Ti-1023合金铸锭铁偏析控制

在工业化生产条件下,分析并阐述了Ti-1023合金铁组元偏析的特点及其影响因素,探索了铁偏析规律,提出了控制铁偏析的措施.     

Ti-1023合金铸锭铁偏析控制

在工业化生产条件下，分析并阐述了Ti-1023合金铁组元偏析的特点及其影响因素，探索了铁偏析规律，提出了控制铁偏析的措施。     

铁碳合金凝固过程微观溶质偏析模型分析

为了选择正确的微观溶质偏析模型研究铁碳合金的凝固过程,利用Thermo-Calc商业软件计算了不同碳含量下铁碳合金的固相线温度、液相线温度和碳的平衡分配系数,利用数值方法研究了不同微观溶质偏析模型下铁碳合金的固液界面温度和无量纲液相溶质浓度.数值结果表明:文献中常用的碳平衡分配系数不准确;C lyne-Kurz模型和Sche il模型不能准确地预测固液界面温度,B rody-F lem ings模型不能正确地预测碳偏析,建议采用杠杆模型和大中逸雄模型计算铁碳合金凝固过程的微观溶质偏析.     

铁基混合料成分偏析分析方法

在利用粉末冶金工艺制备铁基混合粉末过程中,由于铁基零部件各组分的密度及粒度差异,混合料经常存在偏析现象,这会引起烧结产品尺寸和性能的不稳定,因此对混合料的成分偏析程度进行测试或评定具有实际意义。本文系统总结了铁基混合料成分偏析分析方法,包括耐扬尘性分析法、成分分析法、色泽观察法、烧损测试法;在实际工程中,可以根据实际需求选取上述试验方法。     

钛在防止球铁复合轧辊反白口中的应用

针对高硬度合金球铁定(减)径机复合轧辊在生产中出现的反白口缺陷进行分析,其主要形成原因为合金元素区域偏析造成;提出了在铁水中加入钛合金,利用钛元素干扰其它合金元素的区域偏析的工艺措施,从而消除反白口缺陷,取得了较好的产品质量。     

点状偏析对一种35Ni—15Cr型铁基高温合金力学性能和热加工性能的影响

在一种35Ni-15 Cr型铁基高温合金90mm方试料上,研究了点状偏析(φ≤1mm)对力学性能和热加工性能的影响。结果表明,点状偏析使横向室温拉仲延伸率、断面收缩率和抗张强度降低,但仍能达到技术条件要求的指标;点状偏析对横向室温拉伸屈服强度、室温冲击韧性和750℃35kgf/mm~2持久寿命没有影响,对纵向室温拉伸性能、室温冲击韧性和750℃35kgf/mm~2持久寿命也没有影响;严重的点状偏析使合金允     

阳极铝合金熔炼铸造工艺研究

研究了合金组织对铝阳极铸造性能的影响，提出了防止或消除铸锭偏析、热裂等缺陷以及控制杂质铁、硅含量的方法。     

中心偏析原因危害评定及预防(下)

（续上期）４中心偏析预防４．１减少易偏析元素的含量硫磷等元素属于偏析元素，在一般情况下应尽量减少其含量。去除的方法除炉内炼钢过程的除硫磷外（目前仍然担负着主要任务，发展较快的偏心炉底出钢技术对净化钢液有明显效果），还有液态铁的预处理和液态钢炉外精炼技...     

半连续铸锭缺陷及其预防措施（9）

3.3 金属化合物一次晶偏析在锰、铁、镍、钛、钒含量较高的变形铝合金中,当化学成分和工艺因素控制不当时,铸锭中可能出现含有这些元素的金属化合物一次晶偏析.3.3.1 组织特征及其本性在铸锭低培试片上发现的金属化合物一次晶偏析,呈黑褐色边界整齐的块状、条状和点状,在断口上也呈块状、针状或点状,但颜色发亮;具有金属光泽(图77).这种金属化     

马钢一铁总厂铁水高硅伴生高磷原因分析

对马钢一铁总厂的铁水硅和磷含量相关性进行统计分析,从检测方法对硅、磷检测结果的影响、磷在铁水样的偏析及高磷块矿加入方式三个方面对一铁总厂铁水高硅伴生高磷现象探索及原因分析,为一铁总厂铁水磷管控提供技术支撑。     

Grain boundary segregation of antimony and nickel in iron

This paper reports a study of grain boundary segregation of antimony and nickel in iron. These results show that nickel additions to the matrix increase antimony segregation. This observation is in agreement with previously reported work. Antimony additions to the matrix or segregation to the grain boundary have no measurable effect on nickel segregation. Decarburization increases segregation of both antimony and nickel.     

