非对称HA/316L不锈钢梯度生物材料的制备与表征

采用干粉铺叠法和热压工艺制备了非对称HA/316L不锈钢功能梯度生物材料,并测定了其相对密度和抗弯强度,采用X射线衍射仪、扫描电镜、金相显微分析技术等对材料进行了物相和显微组织分析.结果表明:非对称HA-316L不锈钢生物FGM在宏观上呈现明显的梯度分布,微观上则各成分分布连续、均匀,各梯度层之间没有明显的宏观界面,界面结合紧密;随着316L不锈钢含量的增大,材料的相对密度增加,抗弯强度提高,平均抗弯强度达450 MPa左右,体现出FGM的热应力缓和行为;此外,在生物FGM中,HA和316L不锈钢两相在热压过程中发生了不同程度的固溶,表明HA和316L不锈钢能够形成好的结合.     

面向等离子体W／Cu FGM的抗热冲击性能

采用循环水淬和脉冲激光冲击法并结合有限元计算考察和分析了用超高压梯度烧结方法制备的W／Cu FGM的抗热震性能。结果表明，W／Cu FGM经受50次800℃～25℃水淬冲击和100MW／m^2以上的激光循环冲击，没有出现界面破坏现象；但随着热冲击次数及冲击能量密度的增加，金属W表面产生了裂纹、晶间断裂以及出现液相及蒸发现象。与非梯度材料相比，W／Cu FGM有优异的抗热冲击性能，大致可以经受100MW／m^2 350次以上的激光循环冲击。     

W/Fe功能梯度材料的制备与性能

采用放电等离子体烧结(SPS)技术,在1050℃下成功制备出了5层W/Fe功能梯度材料,并通过钎焊与纯W结合。采用光学显微镜、扫描电镜和显微硬度计等研究了W/Fe功能梯度材料的表面形貌、断口形貌及硬度。结果表明:所制备的W/Fe功能梯度材料的成分和显微硬度符合梯度变化趋势;纯W层与钎料层间界面平整无孔洞及裂纹,只有少量W扩散至钎料层,而80W20Fe层与钎料层间的界面出现较多宏观孔洞,并出现相互扩散行为。随着W含量的增加,W/Fe功能梯度材料的断裂行为从韧性断裂(316L钢层)到部分韧性断裂(W含量20%),再到完全脆性断裂(纯W层)。     

羟基磷灰石／钛生物功能梯度材料种植体与骨的结合强度

采用动物兔活体植入与剪切强度试验考察r羟基磷灰石(HA)／Ti生物功能梯度材料(FGM)种植体与头骨基体的结合强度。结果表明，HA—Ti FGM种植体／骨结合强度随植入时间延长迅速增高，其强度值与纯HA植入体相当而大大优于纯Ti种植体；植入3个月时，HA—Ti FGM与周围骨组织的结合强度可达6．49MPa。剪切断口形貌表明，FGM种植体断裂发生在界面的新骨一侧，说明其界面结合强度甚至超过了新生骨组织本身的剪切强度。     

Ti／Al2O3梯度功能材料热疲劳裂纹扩展机理

对Ti／Al2O3梯度功能材料进行了物相分析，研究了在热应力作用下的热疲劳裂纹产生的根源及其扩展方式和形态。结果表明：该体系主要有Ti，Al2O3，还有少量的TiAl，Ti3Al，AlNb2组成。Ti/Al2O3界面处生成的Ti3Al相以及Ti3Al周围的气孔是热疲劳裂纹的主要萌生和扩展地；随着成分的变化，裂纹的扩展由沿晶开裂转变为穿晶断裂，裂纹扩展的路线并不是直线，在各梯度层间发生了裂纹的偏转。     

基于MoSi2/316L连接梯度过渡层的组织与形貌

采用MoSi2/316L梯度过渡层,借助放电等离子烧结技术实现了MoSi2与316L不锈钢的连接,着重研究了MoSi2/316L连接梯度过渡层的组织、形貌、显微硬度及界面结合情况.结果表明,MoSi2/316L不锈钢梯度过渡层组织呈梯度分布,表现为宏观组织的不均匀性和微观组织的连续性,各梯度层的显微硬度基本呈梯度变化;梯度过渡层界面之间结合良好,没有明显的宏观界面,在各梯度层内部及界面都没有裂纹及大孔洞,界面结合紧密.     

