AI／TiO2摩尔比对热扩散反应合成的影响

本文提出了ＡＩ－ＴｉＯ２系ＸＤ合成ＡＩ３Ｔｉ－ＡＩ２Ｏ３／ＡＩ自生复合材料的微观反应模型,分析了不同的ＡＩ／ＴｉＯ２摩尔比对燃烧过程的影响。原位生成的ＡＩ２Ｏ３呈等轴颗粒状,尺寸达亚微米级;ＡＩ３Ｔｉ的生成受扩散控制,呈棒状;随着ＡＩ／ＴｉＯ２摩尔比的增加,燃烧温度降低,燃烧时间和体密度增加。     

复合材料的制造

利用溶液浸渗—燃烧合成法能够就地生产轻质高强度材料———铝基复合材料。利用燃烧合成反应制得ＴｉＡｌ金属间化合物(ＴｉＡｌ3)作为强化剂,所获得的这种金属间化合物是多孔质的,该新工艺在完成燃烧合成反应的同时进行金属熔体(铝)浸渗,即在形成多孔质化合物骨架的同时进行金属熔液的浸渗进入,这样就会在进行燃烧合成反应的同时,促进反应前方的金属熔液浸渗。在实际生产时可以用钛粉压坯或钛铝混合粉末合成的ＴｉＡｌ化合物多孔体浸于铝溶液中,来完成合成反应熔体浸渗过程。在合成反应充分完成的部位,通过与传统液相烧结时同样的颗粒再分…     

燃烧合成TiAl合金结构转变动力学的端部淬火熄灭法分析

采用端部淬火熄灭法分析了蔓延工燃烧合成了Ｔｉ－５０ａｔ％Ａｌ合金中的组织结构转变动力学过程,发现合成反应从铝粉熔化处开始,合成反应表现为Ｔｉ＋Ａｌ→１／３ＴｉＡｌ３＋２／３Ｔｉ→ＴｉｘＡｌ＋（１－ｘ）Ｔｉ→ＴｉＡｌ等一系列过渡反应过程,这些反应的前期是可依赖液态反应物流动铺展进行质量传递的快速液－固型反应,可使试样温度迅速升高,为后续固－固型反应奠定良好扩展条件,由于扩散质量传递速度明显代于液相流     

Ti—C—Al体系热爆合成过程

采用整体加热燃烧合成法（即热爆合成）制备了ＴｉＣ－Ａｌ复合体系，利用差热分析（ＤＴＡ）、Ｘ射线衍射分析（ＸＲＤ）和扫描电镜（ＳＥＭ）等手段研究了Ｔｉ－Ｃ－Ａｌ体系中升温速度及Ａｌ含量对ＴｉＣ反应合成过程的影响，分析了Ａｌ基体对ＴｉＣ粒子的形成机理．结果表明，在ＴｉＣ反应合成过程中，首先是Ｔｉ与Ａｌ反应形成Ｔｉ与Ａｌ的化合物，放出热量，随后促使Ｔｉ与Ｃ的放热反应发生，合成ＴｉＣ时放热产生的高温使Ｔｉ与Ａｌ的化合物分解，从而制得ＴｉＣ－Ａｌ复合体系；升温速度及Ａｌ含量只有超过一定值时，该体系才能在较低温度发生热爆反应；当Ａｌ的质量分数从１０％升至５０％时，ＴｉＣ的粒度从５．０μｍ阵至０．５μｍ．     

Ti－C－Al体系热爆合成过程

采用整体加热燃烧合成法（即热爆合成）制备了ＴｉＣ－Ａｌ复合体系，利用差热分析（ＤＴＡ）、Ｘ射线衍射分析（ＸＲＤ）和扫描电镜（ＳＥＭ）等手段研究了Ｔｉ－Ｃ－Ａｌ体系中升温速度及Ａｌ含量对ＴｉＣ反应合成过程的影响，分析了Ａｌ基体对ＴｉＣ粒子的形成机理．结果表明，在ＴｉＣ反应合成过程中，首先是Ｔｉ与Ａｌ反应形成Ｔｉ与Ａｌ的化合物，放出热量，随后促使Ｔｉ与Ｃ的放热反应发生，合成ＴｉＣ时放热产生的高温使Ｔｉ与Ａｌ的化合物分解，从而制得ＴｉＣ－Ａｌ复合体系；升温速度及Ａｌ含量只有超过一定值时，该体系才能在较低温度发生热爆反应；当Ａｌ的质量分数从１０％升至５０％时，ＴｉＣ的粒度从５．０μｍ阵至０．５μｍ．     

