Thermal properties of diamond/Al composites by pressure infiltration: comparison between methods of coating Ti onto diamond surfaces and adding Si into Al matrix

This study was pertained to the effects of Ti coating on diamond surfaces and Si addition into Al matrix on the thermal conductivity(TC) and the coefficient of thermal expansion(CTE) of diamond/Al composites by pressure infiltration.The fracture surfaces,interface microstructures by metal electro-etching and interfacial thermal conductance of the composites prepared by two methods were compared.The results reveal that Ti coating on diamond surfaces and only12.2 wt% Si addition into Al matrix could both improve the interfacial bonding and increase the TCs of the composites.But the Ti coating layer introduces more interfacial thermal barrier at the diamond/Al interface compared to adding 12.2 wt% Si into Al matrix.The diamond/Al composite with 12.2 wt% Si addition exhibits maximum TC of 534 W·m~(-1)·K~(-1)and a very low CTE of 8.9×10~(-6)K~(-1),while the coating Ti-diamond/Al composite has a TC of 514 W·m~(-1)·K~(-1)and a CTE of 11.0×10~(-6)K~(-1).     

镀TiC金刚石/铝复合材料的界面及热膨胀性能

采用气压浸渗法制备高体积分数的镀TiC金刚石/铝复合材料,通过SEM和EDS等手段对复合材料的断口形貌进行分析,并研究TiC镀层对复合材料界面和热膨胀性能的影响。结果表明:TiC镀层改善金刚石颗粒与铝合金基体之间的选择性粘结现象,断裂方式以基体断裂为主。部分TiC会被氧化成TiO2并与铝合金基体反应生成Al2O3,从而实现金刚石颗粒与铝合金基体之间良好的界面结合;TiC镀层有效地降低复合材料的热膨胀系数(CTE),增强复合材料热膨胀性能的稳定性。在体积分数相同的情况下,CTE随金刚石颗粒尺寸的减小而减小。     

Si含量对Si/Al复合材料组织及性能的影响(英文)

采用放电等离子烧结(SPS)技术制备不同Si含量的电子封装用Si/Al复合材料,测试复合材料的性能,包括密度、热导率、热膨胀系数及弯曲强度;进行成分及断口分析,研究Si含量对Si/Al复合材料微观组织及热、力学性能的影响规律。结果表明:Si/Al复合材料由Si、Al组成,Al均匀分布于Si晶粒之间;随着Si含量的降低,Si/Al复合材料的相对密度不断增大,当Si含量为50%(体积分数)时,复合材料的相对密度达到98.0%;复合材料的热导率、热膨胀系数及弯曲强度均随着Si含量的增加而减小,当Si含量为60%(体积分数)时,复合材料具有最佳的热导率、热膨胀系数及强度匹配。     

Al对CNTs增强Nb/Nb5Si3复合材料组织和性能的影响

以Nb、Si、CNTs和Al粉末为原料,采用放电等离子烧结法(SPS)原位合成了Nb-20Si-2 mass%CNTs-xAl(x=0、1、2、3、4 mass%)复合材料。利用扫描电镜(SEM)、电子探针微区分析(EPMA)和X射线衍射(XRD)等对复合材料的组织结构进行了分析,研究了Al对CNTs增强Nb/Nb5Si3复合材料的组织和性能的影响。结果表明:Al能部分固溶于Nb5Si3和Nbss相中,多余的Al会与Nb反应生成AlNb3相,较均匀地分布中Nb5Si3相中,并大部分聚集在Nb/Nb5Si3的界面处。Al元素的加入能明显改善Nb/Nb5Si3复合材料的断裂韧性,随着Al含量的增加,复合材料的断裂韧性先升高后降低,其中Al含量为2 mass%时达到最大值,即6.94 MPa·m^1/2,相对于未加时提高了约56.9%。同时Al元素还能有效降低Nb/Nb5Si3复合材料高温氧化速度,提高高温抗氧化性能,而Al元素的加入量越高,其高温抗氧化性能越好。     

金刚石混杂碳化硅/铝复合材料的组织与热物理性能(英文)