生物植入用碳纳米管增强混合功能梯度材料的力学性能(英文)

利用羟基磷灰石(HA)、不锈钢316L(SS316L)和碳纳米管(CNT)制备生物医学植入体用混合功能梯度材料(FGM)。加入SS316L和CNT增强功能梯度材料离散层的HA制成三种不同类型的功能梯度材料。第一种功能梯度材料加入10%~40%(质量分数)的SS316L强化微米HA,浓度梯度为10%。第二种功能梯度材料,在第一种功能梯度材料的基础上加入0.5%(质量分数)的功能化碳纳米管。第三种功能梯度材料在第二种功能梯度材料的基础上加入微米HA和纳米HA(1:1)的混合物。所有类型的功能梯度材料在相似的压缩参数和烧结参数下,进行单轴压缩实验,并采用无压烧结技术进行烧结。结果表明,加入碳纳米管和纳米晶体HA提高了功能梯度材料的致密度。碳纳米管增强的功能梯度材料的硬度和断裂韧性增加,但是微米和纳米晶体HA增强的功能梯度材料的硬度和断裂韧性的增加更明显。     

Ti/Al2O3梯度功能材料热疲劳裂纹扩展机理

对Ti/Al2O3梯度功能材料进行了物相分析,研究了在热应力作用下的热疲劳裂纹产生的根源及其扩展方式和形态.结果表明:该体系主要有Ti,Al2O3,还有少量的TiAl,Ti3Al,AlNb2组成.Ti/Al2O3界面处生成的Ti3Al相以及Ti3Al周围的气孔是热疲劳裂纹的主要萌生和扩展地;随着成分的变化,裂纹的扩展由沿晶开裂转变为穿晶断裂,裂纹扩展的路线并不是直线,在各梯度层间发生了裂纹的偏转.     

SiC/BN层状陶瓷的阻力曲线行为

利用压痕一强度法测定了SiC／BN层状陶瓷的阻力曲线行为，并与SiC单相陶瓷做对比。结果表明：2种材料均呈现出上升阻力曲线行为，其中，SiC／BN层状陶瓷显示出更为优越的抗裂纹扩展能力，其阻力曲线上升较陡，上升幅度较大；SiC单相陶瓷的阻力曲线上升较缓且上升幅度较小。分析认为，这与其不同的增韧机制有关。原位增韧是SiC单相材料韧性提高的主要原因，而裂纹遇到弱界面时发生偏转、分叉、脱层等是层状陶瓷材料抗裂纹扩展能力提高的主要原因。     

SiC／C层状陶瓷的断裂行为研究

利用流延法成膜和热压烧结工艺制备出了SiC层和石墨层交替排列、层厚均匀、界面清晰的SiC／C层状陶瓷。力学性能与单相SiC陶瓷相比，SiC／C层状陶瓷的抗弯强度略有降低，但断裂韧性却得到了大幅度的提高。层状陶瓷的载荷-位移曲线不同于单相陶瓷的1次性断裂曲线，而是呈锯齿状；同理论计算所得载荷-位移曲线相似。层状陶瓷的断裂路径呈台阶状，裂纹遇到弱界面时发生分叉产生并行扩展裂纹、晶须状微裂纹以及裂纹遇到弱界面时被吸收。认为裂纹偏转、裂纹分叉、裂纹并行扩展、裂纹遇弱界面被吸收等是SiC／C层状陶瓷的几种主要增韧机制。     

Influence of metal ions on the formation of artificial zinc rusts

The artificial rust particles were prepared from ZnCl₂ solutions dissolving Al(III), Fe(III), Fe(II), Ni(II), Co(II) and Mg(II) at different atomic ratios from 0 to 0.3 in metal/Zn. With increasing metal/Zn the crystal phases of the products turned following as ZnO → a mixture of ZnO and Zn₅(OH)₈Cl₂ · H₂O (ZHC) → ZHC. Al(III) most facilitated the formation of ZHC but Mg(II) and Fe(III) produced no ZHC. The morphology of the formed particles varied following as agglomerate → fine → rod → sheet → irregular with the increase of metal/Zn. The sheet and irregularly shaped particles were identified as ZHC and the other particles as ZnO.     

Effect of dislocation density on the low temperature aging behavior of an ultra low carbon bake hardening steel

Strain aging was studied in an ultra low carbon (ULC) steel with a total carbon content of 20 ppm (wt.%) in order to identify the process stages and mechanism of bake hardening in this type of steel. The effects of dislocation density, varied by means of uniaxial tensile prestraining (1–10%) on the aging kinetics were investigated within an aging temperature range of 50–170°C. The aging was evaluated by means of strength measurements and the determination of interstitial carbon content after aging using a piezoelectric composite oscillator operating at 40 kHz. The interaction between interstitial carbon and dislocations was examined through amplitude dependent internal friction measurements. The influence of dislocation density on the aging behavior have been discussed with reference to the kinetics and mechanism of the aging process.     

