奥氏体不锈钢焊缝中δ铁素体含量测量方法对比

采用金相法、化学法和磁性法对308奥氏体不锈钢焊缝中δ铁素体含量(质量分数)进行了检测.结果表明:采用金相法中的网格数点法、网格截线法和八线法时,在500倍显微镜下测得δ铁素体含量均为7.6％,是较为可信的结果;采用化学法中的Schaeffler图法时,测得δ铁素体含量约为8.5％,和金相法的测量结果接近;采用磁性法测...     

铸态双相不锈钢彩色金相异常组织分析

采用金相分析、扫描电镜及能谱分析、X射线衍射分析、透射电镜分析以及显微硬度测试等方法研究了铸态2507双相不锈钢中各相的形貌和特征。结果表明:采用彩色金相侵蚀剂(1g偏重亚硫酸钠+10mL浓盐酸+50mL水)侵蚀后,彩色金相组织中的土黄色相为奥氏体相,黄绿色相为铁素体相,斑马纹状组织为(σ+γ2)共析组织。     

304L不锈钢形变诱导马氏体的X射线衍射分析

为准确测定304L奥氏体不锈钢中形变诱导马氏体的含量,更好地解释该材料中形变诱导马氏体相变机制,使用X射线衍射法对一系列形变后的奥氏体不锈钢样品进行研究,采用Rietveld全谱拟合法对各物相含量进行分析,并与传统的直接对比法、K值法进行比较,该法能最大限度克服传统方法的缺点。分析结果显示:304L奥氏体不锈钢形变过程中会发生α′和ε马氏体相变,且低温形变会加速奥氏体不锈钢中奥氏体相向马氏体相的转变。     

双相不锈钢2205激光焊接接头组织和性能研究

目的 针对双相不锈钢激光焊接接头两相比例失衡的问题,研究双相不锈钢2205激光焊接接头组织和性能。方法 采用Disk 6002碟片激光器对2205双相不锈钢进行激光焊接,通过在纯氩气保护气中添加体积分数为60%的氮气,向熔池中过渡氮元素,以提高焊缝中的奥氏体含量;采用金相显微镜、电子背散射衍射技术、电子探针X射线显微分析仪、显微硬度仪和上海辰华CHI760E电化学工作站等手段,对激光焊接接头表面组织、元素含量、显微硬度和耐腐蚀性能进行表征和测试。结果 与纯氩气保护焊接接头相比,当在保护气中添加60%（体积分数,下同）的氮气后,奥氏体相体积分数达到39.89%,提升了25.94%,奥氏体中氮元素的质量分数达到0.679%时,氮元素的质量分数提升了0.196%,焊缝中奥氏体显微硬度为307.4HV,铁素体显微硬度为298.9HV,极化曲线腐蚀电流密度升高,阻抗弧半径减小。结论 在保护气中添加60%的氮气后,激光焊接接头中奥氏体的体积分数提升,增加的奥氏体组织以晶内奥氏体为主,并且更多的氮元素进入到奥氏体相中,焊缝中的奥氏体和铁素体硬度略有升高,耐蚀性和钝化膜稳定性有所下降。     

高炉渣中非晶态物质含量的定量分析

首先通过化学分析法和X射线衍射法,准确确定高炉渣中的物相组分,然后通过加入标准物质CaF_2,对高炉渣的物相组分进行定量分析,并使用K值法计算出非晶态物质的含量。结果表明:采用X射线衍射法和K值法相结合的方法可以快速准确地测得高炉渣中非晶态物质含量;且标准物质CaF_2的加入质量分数控制在20%时,测定结果更加准确。     