采用理论计算与实验相结合的方法对金刚石混杂SiC/Al复合材料的热物理性能进行研究,采用微分有效介质(DEM)理论和扩展的Turner模型分别计算金刚石混杂SiC/Al复合材料的热导率和热膨胀系数。从金刚石混杂SiC/Al复合材料的微观组织可以看到SiC颗粒与Al之间结合较紧密,金刚石颗粒与Al之间结合不紧密。金刚石混杂SiC/Al复合材料的热物理性能的实验结果与理论计算趋势一致。当金刚石颗粒与SiC颗粒的体积比为3:7时,混杂SiC/Al复合材料的热导率和热膨胀系数分别提高了39%和30%。因此,当在复合材料中加入少量金刚石颗粒时,其热物理性能得到显著提高,而复合材料的成本略有提高。     

电子封装用Al/Si/SiC复合材料的显微组织与性能(英文)

采用气压浸渗法制备中体积分数电子封装用 Al/Si/SiC 复合材料。在保证加工性能的前提下,用与 Si 颗粒相同尺寸(13 μm)的 SiC 替代相同体积分数的硅颗粒制得复合材料,并研究其显微组织与性能。结果显示,颗粒分布均匀,未发现明显的孔洞。随着 SiC 的加入,强度和热导率将得到明显提高,但热膨胀系数变化较小,对使用影响也不大。讨论几种用于预测材料热学性能的模型。新的当量有效热导被引入后,H-J 模型将适用于混杂和多颗粒尺寸分布的情况。     

铝基金刚石复合材料热性能的数值模拟与实验验证

利用有限元软件建立铝基金刚石复合材料的代表性体积单元,研究了不同的金刚石体积分数及粒径对铝基金刚石复合材料导热系数和热膨胀系数的影响.同时采用挤压铸造的方式制备出各种铝基金刚石复合材料样件,并测量出其导热系数和热膨胀系数,将有限元模拟结果与实验结果进行了对比验证.结果表明:有限元模拟结果与实验结果吻合较好;当金刚石粒径...     

原位自生TiB2/Al复合材料的组织与力学性能

采用钛盐与硼盐反应法成功制备原位自生TiB2/纯Al复合材料。利用扫描电子显微镜、透射电子显微镜和拉伸试验机研究不同粒子含量(质量分数为1%、2%和3%)对复合材料组织和力学性能的影响。结果表明:原位生成的TiB2粒子有矩形、近圆形和六边形三种形貌,尺寸为200~500 nm;粒子与Al基体界面洁净无反应层。随着粒子含量的增加,复合材料的强度随之升高,而伸长率则随之降低;当TiB2含量为3%时,屈服强度和抗拉强度分别达到78.1 MPa和102 MPa,相比于纯Al分别提高58%和43%,而伸长率降至32.5%,下降了24%。断口分析表明:随着TiB2粒子含量的增加,粒子团聚机率增加,在拉伸过程中,裂纹在粒子团聚处萌生并扩展,导致材料的塑性降低。     

Microstructure and mechanical properties of extruded Al/Al2O3 composites fabricated by stir-casting process

A novel two step mixing method including injection of particles into the melt by inert gas and stirring was used to prepare aluminum matrix composites (AMCs) reinforced with Al₂O₃ particles. Different mass fractions of micro alumina particles were injected into the melt under stirring speed of 300 r/min. Then the samples were extruded with ratios of 1.77 or 1.56. The microstructure observation showed that application of the injection and extrusion processes led to a uniform distribution of particles in the matrix. The density measurements showed that the porosity in the composites increased with increasing the mass fraction of Al₂O₃ and stirring speed and decreased by extrusion process. Hardness, yield and ultimate tensile strengths of the extruded composites increased with increasing the particle mass fraction to 7%, while for the composites without extrusion they increased with particle mass fraction to 5%.     

《搅拌摩擦加工制备GNPs/Al复合材料的微观结构与力学性能》

本文以纯铝为基体,利用搅拌摩擦加工(FSP)制备GNPs/Al复合材料,研究了复合材料基体组织、增强相与界面等微观结构与力学性能,探讨了其增强机理。结果表明,添加GNPs并经FSP后复合材料基体晶粒得到明显细化且晶界由小角度为主转变为大角度为主;FSP制备过程致使GNPs片层一定程度剥离的同时,较大片径的GNPs被破碎而形成众多边缘缺陷,使其易发生Al-C原子扩散,结果在GNPs边缘与基体形成界面过渡;GNPs加入量约1.8vol%时,复合材料的屈服强度和抗拉强度达到72MPa和147MPa,较同等条件FSP的基体分别提高了89.5%和79.3%,理论计算界面载荷传递、Orowan和细晶强化依次是复合材料的主要增强机制;随着GNPs加入量的增加,复合材料屈服强度实验值与理论值的增长趋势一致,且偏差也略有提高,但可能因GNPs在复合材料中的杂乱排布,界面载荷传递强化不能充分发挥,实际的复合材料屈服强度与理论值尚有差距。     