A corrosion study of the main constituent phases of AZ91 magnesium alloys

The different constituents of an AZ91 alloy (α,β, and MnAl phases) were synthesized and their corrosion resistance was studied by electrochemistry in ASTM D1384 water, pH 8.3. The pure phases were characterised through the corrosion potential, the polarisation resistance, and polarisation curves, then systematically coupled to assess the galvanic corrosion occurring in the AZ91 alloy. The aluminium content of the oxide film was obtained by X-ray photoelectron spectroscopy measurements. The corrosion rate of the α solid solution alloys depends closely on their Al content. Aluminium enhances the corrosion resistance of the α-phase through the formation of an Al enriched superficial layer. The β-phase is 150 mV nobler than the α-phase, but their corrosion rates are similar. The galvanic currents are low (below 20 μA cm⁻²) whatever the implemented couples and close to the corrosion current previously measured for the AZ91 alloys.     

Effect of solution heat treatment on galvanic coupling between intermetallics and matrix in AA7075-T6

Susceptibility to localised corrosion is strongly affected by heat treatments performed on Al-Zn-Cu-Mg alloys. In order to study how galvanic coupling between intermetallics and matrix is affected by solution heat treatment, AA7075-T6 and solution heat treated AA7075 have been characterised by means of scanning electron microscopy and scanning Kelvin probe force microscopy. Solution heat treatment strongly increased the Volta potential difference between the intermetallics and the surrounding matrix showing a strong increase in galvanic coupling. This is explained by Zn and Mg enrichment of the matrix caused by dissolution of strengthening particles during solution heat treatment.     

硬质合金Hc、Com、D、HV_3的初步探讨

通过研究硬质合金的矫顽磁力、钴磁、密度和硬度,阐述了这些性能之间的相互关系,以及影响这些性能的主要原因,说明了其对生产实践中质量控制的重要意义。     

Characterizing corrosion behavior under atmospheric conditions using electrochemical techniques

AC and DC electrochemical experiments were performed as a function of humidity and contaminant concentration in an effort to identify the range of atmospheric environments where corrosion processes could be detected and possibly quantified. AC measurements exhibited two time constants at 25% relative humidity (RH), possibly indicating the ability to resolve both electrolyte resistance and interfacial impedance. Galvanic current measurements were sensitive to the presence of Cl_2(g) at 30% RH and electrochemical transients were detected at both 30% and 50% RH levels, also indicating sensitivity to interfacial processes. Higher humidity levels allowed better quantification due to decreasing electrolyte and interfacial impedances.     

Electrochemical behaviour of amorphous and nanoquasicrystalline Zr-Pd and Zr-Pt alloys in different environments

The corrosion behaviour of melt spun amorphous and nanoquasicrystalline Zr₇₀Pd₃₀ and Zr₈₀Pt₂₀ alloy ribbons has been investigated using potentiodynamic polarization study in NaCl, H₂SO₄ and NaOH solutions at different concentrations. The amorphous and nanoquasicrystalline alloys show better corrosion resistance than Zr in all the solutions studied. Both the alloys are susceptible to chloride attack and pitting has been observed. Complete passivation has been observed in H₂SO₄, while gradual break down of passivating layer occurs in NaOH. In general, nanoquasicrystalline state in both the alloys shows better corrosion resistance than amorphous state in all the solutions studied.     

A study on the deactivation of an IrO2–Ta2O5 coated titanium anode

The deactivation of an IrO₂–Ta₂O₅ coated titanium anode was studied during an accelerated life test at 2 A cm⁻² in 1 mol dm⁻³ H₂SO₄ solution using CV, EIS, SEM and EDX. The changes of voltammetric charge, double layer capacitance, oxide film resistance and charge transfer resistance of oxygen evolution with time during the electrolysis were monitored. The morphology and surface composition of the oxide anode before and after electrolysis test were analysed. A comprehensive process of deactivation of the oxide anode was proposed based on the test results and analysis.     

加速发展我国的快速成形技术

介绍了第二届北京国际快速成形及制造会议概况，分析了快速成形（RP）技术的发展趋势，指出RP技术研究领域的重大进展及学科发展的主攻方向是：由RP向快速制造（RM）发展，由RP向快速模具（RT）发展，RP技术在生物医学领域的应用。     

Corrosion behaviour of powder metallurgical and cast Al-Zn-Mg base alloys

The behaviour of Al-Zn-Mg base alloys produced by powder metallurgy and casting has been studied using potentiodynamic polarisation in 0.3% and 3% NaCl solutions. The influence of alloy production route on microstructure has been examined by scanning electron microscopy, Auger electron spectroscopy and secondary ion mass spectrometry. An improvement in performance of powder metallurgy (PM) materials, compared with the cast alloy, was evident in solutions of low chloride concentration; less striking differences were revealed in high chloride concentration. Both powder metallurgy and cast alloys show two main types of precipitates, which were identified as Zn-Mg and Zr-Sc base intermetallic phases. The microstructure of the PM alloys is refined compared with the cast material, which assists understanding of the corrosion performance. The corrosion process commences with dissolution of the Zn-Mg base phases, with the relatively coarse phases present in the cast alloy showing ready development of corrosion.