一种改进的X射线衍射定量相分析方法

在基体清洗法的基础上提出一种新的X射线衍射定量相分析方法。该方法是利用混合样品X射线衍射谱图中的全部衍射峰数据，把清洗剂同样品中所包含的所有待测物相的纯相按比例混合，在同一水平下同时测定各物相与清洗剂对应的几个K值，结合JCPDS卡中的各相标准谱峰的相对强度分布数据进行最小二乘方程组的抛弃平均法回归分析^[2]，求得混合物样品中各相间的全谱峰匹配强度比，用于混合物样品的X射线衍射定量相分析，有利于提高定量相分析的精度。通过对四组分混合物样品的分析，证实实验结果和理论完全一致。     

Mn含量对中锰钢微观组织及力学性能的影响

通过金相观察、X射线衍射、透射分析及力学性能测试,探索了Mn含量对中锰钢微观组织及力学性能的影响。结果表明,通过临界区退火处理,不同锰含量的中锰钢(w(Mn):3.86%～5.4%)在室温下均可获得铁素体和奥氏体复相组织,奥氏体含量随Mn含量的增加而增多,而其稳定性呈相反的变化趋势。试验钢强度随Mn含量的增加而增加,断后伸长率及断面收缩率两塑性指标随Mn含量变化呈相反的变化趋势,冲击韧性随Mn的增加而降低。试验钢力学性能随Mn含量的变化与试验钢中Mn的存在形式、逆转奥氏体的含量及稳定性相关。     

Mssbauer 效应在高速钢中残留奥氏体测定上的应用

本文首先应用透射 Mssbauer 法测定了一组标准样品中奥氏体的含量,并且从实验上得到了与已知含量相吻合的结果。然后用背散射 X 射线 M(?)ssbauer 法和 X 射线衍射法测量了一组不同热处理制度下 M_2高速钢中的残留奥氏体含量,两种方法的测量结果可相互比较.     

THE APPLICATIN OF MSSBAUER EFFECT IN MEASUREMENT OF RETAINED AUSTENITE IN HIGH SPEED STEEL

本文首先应用透射Mssbauer 法测定了一组标准样品中奥氏体的含量,并且从实验上得到了与已知含量相吻合的结果。然后用背散射X 射线M(?)ssbauer 法和X 射线衍射法测量了一组不同热处理制度下M_2高速钢中的残留奥氏体含量,两种方法的测量结果可相互比较.     

304不锈钢在ECAP过程中形变诱发马氏体的定量计算

利用X射线衍射对经ECAP挤压及退火处理后的304奥氏体不锈钢进行了物相标定及各物相含量的定量计算.结果表明,经ECAP挤压后,不锈钢内明显形成α'和ε两种形变诱发马氏体,且α'马氏体含量高于ε马氏体含量.挤压后的不锈钢经退火处理后,α'马氏体含量显著下降,ε马氏体含量相对增加.奥氏体含量在第一道次挤压后明显下降,以后道次的挤压和退火处理对其影响较小.     

Quantitative phase analysis of metastable structure in a laser melted Fe-C alloy

Pure Fe-3.5wt% C alloy was surface melted using a cw C0₂ laser and the microstructure of the laser tracks was investigated by scanning and transmission electron microscopy. Structure of the melted zones consisted of dendrites of partially transformed primary austenite and of very fine lamellar ledeburite. The secondary dendrite arm spacings were indicative of a cooling rate of 10⁵ Ks^–1, in good accord with calculations based on the model of a moving Gaussian beam. Using methods of quantitative metallography the volume fraction of dendrites within the melted zone and the volume fractions of the carbide and ferrite phases in the decomposed ledeburite were estimated. These data were combined with the results of a quantitative X-ray diffraction phase analysis (see Part II) and compared with the equilibrium phase diagram. It was found that the volume fraction of dendrites was near the equilibrium value while the volume content of cementite in the rapidly solidified structures was considerably higher than predicted from the equilibrium phase diagram.     

