金属玻璃基复合材料的微结构效应

基于自由体积理论和Ramberg-Osgood模型,并利用ABAQUS软件,建立颗粒随机分布代表性体积单元模型,模拟了Ti_(64.5)Zr_(14.5)V_(18.5)Cu_(2.5)颗粒增韧Ti基金属玻璃基复合材料在单轴拉伸状态下的微结构效应,讨论了颗粒的体积分数、团聚数目、长径比、定位取向和界面对金属玻璃韧性的影响。结果表明:提高颗粒体积分数能显著提高复合材料的塑性,但部分牺牲了复合材料的强度;增大颗粒长径比能够增强复合材料的塑性和屈服强度;使颗粒的取向与荷载方向成90°或0°,不仅增强了复合材料的塑性,而且与其他排布相比也增强了复合材料的强度;减少团聚数目至2个以下,能明显减少金属玻璃基复合材料的塑性和强度的损失,使团聚中颗粒与荷载成90°,却能改善复合材料的塑性和强度;在颗粒增韧金属玻璃基复合材料中加入零厚度界面,能观察到在主剪切带上颗粒和基体在界面处脱粘,得到与实验现象更加吻合的结果。通过上述的研究能够很好地理解复合材料的微结构效应,并有利于材料的设计。     

无压熔渗制备TiC/Ni_3Al复合材料的微观组织与断裂韧性研究(英文)

以化学纯镍粉、钛粉、铝粉、石墨粉为原料,采用燃烧合成方法制备了TiC/Ni3Al含孔预制件,用无压熔渗法制备了TiC/Ni3Al复合材料。对TiC/Ni3Al复合材料的微观组织、硬度和断裂韧性进行了研究并采用XRD和SEM分析了复合材料的相组成、微观结构、断口形貌。采用压痕法计算了TiC/Ni3Al复合材料的断裂韧性。试验结果表明:无压熔渗法是制备致密的TiC/Ni3Al复合材料的有效方法。在完成渗透获得致密组织的前提下,渗透温度和渗透时间对TiC/Ni3Al复合材料的硬度及断裂韧性无显著影响。渗透后复合材料的组成相主要为Ni3Al和TiC两相,Ni3Al相和TiC颗粒结合良好。本文制备的Ni3Al/TiC复合材料的维氏硬度随TiC体积分数的增加而增加,TiC含量分别为70%和80%时,复合材料的维氏硬度平均值分别为569.6(Hv)和610.8(Hv)。复合材料的断裂韧性最高达到了10.5MPa.m1/2,TiC颗粒和Ni3Al界面的分离是复合材料断裂过程中存在的主要失效形式。断裂过程中Ni3Al可以有效地吸收裂纹扩展能量,阻止了裂纹的直线扩展,使裂纹扩展方向发生偏转,大大增加了材料的断裂韧性。     

球形铁基金属玻璃单分散粒子的制备及评价

利用脉冲小孔法在He气氛下制备出了球形粒径可控的[(Fe_0.5Co_0.5)_0.75B_0.2Si_0.05]₉₆Nb₄金属玻璃单分散微粒子, 这些粒子具有粒径均匀和圆球度高等优良特点. 通过XRD、DSC以及TEM对所获得的粒子进行了检测分析, 结果表明随着粒径尺寸的减小, 微粒子的微观结构从混合相逐渐向全金属玻璃相转变, 制备的粒子均为全玻璃相, 临界尺寸小于645 μm. 通过冷却速率的计算, 得到全玻璃相微粒子的临界冷却速率为800~1100 K/s, 该速度与环境气氛的改变无关, 并且该计算值低于同成分的大块金属玻璃合金TTT曲线的测量值.     

层板复合材料动态断裂韧性测试的SHPB技术研究

为测试层板复合材料的断裂韧性,对传统的Hopkinson压杆测试系统进行了改进,建立了应力波载荷作用下材料动态断裂韧性的测试方法。该方法采用三点弯曲试样进行动态断裂试验,应用动态断裂韧性测试系统ANSYSED5．4确定动态应力强度因子的响应曲线,进而测试材料动态断裂韧性。对层板复合材料试验结果的分析表明,设计的测试装置有效,建立的测试方法是对层板复合材料断裂韧性测试的有益尝试,有较大的参考价值。     

金属—PTC陶瓷复合材料制备工艺及机理的研究

金属－ＰＴＣ陶瓷复合材料是电子功能型的陶瓷基复合材料。本文介绍了Ｆｅ、Ｃｏ、Ｎｉ－ＰＴＣ陶瓷复合材料的制备方法，测定了材料的阻温特性，讨论了样品的ＮＴＣ现象及阻温特性机理。     

大块金属玻璃及其复合材料的粉末冶金成形研究进展

简要介绍了大块金属玻璃及其复合材料的研究现状及其应用领域.针对大块金属玻璃塑性低的不足,回顾了提高其塑性的原理和方法;通过对比铸造法,提出了粉末冶金法制备大块金属玻璃及其复合材料的成形原理和方法,进而详细介绍了电火花烧结、挤压、热压、扭转等方法制备大块金属玻璃及其复合材料的研究进展.最后,指出制备具有延性析出相的大块金属玻璃基复合材料将可能是未来粉末冶金法的研究趋势之一.     

