发动机冷却系统日常维护及保养.doc

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1、利用高炉水淬渣制备(Ca/Y)-Sialon陶瓷的组织与性能论文作者XX（XX大学 材料各向异性与织构教育部重点实验室，辽宁沈阳 XXXXXX）摘要： 研究了以高炉水淬渣合成的Ca-Sialon粉体为原料制备(Ca/Y)-Sialon的烧结致密化过程、材料的力学性能、显微组织、相组成和材料的断裂特征。结果表明，适量的Y2O3促进材料的烧结致密化和提高材料的力学性能，但Y2O3（大于10%）过量时对材料的烧结和力学性能不利。掺杂Y3+的(Ca/Y)-Sialon呈柱状晶，随着Y2O3含量的增加和烧结温度的提高，(Ca/Y)-Sialon呈柱状晶出现粗化和等轴化。含10Y2O3的材料在1700烧结

2、时可获得较高的力学性能。关键词：(Ca/Y)-Sialon，水淬渣，无压烧结，力学性能，显微组织中图分类号: TQ174高炉水淬渣是炼铁过程中产生的副产品，它的主要成分为SiO2、Al2O3、CaO和一些含Fe杂质相，目前主要用于制造水泥。如何提高炉水淬渣的附加值，是人们梦寐以求的事情1。目前利用高炉渣合成Sialon粉体已经进行了广泛的研究，如刘克明2等研究了利用高炉渣合成Ca-Sialon的热力学分析与工艺优化，姜涛等3研究了高炉渣合成Ca-Mg-Sialon的工艺参数，蒋久信等4研究了炉渣Ca-Sialon粉体的高温自蔓延燃烧合成工艺。但目前利用炉渣合成Sialon粉体无压烧结制备Sia

3、lon陶瓷的性能还不高，并且工艺复杂，如陈卫武等5利用采用埋粉的方式无压烧结（1800）和热压烧结制备了（Ca，Mg）-Sialon陶瓷。Sialon陶瓷具有优良的性能，在结构陶瓷方面具有广泛的用途，被认为是最有希望的结构陶瓷之一6。但由于-Sialon材料的高含氮量, 给材料的无压烧结致密化带来一定的困难7.作为添加剂的金属离子在烧结后能进入-Sialon结构从而减少晶界相的含量, 并改善材料的力学性能.最近的研究表明Y2O3可以降低陶瓷的烧结温度8.本工作以矿渣合成Ca-Sialon为原料、以Al2O3和Y2O3为添加剂，研究了无压烧结(Ca/Y)-Sialon陶瓷的致密化行为、力学性能、

4、相组成及显微结构，为矿渣的利用提供了新的途径。1 实验过程实验采用由高炉水淬渣合成的Ca-Sialon粉(上海宝田公司提供，主相为Ca-Sialon, 杂质主要为Fe4N，同时还有Cr、Mo、Mn等元素)为原料，以Al2O3 (平均粒径小于1m) , Y2O3 (含量为99.9 wt%，平均粒径小于1m) 为烧结助剂。试样中Al2O3的含量为5，Y2O3 的含量分别为4、6、8、10、12和14wt，成形粘结剂为聚乙烯醇，加入量为总质量的10。将按组份配置的初始粉料球磨混合12h，磨球为氧化铝球，介质为无水乙醇。球磨后的物料经干燥、造粒后，在40MPa压力下单向预压成形（条样尺寸为6636mm

5、），再在200MPa下冷等静压成形。成形坯体经10012h烘干后，在纯0.1MPa的N2气氛下烧结，烧结制度分别采用17001.5h和17501.5h两种制度。利用阿基米德定律测定试样的体积密度。用理学D/max-rB型X射线衍射(X-ray diffraction，XRD)仪进行相组成分析。采用WD210型电子万能试验机测量材料的三点弯曲强度,加载速率为0.5mm/min。弯曲强度值取5个样品的平均值。使用维氏硬度计测量材料的维氏硬度，加压载荷为5kg，取4个样品的平均值。利用SSX-550型扫描电镜观察试样的显微形貌，并利用EDX进行微区成分分析。采用GX71金相显微镜进行组织分析。利用L

6、EXT OLS3000激光扫描共聚焦显微镜进行材料断裂行为分析。2 结果与讨论2.1 不同Y2O3含量材料的烧结行为图1为试样的体积密度随Y2O3含量的变化曲线。由图可知，随着Y2O3含量的增加，试样的体积密度呈现先增加后降低的变化规律，不同Y2O3含量试样在1750烧结的密度均比1700烧结的低，当Y2O3含量含量为10、烧结温度为1700时材料的体积密度最高为3.32g/cm3。这是由于Y2O3一方面其Y3+和O2容易固溶到Sialon晶格中使Sialon晶格发生畸变9，另一方面Y2O3与试样中添加的Al2O3形成YAG10，从而促进了材料的烧结行为. 但当Y2O3含量超过10时，固熔于S

