensile specimen testing are reported at their low temperature behaviour. On the other hand, systematic study of crossweld local material properties at high service temperatures have not yet been reported. In the present study, MT tests are conducted across similar welds of P22 and P91 steels at 550 and 600°C, respectively. In order to study deformation mechanisms and the role of surface condition on properties, specimens with different surface conditions (i.e. machined, polished and electropolished surfaces) are tested. Two different loading rates of 0.2mm/min and 0.5mm/min are used to study the effect of loading rate on deformation and mechanical properties. Variations of material properties yield strength (R_p0.2) and ultimate tensile strength (R_m), for the weldments are presented as a function of surface conditions of specimens and loading speeds. Higher loading rates yield higher values of R_p0.2 and R_m, and specimens with machined and polished surfaces show consistent and higher values of R_p0.2 and R_m compared to specimens with an electropolished surface finish. Deformation behaviour is studied on the side surfaces of tested microtensile specimens using an SEM. Deformation is correlated to microstructural constituent that is observed on specimen side surfaces. The metallographic information is used to interpret the variation of mechanical properties determined in tension at high temperatures. The MT data are compared with standard tensile data obtained on specimens with simulated microstructures. The prospects of using MT tests for characterising the material at high temperatures and feasibility of use of data for assessment of components under service loading conditions are reported.     

纳米氧化铋基材料高温相变的研究

以分析纯Bi(NO3)3·5H2O和Y(NO3)·6H2O为原料制备纳米β-Bi2O3和Bi2O3-Y2O3(75%(摩尔分数)Bi2O3 25%(摩尔分数)Y2O3)粉体,平均粒度分别为40和30nm.经TG-DTA、高温XRD以及高温拉曼的研究结果表明,亚稳态的纳米β-Bi2O3粉体在升温过程中于420℃先向低温稳定的α-Bi2O3转变,在720℃时向δ-Bi2O3相转变,降温过程则是由δ→β→α.由于纳米Bi2O3具有很高的活性,使得相变温度比微米Bi2O3有所降低.纳米Bi2O3-Y2O3复合粉体升温过程中,Y2O3的固溶反应在较低温度(400℃)开始,500℃时β-Bi2O3完全转变为δ相,同时Y2O3完全固溶到δ-Bi2O3晶体中.Y2O3的掺杂使得Bi2O3的β→δ相转变温度大幅降低.