中南大学粉末冶金原理PPT1.ppt

Powder Metallurgy PrincipleRuan Jianming Powder Metallurgy Research Institute 2007,Particle Science and Engineering粉末冶金原理(课程分布)40学时,教学方式:双语讲学 Chinese/English课程内容:Part I Powder fabrication 粉体制备 Part Powder characterization 性能 How do the powders fabricate？Main methods to fabricate powders What physio-chemical phenomenon could be observed during powder fabrication？Which method is suitable to sphere particles？,How about the particle morphologies？How can we obtain the high purity？What takes place during the powder fabri.?Which condition to control the particle size?What can we do?related powder makings.Continuers What are the microstructures of the particles?What is the apparent density of the powders?Which equipment can measure the fine particles?,课时安排 Talking arrangements,参考书籍:References Powder Metallurgy Science 粉末冶金原理 黄培云 P/M.Principle考核成绩 Score 作业30%卷面考试70%,What is Powder Metallurgy,Powder metallurgy Study of the processing of metal powders,including the fabrication,characterization,and conversion of metal powders into useful engineering components.Study of the basic laws and mechanisms of powder fabri.,powder compaction,sintering and surface treatments.R&D of novel materials and products.,Powder Metallurgy Processing,Powder Metallurgy Processing,粉末冶金材料和制品的工艺流程举例,Reasons for using powder metallurgy,refractoryreactive(example:tungsten lamp filaments),alloysmicrostructures(example:stainless steel filters),Ideal Applications(example:porous tantalum capacitors),The future of powder metallurgy,A comparison of the relative production for some common metal powders,logarithmic scale.,High volume production of precise,high quality structural parts from ferrous alloys;Consolidation of high performance materials,where full density and reliability are primary concerns;Fabrication of difficulty to process materials,where fully dense high performance alloys can be fabricated with uniform microstructure;,Further considerations 1,Economic consolidation of specially alloys,typically composites containing mixed phase;Synthesis of non equilibrium materials such as amorphous,microcrystalline,or some special alloys;Processing of complex parts with unique ingredients(组元）or uncommon shapes.,Further considerations 2,历史部分:武器,生活用具,艺术建筑Weapon,life facilities,arts-construction,etc.现代部分:硬质合金,高温材料,汽车部件,军事工程Cement carbide,refractory materials,automobile parts,equipments in defensive,civilization products,etc.目前,粉末冶金最发达的国家瑞典(Sweden)硬质合金工业非常发达Hoganess,建立许多子公司,Be number one 其次是北美(North American)和西欧(western European)。德国的粉末冶金工业也是处于世界前列-工具钢.,tooling steel.,粉末冶金发展 History and development of P/M,美国的粉末冶金公司主要产品用户是汽车制造商producer，汽车工业auto vehicle industry发达，带动了美国的粉末冶金工业发展，这是因为发达的汽车工业，大量a huge of application 用粉末冶金部件。Same to American，日本Japan的汽车工业的发展带动了粉末冶金工业发展。Different to China与中国不一样，the western countries and Japan西方或日本的粉末冶金工业是由两部分构成 conbined by two part制粉公司：制备各种粉末：Companies to fabricate and supply powders制品公司：买进粉末，制备零部件：Companies to fabricate final parts,能够大量节约材料、low cast无切削、less cuting少切削，普通铸造合金切削量在30-50%，粉末冶金产品可少于5%。