Cu-15Cr-0.1Zr原位复合材料的组织与性能

采用冷变形+中间热处理方法制备Cu-15Cr-0.1Zr原位复合材料.这种Cr纤维原位强化复合材料的强度为1200 MPa,导电率为73%IACS.研究了不同应变量下材料的微观组织演变和力学性能.随应变量的增加,强度增加,Cr相形态由枝晶演变为细小丝带状.研究不同中间退火工艺对材料性能的影响,结果表明,通过冷变形及适当的中间热处理可获得强度和导电率的较好组合.     

Cu-15%Cr形变原位复合材料的组织与性能

采用大气熔铸与形变原位复合的方法制备了Cu-15%Cr形变原位复合材料,测定了不同应变量和中间热处理温度下的显微硬度、抗拉强度和电导率,并研究了Cu-15%Cr原位复合材料的显微组织。结果表明,大气熔铸与真空熔铸制备的Cu-15%Cr复合材料铸态组织没有明显差别;通过改变应变量以及调整中间热处理,可以获得不同的显微硬度、强度和电导率的组合;中间热处理温度在480℃以下,可以获得抗拉强度>1000MPa、电导率>71%IACS的Cu-15%Cr形变原位复合材料,其综合性能与真空熔铸制备的形变Cu-15%Cr原位复合材料相当。     

形变Cu-10Fe-1Ag原位复合材料的组织和性能

采用大气熔铸与形变原位复合的方法制备了形变Cu-10Fe-1Ag原位复合材料.测定了不同应变量下材料的抗拉强度和导电率;用SEM观察分析了材料的显微组织;用EDS分析了Fe和Ag在铜基体中的分布.结果表明,形变Cu-10Fe-1Ag原位复合材料采用合适的变形量和中间退火工艺,可以获得强度和导电率较好的结合.当应变量为6.7时,抗拉强度达到913 MPa,导电率达到51%IACS.     

形变Cu-20vol%Fe原位复合材料研究

研究了形变Cu-20vol％Fe原位复合材料的组织结构，结果发现，合金经室温变形后，Fe相由铸造态的树枝状变成纤维状组织，在纵截面上呈现片状，其厚度随变形量增加而减小，在横断面上呈弯曲的薄片状。随变形量增加，Cu-20vol％Fe合金的强度提高。适当的中间热处理可以大大降低其电阻率，经过室温形变和中间热处理的合理配合，可获得良好强度和电导率的结合。     

Cu-10Cr-2Zr原位形变复合材料性能研究

采用大气熔铸与形变原位复合的方法制备了Cu-10Cr-2Zr形变原住复合材料,测定了不同应变量和中间热处理温度下的显微硬度、抗拉强度和电导率,并研究了Cu-10Cr-2Zr原位复合材料的显微组织.结果表明:Cu-10Cr-2Zr合金通过中间热处理和大变形,合金元素Cr及Zr由铸态不连续的枝晶组织演变成纤维组织,且随应变量的增加,合金的显微硬度升高;通过调整中间热处理温度,可以获得抗拉强度≥950 MPa,电导率73%IACS,中间热处理温度在450～500℃为宜.     

大变形Cu-10Ag原位纤维复合材料的结构和性能

研究了低Ag含量 (10 % ,质量分数 )的Cu Ag原位纤维复合材料的结构和性能 ,结果表明通过原位复合技术可获得强度 >1.5GPa、导电率 (IACS) >6 5 %的原位纤维复合材料。研究了不同中间热处理温度对材料性能的影响 ,并考察了材料的稳定性 ,结果表明通过控制变形量、调整中间热处理及稳定化热处理规范 ,可以获得具有不同强度和导电率组合的Cu 10Ag原位纤维复合材料。材料在自然时效与低温退火过程中 ,有沉淀强化效应产生 ,但导电率基本保持稳定。     