超声波搅拌功率对原位自生Mg_2Si/Al基复合材料凝固组织和力学性能的影响

采用超声波搅拌方法制备了原位自生Mg_2Si/Al基复合材料,研究了超声波功率对复合材料凝固组织和力学性能的影响。结果表明:超声波搅拌不但能够细化初生Mg_2Si颗粒,改变凝固组织形貌,而且具有除气除杂功能,二者共同提高了Mg_2Si/Al基复合材料的力学性能。在本实验条件下:超声波功率为150 W时,Mg_2Si/Al基复合材料抗拉强度最高,为178 MPa;而伸长率则在超声波功率为100 W时最好,为4.94%。     

无压浸渗制备Si3N4/Al-AlN复合材料的动态性能

利用分离式霍普金森压杆(SHPB)装置对无压浸渗制备的Si3N4/Al-AlN复合材料进行不同应变速率下的动态压缩实验,并与准静态压缩实验相比较;利用X射线衍射仪和扫描电子显微镜分析了复合材料的相组成和断口形貌.结果表明:Si3N4/Al-AlN复合材料的准静态压缩强度和断裂应变均高于动态压缩,分别达到1 748MPa和10.87%;在动态压缩中,当应变率从740提高到1 850,压缩强度稍有提高,断裂应变则增大1倍,达到7.6%,具有明显的应变率效应.准静态压缩中复合材料发生粉碎性解体而动态压缩中主要为劈裂,断裂面平整;微观断裂机制为解理脆断和韧性撕裂,随着应变率增加,断口上韧性撕裂形貌增加.复合材料内Si3N4与Al-Mg合金熔体的置换反应产物AlN相的大量存在是复合材料在高应变率冲击压缩载荷下显现由脆至韧转变的重要原因.     

Ti 元素对B4C/Al复合材料力学性能的改善作用研究

B₄C/Al复合材料是目前最理想的中子吸收材料,广泛用于乏燃料储存。本文利用液态搅拌法制备B₄C/Al复合材料,通过添加Ti元素,探讨了界面反应对材料的界面结构和力学性能的影响。研究发现,Ti元素通过参与界面反应,改变了界面结构,在B₄C颗粒表面形成了紧密结合的纳米TiB₂界面层;Ti的添加消除了界面微裂纹、微孔、分离等缺陷。随着界面反应程度的加强,材料强度提高,尤其反应脱落的纳米TiB₂颗粒作为原位第二强化相进一步增强基体。B₄C/Al复合材料断裂过程表现为韧窝延性断裂;TiB₂界面层增强了B₄C颗粒与基体的结合,断裂行为从B₄C-Al界面脱落转变为B₄C颗粒断裂;但过渡的界面反应会形成微韧窝,引起材料延伸率下降。     

热处理对金刚石/2024Al复合材料微观组织和热物理性能的影响

采用挤压铸造法制备粒径为5μm、体积分数为50%的金刚石/2024Al 复合材料。退火处理后对其金相组织界面反应、界面结合情况以及金刚石颗粒的内部缺陷进行观察与分析,并对其热物理性能进行测试与研究。结果表明,金刚石/2024Al 复合材料的组织致密,无明显的气孔、夹杂等缺陷;颗粒为不规则多边形,有棱角,分布比较均匀。透射电镜观察表明,部分金刚石颗粒内部有位错和层错存在,而2024Al 基体中的位错密度较大,金刚石/2024Al界面处有较多的界面反应物生成,可能为Al2Cu。复合材料在20~100°C温度区间内的平均热膨胀系数为8.5×10-6°C-1,退火处理的复合材料其热膨胀系数有一定程度的降低;随着温度的升高,复合材料的平均热膨胀系数也呈现增加的趋势。复合材料的热导率约为100 W/（m·K）,退火处理能够提高复合材料的热导率。     

Load transfer mechanism and mechanical properties of SiCw/Al metal matrix composites

