Mg-Sm系合金的显微组织及力学性能

研究了Mg-(1%～3%)Sm(质量分数)合金在多种状态下的显微组织和力学性能.采用光学金相分析(OM),扫描电子显微分析(SEM),X射线衍射分析(XRD)等多种分析和测试手段,系统研究了挤压工艺及热处理(固溶处理、时效处理)对Mg-Sm系合金显微组织和力学性能的影响.结果显示,合金的铸态组织由a-Mg基体和Mg41Sm5组成.合金经热挤压加工后,Mg41Sm5相沿挤压方向呈纤维或颗粒状分布.在420℃挤压时,试样内发生了动态再结晶,致使挤压后合金的强度和塑性得到大幅度改善.固溶以及时效处理后,合金的性能比铸态有较大提高;而采用挤压后的直接时效(T5)处理,可获得良好的综合力学性能.因此,Sm可以考虑作为强化变形镁合金的添加元素.     

挤压态Mg-9Li-3Al-xSr镁合金的微观组织与力学性能

采用SEM、EDS、XRD、TEM和力学性能测试等手段研究了挤压态Mg-9Li-3Al-xSr(LA93-xSr,x=0,1.5,2.5,3.5wt%)镁合金的微观组织与力学性能,探讨了Sr含量对挤压态合金的微观组织及力学性能的影响规律。结果表明:LA93-xSr镁合金包括α-Mg(hcp)和β-Li(bcc)两种基体相。Sr含量对挤压态合金的晶粒大小没有明显影响。随着Sr元素的加入,合金中形成Al4Sr新相,主要分布于α/β相界面,并沿挤压轴向呈流线分布。合金的强度随着Sr含量的增加呈现先增加后降低的趋势,合金的延伸率随着Sr含量的增加呈现逐渐降低的趋势。当Sr含量为2.5wt%时,挤压态Mg-9Li-3Al-2.5Sr(LAJ932)合金的抗拉强度达到最大值235.2MPa,屈服强度达到220.6MPa,延伸率为19.4%,合金呈现出良好的力学性能。挤压过程中,α-Mg相中发生形变诱发的晶粒细化,β-Li相中发生常规动态再结晶。     

医用材料Mg-Y-Nd-Zr合金的组织及力学性能

采用电阻炉和316L不锈钢坩埚,在RJ-2覆盖剂的保护下制备4种不同质量分数钕(Nd)的Mg-Y-Nd-Zr合金.采用电子探针、X射线衍射分析、拉伸测试、扫描电镜等方法研究4种合金的组织及力学性能.结果表明,Mg-Y-Zr合金主要由-αMg和Mg24Y5相组成,加入Nd后,形成了新相Mg12Nd;Mg-Y-Nd-Zr合金断口具有准解理和韧性断裂的混合特征,其力学性能因Nd的质量分数不同而变化,弹性模量为25.8~35.8 GPa,接近人体骨的模量,可满足医疗器械及用于心脏介入治疗生物可降解材料力学相容性要求.     

锻态粉末冶金铁基合金的显微组织和力学性能

采用金相观察、能谱分析、X线衍射和洛氏硬度测定等研究锻态粉末冶金铁基合金显微组织和力学性能演变的规律。研究结果表明:锻造态铁基合金已经开始发生再结晶,但再结晶晶核较少,再结晶不完全,晶界处有第二相析出,析出相成分主要为Ti,Y和O;经1300~1450℃热处理后发生了再结晶,在1300℃再结晶完全,晶粒细小,第二相弥散分布于晶粒内部,样品最高洛氏硬度达54.8;随着热处理温度的提高,晶粒长大明显,强化相颗粒长大,导致洛氏硬度下降;经700℃退火后,铁基合金材料晶粒尺寸变化不明显,X线衍射峰向右发生偏移,Cr的固溶度降低,洛氏硬度下降明显。     

Microstructure and mechanical properties of Nb–Si alloys fabricated by spark plasma sintering

