900℃时效条件下超级奥氏体不锈钢904L的析出相研究

采用Factsage热力学软件计算和实验相结合的方法,借助金相显微镜、扫描电镜、透射电镜等检测技术,研究了900℃时效条件下超级奥氏体不锈钢904L热轧板的组织变化情况。结果表明:904L不锈钢在1080℃×40min固溶处理为单一奥氏体组织;900℃时效处理过程中,析出相优先在晶界上形成,随着时效时间延长,析出相数量逐渐增加,尺寸不断增大,最终在晶界上形成网状分布;TEM和EDS表征确定为富Cr、Mo和低Ni的σ析出相,形貌以条状和块状分布为主;热力学计算结果表明904L不锈钢在平衡状态下主要析出相为σ相,与实验结果吻合。     

时效处理对4A双相不锈钢σ相析出及性能的影响

对固溶处理后的4A双相不锈钢(DSS4A)进行不同温度(750~900℃)的等温时效处理,利用OM观测各个时效温度下σ相的析出行为,重点观测了σ相在850℃时效不同时间(1h、2h和4h)的析出过程,并通过SEM、EDS和TEM等检测手段对850℃、4h时效处理后的σ相析出形貌进行分析,揭示了σ相的析出特征及形成机理。最后对时效条件下4A双相不锈钢的力学性能和耐蚀性能也进行了相应研究。结果表明:σ相富Cr、Mo而贫Ni,属于四方结构,由高温铁素体分解而成;σ相析出量随时效温度的升高先增加后降低并在850℃时达到峰值,同一温度下时效时间越长,σ相析出越多;σ相使材料硬度提高,但材料抗拉强度、冲击韧性和耐腐蚀性整体呈下降趋势,其中冲击韧性对σ相析出尤为敏感。     

23Cr-14Ni高氮奥氏体不锈钢σ相析出行为EI北大核心CSCD

采用经验公式、热力学计算方法、Gleeble热/力模拟实验技术,结合光学显微镜、扫描电镜及透射电镜分析,研究了23Cr-14Ni高氮奥氏体不锈钢中σ相的析出行为。结果表明,23Cr-14Ni高氮奥氏体不锈钢中σ相可在960~1030℃析出,高于1050℃溶解。σ相析出具有异常快速的动力学特征,在经过1030℃保温1 min固溶处理后,σ相可直接从奥氏体晶界快速析出,析出先于碳氮化物相。σ相析出动力学行为及相对碳氮化物的析出次序和传统奥氏体不锈钢显著不同。铬、锰、钼元素含量较高且钼元素在晶界处偏聚提高了σ相平衡析出温度,是加速σ相析出的主要原因。     

316L奥氏体不锈钢中时效条件下析出相演变行为的研究

通过定量金相,SEM&EDS、TEM等实验技术分析316L奥氏体不锈钢中析出相随时效时间、温度的变化,并测定析出相的体积分数与尺寸.结合热力学计算表明:在316L奥氏体不锈钢中,经850℃时效处理后,析出相为M23C6型碳化物,且随着时效时间的延长,析出量明显增多,尺寸增大;经650℃时效处理100 h后,主要析出相类型为χ相.     

Ti和Ti-V微合金化低碳贝氏体钢组织性能及析出行为的研究

利用场发射扫描电子显微镜(FE-SEM)、高分辨透射电子显微镜(HRTEM)和能谱仪(EDS)等,研究了不同Ti含量的低碳贝氏体钢的显微组织和析出相的成分、尺寸、形貌以及分布等特征.结果表明:在450℃和520℃保温2h,三种实验钢组织为粒状贝氏体.与低Ti实验钢相比,高Ti及Ti-V复合实验钢的屈服强度增加了150MPa以上.高Ti钢中纳米级析出相有两种类型:一种大于15nm的TiC析出相;另一种是在10nm以下,具有面心立方结构的(Ti,Mo)C复合析出相.Ti-V钢基体中存在大量尺寸在10nm以下的(Ti,V,Mo)C复合析出相.     