Less or absent cutting machining.“Net shaping”能够大量节省能源 energy saving能够大量节省劳动 labor saving能够制备其他方法不能制备的材料 specific materials and/or products 能够制备其他方法难以生产的零部件 the material and part that are difficultly to be produced by other methods,粉末冶金技术的优越性与局限性 advantages and limitation,粉末冶金的特点 particularly points,能生产用普通熔炼方法无法生产的具有特殊性能的材料；ability to produce materials which can not be produced by other method.,Powder metallurgy disadvantages and limitation,Rather lower mechanical properties,for their pores in partsSize and morphological limitation,for press machine.Rather lower wrought properties,for the products may contain oxide that induce materials brittle.Rather small industry background compared with casting and conventional materials industry,such iron and steel produced on big scale.1+12,new materials and high performancePowder metallurgy plus conventional material processing,快速原形制备技术,RSP粉末注射成形、PIM快速冷凝技术获得非晶粉末、RST粉末溅射成形、powder spray forming机械合金化技术、MA 温压成形技术,Worm Comp.纳米粉末技术,Namo-Tech等静压成形-烧结技术,ISP-sintering 高性能材料研发，等等.,粉末冶金新技术 Novel techniques of powder metallurgy,A Interest Comparison,Metal powders:109 kg/yearIndustry minerals:300 times 109 kg/yearCoffee,tea,and tobacco:1010 kg/yearPowder metallurgy is a prolonged growth phase;Iron and steel,aluminum,copper,nickel,and tungsten are the main consumption,worldwide.,Automobile industry,Gear parts,Mechanical industry,P/M Industry 2005,1）铁基结构合金的高精度high precise高质量high quality大数量产品。2）致密高性能材料，主要是理想的密度和牢固性full density and reliability。3）难加工材料的制造，difficulty to process materials全密度具有统一微观结构的高性能合金。4）特殊合金，主要为包含有多相的组分multi-composites containing mixed phase，通过增强密度的工艺来制造。These will often be fabricated by enhanced densification.5）非平衡nonequilibrium材料的合成例如such s amorphous非晶，micro-crystalline,or metastable alloys微晶和亚稳合金。6）具有独特组分或不常用形状的特殊附件的工艺。,粉末冶金未来 The future of the powder metllurgy,Copper and Copper base powder in North AmericaCopper and copper-base powder in 2004 increased 11.3%and copper powder base parts increased 7%.,International iron and steel powder Metal powder in 2004 increased by 6.5%to 527,918(mt),figure Iron powder increased 7%over 2003 to 430,119mt.,International copper and copper base powders in 2004,*st,P/M parts content in a typical vehicle,North America copper and copper base powder,Stainless steel powder increased 5%to an estimated 8,488 mt.Tungsten powder increased 16%to 3,177 mt and tungsten carbide powder increased almost 12%.Although there are about 10 companies making aluminum P/M parts,two players dominated the market in North America.European iron and steel powder in 2004 fared better than North America,increasing by 8.8%to 172,952mt.Increases in iron powder in Japan did not match North America.Estimate that that the iron powder market now exceeds 908，000mt,Impact of China,In the last several years,China poses both a competitive threat and potentially huge opportunity.It has an estimated 680 P/M part makers,but only about five of these are considered capable