Cutting tool materials for high speed machining

High speed machining (HSM) is one of the emerging cutting processes, which is machining at a speed significantly higher than the speed commonly in use on the shop floor. In the last twenty years, high speed machining has received great attentions as a technological solution for high productivity in manufacturing. This article reviews the developments of tool materials in high speed machining operations, and the properties, applications and prospective developments of tool materials in HSM are also presented.     

Synthesis and properties of a Pr（Ⅲ） complex with 2-acetylbenzimidazoledehyde-glycine Schiff-base ligand

Abstract The 2-acetyl-benzimidazoledehyde-glycine Schiff-base ligand and the corresponding Pr（Ⅲ） complex Pr2L3（NO3）3· 2CH3OH （L=C11H10N3O2） were synthesized in methanol and characterized by a series of methods, including chemical analysis, elemental analysis, TOF-MS, ^1H NMR, UV-, IR-, Raman spectra, thermal analysis, and the three-dimension fluorescence excitation and emission spectra. The Pr（Ⅲ） complex exhibits extraordinary water-solubility and the Pr（Ⅲ） hydroxide appears at pH≥13. The complex also possesses specific fluorescent properties. Thus, at the excitation wavelengths 200.0-280.0 and 260-350 nm the fluorescence bands were observed at 290.0 and 400.0 nm, respectively.     

Effect of Ce addition on microstructures and mechanical properties of A380 aluminum alloy prepared by squeeze-casting

The effect of cerium (Ce) addition on the eutectic Si, β-Al₅FeSi phase, and the tensile properties of A380 alloy specimens prepared by squeeze-casting were studied by optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The experimental results showed that Ce more effectively modified the eutectic Si and refined the β-Al₅FeSi. The refinement effect significantly increased under a specific pressure of 100 MPa with the addition of Ce from 0.1wt% to 0.9wt%. In contrast, the average length and the aspect ratio of the eutectic Si and β-Al₅FeSi exhibited their optimal values when the content of the added Ce was greater than 0.5wt%. Needle-like Al8Cu4Ce was precipitated with the addition of excessive Ce; hence, the mechanical properties of A380 gradually decreased with increasing Ce content in the range from 0.3wt% to 0.9wt%.     

Damage evolution and failure mechanism of thermal barrier coatings under Vickers indentation by using acoustic emission technique

Acoustic emission(AE) technique was adopted to monitor the damage evolution of air plasma-sprayed(APS) yttria-partially-stabilized zirconia(YSZ) thermal barrier coatings(TBCs) during instrumented indentation testing, and then the failure mechanisms were investigated by cluster analysis and wavelet transform methods.The results of cluster analysis showed that there were three classes associated with distinct failure types for the 8YSZ coatings under Vickers indentation. Based on wavelet transform, these three clusters could be clearly distinguished from their dominant frequency bands, which were concentrated on levels A5(0–156.25 kHz), D5(156.25–312.5 kHz) and D4(312.5–625 kHz), respectively. Thus, the failure mechanism of 8YSZ coatings under Vickers indentation could be clarified by the distribution of different failure types in indentation depth. To sum up, as indentation load increases, the 8YSZ coatings can accommodate the indenter by elastic or little plastic deformation, microcracks propagation and then debonding at the splat boundaries. By comparing the distribution of AE signals induced by different failure types in indentation depth for samples with different thermal exposure time, it can be inferred that thermal exposure treatment can accelerate the degradation of APS 8YSZ TBCs.     

Deep cleaning of a metallurgical zinc leaching residue and recovery of valuable metals

Huge quantities of zinc leaching residues (ZLRs) generated from zinc production are dumped continuously around the world and pose a potential environmental threat because of their considerable amounts of entrained heavy metals (mainly lead). Most ZLRs have not been properly treated and the valuable metals in them have not yet been effectively recovered. Herein, the deep cleaning of a ZLR and recovery of valuable metals via a hydrometallurgical route were investigated. The cleaning process consists of two essential stages:acid leaching followed by calcium chloride leaching. The optimum conditions for extracting zinc, copper, and indium by acid leaching were a sulfuric acid concentration of 200 g·L-1, a liquid/solid ratio of 4:1 (mL/g), a leaching time of 2 h, and a temperature of 90℃. For lead and silver extractions, the optimum conditions were a calcium chloride concentration of 400 g·L-1, a pH value of 1.0, a leaching time of 1 h, and a temperature of 30℃. After calcium chloride leaching, silver and lead were extracted out and the lead was finally recovered as electrolytic lead by electrowinning. The anglesite phase, which poses the greatest potential environmental hazard, was removed from the ZLR after deep cleaning, thus reducing the cost of environmental management of ZLRs. The treatment of chlorine and spent electrolyte generated in the process was discussed.     