7、ialon中的量明显增加，使Sialon的熔点大大降低，试样中易出现挥发物和气泡，使试样的密度降低，当烧结温度增加时，这种出现挥发物和气泡的情况也增加，因此试样的密度也降低。2.2 材料的力学性能图2和图3分别为Y2O3含量对材料维氏硬度和抗折强度的影响曲线。由图可知，材料的维氏硬度和抗折硬度均随Y2O3含量的增加呈现先增加后降低的变化趋势，这与Y2O3含量对材料体积密度的影响规律（图1）相同，说明适量的Y2O3促进材料烧结，使材料的力学性能均提高，但Y2O3含量过高使材料密度降低，因此材料的力学性能也降低。从图2和图3还可以看出，烧结温度对维氏硬度的影响与Y2O3含量有关，当Y2O3含量小于

8、10%时1750烧结材料的维氏硬度比1700烧结的高，而Y2O3含量大于10%时则相反. 1750烧结材料的抗折强度均小于1700的烧结材料。这可能是因为维氏硬度与Sialon中的Y2O3固熔量有关，抗折强度与Sialon的晶形有关，当Y2O3含量小于10%时Sialon中的Y2O3固熔量随烧结温度的增加而增加，因此1750烧结材料的维氏硬度比1700烧结材料的高，但Y2O3含量大于10%时，材料密度对维氏硬度的影响起主要作用，因此1750烧结材料的维氏硬度比1700烧结材料的低；烧结温度高导致Sialon的棒状晶形减少、粒状晶形增加，因此1750烧结材料的抗折强度比1700烧结材料的低。当1

9、700烧结时材料的维氏硬度峰值达到13.68GPa、而抗弯强度最高为237MPa。2.3 材料的组织和物相图4为不同Y2O3含量的材料在不同烧结温度下的金相组织。由图可知随着Y2O3含量的增加材料中Sialon柱状晶的比例在增加（图4a、b到图4c、d），随着烧结温度的增加材料中Sialon等轴晶的比例在增加。这是由于单相Ca-Sialon通常形成等轴晶体11，而固溶Y3+ 的(Ca/Y)-Sialon则可能形成柱状晶体12-13，烧结温度高可以促进(Ca/Y)-Sialon柱状晶的粗化和等轴化。图4中的白色球形颗粒为Fe4N，烧结温度的增加促进了Fe4N的长大。图为Y2O3含量为10%材料在

10、不同烧结温度下的XRD衍射图谱，由图可知，随着烧结温度的增加材料中FeN的衍射峰明显，并逐渐出现出YAG的衍射峰，说明烧结温度促进了Fe4N的长大，Y2O3和Al2O3的加入生成了少量的YAG。2.4 材料的断裂特点图6为Y2O3含量分别为6%和10%的材料在1700烧结后的断口照片。由图可知，两种成分样品均为沿晶断裂，图6a中比图6b存在较多的亚裂纹，也说明Y2O3含量的增加促进了材料的烧结，减少了材料中的亚裂纹，这也是Y2O3提高材料强度的另一个原因。3 结论（1）适量的Y2O3促进材料的烧结致密化和提高材料的力学性能，但Y2O3（大于10%）过量时对材料的烧结和力学性能不利。（2）掺杂Y

11、3+的(Ca/Y)-Sialon呈柱状晶，随着Y2O3含量的增加和烧结温度的提高，(Ca/Y)-Sialon呈柱状晶出现粗化和等轴化。（3）含10Y2O3的材料在1700烧结时可获得较高的力学性能。Construction and properties of (Ca/Y)-Sialon ceramics synthesized from blast furnace water quenching slagXXXXXXXAbstract: Rare-earth composite (Ca/Y)-Sialon ceramics were fabricated using Ca-Sialon pow

12、ers synthesized from blast furnace water quenching slag. Investigations were carried out to analyze the densification process in sintering, mechanical properties, and microstructure, phase-transformation and fracture characteristics. The results show that a certain amounts of Y2O3 additions can prom

13、ote the densification action of sintering and improve mechanical properties of (Ca/Y)-Sialon ceramics. But the excess amounts of Y2O3（more than 10%）is disadvantaged. In the samples elongated (Ca/Y)-Sialon grains were found and the microstructure changed from elongated to agglomerate with increasing