形状记忆合金的力学及界面参数和体积分数对大块金属玻璃基复合材料增韧的影响

采用考虑塑性的超弹性材料模型和基于损伤塑性的准脆性材料模型,建立了三维单胞有限元模型,模拟了形状记忆合金颗粒增韧大块金属玻璃基复合材料的单调拉伸行为。讨论了形状记忆合金的力学参数、体积分数、界面厚度和界面材料参数对金属玻璃增韧效果的影响。结果表明:提高形状记忆合金的相变应变和马氏体塑性屈服应力将显著提高形状记忆合金颗粒增韧大块金属玻璃基复合材料的拉伸失效应变;形状记忆合金弹性模量超过50.0GPa、马氏体塑性屈服应力超过1.8GPa后,复合材料的拉伸失效应变变化不大。能同时兼顾失效应变和失效应力的形状记忆合金体积分数为15%左右。复合材料界面弹性模量和界面屈服应力的增加将提高复合材料的失效应力,但对失效应变影响不大;复合材料界面厚度的增加在提高失效应变的同时,也降低了复合材料的失效应力。     

异种金属层状复合材料金相试样的制备技术

通过对金属层状复合材料金相试样制备经验的总结,介绍了异种金属层状复合材料界面金相试样制备过程中磨、抛光和侵蚀等关键操作,提出了在金相试样制备过程中应注意的事项和技术要点.实践表明,提出的制备技术具有技术上的合理性和可操作性,可得到较满意的样品.     

塑性钛基非晶复合材料的制备及性能

通过铜模喷铸法成功制备了一系列内生β-Ti（Zr,Nb）枝晶增塑的Ti—Zr—Nb—Cu—Be非晶复合材料,研究了成分对枝晶体积分数及尺寸的影响及其对复合材料力学性能的调节作用。结果表明,Ti48Zr20Nb12Cu5Be15合金压缩强度达到2061MPa,塑性变形高达22．5％,表现出优异的综合力学性能。非晶复合材料的塑性不仅与β—Ti（Zr,Nb）枝晶相的体积分数有关,而且受到枝晶尺寸的强烈影响,在一定体积分数条件下,枝晶相的尺寸越大,对剪切带的阻碍作用越明显,合金的塑性越高。     

CuZr-based bulk metallic glass and glass matrix composites fabricated by selective laser melting

Monolithic bulk metallic glass and glass matrix composites with a relative density above 98 ％ were produced by processing Cu46Zr46Al8 (at.％) via selective laser melting (SLM).Their microstructures and mechanical properties were systematically examined.B2 CuZr nanocrystals (30-100 nm in diameter) are uniformly dispersed in the glassy matrix when SLM is conducted at an intermediate energy input.These B2 CuZr nanocrystals nucleate the oxygen-stabilized big cube phase during a remelting step.The presence of these nanocrystals increases the structural heterogeneity as indirectly revealed by mircrohardness and nanoindentation measurements.The corresponding maps in combination with calorimetric data indicate that the glassy phase is altered by the processing conditions.Despite the formation of crystals and a high overall free volume content,all additively manufactured samples fail at lower stress than the as-cast glass and without any plastic strain.The inherent brittleness is attributed to the presence of relatively large pores and the increased oxygen content after selective laser melting.     

Temperature dependence of pressure sensitive flow in bulk metallic glass composites

The constraint factor,C,defined as hardness,H,to the yield strength,σy,ratio,is an indirect measure of the pressure sensitivity in materials.Previous investigations determined that while C is less than 3 for crystalline materials,and remains invariant with change in temperature,it is greater than 3 for bulk metallic glasses(BMGs)and increases with increasing temperature,below their glass transition temper-ature,Tg.In this study,the variations in C for two BMG composites(BMGCs),which have an amorphous matrix and in situ precipitated crystalline ß-Ti dendrites,which in one case transforms under stress toα\"-Ti and deforms by slip in the other,as a function of temperature are examined and compared with that of a BMG.For this purpose,instrumented indentation tests,with a Berkovich tip,and uniaxial com-pression tests were performed to measure the H and σy,respectively,on all alloys and their constituents at temperatures in the range of 0.48Tg and 0.75Tg.σy and H of the BMGC with transforming dendrites(BMGC-T)increase and remain invariant with increasing temperature,respectively.Alternately,in BMG and the BMGC with non-transforming dendrites(BMGC-NT),the same properties decrease with increas-ing temperature.BMGC-T has the highest C of～4.93 whereas that of BMGC-NT and BMG are～3.72 and～3.28,respectively,at 0.48Tg.With increasing temperature,C of the BMG and BMGC-NT increases with temperature,but that of the BMGC-T decreases.The values of C and their variations as a function of temperature were explained by studying the variation of pressure sensitivity of the amorphous phase and concluding that the plastic flow in BMGCs under constrained conditions,such as indentation,is con-trolled by the flow resistance of the amorphous matrix whereas that in uniaxial compression,which is only partially constrained,is controlled by plasticity in both the dendrites and matrix.     