The effect of fe additions on the embrittlement of Cu-Bi alloys

The effect of iron additions on the embrittlement of Cu-Bi alloys was studied by monitoring the ductility and grain boundary chemistry of embrittled specimens as a function of iron content. Mechanical properties improved for the same embrittling heat treatment as the bulk iron level increased, and this was correlated with a decrease in bismuth segregation to the grain boundaries. No iron was detected segregated to the boundaries, and several possible mechanisms were proposed to explain the beneficial effect of the iron additions. It was also found that approximately 70 min at 530°C is required to attain equilibrium for segregation of bismuth to the grain boundaries, and a diffusion coefficient derived from this data was found to be reasonable for bulk diffusion of bismuth in copper.     

The effect of fe additions on the embrittlement of Cu-Bi alloys

The effect of iron additions on the embrittlement of Cu-Bi alloys was studied by monitoring the ductility and grain boundary chemistry of embrittled specimens as a function of iron content. Mechanical properties improved for the same embrittling heat treatment as the bulk iron level increased, and this was correlated with a decrease in bismuth segregation to the grain boundaries. No iron was detected segregated to the boundaries, and several possible mechanisms were proposed to explain the beneficial effect of the iron additions. It was also found that approximately 70 min at 530°C is required to attain equilibrium for segregation of bismuth to the grain boundaries, and a diffusion coefficient derived from this data was found to be reasonable for bulk diffusion of bismuth in copper.     

Surface segregation of calcium oxide in wustite and its effects on the reduction

The segregation of calcium oxide to the surface of wustite was investigatedin situ by Auger electron spectroscopy at temperatures in the range of 973 to 1223 K. Calcium oxide indicated a strong tendency to segregate, with the molar fractions at the surface being 10 to 1000 times the molar fractions in the bulk (X _CaO ^bulk ). The segregation isotherms showed maxima at intermediate molar fractions in the bulk (X _CaO ^bulk = 0.003 or 0.005). The enthalpy change for the segregation increased from −43.3 to −5.20 kJ/mol with increasing X _CaO ^bulk . The main driving force of the segregation may be the relaxation of the strain energy generated around calcium ions. Calcium oxide also segregates at the surface of iron in contact with the wustite. By the segregation of calcium oxide, the surface energies of wustite and iron may decrease whereas the wustite/iron interfacial energy may increase. The enhancement of the reduction of wustite by calcium oxide is concluded to essentially occur by the good and continuous direct contact of wustite surface with reducing gases owing to the suppression of new iron nucleus and owing to the contraction of the wustite/iron-nuclei interfacial area compared with the free-surface area of wustite in order to decrease the total energy.     

Effect of Carbon on Grain Boundary Segregation of Phosphorus and Phosphorus-Induced Intergranular Fracture in High Purity Iron with Phosphorus

Ａｓｗｅｌｌｋｎｏｗｎ ,ｔｈｅａｄｄｉｔｉｏｎｏｆｃａｒｂｏｎｃａｎｐｒｅ ｖｅｎｔｔｈｅｐｈｏｓｐｈｏｒｕｓ ｉｎｄｕｃｅｄｉｎｔｅｒｇｒａｎｕｌａｒｆａｉｌｕｒｅｉｎｉｒｏｎ .ＢｕｔｉｔｉｓｔｈｅｒｅｓｕｌｔｏｆｕｓｉｎｇＡＥＳ (Ａｕｇｅｒｅｌｅｃ ｔｒｏｎｓｐｅｃｔｒｏｓｃｏｐｙ)ａｎａｌｙｓｉｓｉｎｆｒａｃｔｕｒｅｄｓｕｒｆａｃｅａｎａｌ ｙｓｉｓ .ＥｒｈａｒｔＨｅｔａｌ[1] ,ｉｎｏｒｄｅｒｔｏｅｘｐｌａｉｎｔｈｅｍｅｃｈ ａｎｉｓｍｏｆｃａｒｂｏｎｓｕｐｐｒｅｓｓｉｎｇｔｈｅｉｎｔｅｒｇｒａ…     