of making high quality P/M parts.The Chinese P/M parts industry is experiencing an estimated 19%annual growth rate.,The typical passenger car in China contains about 4.7kg of P/M parts.China produced about 85000mt of P/M parts.Chinese P/M industry will undoubtedly increase its quality capability as more funds are invested,particularly by Western companies.Currently more than 20 non-Chinese firms representing the U.S,Europe,Japan,Korea,and Taiwan have P/M plants in China mainland.On the other hand,China is beginning to impact the European automotive market,selling inexpensive cars.,Chapter 2 粉末制备方法 Powder fabrication methods,1 物理机械法 Physio-Mechanical Protocol1.1 机械研磨法制备粉末 Milling 1.2 高温雾化法制备粉末 Atomization2 物理化学法制备粉末2.1 氧化物还原法制备粉末 reduction of metallic oxides,2.2 气相沉积法制备粉末 precipitation from atmosphere phase2.3 液相沉积法制备粉末 precipitation from liquid phase2.4 电解法制备粉末 electrolytic fabrication techniques from the electrode2.5 纳米及超细粉末制备技术 nano/ultro fine powder preparation,从过程的实质来看，大体上可以归纳为两大类，即物理机械法mechanical 和物理化学physio-chemical 法粉末的生产方法很多，从工业规模industrial scale而言，应用最广泛pervasive used method的是还原法reducing、雾化法和电解而气相沉淀法vapor decomposition 和液相liquid precipitation 沉淀法在特殊应用时亦很重要。,从材质范围来看type of the materials，不仅使用金属粉末、也使用合金alloying粉末、金属化合物粉末、ceramics；从粉末外形shape来看，要求使用各种形状的粉末，如生产过滤器时filter，就要求球形粉末；spherical morphology,spherical particles从粉末粒度来看，要求各种粒度的粉末，从粒度为5001000um的粗粉末到粒度small than 0.1um的超细粉末superfine powders。,Chapter 3 机械研磨 Mechanical Milling,利用机械力将金属或其它材料破碎制取粉末的方法应用非常Pervasive广泛:Suitable for 脆性粉末制备 Brittle powders陶瓷粉末 Ceramic powder,碳钢 Carbon steel,陶瓷粉末:Hard alloying 硬质合金;Mixing and Blending 混合及合批;机械能粉末颗表面转化 Mechanical E-Surface E Transformation,缺点 Disadvantages,化学脏化 chemical Contamination,dust,Oil油西方:高碳钢high carbon steels and 牙科粉末 dental powder 银汞合金 dental amalgam powder 铝粉 Aluminum Powder 机械夹杂 Machining Impurities,最简单的方法(Simplest method),最简单的设备(Simplest Equi.),最有效(Most effect)有方法之一.也是能量效能利用率低的方法,能量利用率10%.Small than 10%percent,Balls 球,Materials,Cyindrical jar 球磨桶,仅需要,干 dry,湿 wet,研磨规律:Grinding Mechanism球磨如图示过程:A jar mill such as diagrammed in figure.,Low speed,(b)suitable speed,(c)high rotation speed,至少有四种作用力在破碎粉末:这些都能形成破碎作用.Crush Particles.那么破碎脆性brittle粉末所需要冲击colliding力 应力与缺陷结构defect和裂纹扩展敏感程度相关.,冲击：Collideing,剪切：Shearing,压缩：Compressing,磨研：Grinding,A view of the action in a jar mill,the impact of the falling balls grinds the material into powder,SEM of milled niobium powder,prepared by hydriding,milling,and vacuum dehydriding leading to an angular particle shape,公式:,Crack tip radusCrack propagation 扩展 grinding efficiency is regulated by ball movement including colliding，sliping，friction，compression.粉末研磨综合有冲击,滑动,摩擦与压缩,研磨效果与球体运动方式相关,式表明:,Large particles require less impact stress to fracture.粗颗粒粉末只需要小的冲击应力,随粉末颗粒直径变小,冲击应力增大.如果我们知道初始粒度(颗粒尺寸)initial Particle Size 当要研磨到所需粒度 时,需要多少能量可以由一个 simple relationship 去估计(estimating)需要的能量.,g:一个常数 a constant a:指数 between 1 and 2 这是一个经验工式,a-经验系数.