1、先进复合材料及其制备,清华大学2008年5月23日,现代材料加工讲座,内容提要,1、先进复合材料概述 2、先进复合材料设计的基本原则 3、先进复合材料的制备技术 4、金属基复合材料及其制备 5、纳米复合材料及其制备 6、案例：镁基纳米复合材料制备 7、先进复合材料发展方向,1、先进复合材料概述,1.1 复合材料的定义和分类1.2 复合材料的结构1.3 复合材料的性能特点与复合效果1.4 先进复合材料的分类与性能特点1.5 先进复合材料的应用,1.1 复合材料的定义和分类,定义：复合材料是由两种或两种以上化学性质或组织结构不同的材料组合而成。复合材料是多相材料，主要包括基本相和增强相。 基体相是
2、一种连续相材料，它把改善性能的增强相材料固结成一体，并起传递应力的作用； 增强相起承受应力（结构复合材料）和显示功能（功能复合材料）的作用。复合材料既能保持原组成材料的重要特色，又通过复合效应使各组分的性能互相补充，获得原组分不具备的许多优良性能。,复合材料是多相材料，主要包括基体相和增强相。基体相是一种连续相，它把改善性能的增强相材料固,纤维增强高分子复合材料,结成一体，并起传递 应力的作用。 增强相起承受应力 （结构复合材料）和 显示功能(功能复合材 料)的作用。,（1）复合材料的定义,（2）复合材料的分类,复合材料按性能高低分为传统复合材料和先进复合材料。 先进复合材料(advanced
3、 composites)：以碳、芬纶、陶瓷等纤维和晶须以及纳米颗粒等高性能增强相与高聚物、金属、陶瓷和碳（石墨）等基体构成的复合材料。 先进复合材料在性能和功能上远远超出其单质组分的性能和功能。,（2）复合材料的分类,按基体材料分类，可分为聚合物基、陶瓷基和金属基复合材料。 按增强相形状分类，可分为纤维增强复合材料、颗粒增强复合材料和层状复合材料。 按复合材料的性能分类，可分为结构复合材料和功能复合材料。,（2）复合材料的分类,结构复合材料按不同基体分类,（2）复合材料的分类,结构复合材料按不同增强体分类,1.2 复合材料的结构,几种典型复合材料结构,1.2 复合材料的结构,a) 单向纤维增强
4、复合材料 b) 颗粒增强复合材料 c) 层状复合材料 d) 蜂窝夹心复合材料 e) 编织复合材料 f) 功能梯度复合材料,1.3 复合材料的性能特点 比强度和比模量高 其中纤维增强复合材料的最高。 抗疲劳性能好 碳纤维增强材料-1可达b的7080%。因纤维对疲劳裂纹扩展有阻碍作用。 减振性能良好 复合材料中的大量界面对振动有反射吸收作用，不易产生共振。 高温性能好。,1.4 先进复合材料及性能特点,（1）颗粒增强复合材料 粒子增强复合材料是将粒子高度弥散地分布在基体中，使其阻碍导致塑性变形的位错运动(金属基体)和分子链运动(聚合物基体)。 这种复合材料是各向同性的。,卫星用颗粒增强铝基复合材料
5、零件,聚合物基粒子复合材料如酚醛树脂中掺入木粉的电木、碳酸钙粒子改性热塑性塑料的钙塑材料(合成木材)等。 陶瓷基粒子复合材料如氧化锆增韧陶瓷等。,粒子增强SiC陶瓷基复合材料,颗粒增强铝基泡沫复合材料,碳黑增强橡胶,金属基粒子复合材料又称金属陶瓷，是由钛、镍、钴、铬等金属与碳化物、氮化物、氧化物、硼化物等组成的非均质材料。 碳化物金属陶瓷作为工具材料已被广泛应用，称作硬质合金。硬质合金通常以Co、Ni作为粘结剂，WC、TiC等作为强化相。,硬质合金主要有钨钴(YG)和钨钴钛(YT)两类。牌号中，YG后的数字为含Co量，YT后的数字为碳化钛含量。 硬质合金硬度极高，且热硬性、耐磨性好，一般做成刀
6、片，镶在刀体上使用。,(2) 层状复合材料 层状复合材料是指在基体中含有多重层片状高强高模量增强物的复合材料。,这种材料是各向异性的(层内两维同性)。如碳化硼片增强钛、胶合板等。,双金属、表面涂层等也是层状复合材料。 结构层状材料根据材质不同，分别用于飞机制造、运输及包装等。,(3) 纤维增强复合材料,纤维增强复合材料是指以各种金属和非金属作为基体，以各种纤维作为增强材料的复合材料。I 纤维增强复合原则,在纤维增强复合材料中，纤维是材料主要承载组分，其增强效果主要取决于纤维的特征、纤维与基体间的结合强度、纤维的体积分数、尺寸和分布。,碳纤维,a) 弹性模量及强度外力方向与纤维轴向相同时，c=
7、f = m (f-纤维、 m-基体、 c-复合材料)，则,当外力垂直于纤维轴向时，则,b) 纤维的临界长径比,c) 纤维最小体积分数,纤维增强复合材料的强度和刚性与纤维方向密切相关。 纤维无规排列时，能获得基本各向同性的复合材料。均一方向的纤维使材料具有明显的各向异性。纤维采用正交编织，相互垂直的方向均具有好的性能。纤维采用三维编织，可获得各方向力学性能均优的材料。,纤维在基体中的不同分布方式,II 纤维的种类和性能i. 玻璃纤维：用量最大、价格最便宜。ii. 碳纤维：化学性能与碳相似。iii. 硼纤维：耐高温、强度、弹性模高。iv. 金属纤维：成丝容易、弹性模量高。v. 陶瓷纤维：用于高温、
8、高强复合材料。,vi. 芳香族聚酰胺纤维: 强度、弹性模量高，耐热。 vii. 聚乙烯纤维: 韧性极好，密度非常小 。 viii. 晶须：是直径小于30m，长度只有几毫米的针状单晶体，断面呈多角形, 是一种高强度材料。分为金属晶须和陶瓷晶须。金属晶须中, Fe晶须已投入生产。工业生产的陶瓷晶须主要是SiC晶须。,SiC晶须,III 聚合物基纤维增强复合材料 通常用碳纤维、玻璃纤维和芳纶纤维增强高分子材料。 这类复合材料的性能较环氧树脂等基体有大幅度的提高，比强度也高得多。,VI 纤维增强金属基复合材料 金属的熔点高，故高强度纤维增强后的金属基复合材料（MMC）可以使用在较高温的工作环境之下。
9、常用的基体金属材料有铝合金、钛合金和镁合金。,作为增强体的连续纤维主要有硼纤维、SiC和C纤维；Al2O3纤维通常以短纤维的形式用于MMC中。,MMC的SEM照片,MMC虽强度和弹性模量（刚度）增加，但塑性和韧性因使用陶瓷纤维而有所降低。这在一定程度上限制了MMC的应用范围。,航天飞机内MMC (Al / B纤维)桁架,V 纤维增强陶瓷复合材料 陶瓷材料耐热、耐磨、耐蚀、抗氧化，但韧性低、难加工。在陶瓷材料中加入纤维增强，能大幅度提高强度，改善韧性，并提高使用温度。 陶瓷中增韧纤维受外力作用，因拔出而消耗能量，耗能越多材料韧性越好。,用晶须作为增强相可以显著提高复合材料的强度和弹性模量，但因为
10、价格昂贵，目前仅在少数宇航器件上采用。现在发现，晶须 (如SiC 和Si3N4)能起到陶瓷材料增韧的作用。,1.5 先进复合材料的应用,1、在航空航天领域的应用 2、在汽车上的应用 3、在民用领域的应用 4、在军事领域的应用 5、在材料加工领域的应用,2、先进复合材料设计的基本原则,复合材料设计的基本步骤,2、先进复合材料设计的基本原则,基体材料的选择：使用要求，组成特点，基体金属与增强物的相容性 增强相的选择：颗粒增强相，纤维增强相，层片状增强相，混杂增强相 性能复合准则（复合效应）： 线性效应平均效应，平行效应，相补效应，相抵效应。 非线性效应相乘效应，诱导效应，系统效应，共振效应。,2、
