半固态热等静压Al/B_4C复合材料液相流动行为与致密化机理（英文）

为了制备具有高密度的铝基碳化硼材料,采用粉末冶金半固态热等静压方法制备了质量分数为30%碳化硼的铝基碳化硼复合材料,采用WANCE100型材料力学性能试验机和SIRION200型扫描电镜研究了复合材料的力学性能及显微形貌。结果表明:半固态热等静压工艺可制备接近理论密度的Al/B4C复合材料;虽然Al/B4C材料抗拉强度可提升至约300MPa,但过高碳化硼含量也使得该材料脆性特征十分明显;同时采用间接的方法观察到了半固态工艺过程中生成的液相,该液相不仅可改善碳化硼颗粒与铝基体的结合,在高温高压下液相的流动还起到填充复合材料内部空隙的作用。半固态热等静压工艺过程中产生的液相是复合材料密度和力学性能提升的主要原因。     

B4C颗粒增强铝基复合材料微观形貌和力学行为分析

通过中温热压法(热压温度在固液相线之间)制备出不同碳化硼含量的铝基复合材料,并轧制成板.经T6热处理后对B4C/Al复合材料进行微观形貌、力学性能分析.结果表明,碳化硼颗粒分布均匀,有较少的微气孔缺陷,随着碳化硼含量的增加,增强颗粒尺寸明显变小.B4C/Al复合材料的抗拉强度、屈服强度和断后伸长率随着碳化硼含量的增加而减小,与6061铝合金相比降低幅度较大,硬度随着碳化硼含量的增加而提高,靠近颗粒处硬度显著提高.B4C/Al复合材料的断裂方式是脆性断裂.     

ZL101/SiCp复合材料制备及其缺陷分析

对于高增强体含量的复合材料,其材料的致密性显得尤为重要,本文采用冷等静压结合热等静压的方式制备SiCp/Al复合材料克服了这个困难,实现净成形,具有工艺简单等优点,使用180#α-SiC颗粒作为增强体,体积分数为20%,同时采用ZL101铝粉作为基体,其中采用冷等静压方法能制备出冷坯料材料的理论密度可达75%,后续采用热等静压制备出的碳化硅颗粒增强铝基复合材料具有致密性良好,颗粒分布均匀,无明显的聚集现象。同时结合SEM和EDS对界面的分析表明碳化硅颗粒增强铝基复合材料产生的缺陷主要是增强体碳化硅颗粒和铝基体结合的界面处有细小的气孔存在,使材料的有效承载面积减小,最终导致材料破断。初步分析了复合材料微缺陷产生的机理。界面处反应生成的界面相对于复合材料的影响。     

SPS+热轧法制备的B_4C/Ti复合材料组织及力学性能的研究

采用不同体积分数的碳化硼粉与钛粉通过放电等离子烧结(SPS)和轧制的方法制备钛基复合材料板材,并对所制备复合材料的密度、显微硬度、微观组织、物相、拉伸性能以及断口形貌等进行了系统研究。结果表明:随着碳化硼颗粒含量的提升,烧结态和轧制态复合材料的密度和显微硬度也相应上升。XRD分析显示,TiC与TiB在碳化硼颗粒与钛基体之间形成,3vol%B_4C的轧制态钛基复合材料的最大抗拉强度能够达到800 MPa,抗拉强度的提高是由于TiC与TiB的作用。断裂主要发生在B4C颗粒和B4C颗粒与基体的界面之间。     

B_4C/Al复合材料的相及其显微组织的研究

用无压浸渗法制备了B4C/Al复合材料。采用X射线衍射仪、能谱仪、扫描电镜、透射电镜以及光学显微镜对复合材料的相及其微观组织进行了观察及分析。结果表明,在B4C/Al复合材料中,Al3BC相沿碳化硼和铝的界面生长,增加了碳化硼和铝的界面结合强度;AlB2是类似棒状的长条晶体,嵌于碳化硼和铝之间,当材料受外力冲击时起增韧作用。该复合材料中碳化硼以连续的骨架结构存在,而渗入的铝相也以连续基体的形式存在,形成了双连续骨架结构。该复合材料的断裂方式是沿陶瓷骨架的穿晶断裂和金属铝的桥接断裂。     