This paper deals with microstructural evolutions and mechanical properties of Nb-Si binaries containing dual-phase Nb/Nb5Si3 with Nb to Nb5Si3 fraction ratios of 90:10,80:20,70:30 and 50:50,prepared by spark plasma sintering(SPS).Dense Nb/Nb5Si3 samples with a relative density larger than 99.5% were obtained by SPS processing.The SPS samples consist of the Nb and Nb5Si3 phases with less than 3% fraction of NbO oxide.Hv at room temperature,and compressive strength at 1150℃ and 1250 1C of the bulk SPS alloys increase monolithically by enhancing fraction of the stiffening Nb5Si3 phase.For example,0.2% yield strength,σ0.2,increases from 175 MPa to 420 MPa at 1150℃ and from 110 MPa to 280 MPa at 1250℃,when the Nb5Si3 fraction increases from 10% to 50%.It is interesting that the fracture toughness,KQ,of the bulk SPS samples seems not to be sensitive to phase fraction.Heat treatment,however,plays a key role on the KQ as compared with that of the as-sintered state,at the corresponding Nb5Si3 fraction and considerably improves the KQ by about 100% for samples with the Nb5Si3 fractions of 10%-30%,and by about 50% for the sample with 50% Nb5Si3 fraction.     

纳米CaCO3-PVC复合材料微观结构和力学性能研究

将纳米CaCO₃进行表面改性,制备了纳米CaCO₃-PVC复合材料。用透射电子显微镜观察纳米CaCO₃改性前后及纳米CaCO₃-PVC复合材料的微观结构。结果表明,表面改性后纳米CaCO₃在PVC基体中达到了纳米级的分散,对PVC复合材料有显著的增韧作用,复合材料的缺口冲击强度达到41.2kJ/m²。此外,还研究了纳米CaCO₃-PVC的流变性能。     

纳米CaCO_3-PVC复合材料微观结构和力学性能研究

将纳米CaCO3 进行表面改性 ,制备了纳米CaCO3 PVC复合材料。用透射电子显微镜观察纳米CaCO3 改性前后及纳米CaCO3 PVC复合材料的微观结构。结果表明 ,表面改性后纳米CaCO3 在PVC基体中达到了纳米级的分散 ,对PVC复合材料有显著的增韧作用 ,复合材料的缺口冲击强度达到 41 2kJ/m2 。此外 ,还研究了纳米Ca CO3 PVC的流变性能     

Microstructure and mechanical properties of spark plasma sintered Ti-Mo alloys for dental applications

Ti-Mo alloys with various Mo contents from 6wt% to 14wt% were processed by spark plasma sintering based on elemental powders. The influence of sintering temperature and Mo content on the microstructure and mechanical properties of the resulting alloys were investigated. For each Mo concentration, the optimum sintering temperature was determined, resulting in a fully dense and uniform microstructure of the alloy. The optimized sintering temperature gradually increases in the range of 1100–1300℃ with the increase in Mo content. The microstructure of the Ti-(6–12)Mo alloy consists of acicular α phase surrounded by equiaxed grains of β phase, while the Ti-14Mo alloy only contains single β phase. A small amount of fine α lath precipitated from β phase contributes to the improvement in strength and hardness of the alloys. Under the sintering condition at 1250℃, the Ti-12Mo alloy is found to possess superior mechanical properties with the Vickers hardness of Hv 472, the compressive yield strength of 2182 MPa, the compression rate of 32.7%, and the elastic modulus of 72.1 GPa. These results demonstrate that Ti-Mo alloys fabricated via spark plasma sintering are indeed a perspective candidate alloy for dental applications.     