固溶时效对1Cr21Ni5Ti双相不锈钢组织的影响

本工作以1Cr21Ni5Ti双相不锈钢为原材料,对1 000~1 350℃固溶30 min+650~1 000℃时效1~1 440 min后的显微组织及σ析出相进行观测,描述了不同处理条件下的组织特征,绘制出σ相析出TTP曲线图。结果表明:随着固溶温度的升高,铁素体含量增加,奥氏体含量减小,双相不锈钢组织发生再结晶和晶粒长大。铁素体与奥氏体中Cr、Ni元素发生均匀化,各相中的含量差异降低。σ相优先在铁素体与奥氏体相界处形核,随着时效温度的升高和时效时间的延长,σ相长大、粗化并向铁素体基体延伸;时效时间越长,析出相越多;当温度达到750℃,σ相析出速度最快,之后随着温度的升高而降低。σ相析出温度范围为650~850℃,析出鼻尖温度为750℃。     

析出相对深冲DP钢组织性能及织构的影响

为了研究析出相对深冲DP钢织构的影响机制,采用Thermo-calc热力学软件计算DP钢的平衡析出相,并利用SEM、TEM与XRD等手段分析了两种不同成分的DP钢组织性能与织构演变.研究表明:试验钢的主要析出相为MC_SHP、M₇C₃、MnS和AlN;与低Mo钢相比,高Mo钢的奥氏体区被缩小,且MoC的析出温度更高,铁素体晶内与沿晶界形成了大量的纳米级MoC析出;860 ℃退火后,高Mo钢中形成了约3%的均匀弥散分布的马氏体,抗拉强度达到445 MPa,r值为1.5,而低Mo钢发生了贝氏体相变,各项力学性能明显降低;两种试验钢的热轧板织构较弱,冷轧后{223}<110>取向密度稳定增加,退火后均形成了强烈的γ纤维织构,而低Mo钢中{001}<110>织构是导致其r值偏低的主要原因.     

Zr对Ti微合金化低碳钢形变奥氏体再结晶和析出相的影响

通过多道次模拟压缩实验，研究不同Zr和Ti含量的三种Ti微合金化低碳钢在950℃~1050℃形变奥氏体再结晶和析出相的变化和最佳变形温度。结果表明，Ti含量的提高和Zr的加入使Ti微合金钢形变奥氏体的再结晶和晶粒长大延迟。Zr的加入还能增加Ti微合金钢中析出相的数量、改善析出相尺寸分布的均匀性进而得到相对均匀的奥氏体组织。变形温度为1000℃时的Ti-Zr微合金钢奥氏体组织最细小均匀。     

900 MPa级热轧TRIP钢的性能特征和析出行为

采用X射线衍射(XRD)、透射电镜(TEM)和拉伸实验等方法,研究了两种常规卷取温度对热轧C-Si-MnNb-V-N钢组织性能及析出行为的影响。结果表明,卷取温度为450℃时试验钢析出物颗粒尺寸要小于卷取温度为400℃时试验钢中的析出物颗粒尺寸,但是数量多于卷取温度为400℃时析出物的数量。在两种卷取温度条件下制备的试验钢中铁素体的平均晶粒尺寸均小于5μm,残余奥氏体数量相差不大,但是在450℃卷取温度下通过细晶与析出强化可制备出抗拉强度900 MPa级、强塑积27000 MPa·%的热轧TRIP钢,其综合性能力学优于400℃卷取温度下制备的热轧TRIP钢。     

强塑积大于30 GPa%的热轧中碳TRIP钢组织及性能研究

为研究贝氏体相变温度对中碳热轧TRIP钢组织与性能的影响,采用扫描电镜(SEM)、X射线衍射(XRD)与高分辨透射电镜(HRTEM)对含Ti与Mo的中碳热轧TRIP钢进行了显微组织观察、残余奥氏体含量测定以及析出相的表征与分析.结果表明:在400℃贝氏体相变温度下,试验钢的残奥含量与强塑积均达到最大值,分别为28.2%和31.14 GPa·%;同时在钢中发现了呈块状、无规则形状以及片层状形貌分布的残余奥氏体,对衍射斑标定后显示,片层状残余奥氏体与铁素体基体同时满足kurdjumov-Sachs(K-S)与Nishiyama-Wasserman(N-W)位向关系;HRTEM分析显示,Mo可以溶入TiC而生成(Ti,Mo)C粒子,而纳米级的(Ti,Mo)C粒子可以显著提高钢的沉淀析出强化效果.     