保温处理对B_4C/Al复合材料组织和性能的影响

为了降低无压浸渗制备的B4C/Al复合材料中铝的含量,增加复合材料中陶瓷相的含量,并提高复合材料的性能,研究了保温处理对B4C/Al复合材料的组织和性能的影响。结果表明,无压浸渗制备的B4C/Al复合材料中主要包含Al、B4C和Al3BC相,保温处理可有效减少B4C/Al复合材料中Al和B4C的含量,并显著提高Al3BC和AlB2相的含量。由于保温处理后B4C/Al复合材料中Al含量明显减少,以及陶瓷相含量明显增多,B4C/Al复合材料的硬度、抗压和抗弯强度均得到了较大的提高。且在850℃下保温24h后,B4C/Al复合材料的组织和性能可达到最佳状态。     

热等静压对电子封装60wt%Si-Al合金组织与性能的影响

采用喷射成形技术制备了新型电子封装材料60wt%Si-Al合金,选用两种热等静压工艺对其进行致密化处理,研究热等静压对材料组织和性能的影响。观察、分析了热等静压致密化后合金组织,测试了热等静压后合金的致密度、导热及热膨胀性能。结果表明,热等静压可有效减少或消除喷射成形60wt%Si-Al合金坯件内部的缩松缩孔,使合金接近理论密度。固态(520℃)热等静压后的合金相比半固态(600℃)热等静压合金,表现出更高的致密度、热导率和更低的热膨胀系数。     

液固分离制备SiCp/Al封装壳体的组织和性能

采用半固态触变液固分离工艺制备出底部具有高体积分数SiC(63 vol%)的Al基功能梯度电子封装壳体,借助光学显微镜和扫描电镜分析了壳体复合材料中SiC的形态分布及其断口形貌,并测定了其热物理性能和力学性能。结果表明,原始30vol%SiCp/Al复合材料在半固态触变成形中SiC颗粒和液相产生分离流动,液相从壳体中流出,SiC颗粒在壳体中聚集,其体积分数从壳体底面向四壁逐渐降低。组织和性能呈梯度变化。壳体底面具有高的热导率和低的热膨胀系数(CTE),这与芯片材料相匹配,壳体四壁具有良好的焊接性能。     

挤压铸造低体积分数SiC_w/Al复合材料的组织与性能

采用挤压铸造工艺制备了SiC_w含量为14%的Al基复合材料,并利用金相显微镜、扫描电镜(SEM)、电子万能试验机等手段分析了退火及T6处理工艺对SiC_w/Al复合材料组织和性能的影响。结果表明,SiC_w/Al复合材料中SiC_w分布均匀,无孔洞、气孔等铸造缺陷。热处理可以显著提高材料的抗拉强度,退火和T6处理后SiC_w/Al复合材料的抗拉强度分别为321.4 MPa和392.7 MPa,相较铸态分别提高了52.9%和86.8%。结果表明,挤压铸造工艺可以制备出高强度的低体积分数铝基复合材料。     

热处理对无压浸渗法制备B_4C/2024Al复合材料相组成及力学性能的影响(英文)

利用无压浸渗法制备B4C/2024Al复合材料,并通过XRD、SEM和力学性能检测研究热处理对复合材料相组成以及材料性能的影响。结果表明,B4C/2024Al复合材料包含B4C、Al、Al3BC、AlB2和Al2Cu相。经过660、700、800和900°C热处理12、24或36 h后,相种类并没有变化,但是相含量发生显著改变。此外,经热处理,材料的硬度得到显著提高,抗弯强度有所下降。经800°C热处理36 h的材料硬度最高,经700°C热处理36 h的材料具有最优良的综合性能。     

AlN-TiN-TiB_2复相陶瓷的显微结构和力学性能

以Al、TiN、B_4C、Si为原材料,采用自蔓延高温合成热等静压(SHS/HIP)技术制备了AlN-TiN-TiB_2复相导电陶瓷,测定其相对密度、维氏硬度、抗弯强度和断裂韧度等力学性能,并确定了最佳原料比.利用XRD、SEM分析了AlN-TiN-TiB_2复相导电陶瓷的物相和显微组织,材料的断裂模式主要是沿晶断裂.并且研究了不同比例复相陶瓷在不同温度下的电阻率.     