Influence of nickel addition on the microstructure and mechanical properties of Al2O3-5vol%ZrO2 ceramic composites prepared via precipitation method

The aim of this work was to investigate the microstructure and mechanical properties of 1vol%-Ni-added yttria-stabilized zirconia (YSZ) toughened alumina composites. First, Ni powders were heterogeneously precipitated in an alumina-zirconia powder mixture suspended in water; the prepared specimens were then pressureless sintered at 1550℃/2 h in a 90vol%Ar/10vol% H₂ atmosphere. The structure of phases and microstructure of the composites were characterized by X-ray diffraction and scanning electron microscopy, respectively. Mechanical characterization of the specimens was carried out through Vickers hardness, Vickers indentation toughness, and three-point flexural bending tests. The fine Ni particles were homogeneously dispersed throughout the alumina matrix because of the employed processing method. Furthermore, hardness and toughness values were found to increase by 8% and 50%, respectively, with Ni addition, whereas the relative densities and flexural strength values were found to remain unchanged.     

TiO2/Al2O3-Al2O3-TiO2/Al2O3绝缘结构的真空沿面闪络特性

基于变插入层介电常数的多层绝缘结构能改善电场分布、提高真空沿面闪络特性.通过真空热压烧结制备了TiO2/Al2O3-Al2O3-TiO2/Al2O3(A-B-A)3层绝缘结构,A层w(TiO2)为0.5%到20%.测量了该绝缘结构的真空沿面闪络特性,发现闪络特性随w(TiO2)的增加而提高,当w(TiO2)为20%时,其脉冲初次闪络电压较同等厚度的Al2O3陶瓷提高了63%.研究发现:A层的介电常数可由w(TiO2)调控,介电常数的增大能有效降低真空-绝缘子-阴极三结合点处的电场强度;A层表面存在的TiO2颗粒可以减小二次电子发射系数并改善表面电荷分布;TiO2的电导率虽比Al2O3高,但其仍为绝缘体,即使TiO2含量较高时也不会形成贯穿的导电通道.     

Thermoelectric properties of quaternary Mg2Sn0.4Si0.6−xGex alloys

Quaternary alloys Mg₂Sn_0.4Si_0.6−xGe_x (x=0, 0.02, 0.05, 0.08 0.1, and 0.2) were prepared using induction melting followed by hot-pressing. Relative densities of the sintered samples were over 97% of the theoretical values. Multiple phases were detected in the samples. It was found that the Seebeck coefficient was sensitive to the content of Mg₂Ge and a maximum value of about 350 μ V.K⁻¹ was obtained. The introduction of Ge increases the electrical conductivity and the thermal conductivity simultaneously. The mechanism of this phenomenon was discussed. A maximum dimensionless figure of merit, ZT, of about 0.28 was obtained for Mg₂Sn_0.4Si_0.55Ge_0.05 at 550 K.     

Fe-N/TiN纳米多层膜的结构与力学特性

该文用磁控溅射法制备了一系列Fe-N/TiN纳米多层膜;利用广角和小角X射线衍射和俄歇电子能谱对多层膜的微观结构和成分进行了测试;利用纳米硬度计和纳米划痕仪研究了多层膜的微观力学性能。固定Fe-N层厚度为20nm,改变TiN层的厚度,研究了TiN层厚度变化对Fe-N/TiN纳米多层膜的附着力、硬度、弹性模量等性能的影响。发现TiN层为2nm时多层膜有最好的力学性能,说明对Fe-N/TiN多层膜来说,对力学性能影响最大的是多层膜的调制周期。     

Al2O3-SiO2∶Ln3+发光陶瓷的合成及发光行为

采用溶胶-凝胶法合成出了Al     

TiO2微粉对Al2O3-MgO-Cr2O3浇注料性能的影响

马克思的市民社会决定国家理论的形成,经历了一个思想交锋、自我批判、绵延提升直至最终导出唯物史观之创建的逻辑进程。马克思立足于《莱茵报》时期的感性经历,先后运用哲学、历史学和政治经济学的方法和知识对黑格尔理性国家观进行系统的理论清算,纠正了黑格尔的市民社会与国家关系的“历史错位”,首次确立了“社会本体论”原则。市民社会决定国家理论的形成是标志着唯物史观开始诞生的第一命题。分析马克思市民社会决定国家理论的发展脉络和演进逻辑,有利于澄清马克思市民社会理论与唯物史观的内在关联,科学评价市民社会理论在历史唯物主义中的历史地位。     