CBS玻璃/堇青石陶瓷复合材料制备与性能

采用电子陶瓷工艺制备了一系列钙硼硅玻璃／堇青石陶瓷复合材料，堇青石含量分别为50％，60％，70％和80％（质量分数）。对复合材料进行了X射线衍射分析、扫描电镜（SEM）观察和性能测试。结果表明：复合材料的介电常数和热膨胀系数随陶瓷含量的增加而减小，显微硬度随陶瓷含量的增加而增加。堇青石的加入抑制了钙硼硅玻璃中石英的析出，并生成了新相钙长石，其数量随堇青石和烧结温度的增加而增加，但它没有恶化复合材料的物理性能。所制得的复合材料具有高的相对密度（≥96％）、低的介电常数（～6）、低的介电损耗（0.3％～0．5％）、低的热膨胀系数（4．2×10^-6℃^-1～5．2×10^-6℃^-1）和低的烧结温度（≤950℃），有望用作介电材料和基板材料。     

Microstructure and mechanical properties of aluminum alloy matrix composites reinforced with Fe-based metallic glass particles

Fe-based metallic glass (FMG) particles reinforced Al-2024 matrix composites were fabricated by using the powder metallurgy method successfully. Mechanical alloying result in nanostructured Al-2024 matrix with a grain size of about 30 nm together with a good distribution of the FMG particles in the Al matrix. The consolidation of the composites was performed at a temperature in the super-cooled liquid region of the FMG particles, where the FMG particles act as a soft liquid-like binder, resulting in composites with low or zero porosity. The microstructure and mechanical properties of the composites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and compression test. The yield and fracture strength of the composites are 403 MPa and 660 MPa, respectively, while retaining a considerable fracture deformation of about 12%. The strengthening mechanism is associated with the grain refinement of the matrix and uniform distribution of the FMG particles.     

基于BPNN的多相复合陶瓷材料断裂韧性预测

为有效缩短陶瓷材料设计中繁琐的试验过程,利用误差反向传播神经网络(BPNN)能够正确逼近非线性映射关系的优点,将其运用到多相复合结构陶瓷材料断裂韧性预测中,克服了陶瓷材料研究中单因素实验法不能正确反映断裂韧性与添加组分多因素之间复杂的非线性映射关系的弱点.对Al2O3/SiC/(W,Ti)C复合陶瓷材料断裂韧性的预测和试验验证表明,该方法可行有效,为快捷、经济地开发研制陶瓷材料提供了新的思路和有效手段.     

Mixed mode fracture toughness of GFRP composites

Glass fibre reinforced polymer (GFRP) composites are used in a wide range of applications as a structural material. They have high specific mechanical properties but are prone to delamination as a result of manufacturing defects and impact/shock loading. The ability of the structure to continue to carry load after damage and the subsequent propensity of the damage to propagate are important considerations for the design of damage tolerant composite structures. In order to accurately predict the stability of damage under load, relevant mechanical properties of the material must be accurately determined. In particular, mixed mode fracture toughness data is required in order to study the damage criticality in such structures. This paper describes an experimental study to determine Mixed Mode fracture toughness for thick glass/vinylester specimens. The test methodology used for the experiments and its difficulties will be discussed. Mixed mode fracture toughness results are presented, as are Mode I and Mode II fracture toughness results obtained via Double Cantilever Beam (DCB) and End Notch Flexure (ENF) tests, respectively.     

Dynamic fracture of berylium-bearing bulk metallic glass systems: A cross-technique comparison

We report on a detailed comparison between two different experimental techniques used to measure the dynamic initiation fracture toughness of a bulk metallic glass system (Vitreloy-1) and its β-phase composite. Both the coherent gradient sensing interferometry (CGS) and one-point impact techniques reveal very similar trends in the relationship for Vitreloy-1. A drastic increase in initiation toughness with the stress intensity rate is observed. By contrast, the one-point impact method shows a relative rate-insensitivity for the of the β-phase composite. The results are rationalized through a detailed characterization of the failure mechanisms.     

片状氧化铝晶种对氧化铝陶瓷断裂韧性的影响

以片状氧化铝晶种作为第二相,采用无压烧结制备了氧化铝陶瓷,分析了片状氧化铝含量对氧化铝陶瓷微观结构的影响,采用扫描电子显微镜（SEM）观察分析试样的断口形貌;采用压痕法计算试样的断裂韧性（KIC）值;研究了不同含量的晶种引入量对氧化铝陶瓷断裂韧性的影响。结果表明烧结温度为1575℃时,相对致密度可以达到96.7%;片状氧化铝晶种的引入能够显著提高氧化铝陶瓷的断裂韧性;其片晶的裂纹偏转、片晶拔出效应等增韧机制发挥了主导作用;随着片状氧化铝含量的提高,氧化铝陶瓷的力学性能逐渐提高,当掺杂含量达到35%（质量分数）时,KIC达到6.4MPa.m1/2,当含量继续增加,KIC呈现逐渐降低的趋势。