采用非夹层液相扩散焊连接铝基复合材料

采用真空扩散焊焊接铝基复合材料ＳｉＣｗ／６０６１Ａｌ通过系列试验研究了焊接工艺参数对接头强度的影响。结果表明：该材料扩散焊时,焊接温度是影响接头强度的主要工艺参数,当焊接温度介于基体铝合金液－固两相温度区间时,接合面上出现了液态基体金属,可获得较高的接头强度。     

Hot Deformation Behavior and Workability of(SiC_p + Mg_2B_2O_(5w))/6061 Al Hybrid and SiC_p/6061 Al Composites

The hot deformation behavior of(3 vol%SiC_p + 3 vol%Mg_2B_2O_(5w))/6061 Al(W_3P_3) hybrid composite and6 vol%SiCp/6061 Al(P_6) composite have been characterized in the temperature range of 300-450 ℃ and strain rate range of 0.0001-0.1 s~(-1) using isothermal constant true strain rate tests.The flow behavior and processing maps have been investigated using the corrected data to eliminate the effect of friction.Under the same deformation conditions,the compressive resistance of the singular composite remains superior to that of the hybrid composites.The processing map of W_3P_3 hybrid composite exhibits a single hot working domain at the temperature between 350 and 450 ℃ with strain rate between 0.0001 and 0.003 s~(-1)(domain A).Two hot working domains exist for P_6 composite:(i) 300-400 ℃/0.0001-0.003 s~(-1)(domain Bl);(ii) 380-450 ℃/0.01-0.1 s~(-1)(domain B2).The processing maps also reveal the flow instability of the two composites,which is associated with whiskers breakage,whisker/matrix interfacial debonding,SiCp/matrix interfacial decohesion,adiabatic shear bands or flow localization,and wedge cracking in the corresponding regions.The estimated apparent activation energies are about 224 kJ mol~(-1) in domain A for W3P3 hybrid composite,177 kJ mol~(-1) in domain Bl and 263 kJ mol~(-1) in domain B2 for P_6 composite,respectively.These values are higher than that for self-diffusion in Al(142 kJ mol~(-1)),suggesting that there is a significant contribution from the back stress caused by the presence of particles and/or whiskers in the matrix.The deformation mechanisms corresponding to domain Bl and domain B2 are dislocation climb controlled creep and cross-slip for P_6 composite,respectively.For W_3P_3 hybrid composite,the deformation mechanisms contain dislocation climb controlled creep and grain boundary sliding caused by DRX in domain A.     

Fabrication of Carbon Nanotube-Reinforced 6061Al Alloy Matrix Composites by an In Situ Synthesis Method Combined with Hot Extrusion Technique

Carbon nanotube(CNT)-reinforced 6061 Al alloy matrix composites were prepared by chemical vapor deposition(CVD) combined with hot extrusion technique. During the preparation process, the 6061 Al flakes obtained by ball milling of the 6061 Al spherical powders were subjected to surface modification to introduce a hydrophilic polyvinyl alcohol(PVA) membrane on their surface(6061Al@PVA) to bond strongly with nickel acetate [Ni(II)]. Then the6061Al@PVA flakes bonded with Ni(II) were calcined and reduced to Ni nanoparticles, which were then heat-treated at580 °C to remove PVA for obtaining even Ni/6061 Al catalyst. After that, the as-obtained Ni/6061 Al catalyst was employed to synthesize CNTs on the surface of the 6061 Al flakes by CVD. After hot extrusion of the CNT/6061 Al composite powders, the as-obtained CNT/6061 Al bulk composites with 2.26 wt% CNTs exhibited 135% increase in yield strength and 84.5% increase in tensile strength compared to pristine 6061 Al matrix.     