NiAl／TiC纳米材料机械合金化合成机理

四种元素粉末的混合物在室温下球磨，当球磨时间达到１０７ｍｉｎ时，原位热分析监测到一个放热化学反应的发生，分析表明大量的ＮｉＡｌ和ＴｉＣ化合物反应生成，其反应合成机理属于燃烧合成反应机制，包含着两个独立的化学反应，即Ｎｉ＋Ａｌ→ＮｉＡｌ，Ｔｉ＋Ｃ→ＴｉＣ燃烧反应后，还存在少量的元素粉末进一步球磨导致ＮｉＡｌ和ＴｉＣ的逐渐生成，终产物中ＴｉＣ的晶粒尺寸约为ＮｉＡｌ晶粒尺寸的２．５倍，与传统观点相反，归     

自生复合材料（Al—TiB2—TiC）的燃烧合成研究

本文研究了Ａｌ－Ｔｉ－Ｂ４Ｃ体系的燃烧合成过程，用粉末（Ａｌ，Ｔｉ，Ｂ４Ｃ）通过燃烧方法，来制备复合材料（Ａｌ－ＴｉＢ２－ＴｉＣ）。采用ＤＴＡ、ＸＲＤ和ＳＥＭ译复合材料的形成和结果进行了分析研究，得到如下结果：分别用８０％Ａｌ＋２０％（３Ｔｉ＋Ｂ４Ｃ），９０％Ａｌ＋１０％（３Ｔｉ＋Ｂ４Ｃ）原料粉末，通过忆热可得到Ａｌ－ＴｉＢ２－ＴｉＣ，在制备过程中会产生少量的ＴｉＡｌ３．     

Al57.1C42.9混合粉在机械合金化过程中的固态反应与相变

利用Ｘ射线，透射电镜和红外光谱研究了Ａｌ５７．１Ｃ４２．９混合粉在高能球磨中的结构变化，Ａｌ和石墨反应形成了Ａｌ４Ｃ３，Ａｌ４Ｃ３的合成是一个受扩散控制的逐渐生成过程，它是在较低温度下进行的纳米尺度界面反应，继续球磨，Ａｌ４Ｃ３的晶粒不断细化，长程有序结构逐渐破坏，致使自由能升高，超过了非晶态的自由能，导致了Ａｌ４Ｃ３失稳转变成均匀的单相晶态。     

自生复合材料（Al－TiB_2－TiC）的燃烧合成研究

本文研究了Ａｌ－Ｔｉ－Ｂ４Ｃ体系的燃烧合成过程，用粉末（Ａｌ、Ｔｉ、Ｂ４Ｃ）通过燃烧方法，来制备复合材料（Ａｌ－ＴｉＢ２－ＴｉＣ）．采用ＤＴＡ、ＸＲＤ和ＳＥＭ技术对复合材料的形成和结果进行了分析研究，得到如下结果：分别用８０％Ａｌ＋２０％（３Ｔｉ＋Ｂ４Ｃ），９０％Ａｌ＋１０％＋１０％（３Ｔｉ＋Ｂ４Ｃ）原料粉末，通过快速加热可得到Ａｌ－ＴｉＢ２－ＴｉＣ，在制备过程中会产生少量的ＴｉＡｌ３．     

Ti—6Al—4V板材细晶粒的控制

借助ＸＲＤ、ＥＰＭＡ、ＴＥＭ和ＳＥＭ等分析测试手段对铝熔体中原位反应合成ＴｉＣ进行的研究表明：（１）形成Ａｌ３Ｔｉ放出的热量可能是引发后续ＴｉＣ反应的原因之一；（２）整个反应过程中，扩散机制和溶解－析晶机制实际上都存在。在相对较低的温度区时，是由较慢的扩散过程控制整个反应。这时，随压制块温度升高，首先发生３Ａｌ（１）＋Ｔｉ（ｓ）→Ａｌ３Ｔｉ的反应，然后通过该反应的反应热引发ＴｉＣ的反应；而高温区时     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

The 15th Global Foundry Sourcing Conference 2014held in Qingdao China

Organized by Suppliers China Co., Ltd and co-organized by the National Technical Committee 54 on Foundry of Standardization Administration of China, the 15th Global Foundry Sourcing Conference 2014 （hereinafter referred to as FSC 2014） was successfully held on Sep. 23rd in Grand Regency Hotel, Qingdao. More than 500 delegates from home and abroad attended this conference, including over 130 purchasers from 20 countries and 380 domestic and foreign suppliers.     

