Nb-Ti微合金化超低碳钢析出物热力学分析及对热塑性影响

建立了基于双亚点阵模型的 (Nb_xTi_1-x) (C_yN_1-y)复合热力学模型,并计算了1023~1623 K时Nb-Ti微合金化超低碳钢(/%:0.02C,0.12Si,1.70Mn,0.012P,0.004S,0.101Nb,0.009Ti,0.010Als)的析出相中各组分的摩尔分数、占位比以及析出顺序。通过Gleeble热模拟机、透射电镜和能谱分析仪研究了析出物对该钢230 mm铸坯热塑性的影响和验证所建立的热力学模型。结果表明,1523 K时,钢中Nb、Ti的固溶摩尔分数分别为5.4×10^-4和3.87×10^-5,降至1023 K时,Nb、Ti固溶含量趋于0。随温度降低析出物中Ti、N占位比逐渐下降,而Nb、C占位比逐步上升,析出物的演变顺序为Nb_0.315Ti_0.685C_0.02N_0.98 , (Nb_xTi_1-x) (C_yN_1-y) , Nb_0.85Ti_0.15C_0.71 N_0.29, 计算值与实验结果基本吻合。析出物尺寸小于60 nm,数量高于5个/μm²时,铸坯热塑性明显降低;1241 K钢的抗拉强度临界应力为63.8 MPa,裂纹易形成;同时,Gleeble试样断口处发现Al、Si、Mn、Nb、Ti在晶界处富集,碳氮化物引起空洞,应力作用下形成裂纹。因此连铸过程的铸坯矫直温度应≥1241 K。      

Ti(C0.5N0.5)颗粒增强钛基复合材料显微组织和力学性能的研究

以纯Ti粉、Ti(C_0.5N_0.5)颗粒为原料,采用粉末冶金工艺,制备了Ti(C_0.5N_0.5)颗粒增强钛基复合材料,研究了Ti(C_0.5N_0.5)含量对钛基复合材料组织和力学性能的影响。结果表明：Ti(C_0.5N_0.5)颗粒的添加,显著细化了钛基体的晶粒,晶粒形貌由粗大的柱状晶转变为细小的等轴晶;随着Ti(C_0.5N_0.5)含量的增加,钛基复合材料的孔隙明显减少,致密度提高,钛基复合材料的硬度和屈服强度逐渐增加,但压缩应变逐渐减小。     

氮含量对稀土钢中夹杂析出热力学的探究

为了探究N含稀土Q345钢中杂质析出的影响,利用热力学软件Fact-Sage对Ti、Ce、N不同含量的Q345钢成分进行计算分析,计算得出不同N含量对各种夹杂析出量的影响。得到随着Ce或Ti含量的增加,含Ce硫化物的转变顺序为Ce₂S₃→Ce₃S₄→CeS。特别是含Ti第二相、铈化合物的析出温度曲线与固溶温度曲线部分的研究,N含量(质量分数)的增加促进了TiN的析出,N含量增加0.01%时,TiN的析出量增加了341.93%,同时也促进了Ce₂O₂S和Ce₂S₃的析出,抑制了TiC、C₂S₂Ti₄的析出,N的百分质量增加0.01%时,TiC的析出量较少了42.73%。N含量的增加使得TiN、TiC在液相凝固时析出的温度提前了3.5℃,且钢液的完全凝固温度降低了3.7℃。     

WC质量分数对Ti(C0.7N0.3)基金属陶瓷组织和性能的影响

采用粉末冶金低压烧结方法制备Ti(C_0.7N_0.3)基金属陶瓷, 结合扫描电子显微镜(scanning electron microscope, SEM)观察、能谱(energy dispersive spectrum, EDS)分析、力学及磁学性能测试, 研究了WC质量分数从0增大到20%的过程中, Ti(C_0.7N_0.3)基金属陶瓷的显微组织、力学性能及磁学性能变化。结果表明, 经1420℃低压烧结1 h后, Ti(C_0.7N_0.3)基金属陶瓷显微组织有明显的芯/壳结构, 且随着WC质量分数增大, 黑色硬质相数量及体积减小, 环形相和黏结相体积增大。WC质量分数从0增大到20%的过程中, 硬度先增大后减小, 抗弯强度先增大后趋于稳定, 饱和磁化强度逐渐减小, 矫顽磁力逐渐增大。WC质量分数为15%时, 力学性能最佳, 其中HRA 91.6, 抗弯强度2160 MPa。     