Mechanical Properties of Laser Welded Joint of Copper and Steel Dissimilar Metals

In this research project, copper and stainless steel were connected by two laser welding methods: straight seam welding and swing welding. Then, electronic tensile test machine, X-ray diffractometer, scanning electron microscope and metallographic microscope were used to analyze the tensile properties, macroscopic and microscopic structure morphology and phase of the welded joint. Based on the experimental results, we determined that the strength of the straight seam welded joint was higher. Bec...     

Cluster Analysis in the Target Countries of China＇s International Oil Investment

China＇s oil demand has been skyrocketed. In 2004 China became the world＇s second largest oil consumer and imported 122.7 million tons of crude oil, which accounted for 41.9% of China＇s crude oil consumption. International oil investment becomes an important channel for China to obtain oil resource. The cluster analysis in the target countries of China＇s international oil investment is studied here. An investment environment model incorporating 9 factors is established firstly, the order of these factors is ranked by their importance. Then the weight of such factors is determined by Analytic Hierarchy Process （AHP） and these countries are classified into 3 categories using cluster analysis. The results provide an important decision-making tool for China＇s international oil investment.     

Density-based clustering method in the moving object database

With the rapid advance of wireless communication, tracking the positions of the moving objects is becoming increasingly feasible and necessary. Because a large number of people use mobile phones, we must handle a large moving object database as well as the following problems. How can we provide the customers with high quality service, that means, how can we deal with so many enquiries within as less time as possible? Because of the large number of data, the gap between CPU speed and the size of main memory has increasing considerably. One way to reduce the time to handle enquiries is to reduce the I/O number between the buffer and the secondary storage. An effective clustering of the objects can minimize the I/O cost between them. In this paper, according to the characteristic of the moving object database, we analyze the objects in buffer, according to their mappiigs in the two-dimension coordiiate, and then develop a density-based clustering method to effectively reorganize the clusters. This new mechanism leads to the less cost of the I/O operation and the more efficient response to enquiries.     

Phase transformation behavior of titanium during carbothermic reduction of titanomagnetite ironsand

The reduction of titanomagnetite (TTM) ironsand, which contains 11.41wt% TiO₂ and 55.63wt% total Fe, by graphite was performed using a thermogravimetric analysis system under an argon gas atmosphere at 1423–1623 K. The behavior and effects of titanium in TTM ironsand during the reduction process were investigated by means of thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. During the reduction procedure, the titanium concentrated in the slag phase, where the phase transformation followed this sequence: FeO + FeTiO₃ → Fe₂TiO₄ → FeTiO₃ → FeTi₂O₅ → TiO₂. The calculated results for the reduction kinetics showed that the carbothermic reduction was controlled by the diffusion of ions through the product layer. Furthermore, the apparent activation energy was 170.35 kJ·mol-1.     

Effect of aluminum oxide on the compressive strength of pellets

Analytical-reagent-grade Al₂O₃ was added to magnetite ore during the process of pelletizing, and the methods of mercury intrusion, scanning electron microscopy, and image processing were used to investigate the effect of Al₂O₃ on the compressive strength of the pellets. The results showed that, as the Al₂O₃ content increased, the compressive strength of the pellets increased slightly and then decreased gradually. When a small amount of Al₂O₃ was added to the pellets, the Al₂O₃ combined with fayalite (2FeO·SiO₂) and the aluminosilicate (2FeO·2Al₂O₃·5SiO₂) was generated, which releases some iron oxide and reduces the inhibition of fayalite to the solid phase of consolidation. When Al₂O₃ increased sequentially, high melting point of Al₂O₃ particles hinder the oxidation of Fe₃O₄ and the recrystallization of Fe2O3, making the internal porosity of the pellets increase, which leads to the decrease in compressive strength of the pellets.