4粉末冶金材料科学基础及烧结理论-material science a.pdf

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1、Material Science and Sintering of PM粉末冶金材料科学基础及烧结理论粉末冶金材料科学基础及烧结理论 Natural States of Mass Aggregation Crystal Structure of Metals Imperfections and Deformation of Metals Diffusion Mechanisms and Sintering Shrinkage during Sintering Swelling during Sintering Change of Porosity during Sintering Phase

2、Diagrams Phase Transformations 物质的自然状态物质的自然状态金属的晶体结构金属的晶体结构金属缺陷和变形金属缺陷和变形扩散机制和烧结扩散机制和烧结烧结收缩烧结收缩烧结膨胀烧结膨胀烧结时孔隙的变化烧结时孔隙的变化相图相图Fe-C相图相图相转变相转变Natural States of Mass Aggregation-ordered structure-constant volume-low atom mobility-disordered structure-approx constant volume-higher atom mobility-disordered

3、structure-non-constant volume-very high atom mobility物质的自然状态物质的自然状态固态液态气态-有序结构有序结构-体积恒定体积恒定-原子运动稳定原子运动稳定-无序结构无序结构-体积基本恒定体积基本恒定-原子运动剧烈原子运动剧烈-无序结构无序结构-体积非恒定体积非恒定-原子运动极其剧烈原子运动极其剧烈Crystal Structure of Metals金属晶体结构金属晶体结构BCCFCCHCPB Body C Centered C Cubic体心立方晶胞F Face C Centered C Cubic面心立方晶胞C Close P Pack

4、ed HHex密排六方晶胞Nucleation of dendrites in the melt熔液中枝晶形核熔液中枝晶形核 Growing of dendrites枝晶长大枝晶长大End of solidification means borders(=imperfections)created between grains having ordered structure called grain boundaries.凝固后形成的晶界，有序结构凝固后形成的晶界，有序结构Imperfections and Deformation of Metals-1金属缺陷及变形金属缺陷及变形-1Imp

5、erfections and Deformation of Metals-2金属缺陷及变形金属缺陷及变形-2Grain boundary晶界晶界Imperfections and Deformation of Metals-3VacancyInterstital atomSustitutional atom金属缺陷及变形金属缺陷及变形-3空位间隙原子置换原子空位间隙原子置换原子Imperfections and Deformation of Metals-4Plastic deformation of ordered structure=dislocation金属缺陷及变形金属缺陷及变形-4有

6、序结构塑性变形有序结构塑性变形=位错位错Diffusion Mechanisms and Sintering-1扩散机制及烧结扩散机制及烧结-1Schematic of iron powder particle which consists of many grains 由许多晶粒组成的铁粉颗粒图Diffusion Mechanisms and Sintering-2扩散机制 及烧结扩散机制 及烧结-2a=surface diffusionb=grain boundary diffusionc=volume diffusiond=evaporation/condensatione=disloc

7、ation movement2 particles in contact连接的两个颗粒连接的两个颗粒a=表面扩散b=晶界扩散c=体积扩散d=蒸发/凝聚e=位错运动Diffusion Mechanisms and Sintering-3扩散机制 及烧结扩散机制 及烧结-3V=体积扩散，b=晶界扩散S=表面扩散，e=蒸发/凝固，=表面张力应力释放(位错去除)Stress relieving(dislocation removal)Diffusion Mechanisms and Sintering-4扩散机制 及烧结扩散机制 及烧结-4Surface DiffusionVarious diffus

8、ion rate inGrain Boundary DiffusionVolume Diffusion在表面扩散，晶界扩散，体积扩散中不同的扩散速率Diffusion Mechanisms and Sintering-5CMoCuNiDiffusion rate of interstitial elements higher than substitutional elements扩散机制 及烧结扩散机制 及烧结-5间隙固溶原子的扩散速率比置换固溶原子高间隙固溶原子的扩散速率比置换固溶原子高Diffusion Mechanisms and Sintering-6扩散机制 及烧结扩散机制 及烧结