Mn-Mo-Nb-B低碳微合金钢的应变诱导析出

采用热模拟及透射电子显微镜结合纳米束能谱技术,研究了Mn-Mo-Nb-B系多元微合金钢奥氏体变形后等温过程中(松弛)的析出行为。实验结果表明:经变形后,在850℃和900℃保温过程中,Mn-Mo-Nb-B多元微合金钢析出颗粒尺寸在各个阶段均小于相同工艺下Nb-Ti钢中析出相的尺寸。统计结果显示,析出颗粒的尺寸均复合正态分布,并且峰位尺寸接近平均尺寸。析出相中Nb/Ti比随着松弛时间而增大。松弛阶段后期,Mo进入(Ti,Nb)(C,N)的晶格当中,其含量随着时间的延长而增加。     

加热工艺对Nb-Ti微合金钢奥氏体晶粒长大的影响

 为了解加热制度对Nb Ti微合金钢的奥氏体晶粒长大和析出行为的影响,采用OM、TEM和EDS分析技术,研究了Nb Ti微合金钢在不同加热温度和保温时间的奥氏体晶粒长大行为,以及微合金元素碳氮化物析出行为。结果表明,随加热温度升高,奥氏体晶粒尺寸逐渐长大,当加热温度超过1 200 ℃时奥氏体晶粒尺寸快速长大。随保温时间延长,奥氏体晶粒尺寸逐渐长大,当保温时间超过2.0 h时奥氏体晶粒尺寸快速长大。EDS分析显示Nb Ti钢中的析出物为(Nb,Ti)(C,N)复合相,随着加热温度升高和保温时间延长,析出相体积分数减少,尺寸增大,从而减弱对奥氏体晶粒的细化作用;Nb Ti微合金试验钢合适的加热温度范围为1 150～1 200 ℃,保温时间低于2.0 h。     

Nb、V、Ti在微合金钢中回溶规律的研究

通过萃取复形薄膜的方法,采用高分辨透射电镜和能量色散X射线光谱技术,研究了Nb-V-Ti和V-Ti微合金钢中,Nb、V、Ti的碳氮化物在不同温度和不同时间下保温时的回溶情况.结果表明,Nb-V-Ti微合金钢中较大的析出物是由少量的Nb、V和大量Ti一起在凝固过程中析出,形成复合的(Nb,V,Ti)(C,N)析出物.V-Ti微合金钢中,Ti的加入对于V的回溶具有拖曳作用.     

高炉炉缸含钛保护层物相及TiC0.3N0.7形成机理

基于高炉破损调查取样分析, 借助X射线荧光分析、X射线衍射分析、电子探针分析、扫描电子显微镜结合能谱分析等手段分析了高炉炉缸、炉底不同部位形成的含钛保护层化学成分、物相组成和微观形貌, 并建立正规溶液热力学模型对Ti (C, N)形成的热力学条件进行分析, 然后针对高炉的实际工况, 明晰高炉炉缸TiC_0.3N_0.7形成的条件.结果表明, 高炉炉缸侧壁最薄处炭砖残余厚度仅为200 mm; 炉缸炉底炭砖表面普遍存在含钛保护层, 保护层平均厚度在300~600 mm左右, 高炉炉缸不同部位形成的保护层中Ti(C, N)主要以TiC_0.3N_0.7形式存在, 并与Fe相聚集在一起.Ti (C, N)固溶体实际混合摩尔生成吉布斯自由能显著低于标准混合摩尔生成吉布斯自由能和理想混合摩尔生成吉布斯自由能.在不同温度条件下, TiC和TiN在固溶体中存在的比例不同, 高温时以析出TiC为主, 低温时以析出TiN为主.Ti (C, N)固溶体的形成与高炉热力学状态条件直接相关, TiC_0.3N_0.7在该高炉炉缸中的形成温度为1423℃.      

