铝-钨粉末合金涡旋定盘热挤压成形工艺研究

试验研究了铝-钨合金粉末的冷压、热压制坯成形工艺,确定主要挤压工艺参数。该合金涡旋定盘挤压件致密度达到99%左右。利用Gleeble-1500热模拟机测试了该合金在变形温度为450℃~540℃,应变速率为（10-3~1）s-1条件下的流变力学行为。采用Fields-Backofen本构模型实现了对该材料应力-应变曲线的拟合。通过引入一个＂软化因子＂,更好地描述了变形温度、应变速率和应变对流变应力的影响,进一步完善了流变应力本构模型。通过有限元模拟对涡旋定盘挤压件成形进行数值模拟,确定合理的挤压成形工艺,并通过试验进行验证,最终获得了合格的涡旋定盘挤压件。

钨含量对钴-铝-钨合金中γ′强化相的影响

为了解元素钨含量对新型钴-铝-钨合金中γ′强化相的影响,用燃烧合成法制备了不同钨含量的合金,通过SEM、XRD、EPMA、DSC等方法分析了钨含量对合金中γ′强化相形貌、数量以及稳定性的影响。结果表明:钴-铝-钨合金显微组织是由富钴基体及其γ′-Co3(Al,W)强化相和少量碳化物组成;γ′-Co3(Al,W)强化相比Co3Al具有更好的稳定性,随着钨含量的增加,合金的液相线温度升高,强化相的数量也增加;当钨质量分数为26.36%时合金中γ′强化相的稳定性最好。

11-钨锌合铝杂多酸的合成、表征及性能研究

用离子交换-冷冻法，以分析纯试剂制备了11-钨锌合铝杂多酸H7[Al（H2O）ZnW（11）O39]·12H2O。通过单因素试验和正交试验，确定了合成11-钨锌合铝杂多酸的最佳条件。用元素分析法、X射线衍射对合成产物进行了表征，采用美国Par公司M378频率响应系统配1286电化学接口测试11-钨锌合铝杂多酸的阻抗谱，并对其导电性能进行了研究。

激光合成Al_2O_3-WO_3线性热敏材料

应用大功率CO_2激光器非平衡态高温、快速合成陶瓷新工艺,合成了Al_2O_3-WO_3系线性NTC热敏材料。并从激光合成工艺、材料组成、热老化、材料的抗氧化性及耐酸碱性等方面对合成陶瓷材料进行了试验。

Fracture behavior of double-pass TIG welded 2219-T8 aluminum alloy joints under transverse tensile test

2219-T8 aluminum alloys were butt welded by the double-pass tungsten inert gas （TIG） arc welding process. The transverse tensile test of the joint showed that the fracture mainly occurred in the partially melted zone （PMZ）. Effects of the PMZ on the fracture behavior were systematically studied. Continuous intergranular eutectics were observed in the PMZ close to the fusion line. Away from the fusion line, the intergranular eutectics in the PMZ became discontinuous. The fracture morphology and the microhardness distribution of the joint showed that the PMZ was gradient material with different mechanical properties, which strongly affected the fracture process. It was observed that the crack initiated in the PMZ near the front weld toe, and propagated in the PMZ away from the fusion line. Then, the crack tip was blunt when it propagated into the PMZ with higher plasticity. Finally, the rest part of the joint was shear fractured.

Microstructure analysis and mechanical characteristics of tungsten inert gas and metal inert gas welded AA6082-T6 tubular joint: A comparative study

The present study is aimed to compare the microstructure characteristics and mechanical properties of AA6082 in T6 condition of tubular joints fabricated by tungsten inert gas welding （TIG） and metal inert gas welding （MIG） processes. The effect of welding processes was analysed based on optical microscopy image, tensile testing, and Vickers micro-hardness measurements. The results showed that the tensile strengths of the TIG-welded joints were better than those of the MIG-welded joints, due to the contribution of fine equiaxed grains formation with narrower spacing arms. In terms of joint efficiency, the TIG process produced more reliable strength, which was about 25% higher compared to the MIG-joint. A significant decay of hardness was recorded in the adjacent of the weld bead zone, shown in both joints, related to phase transformation, induced by high temperatures experienced by material. A very low hardness, which was about 1.08 GPa, was recorded in the MIG-weldcd specimens. The extent of the heat-affected-zone （HAZ） in the MIG-welded joints was slightly wider than those of the TIG-welded specimens, which corresponded with a higher heat input per unit length.

Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy TIG-welded joint

Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas(TIG)welded joint were analyzed in detail.In weld zone(WZ),α+θeutectic structure formed at grain boundaries with no precipitates inside the grains.In partially melted zone(PMZ),symbiotic eutectic or divorced eutectic formed at grain boundaries and needle-likeθ′phases appeared in the secondary heated zone.In over aged zone(OAZ),the coarsening and dissolution ofθ′phases occurred and mostθ′phases transformed intoθphases.In general heat affected zone(HAZ),θ′phases coarsened.Factors such as the strengthening phases,the grain size,the Cu content in matrix and the dislocation density can affect the mechanical properties in different regions of the joint.Moreover,a model describing the relationship between mechanical properties of the material and the volume fraction of precipitates,the average diameter of precipitates and the concentration of soluble elements was proposed.

Mechanical behaviors of NiAl-Cr(Mo)-based near eutectic alloy with Ti, Hf, Nb and W additions

Effects of Ti, Hf, Nb and W alloying elements addition on the microstructure and the mechanical behaviors of NiAl-Cr（Mo） intermetallic alloy were investigated by means of XRD, SEM, EDX and compression tests. The results show that Ni-31Al-30Cr-4Mo-2（Ti, Hf, Nb, W） alloy consists of four phases： NiAl, ？？Cr solid solution, Cr2Nb and Ni2Al（Ti, Hf）. The mechanical properties are improved significantly compared with the base alloy. The compression yield strength at 1 373 K is 467 MPa and the room temperature compression ductility is 17.87% under the strain rate of 5.56？？0-3 s-1, due to the existence of Cr2Nb and Ni2Al（Ti, Hf） phases for strengthening and Ti solid solution in NiAl matrix and coarse Cr（Mo, W） solid solution phase at cellular boundaries for ductility. The elevated temperature compression deformation behavior of the alloy can be properly described by power-law equation： ε=0.898 σ8.47exp[-615/（RT）].

Influence of Heat Treatment on Microstructure and Sliding Wear Behavior of Fe-Al/WC Composite Coatings

An experimental study has been carried out to investigate the influence of heat treatment at 300 ℃,450 ℃,550 ℃,650 ℃ and 800 ℃ on the microstructure and sliding wear behavior of Fe Al/WC intermetallic composite coatings produced by high velocity arc spraying (HVAS) and cored wires. The result shows, the main phases in both as sprayed and heat treated Fe Al/WC composite coatings are iron aluminide intermetallics (Fe 3Al+FeAl) and α as well as a little oxide (Al 2O 3) and carbides (WC, W 2C, Fe 2W 2C and Fe 6W 6C). After heat treated at 450-650 ℃, dispersion strengthening of Fe 2W 2C and Fe 6W 6C will lead to a rise in microhardness of the coatings. The microhardness is likely to be the most important factor which influences the sliding wear behavior of the coatings. Increasing the microhardness through heat treatment will improve the sliding wear resistance of the Fe Al/WC composite coatings.

Effect of post weld heat treatment on microstructure and mechanical properties of gas tungsten arc welded AA6061-T6 alloy

Double-V butt TIG welding process was performed on two plates of AA6061-T6 using ER5356 filler. The microstructure,mechanical and nanomechanical properties of the joint were evaluated in as-welded and after post weld heat treatment (PWHT) usingXRD, FESEM, EBSD, nanoindentation and tensile tests. The results show that PWHT led to microstructural recovery of the heataffected zone (HAZ) in addition to the appearance of β-phase (Al3Mg2) at the grain boundaries of weld zone. The hardness (Hnano) inall zones increased after PWHT while the elastic modulus (Enano) was improved from 69.93 GPa to 81 GPa in weld area. All resultsindicate that PWHT has created a homogenous microstructure in the weld zone in addition to outstanding improvement inmechanical properties for the weld zone which surpass the base metal.