球磨效应影响因素,Factors to 干/湿.Dry/wet,脆性/还原性 Brittle/Ductile,Plastic/Rigid粉末粒度 Particle Size球体尺寸 Ball Size旋转速度:Jar Rotation on speed.,Total energy change during milling 由颗粒尺寸变化与总能关系:,1 计算:一青铜粉末Boron Powder 40um,5小时到20 um,若磨到10um需要多少时间.2 假设一立方形纳米颗粒晶粒,晶界宽度Width约1.2nm,如果该晶粒中有20%原子是处于晶界上,估计该晶粒Size.Estimate,作业1、复合粉末材料,屈服强度(yielding strength)与第二相关系如下:Particle size(m)(MPa)6.4 90 5.9 118 3.6 160 2.8 186求:第二相粉末为200nm时,材料的屈服强度,第二相为球形.Sphere shape powder,Jar旋转速度最为重要.Decide ball 的运动Behavior 球体受力分析:suppose:only one Ball 只有一个球的情况.P:离心力 Centrifuge ForceG:重力 G ForceP1:向心力 R:筒体半径A1:临界点 V:线速度A:落点Falling point,Rotation of small steel ball and force action,球磨的基本规律 Basic regulation of mill,球在滚筒中的基本状态,转速慢，泻落状态，摩擦效果 grinding,转速快，抛落状态，摩擦,撞击破碎,转速快，抛落状态，撞击破碎colliding,假设:we suppose thata 只一个球，only one ball,b 球直径比桶直径小球受到两个力作用，Two force acting on the ballP：离心力 centrifuge forceG：重力 gravity V：线速度 linear velocity of the small ball.,球的受力分析,在抛落点平衡时（A点）：二力相等，PP，,Relation of linear speed and rotate speed is,所以,Force action on the small steel ball include centrifuge and gravity force,suppose only one ball in the jar.,Thus，the critical rotation speed is,以g9.8m/s2代入得：,代入,得,临界状态 当转速加快，球不落下，球转到最高点A1点，此时在这临界状态下，,D，the diameter of the jar,In fact，in order to obtain the efficiency ground theexperienced working rotation speed should lower than the critical speed，and the experienced working speed：工作经验表示：n0.6n临界时，可制取细粉 fine particles n0.75n临界时，一般只能制取较粗的粉末 coarse particles,影响球磨效果的因素 factors to influence milling efficiency,a、球料比：ratio of powder and balls，一般粉末填满 球体之间的间隙,b、球体直径：diameter of the balls 选择范围,c、研磨介质：medium 空气、protective atmosphere，lessen oxidation，alcohol，gas，avoiding assemble（团聚）component segeration成分偏析，and dust（粉尘飞扬）,研磨介质:the excellent action of the ground medium：干磨:保护气氛Atmosphere Protective.Anti-Oxidation 湿磨:保护和效率;wet milling 湿磨介质:水,乙醇等;milling medium wet grind split 湿磨尖壁 作用,有利于裂纹扩展Crack propagation 减少泠焊.Decrease cold welding Increasing the grinding efficiency,如要产生Colliding action 冲击作用,Apart from above factors.There are:球料比:Ball:Mater ratio:4:15:1 装料比 Filling volume:0.40.5 packing 球体直径:1020mm Jar diameter:300500mm,Experienced Relation，n实=0.70.75n临界如果要Colliding+Slipping action，n实=0.6n临界,物料性质 future of the grounding particles,脆性粉末破碎，Brittle powder延性粉末，ductile powder，精细分层，fine lamination，and cold welding.Relation of powder surface area and ground time is follow；Sm 粉末极限研磨后的比表面积 S0 粉末研磨前的比表面积 S 粉末研磨后的表面积,t 研磨时间,k 常数 氧化铝、氧化锆、炭化硅、钛、镍等都符合这种关系,缺点，Disadvantages:(1)Contamination 脏化,(2)Limited particle size,(3)Brittle materials 脆性材料.例1.车削粉研磨 a=2.(assumed)Vacuumed milling,8hrs Di=300m,Df=110 m,if milling to 75 m,how many hrs are needed?8 的1.33 folds,10.6 hrs.,强化球磨:Enhanced grinding,a.机械合金化Mechanical alloying Stirred mill 搅拌当球体冲击粉末,产生功能,功能越大,冲击力越大,导致粉末破碎。为了提高球的冲击速度,采用了机械合金化技术。The input material goes through a sequence of cold welding and fracture steps.As a consequence of attrition,the microstructure becomes more homogeneous as sketched at the bottom of the figure.,A view of mechanical alloying where the rotating impeller stirs a tank filled with balls,d:研磨介质(粉体)颗粒直径，粉体直径减少转速增大,时间减少。