异种钢焊接接头熔合线附近块状铁素体的彩色金相鉴别方法

在对进口及国产受热面管T92-S30432异种钢焊接接头进行常规金相检验时发现,在T92钢侧熔合线附近有块状组织析出。采用先浅侵蚀再染色的复合彩色金相显微组织显示方法并结合显微硬度测度以及能谱分析等方法,对该块状组织进行定性分析以鉴别该块状组织。结果表明：采用该彩色金相显示方法得到显微组织的衬度和清晰度都较高,较好地弥补了黑白金相的不足,可以有效地鉴别出该异种钢焊接接头熔合线附近的块状组织为铁素体相。     

Simulation of hot-rolled dual-phase weathering steel 09CuPCrNi

The continuous cooling transformation diagram of deformed austenite for steel 09CuPCrNi was constructed by means of a combined method of dilatometry and metallography. The diagram exhibits an elongated polygonal ferrite C-curve with a delayed pearlite start and a metastable austenite gap between the polygonal ferrite and pearlite regions and between the ferrite and bainite regions. For this experimental steel, it is possible to obtain a dual-phase microstructure directly by hot rolling and appropriate cooling. Based on the diagram, the technical process of a hot-rolled dual-phase treatment was established and simulated using a thermal simulation testing machine. Dual-phase microstructures were obtained that show some bainite phase and are characterized by an irregular distribution of island-shaped martensite in a matrix of equiaxed ferrite grains. The morphology of the martensite phase is essentially of the lath type, with small areas of micro-twins appearing.     

Thermal,magnetic and composition analyses of the reverse transformation of intermetallic sigma phase to ferrite

The reverse transformation of the sigma phase to ferrite in a duplex stainless steel upon heating has been studied by using differential thermal analysis (DTA), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), quantitative metallography and magnetic susceptibility measurement. It has been demonstrated that the reverse transformation of the sigma phase to ferrite is sensitively affected by the morphology of the sigma phase. However, EDS has shown that the composition of the sigma phase does not significantly affect its reverse transformation behaviour. Magnetic susceptibility measurements and TEM have revealed that untransformed, residual ferrite is present even after prolonged annealing between 873 and 1173 K and hence it does play a role in the sigma-to-ferrite reverse transformation. Quantitative metallography was employed to follow the coarsening of the sigma phase upon annealing and DTA was used to estimate its enthalpies of dissolution. As a potential application, a method for temperature monitoring using duplex stainless steels and DTA is suggested.     

Distinguishing between Chi and Sigma phases in duplex stainless steels using potentiostatic etching

A color interference film etching technique based on the principle of potentiostatic etching has been developed to distinguish, by optical metallography, between Cr-rich sigma and Mo-rich chi phases as well as with simultaneous identification of the ferrite and austenite phases in duplex stainless steels. The optical metallography results are confirmed by semi-quantitative energy dispersive spectrometry analysis and back-scattered electron imaging. The technique is relatively simple and rapid, and makes use of low voltages and a hot etchant. Results have shown distinctively the sigma, chi, ferrite, and austenite phases, and enable observation of the microstructural development, morphology, and kinetics of formation of the phases in duplex alloys. The method, by giving excellent color contrast between sigma and chi, also facilitates quantitative image analysis of the sigma and chi volume fractions.     

Comparison of different methods for measuring strain induced α-martensite content in austenitic steels

Abstract

Several techniques for measuring the strain induced α-martensite content in EN 1.4318 (AISI 301LN) and EN 1.4301 (AISI 304) austenitic stainless steels were compared in order to determine a correlation curve between Ferritescope measurement results and actual α-martensite contents. The studied methods involved Satmagan measurement, magnetic balance measurement, X-ray diffraction, density measurement and quantitative optical metallography. Satmagan, magnetic balance and density measurements were found to give equal α-martensite contents. X-ray diffraction results were affected by the texture but averaging of several diffraction peaks improved the reliability of the results. It was shown that α-martensite can be detected by means of optical metallography, but quantitative analysis is time consuming and inaccurate. The relationship between the Ferritescope results and actual α-martensite contents measured with the other techniques was found to be linear. According to the results, the Ferritescope readings can be converted to actual α-martensite contents by multiplying with a correction factor of 1.7.     