Electronic Structure ofTiAl-2M(M=V,Nb,Ta,Cr,Mo,W,Mn) Alloy

The electronic structures of TiAl-2M(M=V, Nb, Ta, Cr, Mo, W,Mn) alloy have been investigated using EHT band calculation method. Their bandstructures and average prperties have been obtained. The results show that doping thetransition metal elements can effectively change the band structure and enable the alloysystem to show the stronger metallic feature. The dopants of V, Cr and Mn increase s-orbital component of Ti and Al in bonding orbital, therefore, there is more sphericalelectronic clound and weakly directional bonds in the crystal, which improve the duictil-ity of the alloy, Nb or Ta makes stronger bonding with Ti and Al, which improvestrength and oxidation resistance of the alloy.

Effect of welding processes on AA2219 aluminium alloy joint properties

AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding （GTAW）, electron beam welding （EBW） and friction stir welding （FSW） processes. The effects of three welding processes on the tensile, fatigue and corrosion behaviour were studied. Microstructure analysis was carried out using optical and electron microscopes. The results show that the FSW joints exhibit superior tensile and fatigue properties compared to EBW and GTAW joints. It is also found that the friction stir welds show lower corrosion resistance than EB and GTA welds. This is mainly due to the presence of finer grains and uniform distribution of strengthening precipitates in the weld metal of FSW joints.

Multiple-aged granitoids and related tungsten-tin mineralization in the Nanling Range, South China

The Nanling metallogenic belt in South China is characterized by well-developed tungsten-tin mineralization related to multi- ple-aged granitoids. This belt is one of the 5 key prospecting and exploration areas among the 19 important metallogenic tar- gets in China. Important progress has been made in recent years in understanding the Nanling granitoids and associated miner- alization, and this paper introduces the latest major findings as follows： （1） there exists a series of Caledonian, Indosinian, and Yanshanian W-Sn-bearing granites; （2） the Sn-bearing Yanshanian granites in the Nanling Range form an NE-SW trending aluminous A-type granite belt that stretches over 350 km. The granites typically belong to the magnetite series, and dioritic micro-granular enclaves with mingling features are very common; （3） the Early Yanshanian Sn- and W-bearing granites pos- sess different petrological and geochemical features to each other： most Sn-bearing granites are metaluminous to weakly per- aluminous biotite （hornblende） granites, with zircon tHe（t） values of ca. -2 to -8, whereas most W-bearing granites are peralu- minous two-mica granites or muscovite granites with CHf（t） values of ca. -8 to -12; （4） based on the petrology and geochemis- try of the W-Sn-bearing granites, mineralogical studies have shown that common minerals such as titanite, magnetite, and bio- tite may be used as indicators for discriminating the mineralizing potential of the Sn-bearing granites. Similarly, W-bearing minerals such as wolframite may indicate the mineralizing potential of the W-bearing granites. Future studies should be fo- cused on examining the internal relationships between the multiple-aged granites in composite bodies, the metallogenic pecu- liarities of multiple-aged W-Sn-bearing granites, the links between melt evolution and highly evolved ore-bearing felsic dykes, and the connections between granite domes and mineralization.

Discovery and preliminary study of the high tungsten and lithium contents in the Dazhuyuan bauxite deposit, Guizhou, China

Bauxite in China remains an urgently needed resource largely dependent on imports. Based on the study of the newly- discovered Dazhuyuan bauxite deposit in northeastern Guizhou, we have found new enrichment of tungsten and lithium in bauxite, with the highest WO3 content up to 0.33% and the highest Li20 content up to 0.58%. The present paper reports the in- itial result, and the spatial distribution feature of W and Li in the ore body （with Li enriched mostly in the north part of the west limb of the Liyuan syncline, whereas W enriched mostly in the central part of the east limb）. The results suggest that it is necessary to delineate lithium and tungsten ore body independently, discuss the feasibility of its industrial utilization, and point out the new direction of synthetic appraisal for such kinds of traditional mineral resources, in order to forecast and assess bauxite resources in the region.