高能球磨+硼/碳热还原法制备(Ti,Mo, Nb,Ta, Zr)B2高熵陶瓷粉末的研究

以TiO₂、MoO₃、Nb₂O₅、Ta₂O₅、ZrO₂、B₄C和炭黑为原料,采用高能球磨+硼/碳热还原法制备(Ti, Mo, Nb, Ta, Zr)B₂高熵陶瓷粉末,并借助XRD、SEM等手段对反应产物的物相组成和微观形貌进行了表征。实验结果表明：球磨时间、还原温度和保温时间是制备高品质(Ti, Mo, Nb, Ta, Zr)B₂高熵陶瓷粉末的重要影响因素。当球磨时间为2 h、真空碳热还原温度为1 700℃、保温2 h时,可制备出粒径约为1～2μm、元素分布均匀且具有单一相成分的高品质(Ti, Mo, Nb, Ta, Zr)B₂高熵陶瓷粉末。     

固溶C对Nb-Ti微合金化ULC-BH钢板烘烤硬化性能的影响

通过定量相分析研究了Nb-Ti微合金化超低碳烘烤硬化钢(%:0.002C、0.01～0.02Nb、0.01～0.02Ti、0.002 8～0.004 2N)的析出相,建立了试验钢固溶C含量的计算公式。结果表明,随固溶C含量计算值的增加,钢板的烘烤硬化性BH₂值增大;随冷轧板退火温度(810～850℃)的增加,BH₂值增加;820℃退火时,640℃卷取的钢板BH₂值高于710℃卷取的钢板BH2值。     

HRB500E抗震钢筋中钛化物析出热力学分析

 钢液凝固过程中钛化物在液相、固相的存在形态对固相组织的性能有着重要的影响,其第二相析出起到细化晶粒的作用。为分析HRB500E抗震钢筋钢中TiN、TiC、Ti(C,N)析出物的析出规律,对TiN、TiC、Ti(C,N)析出物进行热力学计算。结果表明,TiN、TiC在钢液成分均质状态下难以析出,TiC_0.19N_0.81在温度为1 843 K时析出;在凝固过程中,由于Ti、N在凝固前沿富集,TiN在凝固过程中具备析出的热力学条件,析出温度为1 745 K;在固相奥氏体中,TiN和TiC粒子具备析出热力学条件,TiC析出温度比TiN的低,铁素体中有TiC的析出。     

Effect of Ti Additions on Micro‐Alloyed Nb TRIP Steel

In the present study, the influence of Ti‐additions on the mechanical properties of Nb‐microalloyed TRIP steel is investigated. Ti micro‐alloying additions to multi‐phase Nb TRIP steel result in a substantial increase of the yield strength and a reduction of strain hardening. The increase of the yield strength can be attributed mainly to grain refinement with a relatively small contribution of precipitation hardening. Based on general principles and well‐known models of alloying strengthening, metallurgical reasons for the observed mechanical behavior of the steel can be formulated. The contribution of precipitation hardening is relatively small as Ti‐addition result in the formation of coarse (Nb,Ti)(C,N) particles. The addition of Ti to a Nb‐microalloyed TRIP steel leads to a pronounced enhancement of precipitation kinetics of (Nb,Ti)(C,N), thereby increasing their phase fraction. The precipitates coarsen and tend to form groups of aggregates of particles rather than single isolated particles with increasing intercritical annealing time. In addition, Ti‐addition to Nb‐microalloyed TRIP steel has a direct influence on the chemical composition of the precipitates, which become Ti‐rich.     

Separate Evaluation of the Kinetics of Carbide Precipitation Occurring at the Interface of Preexisting Particles and Within the Austenitic Matrix in a Microalloyed Steel