11、先进复合材料设计的基本原则,各种增强体的力学性能比较,3、先进复合材料制备技术,3.1 制备方法分类 固态法：基体金属在固态下与增强材料混合组成复合材料，包括：粉末冶金法、热压法、热等静压法、轧制法、挤压和拉拔法、爆炸焊接法。 液态法：基体金属在熔融状态下与增强材料混合组成复合材料，包括：真空压力浸渍法、挤压铸造法、搅拌铸造法、液态金属浸渍法、共喷沉积法、原位反应生成法 表面复合法：物理气相沉积法、化学气相沉积法、热喷涂法、化学镀法、电镀法、复合镀法。,3、先进复合材料制备技术,3.2 制备应满足的条件 能使增强材料均匀地分布于基体中，满足复合材料结构和强度设计要求 能使复合材料界面效应、混杂
12、效应或复合效应充分发挥，有利于复合材料性能的提高与互补 能够充分发挥增强材料对基体的增强、增韧效果 设备投资少，工艺简单，可操作性强 尽量实现复合材料产品的近净形制造，减少或避免后序加工,3、先进复合材料制备技术,3.3 制备关键技术问题 避免发生不利的化学反应（特别是金属基复合材料） 改善增强材料与基体的润湿性 使增强材料按所需方向均匀地分布于基体中,4、金属基复合材料及制备,原位反应合成技术 机械合金化制备技术 高能超声辅助制备技术 半固态搅拌复合技术 气孔/金属基复合材料（多孔金属）制备技术 液相浸渗制备技术,5、纳米复合材料及制备,机械合金化制备技术 高能超声辅助制备技术 半固态搅拌复
13、合技术 纳米复合涂层制备技术 液相浸渗制备技术,6、案例：镁基纳米复合材料制备,结构零件的轻量化要求 在汽车和航空航天领域，结构零件的轻量化要求受到了越来越广泛的重视，并为此开展了大量的研发工作。其中作为结构材料中密度最小的镁合金，正在得到越来越广泛的应用。 镁合金的缺点 力学性能特别是高温力学性能有限，因此镁合金常常需要进行时效处理以提高性能，但时效处理却使镁合金的耐蚀性大大降低。因此研究和开发轻量化的镁基复合材料就势在必然。,镁及镁基复合材料在不同温度下的性能,Stressstrain curves for unreinforced magnesium and its composite
14、tested at elevated temperatures.,R.A. Saravanan, M.K. Surappa : Materials Science and Engineering A276 (2000) 108116,镁基纳米复合材料制备,1、制备方法 粉末冶金法(Powder Metallurgy) 搅拌铸造法(Stir Casting) DMD法(Disintegrated Melt Disposition) 搅拌摩擦法(Stir Friction) 2、复合类型 纳米陶瓷颗粒增强(Nano-sized Ceramic Particles) 碳纳米管增强(CNTs),Pow
15、der Metallurgical Technology,Nanosized SiC (30nm in diameter) with 3% vol.% and Mg micropowder (40m in diameter) was mixed for 8 h, the nanoscaled SiC powder in a asymmetrical moved mixer followed by milling the half of the batch for 8 h at 200 rpm in a planetary ball mill (Retsch, PM400) in a seale
16、d argon atmosphere. The milling vessel of 500 ml volume was made of corundum and the milling balls having a diameter of 11 mm were made of hardened stainless steel (100Cr6).The weight ratio of ball-to-powder was 10:1.,Magnesium Matrix Nano-composite Fabrication Case 1,Powder Metallurgical Technology
17、,The composites were encapsulated in a evacuated magnesium container, degassed at about 350 and extruded by a preheated (350) 400 t horizontal extrusion press (outlet 14 mm). For comparison also some Mg powder (no additives) was consolidated in the same way. In order to study the sample regarding co
18、ntaminations, they were analysed in an optical spark analyser (Spectrolab,Spectro Analytical Instruments). Tensile test of the as prepared materials were performed with a PC controlled universal testing machine at strain rate do:dt3.3104 s1 at different temperatures in air. Creep tests were carried
19、out at constant stresses (Andrade cam) at 200 and 300 in air. All testing specimens were machined from the extruded bars with their symmetry axis parallel to the extrusion direction. The microstructure of the materials was investigated by light and transmissions electron microscopy.,Magnesium Matrix
20、 Nano-composite Fabrication Case 1,Transmission electron micrographs of Mg3vol.% SiC nanoparticles; powder only mixed (left) and also milled for 8 h before extrusion (right).,Light microscopical pictures of the extruded Mg based materials.Pure Mg (upper part); mixed Mg3vol.% n-SiC composite (middle
21、part); and milled Mg3vol.% n-SiC composite (lower part).,H. Ferkel, B.L. Mordike : Materials Science and Engineering A298 (2001) 193199,Stressstrain curves of Mg and different n-SiC/Mg composites at (a) room temperature, (b) 100, (c) 200 and (d) 300C. The strain rate was 3.310-4 s-1.,Magnesium Matri