Detection of Precipitation Cloud over the Tibet Based on the Improved U-Net

Aiming at the problem of radar base and ground observation stations on the Tibet is sparsely distributed and cannot achieve large-scale precipitation monitoring. UNet, an advanced machine learning (ML) method, is used to develop a robust and rapid algorithm for precipitating cloud detection based on the new-generation geostationary satellite of FengYun-4A (FY-4A). First, in this algorithm, the real-time multi-band infrared brightness temperature from FY-4A combined with the data of Digital Elevation Model (DEM) has been used as predictor variables for our model. Second, the efficiency of the feature was improved by changing the traditional convolution layer serial connection method of U-Net to residual mapping. Then, in order to solve the problem of the network that would produce semantic differences when directly concentrated with low-level and high-level features, we use dense skip pathways to reuse feature maps of different layers as inputs for concatenate neural networks feature layers from different depths. Finally, according to the characteristics of precipitation clouds, the pooling layer of U-Net was replaced by a convolution operation to realize the detection of small precipitation clouds. It was experimentally concluded that the Pixel Accuracy (PA) and Mean Intersection over Union (MIoU) of the improved U-Net on the test set could reach 0.916 and 0.928, the detection of precipitation clouds over Tibet were well actualized.     

7050铝合金在不同温度变形的动态析出行为

研究了7050铝合金在不同温度变形的动态析出行为,结果表明:7050铝合金在不同温度的变形过程中MgZn2相动态析出不影响流变应力的波动,变形加速了动态析出过程;随着变形温度的升高,部分析出相MgZn₂颗粒由球状变成板条状,尺寸增大数量减少,在450℃变形过程中粗大的板条状MgZn₂相易破碎;同时,位错密度减低,位错胞团变成离散位错墙。析出相钉扎位错和阻碍晶界迁移,主要以亚稳态η′和平衡态η形式存在,在变形过程中不会产生微裂纹。     

沉淀强化镍基合金屈服强度的理论计算EI

本文提供了依据合金的化学成分、显微组织参数定量计算合金屈服强度性能的理论方法。具体计算了一组镍基合金的室温屈服强度，计算值与实测值很好地符合。     

钢中MnS对BN析出行为的影响

采用α粒子径迹法和电子显微镜研究了含微量硼的低碳钢中MnS对BN析出行为的影响。结果表明,当加热温度低于1150℃时,BN多以球状的MnS为结晶核心在其周围析出,呈MnS+BN复合体形态;当加热温度超过1150℃时,未固溶的MnS大部分由球形变成多面体形,这种形状的MnS已失去BN结晶核心的作用。除了呈MnS+BN复合体存在的BN外,也有单体的BN,随着温度的提高和保温时间的延长,其尺寸变大,形貌各异。     

Cu-Ni-Si合金的时效与析出研究

分析了冷变形量和时效温度与时间等工艺参数对Cu Ni Si合金显微硬度和导电率的影响 ,同时研究了该合金的析出物结构。结果表明 ,冷变形可加速时效过程和提高时效效果 ,在 5 0 0℃时效 1h可使合金获得较佳综合性能。合金的显微硬度和导电率等性能主要取决于析出物的析出量和颗粒大小以及弥散程度     