Analysis of ferrite formed in 321 grade austenitic stainless steel

A significant fraction of ferrite has been identified in a 321 grade austenitic stainless steel in the solution heat treated condition. The microstructures were analysed using electron backscatter diffraction, energy dispersive X-ray spectroscopy and X-ray diffraction (XRD) and the stability of the ferrite investigated using heat treatments in a tube furnace, dilatometry and high temperature XRD. The ferrite dissolved ～800°C, then formed again on cooling at temperatures under 200°C. Thermodynamic predictions showed a significant ferrite content at room temperature under equilibrium conditions, and the DeLong diagrams predict an austenite+martensite microstructure in the cast condition. Sensitivity analysis on the DeLong diagram has shown that the nitrogen content had a large effect on the austenite stability. The instability of the austenite and the subsequent transformation to ferrite on cooling can be attributed to low nitrogen content measured in the as received material. It was found that thermal aging of the material caused further transformation of austenite to ferrite as well as the formation of sigma phase that appears higher in nitrogen than the matrix phases. The diffusion of nitrogen into sigma phase may cause instability of the austenite, which could cause further transformation of austenite to ferrite on cooling from the aging temperature. The transformation of austenite to ferrite is known to be accompanied by an increase in volume, which may be of relevance to components made with tight dimensional tolerances.     

Quantitative phase analysis of duplex stainless steel using incomplete pole figures

Abstract

The use of a single, accurate, and relatively quick experimental method suitable for determination of crystallo graphic texture and amounts of phases in the final product is of interest to some manufacturers. The suitability of an X-ray method for this purpose is evaluated in the present paper. The Schulz back reflection technique has been used to record incomplete pole figures of ferrite and austenite in a sample of commercial duplex stainless steel tube. The orientation distribution function was calculated for each phase and then used for the reproduction of complete pole figures. The complete pole figures were applied in quantitative phase analysis (QPhA), by a new method, free from texture induced errors. For comparison, the volume fraction of austenite and ferrite was also determined by means of the classic direct comparison method of Averbach and Cohen as well as by standard quantitative metallography. The proposed method of QPhA was applied for the examination of the amount of retained austenite in certain bearing construction elements.     

Initial stage of isothermal decomposition of austenite to ferrite and graphite in spheroidal graphite cast iron

Abstract

The isothermal decomposition of austenite to ferrite and graphite in a spheroidal graphite cast iron was investigated by dilatometry, metallography, and image analysis. The results gave quantitative, although indirect, information on the kinetics of carbon transfer from austenite to graphite, as well as on the kinetics of the austenite to ferrite and graphite transformation. The relationship between the kinetics and the graphite nodule count was highlighted. The incubation period before ferrite growth was found to be associated with a global contraction of the material, in spite of the related increase in the graphite volume fraction. Calculations showed good agreement with experimental results, except for the rate of carbon transfer, which was found to be much slower experimentally than predicted by calculations based on the volume diffusion of carbon. Possible reasons for this discrepancy are discussed.     

金相学史话(1)：金相学的兴起

Widmanstatten在 19世纪初用硝酸水溶液腐刻铁陨石切片 ,观察到片状 Fe- Ni奥氏体的规则分布 (魏氏组织 ) ,予告金相学即将诞生。 Sorby在 1863年用反射式显微镜观察抛光腐刻的钢铁试样 ,不但看到珠光体中的渗碳体和铁素体的片状组织 ,还对钢的淬火和回火作了初步探讨 ,金相学已基本形成。到 19- 2 0世纪之交 ,Martens(马氏 )和 Osmond对金相学的发展和金相检验在厂矿中的推广做了重要贡献 ,同时 Roberts- Austen(奥氏 )和 Roogzeboom初步绘制出 Fe- C平衡图 ,为金相学奠定了理论基础。到了二十世纪中叶 ,金相学已逐步发展成金属学、物理冶金和材料科学。