,制备弥散强化。ODS Oxide DispersionStrengthening Alloys.Ni Base,Co Base,Fe Base Super alloys.Oxide Particles Sub.micrometer 亚微米粉 末。Alloying mechanism 合金化机理:破碎与冷焊 Fractural/cold welding导致均匀化homogenization研磨过程所需的能量与搅拌旋转时速度N相关:,高能球磨(Mechanical alloying)并不在乎粒度减少,而在乎have finer microstructure.精细结构,产生复合材料.result in Composite materials。Fe,Co,Ni base 均为韧性ductile 材料,、航空材料、高温合金,Super-alloys，要的是产生一个结构去达到性能.b.振动球磨Vibratory Milling 粉末靠冲击Colliding 碰撞,提高单位时间内球体的碰撞次数,可提高破碎效果,特别是当磨到一定程度,只要小的碰撞,即可使粉末破碎。,随着研磨的进行,粉末平均粒度Mean particle size 减小,单位质量(单质体积)粉末表面积增加.-比表面积:Specific Surface Area/per unit powder.,单位时间内球体的总冲击数 empirical Equation,m=VKBnZE 次/min,C.行星式球磨:增加球Colliding次数自转+公转 Protective Atmosphere 机械合金化,搅拌:非晶,纳米晶,纳米particles,脆性,韧性金属,粉末 振动球磨,破碎micrometer grade 纳米级,脆性粉末WC 行星式球磨,纳米非晶粉末.,研磨过程所需要时间与粉末性质相关。同样用比表面积表达:ln=t:milling time，k：constant Sm：the limitation specific area So：the initial specific area St：specific area at t time,Powder Metallurgy PrincipleRuan Jianming Powder Metallurgy Research Institute 2006,Chapter 4.氧化还原制粉方法Chemical Fabrication.,定义:用还原气体(固体)或活泼金属将氧化物还原制备粉末的过程.(Reduction of Oxide Decompose of a solid by a gas.)1.最简单地.反应平衡常数.Reaction Equilibrium Constant 气体的分压之比.Gas partial pressure.(Ratio),O2+2H2=2H2OO2+2CO=2CO2O2+C=CO2,FeO,Fe3O4,Fe的稳定存在与分压有关温度升高：Fe3O4 FeO Fe反应速率J与反应过程活化能,反应温度T，气体分压比相关：J=Aexp（-/RT）A：物质常数，频率因子 frequency factor活化能降低，反应温度升高，提高反应速度，有利于还原进行；Metal oxides can be produced by H2，CO，etc.,WO3+H2=WO2+H2OWO2+2H2=W+2H2OTiCl4+2Mg=Ti+2MgCl2,Reducing agents(还原剂)a:Gas reducing agents:H2,CO b:Solid reductant:C,metal,alkaline metals;The necessary conditions as reductant:还原剂对氧的亲和力大于对被还原物质的亲和力-热力学thermo-dynamic 必要条件,Only fit the necessary condition,the reaction can go through.,Discussion,For a close system,the equilibrium constant,energy,determines the terminal concentration ratio of the products to reactants,For the reduction of WO3 by H2,the equilibrium constant K is given as,K=PH2O/PH2Where PH2 and PH2Oare the partial pressure of hydrogen and water steam,金属物质 对氧的亲和力 affinity 氧离解压Oxide decomposition pressureGoing to change with temperature，and in general，Temperature increase，decomposition pressure will提高，亲和力 affinity will decrease.Thermo dynamics 热力学,必要条件.Necessary ConditionsKinetic dynamics 动力学,充分条件.Complementary condition,2.还原过程基本原理 热力学基本因素,必要条件,充分条件.,(1)还原过程标准 Standard free energy X:还原剂.XO:金属氧化物.Me:还原金属.系统中温度一定,各物质离解压一定,通过各 物质离解压不同,物质decomposed pressure 越低,氧化物越稳定.,1.金属氧化物还原热力学条件 Thermodynamic condition,1）、还原过程标准等压位或自由能free energy(焓)的变化如果还原 反应的化学式为 X-还原剂,Me-金属氧化物,XO-金属氧化物 metal oxide每种氧化物都有各自的离解压，离解压越低，氧化物越稳定MeO有离解压，XO也有离解压decomposed pressure，前者离解压大于后者,MeO才能被X还原，他们的离解反应为：,(1)(2)上述金属氧化物还原过程标准自由能变化是 即 Z(2)Z(1)PO2(XO)PO2(MO),The higher decomposed pressure,the more unstable the metal oxide,then the greater the free energy change,the metal oxide will be reduced by reductant.即XO离解反应标准自由能变化应小于MO离解反应自由能的变化，这样XO才比MO稳定，这时，这时，XO的离解压小于MO的离解压，还原反应正向进行。氧对X的亲和力大于对Me的亲和力，推广之，对氧的亲和力大于被还原的金属时，都可以作为该金属氧化物的还原剂。,金属氧化过程标准自由能变化与温度的关系是：直线关系,截距A表示在绝对零度absolute temperature:T=0时，形成该金属氧化物的自由能,0