铜包铁粉的应用及制备

铜包铁粉是一种将铜包在铁粉表面形成包覆层的复合粉末,被用来改善铜铁混合粉末组织不均、成分偏析等问题。本文综述了铜包铁粉的应用及制备方法,介绍了机械球磨涂覆法、置换镀铜法、化学镀铜法等铜包铁粉制备技术的基本原理及研究进展,总结了铜包铁粉制备过程中存在的问题,并展望了铜包铁粉的发展方向。     

Influence of phosphorus addition on the surface tension of liquid iron and segregation of phosphorus on the surface of Fe-P alloy

This article presents a study of the surface tension and phosphorus surface segregation in Fe-P alloys. The surface tension was measured by the sessile drop technique. The result of the dynamic surface tension for the low phosphorus content alloys shows that the alloy surface vaporization has a clear effect on the surface tension and causes a positive surface tension temperature coefficient. However, from this article, it is evident that phosphorus in liquid iron acts as a surface active element similar to arsenic. The surface segregation was determined using Auger electron spectroscopy. The result on the surface analysis of as-solidified sample indicates that the adsorption of impurity elements, such as oxygen, carbon, and nitrogen, can conceal phosphorus segregation on the free surface. Phosphorus segregation was also examined in the samples as-cleaned by Ar⁺ and then treated 30 minutes at 650°C. Phosphorus was found to segregate extensively on the surface of the alloys. On the basis of the analysis of the published data, the surface active intensity sequence of some nonmetallic elements was arrayed, and the surface active intensity of fluorine and boron in liquid iron was estimated.     

An investigation of grain-boundary embrittlement in Fe−P,Fe−P−S,and Fe−Sb−S alloys

Grain-boundary embrittlement of pure iron due to phosphorous, antimony and sulfur is studied using fracture appearance transition temperature measurements and Auger electron emission spectroscopy chemical analysis of fractured surfaces. Phosphorus and sulfur are found to segregate to grain boundaries in the entire ferrite range. Segregation to grain boundaries of these elements in the austenite appears to be negligible. It is shown that the segregation of these elements to grain boundaries in iron does not conform to the Gibb's equilibrium segregation model. Sulfur appears to be a more severe embrittler of iron than does phosphorous. P. V. RAMASUBRAMANIAN formerly was Graduate Research Assistant, University of Minnesota. D. F. STEIN, formerly Professor, Department of Mechanical and Chemical Engineering, University of Minnesota     

Grain boundary segregation of sulfur in iron

This paper reports a study of grain boundary segregation of sulfur in iron. The results show that if the amount of sulfur in the alloy is greater than the solubility limit, the amount of segregation increases with increasing ageing temperature. When the temperature is raised above the point where all sulfur goes into solution, the amount of segregation decreases with increasing temperature. These results can be explained quite straightforwardly by McLean's model for segregation. However, at high bulk concentrations. Auger analysis may be difficult because the signal obtained from a grain boundary facet will arise from a combination of segregated sulfur and precipitated sulfur.     

Grain boundary segregation of sulfur and antimony in iron alloys

A correlation between sulfur and antimony grain boundary segregation has been observed on inter-granular surfaces of iron by Auger electron spectroscopy (AES). The slope of a plot of S/Sb indicated a ratio of two antimony atoms per sulfur atom arriving at the grain boundary, while the ratio for the total S/Sb at the grain boundary was about 1.2. These results were obtained with Fe, Fe + 0.07Mn, Fe + 0.03Sb, Fe + 0.1Mn + 0.02Sb, and Fe + 0.1Mn + 0.05Sb (at. pct) alloys. Possible expla-nations for this correlated segregation, such as cosegregation of sulfur and antimony, precipitation of a thin layer of antimony sulfide, and compctitive segregation with carbon and nitrogen, were evalu-ated using AES, X-ray photoelectron spectroscopy (XPS), and scanning transmission electron mi-croscopy with energy-dispersive X-ray (STEM-EDS). The results of these analyses indicated that there was no resolvable antimony sulfide phase in the grain boundary and that S and Sb were not chemically bound at the grain boundary in a two-dimensional phase. The S was shown to be strongly bound to the iron in a chemical state close to that of an iron sulfide, but the Sb was in the elemental state. Nor could this correlated segregation be satisfactorily explained by a cosegregation process nor by compctitive segregation with other elements. The most plausible explanation appears to involve the effect of sulfur on the activity/solubility of antimony or antimony on the activity/solubility of sul-fur, as explained by an increase in the ratioX _c /X _Co in the Brunauer-Emmett-Teller (BET) adsorption isotherm adapted for equilibrium segregation in solids.