14、yttrium levels. The excellent mechanical properties of (Ca/Y)-Sialon ceramics are obtained when sintering at 1700 with the addition of 10% Y2O3.Keywords: (Ca/Y)-Sialon, water quenching slag, pressureless sintering, mechanical properties, microstructureBlast furnace water quenching slag is a by-produ

15、ct produced in the iron-smelting course. Its main constituent includes SiO2 , Al2O3 , CaO and some impurity phase of Fe, which mainly used for making cement at present. How to improve added value of blast furnace water quenching slag is the thing that people dream of 1. at present People utilize Bla

16、st furnace slag to synthesis Sialon powder and it already to be carried on extensive research, for instance Liu KeMing 2 ,etc. have studied that thermodynamics analysis and craft optimization of utilizing Blast furnace slag to synthesis Ca-Sialon, Jiang Tao ,etc. 3 have studied that processing param

17、eter of utilizing Blast furnace slag to synthesis Ca-Mg-Sialon, Jiang JiuXin ,etc. 4 have studied high temperature SHS synthesis craft of slag Ca-Sialon powder. But at present the property of the pressless-sintered Sialon ceramic using Sialon powder synthesis form slag is not good enough, and the cr

18、aft is complicated, for instance Chen WeiWu, etc. 5 utilizes the methods of burying powder pressless-sintered(1800) and the hot-press sintered to get ( Ca, Mg)-Sialon ceram. Sialon ceram has fine property, has extensive uses in the structure ceramic, and to be considered one of the most promising st

19、ructural ceramics 6 . But because of the high nitrogen content of the -Sialon material, there are some difficulties in the pressless-sintering densification of the material. 7 After sintering, the metal ion as of additive can enter -Sialon structure to reduce the content of grain boundary phase, and

20、 improve the mechanics property of the material. Recent research indicates that Y2O3 can reduce the ceramic sintering temperature 8 .In our work, investigations were carried out to analyze the densification process in sintering, mechanical properties, phase, microstructure of the pressless-sintering

21、 (Ca/Y)-Sialon with Ca-Sialon synthesized from slag as raw materials, with Al2O3 and Y2O3 as additive. It offers a new way for the use of the slag. 1 An experiment course The experiment adopted Ca-Sialon powder synthesis from blast furnace water quenching slag (offered by BaoTian Company of Shanghai

22、, main constituent is Ca-Sialon, Fe4N is the mainly impurity elements, there are also some impurity elements such as Cr, Mo, Mn, etc.) for raw materials, with Al2O3 (average grain size is smaller than 1m) and Y2O3 (content is 99.9 wt%, average grain size is smaller than 1m) as sintering assistant. T

23、he content of Al2O3 is 5%, which of Y2O3 are 4, 6, 8, 10, 12 and 14wt% respectively in the Sample. Confectioning binding admixture is polyvinyl alcohol; add 10% of total quality. Then ball milling the initial powder material according to batch formula and mix 12h. Use alumina as ball grinding ball,

24、the medium is the ethyl alcohol. After the ball milling, the material was dried, prilled, and then made a single-phase-pre-extrude under 40MPa pressure (the size of sample is 6* 6* 36mm), and then cold isostatic compaction under 200MPa. The body dried at 100 for 12h, then sintered under pure N2 atmo

25、sphere of 0.1MPa, sintering system adopt 1700 for 1.5h and 1750 for 1.5h two kinds of systems respectively. Utilize Archimedes principle to determine the volume density of the sample. Utilize Model D/max-rB X ray diffraction (X-ray diffraction, XRD) to analyze the phase. Adopt the universal material

26、 testing machine of Model WD210 electron to measure flexural strength three of the material, its load speed is 0.5mm/min. flexural strength value fetches the averages of 5 samples. Use Vickers hardness tester to measure the Vickers hardness of the material, the load is 5kg, fetch the averages of 4 s

27、amples. Utilize the Model SSX-550 stereo scan to scan the micro- pattern, and utilize EDX to carry on micro-area composition analysis. Adopt GX71 metallographical microscope to analyse the microscopic structure. Utilize LEXT OLS3000 microscope to carry on material fracture behavior analysis. 2 resul

28、ts and discussing 2.1 Sintering behavior of different Y2O3 content materials Fig.1 shows volume density of the samples varies with Y2O3 content. We can see from the figure, with the increase of Y2O3 content, volume density of the samples reduced after increasing, density of samples of different Y2O3