The isothermal kinetics of carbide precipitation occurring at the interface of preexisting (Ti,Nb)(N,C) particles and within the deformed γ-austenite matrix were separately evaluated using a Nb-Ti-V microalloyed steel through small-angle neutron scattering and transmission electron microscopy. While the specimen was isothermally held after deformation at 1223 K (950 °C), (Nb,Ti)(C,N) particles were precipitated at the interface of coarse (Ti,Nb)(N,C) particles preexisting in the recrystallized γ matrix. This resulted in a single size distribution curve, which was converted from the measured magnetic scattering cross section. However, during isothermal holding after deformation at 1123 K (850 °C), fine (Nb,Ti,V)(C,N) particles formed mainly within the deformed γ matrix, although some of them were precipitated at the interface of preexisting coarse (Ti,Nb)(N,C) particles. Accordingly, the specimens held at 1123 K (850 °C) exhibited double size distribution curves. The separate evaluation between matrix and interface precipitation kinetics was successfully performed using the size distribution curves due to the difference in particle size according to the nucleation site. The reliability of carbide precipitation kinetics was confirmed by comparing the measured ratio between magnetic and nuclear scattering cross sections with the ratio calculated based on the measured chemical composition of precipitates.     

铌-钛微合金化0.36C-0.83Ni-1.2Cr-0.23Mo超高强度淬火-210℃回火马氏体钢组织与性能

利用拉伸试验机、冲击试验机、光学显微镜、透射电镜等研究了 Ni-Ti微合金化超高强度钢(/％:0.36C,0.45Si,0.63Mn,0.005P,0.002S,0.83Ni,l.2Cr,0.23Mo,0.04Nb,0.01Ti,0.0040N,0.002 0O)的组织与性能.200 kg真空感应炉冶炼的试验钢开轧温度...     

A new theory and kinetic modeling of strain-induced precipitation of Nb(CN) in microalloyed austenite

A new theory of strain-induced precipitation of Nb(CN) in microalloyed austenite has been developed by considering the effect of nonequilibrium segregation of Nb on the nucleation and growth of the precipitates. With the aid of the theory, the discrepancy existing between the conventional theory for strain-induced precipitation and experimental data can be reconciled. A kinetic model has been developed based on the new theory. The model is capable of predicting both the Nb(CN) precipitation kinetics and the resulting microstructure in microalloyed austenite. Excellent agreement has been obtained between the model predictions and the experimental observations reported by different investigators.     

Effects of Rare Earth on Behavior of Precipitation and Properties in Microalloyed Steels

The influence of rare earths on the behavior of precipitation of 14MnNb,X60 and 10Mn V steels was studied by STEM, XRD, ICP and thermal simulation method. The main carbonitride precipitates are Nb(C, N), (Nb, Ti) (C, N) and V(C, N). In austenite RE delays the beginning of precipitation, and decreases the rate of precipitation. In ferrite RE promotes precipitation and increases the amount of equilibrium carbonitride precipitation. RE can make precipitates fine,globular and dispersed in the microalloyed steels. With the increase of the amount of RE in steel, the amount of precipitation increases. The promotion effect is weakened with excessive RE. RE has only little influence on the strength of microalloyed steel, but it can improve impact toughness effectively.     

Mo、Ce对贝氏体钢第二相及组织与硬度的影响

为了明确Mo、Ce、Ti在贝氏体钢中的作用,采用热力学计算结合试验,研究含钛贝氏体钢中Mo和Ce对钢中第二相析出、组织转变及性能的影响机制.结果 表明,贝氏体钢中加入Mo后,部分固溶于钢基体中,部分以碳化钼的形式析出,Ti以C2S2Ti4析出为主,Ce在钢中以Ce2 O3和Ce2O2S的形式存在,加Ce后Ti的第二相析...     

Hydrothermal Synthesis and Crystal Structure of Lanthanum Orotate Supermolecule with A Honeycomb Structure Constructed from Mononuclear Molecules via Hydrogen Bonds

A new complex of lanthanum orotate [La（C5H3N2O4）2（OH）（H2O）6 ]·2（C5H4N2O4）·9H2O was synthesized using a hydrothermal method. The crystal structure was determined with help of single crystal X-ray diffraction analysis. The complex crystallized in orthorhombic system, Cmc2（1） space group. In the complex, the center lanthanum （Ⅲ） ion was nine-coordinated with coordination geometry of a distorted monocapped square antiprism, in which two of the nine coordinated oxygen atoms were from two orotate ligands in a monodentate mode, one oxygen atom from a hydroxyl, and the others from six coordinated water molecules. The mononuclear complex [La（C5H3N2O4）2（OH）（H2O）6 ]·2（C5H4N2O4）·9H2O was linked through the hydrogen bonds into an infinite supermolecular honeycomb structure.