22、x Nano-composite Fabrication Case 1,Creep curves of Mg and different n-SiC/Mg composites at 200 at 35 MPa,Magnesium Matrix Nano-composite Fabrication Case 1,Creep curves of Mg and different n-SiC/Mg composites recorded at 200 at 45 MPa In the lower part, an extended part of the creep curve of the mi
23、lled composite is given,Magnesium Matrix Nano-composite Fabrication Case 1,Summary of PMT,In the case of the mixed powders the nanoparticles decorate the elongated coarsen grained Mg grain boundaries after extrusion. In the case of the milled powders a submicrograined Mg structure was developed with
24、 the nanoscaled SiC particles decorating the shear band within the heavily deformed Mg and also were at least partly dispersed into the submicronsized matrix grains after extrusion. The mechanical investigations reveal that the milled composite exhibits the largest flow stress and lowest creep rates
25、 in comparison to the other composite and pure Mg. The microscopy of the composites after thermal treatments up to 330 shows that their morphology is essentially preserved. It was shown that the incorporation of a low-volume fraction (3%) of SiC nanoparticles into Mg by ball milling allows the devel
26、opment of creep resistant lightweight submicrocrystalline Mg based composites.,Magnesium Matrix Nano-composite Fabrication Case 1,Disintegrated Melt Deposition,MATERIALS: magnesium turnings of more than 99.9% purity were used as the base material and nanosized Al2O3 particulates with an average size
27、 of 50 nm, were used as reinforcement phase.,Magnesium Matrix Nano-composite Fabrication Case 2,S. F. Hassan, M. Gupta: Materials Science and Technology 20(2004) 1383-1388,Disintegrated Melt Deposition,PRIMARY PROCESSING (DMD): (1) heating the magnesium turnings with reinforcement particulates (plac
28、ed in a multilayer sandwich form) to 750 in an inert Ar gas atmosphere in a graphite crucible using a resistance heating furnace. The crucible was equipped with an arrangement for bottom pouring. Upon reaching the superheat temperature, the molten slurry was stirred for 2.5 min at 460 rev/min using
29、a twin blade (pitch 45) mild steel impeller to facilitate the incorporation and uniform distribution of reinforcement particulates in the metallic matrix. The impeller was coated with Zirtex 25 (86%ZrO2, 8.8%Y2O3, 3.6%SiO2, 1.2%K2O and Na2O, and 0.3% trace inorganic) to avoid iron contamination of t
30、he molten metal. (2) The melt was then released through a 10 mm diameter orifice at the base of the crucible. The composite melt was disintegrated by two jets of argon gas orientated normal to the melt stream and located 265 mm from the melt pouring point. The argon gas flow rate was maintained at 2
31、5 L/min. The disintegrated composite melt slurry was subsequently deposited onto a metallic substrate located 500 mm from the disintegration point. Preform of 40 mm diameter was obtained following the deposition stage. The synthesis of monolithic magnesium was carried out using steps similar to thos