Precipitation of carbonate crystal on surface active glasses

Anions, such as CO₃ ^2– and SO₄ ^2– ions, in industrial wastewater can cause serious scale problem in drainage pipes and vessels, when combined with other metal ions in the water. In this study, it was attempted to remove CO₃ ^2– ions from an aqueous solution by using surface active glasses. Glasses with various compositions of SiO₂-Na₂O-B₂O₃-RO (R = Mg, Ca, Sr, Ba) system were reacted in a CO₃ ^2– ion-containing solution with various pH, then the glass surfaces were analyzed by XRD and SEM, and CO₃ ^2– ions in the reacted solution were also measured. CO₃ ^2– ions in the solution were combined with alkaline earth metal ions, which were leached out of the glass, and were precipitated on the glass surface as carbonate crystals. In this way, the carbonate ions could be removed from the solution. The removal capacity of CO₃ ^2– ions is closely related to the surface reactivity of the glass and solubility product constants of the newly formed carbonate crystals. Glass containing either SrO or BaO showed a strong uptake capacity of CO₃ ^2– ions from the solution.     

Influence of RPC Parameters on the Precipitation of Nb in Microalloyed Steel

Thermo-simulation test, metallographic analysis, measurement of hardness, TEM(including diffraction contrast technique and nano-beam anylasis)along with calculating software of Metlab, etc. were used to study the influence of RPC parameters(relaxation time, aging time)on the precipitation of Nb in microalloyed steel. Following work was undertaken in this study:Strain-induced precipitation in Nb-bearing multi-microalloyed steel was monitered and analyzed. The interaction between dislocation evolution and precipitates in deformed austenite was directly observed(an Fe-Ni-Nb alloy was employed to simulate austenite in steel). The(a low carbon microalloyed steel only by Nb was adopted)effect of relaxation of deformed austenite on aging behavior occurring in bainite was investigated. Finally, the thermal stability and variation of composition of carbonitride precipitates during dissolving process in Nb-Ti microalloyed steel were alsodetected. These results indicate:(1)During the stress relaxation, the process of precipitation happened in deformed austenite of multi-microalloyed steel can be divided into three stages, i. e. nucleation, growth and coarsening. In the final stage of relaxation, Mo atoms would enter the lattice of(Nb,Ti)(C,N)precipitates and its concentration in the precipitates increases with the relaxation time.(2)In the earlier stage of relaxation, the dislocations in deformed austenite demonstrate twisted and distribute randomly. The precipitates have the tendency to occur along those dispersed dislocations. The dilocation cells would form gradually with the relaxing time prolonged and would become more stable by the subsequent precipitates formed on them in the later relaxation period. The paralleled dislocations in dislocation cells exhibit the same Burgers vector. The dislocations get rid of pinning by the bypassing mechanism.(3)When the samples are reheated to hold isothermally at 525℃,which are relaxed for different time in deformed austenite followed by accelerated cooling, their microstructures evolve very slowly with the aging time but two hardness peaks can be found one each hardness-time curves. The position of hardness peaks nearly raimains unchanged while their height varies obviously with the relaxation time. In no relaxtion samples, only one hardness peak could be observed. During the process of aging at 525℃, The growth and coarsening of as-existed strain-induced precipitates formed in deformed austenite contribute to formation of the first hardness peaks. While the second hardness peaks result from the further precipitates which nucleate in a phase after γ→α transformation(after aging for about 10 hours).(4)It was found that the precipitates formed during solidification are monophase(Ti,Nb)(C.N)rather than TiN enclosed with NbC. With addition of Ti to the steel, the thermal stability of the carbonitrides would enhance remarkably.     

均匀沉淀法制备碱式碳酸锌的过程研究

以硝酸锌和尿素为反应物,采用均匀沉淀法,通过改变均匀沉淀温度、反应物物质的量比,考察了反应时间对所形成沉淀的Zn原子利用率的影响,并利用X射线衍射(XRD)和扫描电子显微镜(SEM)对不同时刻的沉淀晶相和形貌进行表征.结果表明,反应开始时,发生了pH值先下降、再上升现象;反应20 min时生成的产物中含有ZnO晶体,但在反应40 min及之后生成的产物中只检测到Zn4 CO3 (OH)6·H2O和Zn5 (CO3i)2 (OH)6晶体,并存在前者向后者转化的现象;碱式碳酸锌呈现球形片状组装体结构,经焙烧形成的ZnO晶体保持了碱式碳酸锌的形貌,随焙烧温度升高,ZnO晶粒长大.