29、 content sintered in 1750 are lower than that in 1700, the highest volume density of the material is 3.32g/cm3 as content of Y2O3 content for 10%, temperature of sintering in 1700. On one hand this is because Y3 + and O2- ion of Y2O3 is easy to get into Sialon crystal lattice, which will make Sialon

30、 crystal lattice distortion 9 , on the other hand, Y2O3 and Al2O3 added in and sample forms YAG 10 , thus promoted the sintering behavior of the material , but when Y2O3 content exceeds 10%, the solid solution in Sialon obviously increases, which makes the melting point of Sialon reduce greatly , it

31、 is easy to present volatile matter and bubble in the sample, make the density of the sample reduce. When sintering temperature increases, volatile matter and bubble increase too, so the density of the sample is reduced too. 2.2 Mechanics performance of the material Fig.2 and Fig.3 shows the influen

32、ce of Y2O3 content on Vickers hardness and flexural strength respectively. We can see from the figures, Vickers hardness and flexural strength of the samples reduced after increasing with the increase of Y2O3 content, this is the same as law of influence on volume density of material with Y2O3 conte

33、nt (Fig. 1), prove that right amount Y2O3 promotes materials to sintered, make the mechanics property of the material raise, but excess Y2O3 content makes the density of material reduce, so the mechanics property of the material is reduced. We can also see from the figures Fig.2 and Fig.3, influence

34、 of sintering temperature on the hardness relate to Y2O3 content, when Y2O3 content below 10%, Vickers hardness is higher sintered in 1750 than that in 1700, but when Y2O3 content is over 10%, the situation is opposite. Flexural strength of the sintering materials is lower sintered in 1750 than that

35、 in 1700. This may because Vickers hardness is related to Y2O3 solid melting amount in Sialon, while flexural strength is related to crystals shape of Sialon, Y2O3 solid melting amount in Sialon increase with the sintering temperature increases when Y2O3 content below 10%, so Vickers hardness of mat

36、erial is higher sintered in 1750than sintered in 1700, when Y2O3 content is over 10%, the influence of material density on hardness is the main one, so Vickers hardness of material is lower sintered in 1750 sintered in than 1700; The numbers of rod like grains of Sialon reduce and equiaxed grains of

37、 Sialon increase with high temperature, so flexural strength of material is lower sintered in 1750than sintered in 1700. The peak value of the hardness of the material reaches 13.68GPa; the highest flexural strength is 237MPa when sintered in 1700. 2.3 The structure and phase of the material Fig. 4

38、is metallurgical structure photos of material of different Y2O3 content under different sintering temperature. We can see from the figures that the rate of Sialon columnar grains of the material increase with Y2O3 content increase (From Fig. 4a, b to Fig. 4c, d), the rate of Sialon equiaxed grains o

39、f the material increase with sintering temperature increase. This is because single-phase Ca-Sialon usually form equiaxed crystal 11 , Y3+ solid melting (Ca/Y)-Sialon may form columnar crystal12-13, high sintering temperature can promote the microstructure changed from elongated to agglomerated. The

40、 white spherical particle in Fig. 4 is Fe4N, increase of sintering temperature promoted the growing up of Fe4N. Fig.5 is X-ray diffraction figure of materials that the Y2O3 content is 10%, sintered at different temperature, We can see from the figure, the diffraction peak of FeN is obvious, and the

41、diffraction peak of YAG appears gradually with the increase of sintering temperature, prove that the increase of sintering temperature promoted the growing up of Fe4N, the joining of Y2O3 and Al2O3 form a small amount of YAG. 2.4 Fracture characteristic of the material Fig. 6 photos of fracture of m

42、aterials which the Y2O3 content is 6% and 10% respectively after sintering in 1700. We can see from the figure, two kinds of composition samples are all 沿晶断裂, samples of Fig. 6a have more inferior crackle than Fig. 6b , prove that the increase of Y2O3 content has promoted the sintering of the materi

43、al too, has reduced the inferior crackle in materials , this is another reason why Y2O3 improves the intensity of material too. 3 conclusions ( 1) Right amount Y2O3 promotes the sintering densification process and improve the mechanics property of the material, but it is disadvantageous to sintering

44、 of the material and mechanics property when Y2O3 is excessive (over 10%). ( 2) Y3+ dope (Ca/Y)-Sialon is columnar crystals, the columnar crystals of (Ca/Y)-Sialon become .thicker and equiaxed with increase content of Y2O3 and improvement of sintering temperature.( 3) The material including 10% Y2O3 can obtain higher mechanics property when sintering at 1700.