造孔剂大小对泡沫钛孔隙结构的影响

采用3种颗粒大小的尿素作为造孔剂,在造孔剂含量相等的条件下进行了泡沫钛的制备,考察了造孔剂大小对泡沫钛结构和力学性能的影响,讨论了造孔剂大小对烧结泡沫孔隙率的影响。添加粒度更小的造孔剂颗粒,有利于提高生压坯的致密度。小颗粒造孔剂制备的泡沫钛的孔径更小,孔棱的结构和厚度分别更加致密和均匀。改变造孔剂的颗粒大小,泡沫钛应力-应变曲线的弹性部分变化不大,坍塌平台有明显的变化。结果表明,泡沫钛的相对密度和杨氏模量随着造孔剂粒径的减小而微弱的增大,而抗压强度则明显的增大。分析表明,泡沫钛的宏观大孔在烧结过程的体积收缩量随着造孔剂粒径的减小而减小。     

以NH_4HCO_3为造孔剂制备的多孔钛及其力学性能

以NH_4HCO_3为造孔剂,采用粉末冶金法在10-3 Pa的真空度下成功烧结出力学性能与骨匹配的多孔钛。利用扫描电镜观察孔的结构,采用X射线衍射仪分析物相组成,利用阿基米德浮水法测定开孔隙率,利用万能材料试验机测量力学性能。结果表明,多孔钛烧结体的主要相为α-Ti,随着造孔剂添加量的改变,并没有出现新相;多孔钛烧结体的开孔隙率范围在6.9%~65.7%之间,且开孔隙率越大平均孔径也越大;抗压强度随开孔隙率的增大而降低,在50~1 558 MPa之间;当造孔剂含量在30%~50%时,所得制品弹性模量在4.1~9.4GPa,理论上很接近人骨的弹性模量(2.3~20GPa)。     

CaCl2作为造孔剂制备泡沫青铜的结构和力学性能

以青铜粉为原料、CaCl_2为造孔剂,采用粉末烧结溶解法制备开孔泡沫青铜。通过改变造孔剂体积分数和粒径成功制备出孔隙率为70%~90%,孔径1~3mm的泡沫青铜试样。研究了孔隙率和造孔剂的关系以及孔隙率、孔径对泡沫试样力学性能的影响,并对其孔结构,相组成和微观形貌进行观察和分析。结果表明:泡沫青铜试样的塑性屈服平台应力随孔隙率增加而减小,当孔隙率为77%~89%时,对应塑性屈服平台应力为12.6~2.6MPa。当应变量为50%时,孔隙率为77%~89%的泡沫青铜单位体积能量吸收值(W)范围为6.21~0.91MJ/m~3。试样的理想吸能效率(I)都接近0.82,说明泡沫青铜可以作为一种理想的吸能材料。     

医用多孔Ti-10Mo合金的制备及力学性能

以元素粉末为原料添加造孔剂碳酸氢铵,采用粉末冶金模压烧结技术制备了多孔Ti-10Mo合金,探讨了烧结工艺与造孔剂含量对合金组织、孔隙特征和力学性能的影响规律。结果表明,在1300℃烧结可制备出具有典型魏氏体组织、孔隙分布均匀的多孔Ti-10Mo合金材料;随着造孔剂含量增加,合金孔隙率增加,孔径变大孔壁变薄,当造孔剂含量达到50%,孔隙结构互相贯通,孔径尺寸大幅增加;添加50%~60%造孔剂,制备Ti-10Mo合金孔隙率为62.8%~66.9%,平均孔径尺寸为485.6~545.9μm,其弹性模量为2.9~1.3 GPa,抗压屈服强度为129.2~56.1 MPa。     

用聚硅氧烷和羟甲基纤维素制备泡沫陶瓷

选用聚硅氧烷为主要原料,用羟甲基纤维素为造孔剂,制备了SiOC泡沫陶瓷。研究了造孔剂含量、成型压力、裂解温度对泡沫陶瓷抗压强度及孔隙率的影响,并对泡沫陶瓷的微观形貌进行了分析。结果表明,随着造孔剂含量的增加,泡沫陶瓷的孔隙率随之增大,而抗压强度则随之降低;在40MPa～120MPa的成型压力范围内,随着成型压力的增加,泡沫陶瓷的孔隙率逐渐降低,而抗压强度不断增加;在10001400℃温度范围内,随着裂解温度的升高,泡沫陶瓷的抗压强度先增加后降低,而孔隙率不断降低;当羟甲基纤维素的含量为50％、成型压力为80MPa、裂解温度为1250℃时,所制备的泡沫陶瓷的抗压强度为43MPa,孔隙率为51％。微观结构分析显示,SiOC泡沫陶瓷微孔分布均匀,以三维交错的网状孔道相互贯穿。     