9、-6Diffusion of Ni and C in Distaloy在 Distaloy 中Ni和C的扩散Shrinkage during Sintering-1烧结收缩烧结收缩-1Center to center approach during neck formation(volume diffusion)在烧结颈形成时（体积扩散）中心点相互靠近Shrinkage during Sintering-2烧结收缩烧结收缩-2CuCu+1%CFe-CuFe-Cu-CC counteract swelling in Fe/Cu/C system在Fe-Cu-C系中碳的添加可以抵消膨胀Swelli

10、ng during Sintering-1烧结膨胀烧结膨胀-1a)粉末压制。b)其中一个组元熔化渗入固体粉末间隙，留下孔隙。c)液相和固相间形成合金，液相逐渐消失。瞬时液相烧结Swelling during Sintering-2烧结膨胀烧结膨胀-290%Fe10%Cu1150 CSwelling and Shrinkage during Sintering烧结时影响收缩和膨胀的因素烧结时影响收缩和膨胀的因素 Particle size 颗粒尺寸 Alloying element 合金元素 Uneven filling and compaction 充填和压制不均匀 Uneven distri

11、bution of alloying elements in the component合金元素分布不均 Liquid phase formation 形成液相 Sintering temperature and time 烧结温度和时间 Uneven temperature distribution of the sintering furnace烧结炉的温度分布不均 Poor gas flow in the sintering furnace烧结炉内气体流动不好Changes of Porosity during Sintering-1烧结时孔隙的变化烧结时孔隙的变化-1After com

12、pactionAfter sintering压制后烧结后Changes of Porosity during Sintering-2烧结时孔隙的变化烧结时孔隙的变化-2V1+V2=V3E1 +E2 E31Driving Force:Surface energy23High energy stateLow energy stateE1 +E2E3EChanges of Porosity during Sintering-3烧结时孔隙的变化烧结时孔隙的变化-3From sharp corners to flatter parts of the pore surface从孔隙表面的尖角区到平坦部分F

13、rom small pores to near-by larger pores and grain boundaries从小的孔隙移动到邻近大的孔隙和晶界上Sintering Questions烧结理论烧结理论-问题问题1.What is the driving force for sintering?烧结的驱动力是什么？2.Describe how the pores develop during sintering.请描述烧结过程中孔隙的形成和变化。3.Sintering of one phase system always causes shrinkage.Why?单相体系的烧结总是造成

14、尺寸收缩，为什么？4.Why do we get swelling when adding Cu to a Fe base material and how can we prevent too much swelling?为什么在Fe基材料中添加Cu会引起膨胀，怎样防止过度的膨胀？Phase Diagrams(1)Eutectic相图相图(1)共晶共晶L=alpha+betaPhase Diagrams(2)Peritectic相图相图(2)包晶包晶L+beta=alphaPhase Diagrams(3)-Fe/C相图相图(3)Fe/CFeo3 Phase diagrams三种相图-Eut

15、ectic共晶-Peritectic包晶-Eutectoid!共析！Fe3CPhase transformations 1相转变相转变-1Growth of lamellas Pearlite层状珠光体长大层状珠光体长大Nucleation of Pearlite at grain boundaries珠光体在晶界形核珠光体在晶界形核Lowering the temperature降低温度Phase transformations 2相转变相转变-2Fe-C systemFePhase transformations 3相转变相转变-3a)Quenching and tempering(Sma

16、ll size and simple shape)淬火及回火（小尺寸，形状简单的零件）b)Martempering马氏体回火(To avoid quenching cracks)（避免淬火裂纹）c)Austempering奥氏体等温淬火(No further tempering)（不用进一步回火）d)Isothermal annealing等温退火(F+P is required)（得到铁素体+珠光体）Material science Questions材料学材料学 问题问题1 What is specific with a eutectic phase diagram?共晶相图中能得到什么信

17、息？共晶相图中能得到什么信息？2 In the Fe rich corner of the Fe/C phase diagram there are 3 different types of phase diagrams.Which types?在在Fe-C相图中有三种不同类型的相图，分别是哪三种？相图中有三种不同类型的相图，分别是哪三种？3 Why do phase transformation diagrams look the way they do?(a”nose”pointing to the left)为什么相转变图中鼻子点朝左？为什么相转变图中鼻子点朝左？4 Which microstructure do you normally receive in a austempered material?在奥氏体等温淬火中，通常会得哪些组织？在奥氏体等温淬火中，通常会得哪些组织？