SiC陶瓷与TiAl合金的真空钎焊

采用Ａｇ－Ｃｕ－Ｔｉ钎料对常压烧结的ＳｉＣ陶瓷与ＴｉＡｌ金属间化合物进行了真空钎焊,并对接头的微观组织和室温强度进行了研究。结果表明,利用Ａｇ－Ｃｕ－Ｔｉ钎料可以实现ＳｉＣ与ＴｉＡｌ的连接;接头界面具有明显的层状结构,即由Ｔｉ－Ｓｉ合金层、富Ｃｕ相与富Ａｇ相的双相层和Ｔｉ－Ａｌ－Ｃｕ合金层组成;在１１７３Ｋ和１０ｍｉｎ的钎焊条件下,接头室温剪切强度达互１７３ＭＰａ。     

采煤机截齿钎焊工艺的研究

研究了３５ＣｒＭｎＳｉ钢和ＹＧ１３Ｃ硬质合金钎焊工艺，分析了影响钎焊强度的各种因素。实验结果表明，在硼砂中添加适量的硼酸可使钎焊强度提高；适当地控制钎加热温度，插接装配间隙及延长回火后随炉冷却时间皆有利于钎焊强度的提高。     

新型Ni48Pd36CrBSi钎料钎焊GH625的接头性能分析

对新型Ｎｉ４８Ｐｄ３６ＣｒＢＳｉ钎料焊高温合金ＧＨ６２５的接头性能进行了分析。钎焊时，只有在液态钎料能充分地流入并致密地填充全部钎缝间隙才能得到一个优质接头。实验结果表明，这种钎料对ＧＨ６２５有良好的润湿性。润湿角仅６°，钎焊后由于在钎缝组织中得到了有利于接头强度的固溶体组织，使得接头抗拉强度室温时为４９８．７ＭＰａ．６５０℃时为４７１．９ＭＰａ，抗剪强度室温时为５０１．７ＭＰａ，６５０时为３９９     

铝板翅式换热器炉中钎焊工艺研究

为了探索铝板翅式换热器更好的钎焊方法，采用无腐蚀钎剂，以Ａｌ－７．５％Ｓｉ作钎料，用中频电源使不锈钢容器产生电阻热，并在氩气保护下，加热钎件，钎焊温度在６０８－６１０℃，经爆破试验，爆破压力为９．３～１４．２ＭＰａ，符合纤缝强度要求，此方法可用于小型产品的钎焊。     

Ni—Cr—Co—B高温镍基钎料的研究

本文提出一种不含Ｓｉ的镍基Ｎｉ－Ｃｒ－Ｃｏ－Ｂ高温钎料，对一系列Ｎｉ－Ｃｒ－Ｃｏ－Ｂ钎料的熔化特性，钎焊工艺性能，钎料组织以及钎焊接头的室温和高温强度，接头韧性进行了研究，并与标准镍基钎料ＢＮｉ－ｌａ和ＢＮｉ－５进行了比较。     

Ni－Cr－Co－B高温镍基钎料的研究

本文提出一种不含Ｓｉ的镍基Ｎｉ－Ｃｒ－Ｃｏ－Ｂ高温钎料．对一系列Ｎｉ－Ｃｒ－Ｃｏ－Ｂ钎料的熔化特性、钎焊工艺性能、钎料组织以及钎焊接头的室温和高温强度、接头韧性进行了研究，并与标准镍基钎料ＢＮｉ－１ａ和ＢＮｉ－５进行了比较研究结果表明，Ｎｉ－Ｃｒ－Ｃｏ－Ｂ钎料钎焊的高温合金接头的高温性能和韧性均超过标准镍基钎料．     

基于CuMnCo钎料的YG6C硬质合金与16Mn钢的真空钎焊工艺研究

采用CuMnCo钎料对YG6C硬质合金与16Mn钢的真空钎焊工艺进行研究。通过三点弯曲试验、光学显微镜观察、扫描电镜及能谱分析等手段研究了真空度、钎焊温度和钎缝间隙对钎焊接头组织和性能的影响。结果表明,钎缝中心区为Cu-Mn基固溶体,两侧界面反应区为Fe-Co基固溶体。真空度、钎焊温度和钎缝间隙对钎焊接头的组织和性能有明显影响。高真空条件下钎焊接头的抗弯强度高于中真空条件下钎焊接头抗弯强度。钎焊温度为1095℃时,钎焊接头的抗弯强度最高。钎焊温度过低时,冶金作用较弱,接头强度较低;钎焊温度过高时,钎料流失较多,接头强度也较低。在高真空以及钎焊温度1095℃、间隙为0.2 mm时,钎焊接头的抗弯强度最高。间隙过小时,钎缝中夹杂物较多,接头强度较低;间隙过大时,Fe、Co原子难以通过长程扩散越过钎缝,冶金作用较弱,接头强度也较低。     

镍基非晶态合金材料真空钎焊特性研究

研究了非晶态Ｎｉ（８０－ｘ）Ｃｒ１０Ｂ２．５Ｓｉ４，５Ｆｅ３Ｃｕｘ合金钎料真空钎焊１Ｃｒ１８Ｎｉ９Ｔｉ的钎焊特性，并对铜的影响进行了探讨。结果表明，非晶态合金钎料钎焊性能优于晶态合金钎料，铜的适量添加有利于提高钎焊接头的综合性能。     

用Al-Zr和Al-V合金加压钎焊Si3N4陶瓷

用Ａｌ－４％Ｚｒ和Ａｌ－５％Ｖ合金真空加压纤焊Ｓｉ３Ｎ４陶瓷研究了压力对钎缝金属与接头强度的影响,结果表明,如果填充金属钎焊时处于固液双相区,适当加压既能减小钎缝宽度,又能改善钎缝组织,接头强度得到提高,但压力过大会影响陶瓷／钎缝金属界面结合降低接头强度。钎缝中含大量Ａ１３Ｚｒ或Ａｌ３Ｖ和Ａｌ６Ｖ的接头与用纯Ａｌ钎焊的接头相比,其高温性能得到明显改善。     

粗真空条件下锡基钎料与Sialon陶瓷的润湿和连接

采用座滴法和四点弯曲方法研究了粗真空条件下锡基钎料在Ｓｉａｌｏｎ陶瓷上的润湿性和连接强度．在１Ｐａ，１１７３Ｋ，２０ｍｉｎ的实验条件下，锡基钎料的静态润湿角小于２０°．加入Ｚｎ，Ｐｂ后，钎料钎焊Ｓｉａｌｏｎ／Ｓｉａｌｏｎ陶瓷时的接头连接强度有明显提高，Ｓｎ－５Ｃｕ－５Ｔｉ，Ｓｎ－５Ｃｕ－５Ｔｉ－２０Ｚｎ，Ｓｎ－５Ｃｕ－５Ｔｉ－１０Ｐｂ的平均接头连接强度分别为９０．８，１５３．４，１６９．１ＭＰａ；最高接头连接强度分别为１１９．８，２００，２１６．７ＭＰａ．在粗真空条件下锡基钎料可以实现陶瓷的良好连接，且接头残余应力较小．本文首次观察到锡基钎料中挥发性组元Ｚｎ对粗真空条件下润湿前驱膜有明显的影响．对临界润湿温度、粗真空条件下第三组元的作用及这种活性钎料的潜在应用价值进行了讨论．     

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.     

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 80m, 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.     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

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.     

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.