32、e employed for the reinforced materials except that no reinforcement particulates were added.,Magnesium Matrix Nano-composite Fabrication Case 2,S. F. Hassan, M. Gupta: Materials Science and Technology 20(2004) 1383-1388,Disintegrated Melt Deposition,SECONDARY PROCESSING: The deposited monolithic an
33、d nanosized Al2O3 containing magnesium preforms were machined to 36 mm diameter and hot extruded using an extrusion ratio of 20.25 : 1 on a 150 ton hydraulic press. Extrusion was carried out at 250 . The preforms were held at 300 for 90 min in a constant temperature furnace before extrusion. Colloid
34、al graphite was used as lubricant. Rods of 8 mm diameter were obtained following extrusion.,Magnesium Matrix Nano-composite Fabrication Case 2,S. F. Hassan, M. Gupta: Materials Science and Technology 20(2004) 1383-1388,Disintegrated Melt Deposition,Magnesium Matrix Nano-composite Fabrication Case 2,
35、S. F. Hassan, M. Gupta: Materials Science and Technology 20(2004) 1383-1388,S. F. Hassan, M. Gupta: Materials Science and Technology 20(2004) 1383-1388,Disintegrated Melt Deposition process,Magnesium Matrix Nano-composite Fabrication Case 2,Summary of DMD,A disintegrated melt deposition technique co
36、upled with hot extrusion can be used to synthesise nanoAl2O3 particulate reinforced magnesium composites. Grain refinement, reasonably uniform distribution of reinforcement particulates, and the presence of minimal porosity in the composite microstructure indicate the suitability of primary processi
37、ng and secondary processing parameters used in the present study. Results of coefficient of thermal expansion measurements indicated that the nanoAl2O3 particulates reinforced magnesium was dimensionally more stable than elemental magnesium. The results of mechanical characterisation revealed that t
38、he presence of increasing levels of nanoAl2O3 particulates in magnesium matrix led to significant improvement in hardness, elastic modulus, 0.2%YS, UTS, ductility, and work of fracture. Fractography revealed that the fracture behaviour of magnesium matrix changed from brittle to ductile as a result
39、of the presence of nanoAl2O3 particulates.,Magnesium Matrix Nano-composite Fabrication Case 2,S. F. Hassan, M. Gupta: Materials Science and Technology 20(2004) 1383-1388,Friction Stir Processing,The AZ61A billets used in this study have a chemical composition in mass percent of Mg6.02%Al1.01%Zn0.30%
40、Mn. This alloy is a solution hardened alloy with minimal precipitation. The billet possessed nearly equiaxed grains around 75 m (based on the linear line intercept method from three cross-sectional planes). The billet was cut as rectangular samples 60 mm in width, 130 mm in length and 10 mm in thick
41、ness. Amorphous SiO2 nanoparticles have an average diameter 20 nm and purity 99.9%. The amorphous SiO2 particles are nearly equiaxed in shape, with a density of 2.65 g/cm3.,Magnesium Matrix Nano-composite Fabrication Case 3,C.J. Lee et al. ：Scripta Materialia 54 (2006) 14151420,Friction Stir Process