微量Ag对形变Cu-Fe原位复合材料组织和性能的影响

采用熔铸-中间热处理-形变工艺制备了Cu-14Fe及Cu-14Fe-0.06Ag原位复合材料,利用光学显微镜、扫描电镜、数字微欧计及液晶电子拉力试验机研究了微量Ag对Cu-14Fe合金微观组织、力学性能及导电性能的影响。结果表明,微量Ag的加入使Cu-14Fe合金枝晶组织更发达且枝晶臂直径更小,相同形变量下形成的纤维更加细小均匀,材料的强度显著提高,电导率也有所上升,伸长率略有提高,冷加工性能明显改善。     

外加入法制备高强高导Cu-5wt%Cr复合材料组织性能研究

通过采用外加入Cr颗粒方制备Cu-5wt%Cr复合材料,研究了冷拔变形量和中间退火工艺对Cu-5wt%Cr复合材料中纤维组织形成过程及力学性能和导电性的影响。结果表明:随变形量的增加,Cr颗粒变形不均匀;退火使纤维发生弯曲、粗化、溶断等现象;材料的冷拔变形量与合理的中间退火工艺相组合,可得到强度和导电率的良好配合。     

形变Cu-Cr-Ag原位复合材料组织和性能

采用熔铸-中间热处理-形变工艺制备了形变Cu-7Cr及Cu-7Cr-0.07Ag原位复合材料,利用光学显微镜、扫描电镜、数字微欧计及液晶电子拉力试验机研究了Cu-7Cr及Cu-7Cr-0.07Ag合金的微观组织、力学性能和导电性能。结果表明,微量Ag的加入使Cu-7Cr合金铸态组织枝晶臂直径更小,相同应变量下形成的纤维更加细小均匀,材料的强度显著提高,电导率略有上升,延伸率小幅提高。     

Cu-Cr原位复合材料组织性能研究

采用感应加热熔炼及通过热锻和线拉变形结合中间热处理制备了Cu-15％Cr原位复合材料，用SEM和TEM等技术对形变Cu—Cr原位复合材料的Cr纤维形成过程、立体形态进行了分析。结果表明，在变形过程中Cr树枝晶发生转动，平行于线轴方向排列；Cr纤维立体形态则为卷边的薄片状。测定了形变Cu—Cr原位复合材料的抗拉强度，分析表明，强度随变形量的增加而提高，与纤维相间距呈Hall—Patch关系。     

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.     

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.     

STUDY ON PROPERTIES OF PULSE ELECTRODEPOSITED RE-Ni-W-P-SiC COMPOSITE COATINGS

The effects of pulse frequency f and duty cycle r on the deposition rate, composition, morphology, and hardness of pulse electrodeposited RE （rare earth）-Ni-W-P-SiC composite coatings have been studied. The results indicate that pulse current can improve the deposition rate of RE-Ni-W-P-SiC composite coatings; W, P, and SiC contents in the coating decrease with the increase of pulse frequency and reach the lowest value at f = 33Hz, whereas the RE content in the composite coatings increases with the increase of pulse frequency. SiC content decreases with the increase of duty cycle, W content reaches the lowest value, and P content reaches the highest value at r = 0.4; pulse current and RE can lead to smaller size of the crystalline grains; however, the effects of different pulse frequency and duty cycle on the morphologies of RE-Ni-W-P-SiC composite coatings are not obvious. The hardness of RE-Ni-W-P-SiC composite coatings is the highest when the duty cycle is at 0.6 and 0.8 and pulse frequency is at 50Hz. At the same pulse frequency, the hardness of RE-Ni-W-P-SiC composite coatings at r= 0.8 is higher than that at r= 0.6.     

RELATIONSHIP BETWEEN J-INTEGRAL AND FRACTURE SURFACE AVERAGE PROFILE

To investigate the causes that led to the formation of cracks in materials, a novel method that only considered the fracture surfaces for determining the fracture toughness parameters of J-integral for plain strain was proposed The principle of the fracture-surface topography analysis （FRASTA） was used. In FRASTA, the fracture surfaces were scanned by laser microscope and the elevation data was recorded for analysis. The relationship between J-integral and fracture surface average profile for plain strain was deduced. It was also verified that the J-integral determined by the novel method and by the compliance method matches each other well.