Microstructure and elevated-temperature mechanical properties of dispersoid-strengthened Al-Mg-Si-Mn alloys produced by twin roll casting

The microstructure and elevated-temperature mechanical properties of dispersoid-strengthened Al-Mg-Si-Mn alloys produced by twin roll casting (TRC) and conventional mold casting (MC) were studied. A specific heat treatment at 430 ​°C for 6 ​h was applied, followed by rolling. Tensile tests were carried out at 300 ​°C. The results show that in the as-cast microstructures, equiaxed grains formed in the MC sample while elongated grains with substructures formed in the TRC sample. The eutectics in the TRC sample were much finer than those in the MC sample. Upon heat treatment, large numbers of α-Al(Fe, Mn)Si dispersoids precipitated, and the TRC sample had a greater number density of dispersoids than those in the MC sample. During the tensile test after rolling, the TRC samples exhibited higher strength than the MC samples, which resulted from the combination of the strengthening effect of the stronger dispersoids and the greater substructure hardening effect in the TRC sample; the TRC sample exhibited better ductility due to its finer initial eutectic than that in the MC sample, which depressed the stress concentration and delayed the occurrence of microcracks and fracture in the TRC sample.     

Microstructure,cold rolling,heat treatment,and mechanical properties of Mg-Li alloys

The magnesium-lithium (Mg-Li) alloy exhibits two phase structures between 5.7wt% and 10.3wt% Li contents, consisting of the a (hcp) Mg-rich and the β (bcc) Li-rich phases, at room temperature. In the experiment, Mg-5Li-2Zn, Mg-9Li-2Zn, Mg-16Li-2Zn, Mg-22Li-2Zn, Mg-5Li-2Zn-2Ca, Mg-9Li-2Zn-2Ca, Mg-16Li-2Zn-2Ca, and Mg-22Li-2Zn-2Ca (wt%) were melted. During the melting process, the flux, which was composed of lithium chloride (LiCl) and lithium fluoride (LiF) in the proportion of 3:1 (mass ratio) and argon gas were used to protect the alloys from oxidation. The microstructure, mechanical properties, and cold-rolling workability of the wrought alloys were studied. The crystal grain of the alloys (adding Ga) is fine. The hardness of the studied alloys decreases with an increase in element Li. The density of the studied alloys is in the range of 1.187 to 1.617 g/cm3. The reduction of the Mg-16Li-2Zn and Mg-22Li-2Zn alloys can exceed 85% at room temperature. The Mg-9Li-2Zn-2Ca alloy was heat treated at 300℃ for 8, 12, 16, and 24 h, respectively. The optimum heat treatment of the Mg-9Li-2Zn-2Ca alloy is 300℃×12h by metallographic observation and by studying the mechanical properties of the alloys.     

Al2O3-SiC纳米复合陶瓷的制备及其表征

以分析纯Al(NO₃)₃·9H₂O, (CH₂)₆N₄和粒径为30 nm的SiC粉末为原料, 采用溶胶-凝胶(sol-gel)方法制备干凝胶, 经煅烧合成Al₂O₃-SiC纳米陶瓷粉, 利用真空热压装置对粉末进行烧结. 通过X射线衍射(XRD)、 扫描电镜(SEM)和维氏硬度实验分析了不同SiC含量和不同烧结温度的Al₂O₃-SiC陶瓷样品的结构、 形貌、 晶粒尺寸和硬度, 并研究了其机理.     

Ni／AI2O3金属陶瓷复合材料

用一种新思路设计一种非常规方法制备金属镍和氧化铝金属陶瓷复合材料获得成功。将分别含有氧化镍和氧化铝的先驱体通过溶胶－凝胶法制取均匀和超细的混合粉体，接着将其在1200℃还原氧化镍成金属镍。将还原后的粉末半干压成型后在1460℃进行真空热压烧结，得到Ni/AI2O3复合材料。结果显示这种材料的抗压强度与断裂韧性明显提高，但硬度有所降低。