42、ing,The simplified FSP machine used in this experiment was a modified form of a horizontal-type milling machine, with a 5 HP spindle. The fixed pin tool was 6 mm in diameter and 6 mm in length. The shoulder diameter was 18 mm, and a 2tilt angle of the fixed pin tool was applied. The pitch distance w
43、as 1 mm. The advancing speed of the rotating pin was kept constant in this study to be 45 mm/min, with a fixed pin rotation of 800 rpm. The plates were fixed by a fixture and ambient air cooling was applied. In order to maintain the entire fixture at the initial temperature (room temperature) after
44、each pass, the back plate of the fixture was designed to contain three cooling channels with cooling water passing through them. Using the methods described in a previous paper 6, the strain rate and the maximum temperature experienced during FSP are around 10/s and 400, respectively. To insert the
45、nano-SiO2 particles, one or two grooves each 6 mm in depth and 1.25 mm in width were cut, in which the nano-SiO2 particles were filled to the desired amount before FSP. The groove(s) were aligned with the central line of the rotating pin. In order to prevent the SiO2 from being displaced out of the
46、groove(s), surface repair was accomplished with a modified FSP tool that only had a shoulder and no pin. The volume fractions of the SiO2 nano-particles inserted into the AZ61Mg alloy were calculated to be around 5% and 10% for the one and two deep grooves (1D and 2D), respectively.,Magnesium Matrix
47、 Nano-composite Fabrication Case 3,C.J. Lee et al. ：Scripta Materialia 54 (2006) 14151420,The FSP procedure: (a) cutting groove(s) and inserting SiO2 particles; (b) using a flat tool to undertake the surface repair; (c) applying a tool with a fixed pin to undertake the FSP; and (d) conducting multip
48、le FSP passes.,TEM micrograph and diffraction pattern of the amorphous 20 nm SiO2 particles.,SEM photograph of the 2D4P specimen showing clustered silica located on grain boundaries or triple junction and some silica embedded in the matrix grains.,TEM micrographs showing the matrix grain size and Si
49、O2 particle distribution in the FSP composites: (a) 1D1P; (b) 1D4P; (c) 2D1P; and (d) 2D4P.,C.J. Lee et al. ：Scripta Materialia 54 (2006) 14151420,Comparison of the mechanical properties of the AZ61 alloy and composites,Magnesium Matrix Nano-composite Fabrication Case 3,Summary of FSP,Friction stir
50、processing successfully fabricated bulk AZ61Mg based composites with 510 vol.% of nano-SiO2 particles. The distribution of amorphous SiO2 nano-particles measuring around 20 nm after four FSP passes resulted in satisfactorily uniform distribution. The grain size of the 2D4P composites could be effect
51、ively refined to 0.8m, as compared with the 78 m in the FSP AZ61 alloys processed under the same FSP condition. Some SiO2 reinforcement would react with Mg to form the Mg2Si andMgO phases during FSP. Nevertheless, both phases are still in the 5200 nm fine scale. The hardness and mechanical strength at room temperature of AZ61Mg composites with nano-fillers was strengthened, as compared with the AZ61 cast billet. And high strain rare superplasticity over 400% was achieved in the 2D4P composites.,