The load transfer mechanism and mechanical properties of SiC whisker reinforced aluminum matrix composites were investigated. A generalized shear-lag model was proposed to analyze the effects of the aspect ratio, misorientation angle and volume fraction of SiC whisker on the mechanical properties of SiCw/Al composites. A new concept on effective aspect ratio was suggested, combining the effects of aspect ratio and alignment of whiskers, to calculate the effective stress acting on the aluminum matrix in SiCw/Al composites. The magnitude and anisotropy of the yield strength of the SiCw/2124Al composite can be estimated more accurately by substituting the average aspect ratio with the effective aspect ratio based on the generalized shear-lag model. The SiCw/2124Al composite with the largest effective aspect ratio showed the lowest minimum creep rate which decreased with increasing effective aspect ratio of SiC whisker, but were found to be almost similar under the same effective stress acting on the Al matrix. It is suggested that the role of SiC whisker is to improve the mechanical properties by reducing the effective stress acting on the Al matrix in the SiCw/Al metal matrix composite. This article is based on a presentation made in the symposium “The 1^st KIM-JIM Joint Symposium: High Strength Ratio Aluminum Alloys”, held at Inha University, Inchon, Korea, October 22. 1999 under the auspices of The Korean Institute of Metals and Materials and The Japanese Institute of Metals.     

Microstructures and mechanical properties of BP/7A04 Al matrix composites

The microstructures and interface structures of basalt particle reinforced 7A04 Al matrix composites (BP/7A04 Al) were analyzed by using OM, TEM, SEM and EDS, and the mechanical properties of 7A04 Al alloy were compared with those of BP/7A04 Al matrix composites. The results show that the basalt particles are dispersed in the Al matrix and form a strong bonding interface with the Al matrix. SiO₂ at the edge of the basalt particles is continuously replaced by Al₂O₃ formed in the reaction, forming a high-temperature reaction layer with a thickness of several tens of nanometers, and Al₂O₃ strengthens the bonding interface between basalt particles and Al matrix. The dispersed basalt particles promote the dislocation multiplication, vacancy formation and precipitation of the matrix, and the precipitated phases mainly consist of plate-like η (MgZn₂) phase and bright white band-shaped or ellipsoidal T (Al₂Mg₃Zn₃) phase. The bonding interface, high dislocation density and dispersion strengthening phase significantly improve the mechanical properties of the composites. The yield strength and ultimate tensile strength of BP/7A04 Al matrix composites are up to 665 and 699 MPa, which increase by 11.4% and 10.9% respectively compared with 7A04 Al alloy without basalt particles.     

Comparative study on the interface and mechanical properties of T700/Al and M40/Al composites

T700/Al and M40/Al composites were fabricated by squeeze casting technology, and their interface and mechanical properties were investi-gated comparatively. The results showed that both of the composites were dense, and the fibers were distributed uniformly in aluminum ma-trix. Aluminum carbide (Al_4C_3) was observed on the interface of the two carbon fiber-reinforced aluminum (Cf/Al) composites. There was little Al_4C_3 with a length of 300-500 nm and a width of 30-60 nm in the M40/Al composite, whereas there was a great deal of Al_4C_3 with a length of 200-400 nm and a width of 100-200 nm in the T700/Al composite, due to a higher graphitization of M40Cf than T700Cf. The M40/Al composite showed a much higher tensile strength than the T700/Al composite, and it was related to inteffacial bonding between carbon fibers and aluminum matrices.     

Optimized interface and mechanical properties of W fiber/Zr-based bulk metallic glass composites by minor Nb addition

W fiber/Zr-based bulk metallic glass composites were prepared by melt infiltration casting and the interface reaction in composites was studied in detail. It was found that minor Nb addition to the matrix can suppress the interface peritectic reaction and optimize the interface structure in W fiber/Zr-based bulk metallic glass composites. Taking the interface characteristics of composites and glass forming ability of the matrix into account, an optimized alloy Zr₄₇Ti₁₃Cu₁₁Ni₁₀Be₁₆Nb₃ was selected as a new metallic glass matrix. The interface in the W fiber/Zr₄₇Ti₁₃Cu₁₁Ni₁₀Be₁₆Nb₃ bulk metallic glass composite has excellent interface bonding, and the compressive strength of 70% W fiber/Zr₄₇Ti₁₃Cu₁₁Ni₁₀Be₁₆Nb₃ metallic glass composite is 2.6 GPa, 58% higher than the unreinfored matrix. Multiple shear band formation in the matrix, which results from the interaction between W fiber and the matrix, can answer for the high ultimate fraction strength and excellent plastic deformation of the composite.