不同孔径分布多孔钛的力学性能

从生物学角度出发设计并制备2种不同孔径分布的多孔钛,并研究其力学性能。采用造孔剂烧结方法制备孔隙率为36%~63%的多孔钛,通过室温压缩测试其力学性能。多孔钛的弹性模量和抗压强度分别在2.662~18 GPa和94.05~468.57 MPa范围内,且都随着孔隙率的增加而降低。抗压强度和孔隙率的关系曲线呈现完全的线性特征,表明抗压强度主要受孔隙率的影响,几乎不受孔径的影响。Gibson-Ashby力学关系分析结果显示：常数项C值的差异说明孔径分布对多孔钛的屈服强度有一定的影响;密度指数n值均大于临界值3,表明这2种不同孔径的多孔钛的变形方式相同,为孔壁的屈曲作用。     

尿素含量对泡沫不锈钢孔隙率和力学性能的影响

采用20 vol%～80 vol%的尿素作为造孔剂制备了泡沫不锈钢。研究了尿素含量对泡沫不锈钢孔隙率、显微组织和力学性能的影响。结果表明:在1200℃下烧结5 h,泡沫不锈钢的孔隙率为18.33%～72.24%。随着尿素含量增加,生坯致密度和烧结体积收缩率增大。在尿素含量大于60 vol%时,烧结体积收缩率骤增。建立了预测孔隙率θ的模型:■,实现了对尿素含量介于0～1的孔隙率的预测。泡沫不锈钢的晶粒尺寸随着孔隙率的增加而减小,多孔结构可以有效抑制晶粒长大。泡沫的压缩屈服强度在低孔隙率时比Gibson-Ashby模型的预测值高,对模型进行修正后可以准确预测泡沫的压缩屈服强度。     

泡沫镁制备及抗压缩性能（英文）

作为一种新型结构和功能材料,泡沫金属具有比实体金属更优异的性能。本研究利用粉末冶金造孔剂法成功制备了孔隙率为38.9%~57.5%泡沫镁。随着孔隙率从38.9%增加到57.5%时,其弹性模量由8.5 GPa下降到3.3 GPa,初始屈服应力从24.90 MPa下降到9.40 MPa。泡沫镁具有较低的初始屈服应力和较长的应力平台,因此,它可以作为优异的缓冲吸能材料。     

以PVB为造孔剂采用硅树脂制备泡沫陶瓷

采用硅树脂为先驱体,利用先驱体转化法与添加造孔剂法相结合制备SiOC泡沫陶瓷.通过对造孔剂聚乙烯醇缩丁醛(PVB)和硅树脂的热分析制定温度曲线,研究了裂解温度、造孔剂含量对泡沫陶瓷抗压强度及孔隙率的影响,采用XRD、SEM及EDS对SiOC泡沫陶瓷进行了物相、微观结构和成分分析.结果表明,在1000～1400 ℃温度范围内,随着温度的升高,泡沫陶瓷的抗压强度先升高后降低,而孔隙率逐渐降低;造孔剂含量对泡沫陶瓷的性能也有明显的影响,随着造孔剂含量的增加,试样的抗压强度逐渐减小,而孔隙率逐渐增大.当裂解温度为1250 ℃,PVB的含量为50%(质量分数,下同)时,所制得的泡沫陶瓷的抗压强度为52.3 MPa,孔隙率为72%.XRD研究表明,随着温度的逐步升高,硅树脂的裂解产物发生了由非晶态向晶态的转变.微观结构分析显示,SiOC泡沫陶瓷呈三维网状结构,微孔分布较均匀.     

生物医用多孔钛的力学性能及孔结构变形行为（英文）

多孔钛材料因其优良的综合性能被视为最有潜力的生物医用材料之一。考虑到生物材料在使用过程中必然受到力的作用,重点研究了多孔钛的力学性能及其孔结构变形行为。采用添加造孔剂的粉末烧结方法制备孔隙率为36%~66%、平均孔径为230μm的多孔钛。采用扫描电镜观察孔结构形貌,通过室温压缩测试检测力学性能。多孔钛的弹性模量和抗压强度分别为1.86~14.7 GPa和85.16~461.94 MPa,具力学性能与人骨的力学性能相近。建立了多孔钛的相对屈服强度和相对密度间关系,结果表明相对密度是影响多孔钛力学性能和变形的主要因素。对于低相对密度的多孔钛而言,其变形方式为孔壁的屈服、弯曲和屈曲;而对于高相对密度的多孔钛,其变形方式主要为孔壁的屈服和弯曲。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

正~~     

Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.