Secondary Recrystallization Behaviors of Grain-Oriented 6.5 wt% Silicon Steel Sheets Produced by Rolling and Nitriding Processes

By rolling and nitriding processes, 0.23- to 0.3-mm-thick grain-oriented 6.5 wt% silicon steel sheets were produced. The core losses of grain-oriented 6.5 wt% silicon steel at frequencies ranging from 400 Hz to 20 k Hz were lower than that of the grain-oriented 3 wt% silicon steel with the same thickness by 16.6–35.8%. The secondary recrystallization behavior was investigated by scanning electron microscopy, energy-dispersive spectroscopy, and electron backscattered diffraction. The results show that the secondary recrystallization in high-silicon steel sheets develops more completely as the nitrogen content increases after nitriding, secondary recrystallized grain sizes become larger, and the sharpness of Goss texture increases. Because more {110}116 grains in the subsurface and the central layer of the sheets have a lot of 20°–45° high-energy boundaries in addition to Goss grains, {110}116 can be the main component through selective growth during secondary recrystallization when the inhibitor quantity is not enough and inhibitor intensity is weaker. The increases in nitrogen content can increase the inhibitor intensity and hinder abnormal growth of a mount of {110}116 grains and therefore enhance the sharpness of Goss texture.     

Laser Cladded TiCN Coatings on the Surface of Titanium

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80?滋m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

Microstructure and Mechanical Properties of X80 Pipeline Steel Joints by Friction Stir Welding Under Various Cooling Conditions

X80 pipeline steel plates were friction stir welded(FSW) under air, water, liquid CO_2 + water, and liquid CO_2 cooling conditions, producing defect-free welds. The microstructural evolution and mechanical properties of these FSW joints were studied. Coarse granular bainite was observed in the nugget zone(NZ) under air cooling, and lath bainite and lath martensite increased signifi cantly as the cooling medium temperature reduced. In particular, under the liquid CO_2 cooling condition, a dual phase structure of lath martensite and fi ne ferrite appeared in the NZ. Compared to the case under air cooling, a strong shear texture was identifi ed in the NZs under other rapid cooling conditions, because the partial deformation at elevated temperature was retained through higher cooling rates. Under liquid CO_2 cooling, the highest transverse tensile strength and elongation of the joint reached 92% and 82% of those of the basal metal(BM), respectively, due to the weak tempering softening. A maximum impact energy of up to 93% of that of the BM was obtained in the NZ under liquid CO_2 cooling, which was attributed to the operation of the dual phase of lath martensite and fi ne ferrite.     

INDUSTRY NEWS

China Securities News reported on March 21, 2014： Guangdong Hongtu Wuhan Die Casting Co., Ltd. （Wuhan Hongtu）, a wholly owned subsidiary of Guangdong Hongtu Technology （Holdings） Co., Ltd., held a groundbreaking ceremony recently. With the registered capital of 50 million Yuan, Wuhan Hongtu has a total land area of 100,000 square meters and a plant construction area of 72,000 square meters. It is expected to have a production capacity of about 30,000 tonnes of aluminum castings annually after it is put into production.     

Microstructure,Mechanical Properties and Corrosion Behavior of Extruded Mg–Zn–Ag Alloys with Single-Phase Structure

Mg–Zn–Ag alloys have been extensively studied in recent years for potential biodegradable implants due to their unique mechanical properties,biodegradability and biocompatibility.In the present study,Mg–3Zn-x Ag(wt%,x=0.2,0.5 and0.8)alloys with single-phase crystal structure were prepared by backward extrusion at 340°C.The addition of Ag element into Mg–3Zn slightly influences the ultimate tensile strength and microstructure,but the elongation firstly increases from12%to 19.8%and then decreases from 19.8%to 9.9%with the increment of Ag concentration.The tensile yield strength,ultimate tensile strength and elongation of Mg–3Zn–0.2Ag alloy reach up to 142,234 MPa and 19.8%,respectively,which are the best mechanical performance of Mg–Zn–Ag alloys in the present work.The extruded Mg–3Zn–0.2Ag alloy also possesses the best corrosion behavior with the corresponding corrosion rate of 3.2 mm/year in immersion test,which could be explained by the single-phase and uniformly distributed grain structure,and the fewer twinning.     

Growth Morphologies of a Binary Alloy with Low Anisotropy in Directional Solidification

Two new classes of growth morphologies, called doublons and seaweed, were simulated using a phase-field method. The evolution of doublon and seaweed morphologies was obtained in directional solidification. The influence of orientation and velocity on the growth morphology was investigated. It was indicated that doublons preferred growing with its crystallographic axis aligned with the heat flow direction. Seaweed, on the other hand, could be obtained by tilting the crystalline axis to 45°. Stable doublons could only exist in a range of velocity regime. Beyond this regime the patterns formed would be unstable. The simulation results agreed with the reported experimental results qualitatively.