热压烧结制备Al2O3/TiCN-Ni-Ti陶瓷复合材料的组织与性能

采用真空热压烧结方法制备Al2O3/Ti(C,N)-Ni-Ti陶瓷基复合材料,采用X射线衍射与扫描电镜分析材料的物相组成和显微结构,研究烧结工艺对材料物相组成、显微结构和力学性能的影响。结果表明:Ni和Ti的添加显著提高复合材料的强度和韧性;温度小于1 600℃时,复合材料的力学性能随热压温度的升高而升高;温度高于1 600℃时,温度升高及保温时间延长不仅会导致Al2O3晶粒的异常长大和Ti(C,N)的分解,而且会使Ni发生聚集现象,复合材料的力学性能下降;当烧结温度为1 600℃、保温时间为30 min时,制备的Al2O3/Ti(C,N)-Ni-Ti陶瓷复合材料的力学性能最佳,其相对密度达到99.4%,抗弯强度为820 MPa,断裂韧性达到9.3 MPa.m1/2。     

Superplastic behavior of PM SiCp/6061 aluminum alloy composites at high strain rates

The superplastic behavior of a powder-metallurgy processed 6061 Al composite was investigated as a function of SiC content increasing from 0% to 30% at 10% increments over a wide temperature range from 430°C to 610°C. The materials were found to be high-strain-rate superplastic. In the temperature range where grain boundary sliding (GBS) controlled the plastic flow, the strength of the composite was lower than that of the unreinforced matrix alloy even after compensating for grain size and threshold stress. This “particle weakening” was in contrast with the particle strengthening observed in the low temperature range where dislocation climb creep was found to control the plastic flow. In the GBS regime, the strength differential between the materials was a function of SiC content and temperature, which increased with the increase in SiC content and temperature. Strong Mg segregation was detected at interfaces between SiC and Al phases in the composites. Evidence for interfacial reaction reported in the Si₃N₄ reinforced 6061 Al composites could not be detected in the current composites. Extensive formation of whisker-like fibers was observed at the fractured surface of the tensile samples above the critical temperature where particle weakening begins to be exhibited. This result suggests the possibility that partial melting in the solute-enriched region near SiC interfaces is responsible for the particle weakening in the SiC reinforced 6061 Al composite.     

等离子烧结Al35Ti15Cr20Mn20Cu10/6061Al复合材料的组织与性能

采用机械合金化与放电等离子烧结工艺制备了体积分数为5%的Al35Ti15Cr20Mn20Cu10增强6061Al复合材料,重点研究了烧结温度对轻质高熵合金增强铝基复合材料微观组织及力学性能的影响。当烧结温度为540℃时,复合材料的致密度最大为98.6%。此时复合材料基体与增强体之间产生明显过渡层,界面结合以扩散结合为主。随着烧结温度升高,复合材料的屈服强度出现先上升后下降的趋势。当烧结温度为540℃时,复合材料的屈服强度达到186MPa,相比基体的屈服强度提升了约75%,复合材料的屈服强度接近Iso-strain模型的计算值。     

Effects of residual stress and dislocation on tensile deformation behavior of SiC_w/Al composites

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Development and performance of new hard and wear-resistant engineering materials

Wear is a major problem in many industrial applications, and the development of wear-resistant materials is therefore both a technical and an economic advantage. Iron-base composites bring new possibilities into the production of wear-resistant materials because of their high hardness and sufficient fracture toughness. They are suitable replacements for the conventional WC/Co cermets owing to their lower fabrication cost, better machinability, weldability, and corrosion resistance. In this study, hot-work steel/Cr₃C₂ composites and reference wear-resistant materials were produced by hot isostatic pressing. It was found that the matrix powder size used during processing did not affect the resultant wear properties of the composite. On the other hand, the impact toughness increased when fine matrix powders were used. The increasing reinforcement volume fraction increased significantly the hardness and wear resistance of the composite; however, the impact resistance decreased. The newly proposed hot-work steel/30 vol% Cr₃C₂ composite demonstrated a better combination of properties than some of the most abrasion-resistant materials available today.