Preparation and Characterization of Coated Alumina/Aluminum Cermet Composite Powder via Ball Milling Method

Cermet is an important new engineering material that not only maintains the excellent properties of ceramic materials, but also has the advantages of metal materials. In this paper, the encapsulated alumina-aluminum composite powder was prepared by ball milling and characterized, which laid a foundation for the development of high properties cermet materials. Through the analysis of experimental results, the conclusions are shown when the ball milling time is greater than 3 h, the alumina particles are more evenly distributed around the aluminum powder. the ball milling for 6 h may have reached a limit of the mixing uniformity of the two powder, so the ball milling is determined 6 h as the better ball milling time. Under the ball milling condition of 50 r/min, the distribution of alumina particles around the aluminum powder is more uniform around the aluminum powder than the ball mill under 75 r/min, the ball milling speed is preferably 50 r/min. As the content of aluminum powder increases, the distribution of alumina in aluminum powder is large and uniform, and there is a small amount of pinning. It provides a package-like composite for the preparation of cermet with a wrapped structure and the thermal conduction mechanism of the controlled cermet.

Modeling the surface roughness in face-end milling process by using general insert at stable cutting conditions

Predicting the quality of the machined components is the grandiose signification in industrial manufacturing. Calculation of the surface roughness is one of the most important elements to predict the quality of machined parts. In this paper, the surface roughness was modeled in the face-end mill process by using general rhombu insert. In the proposed mathematical model, with the stable milling condition, the surface roughness is formulated by a function of feed rate, and insert geometry such as nose radius and nose angle. An experimental method is proposed based on the stable milling condition to estimate the surface roughness. The developed surface roughness calculation model has been successfully verified by both simulation and experiment with very promising results. The average difference between predicted and experimental results is 7.59%. The proposed model can be applied to predict the surface roughness in face-end mill processes by using general insert at stable cutting condition.

Corrosion Behaviour and Microhardness during Dry and Flood Milling of Ti-6Al-4V Alloy

Milling process is the removal of unwanted materials so as to produce the required shape. The purpose of this study was to investigate the effect of milling process parameters and the cooling technique on corrosion behaviour and microhardness of TI-6AL-4V. Milling of Ti-6Al-4V was carried out using tungsten carbide cutting tool while varying spindle speed (120,150, and 180 rev/min), depth of cut (1, 1.5 and 2 mm) and the feed rate remained unchanged at 4.6 mm/min. Subsequent to milling, characterization of subsurface microhardness and corrosion behaviour was conducted. It was found that varying spindle speed and depth of cut had an impact on microhardness. Furthermore, it was noticed that the type of milling condition (flood and dry milling) affected the subsurface microhardness and the corrosion behavior. The corrosion resistance of the milled surface was generated at 180 rev/min and 150 rev/min for the dry and flood milling respectively. Furthermore, the most corrosion resistance was obtained at 2 mm and 1.5 mm depth of cut during dry and flood milling respectively.

Facile nitration of aromatic compounds using Bi(NO3)3·5H2O/MgSO4 under mechanochemical conditions

Bi(NO3)3·5H2O/MgSO4 was developed as an efficient and green reagent for the nitration of aromatic compounds under mechanochemistry (or ball milling) condition. While aromatics with weak activating groups such as phenyl could be nitrated by this reagent with 100% conversion, aromatics with weak deactivating groups such as chloro- or bromo- could also be nitrated but with moderate conversion and regioselectivity with big para/ortho ratios. The in situ generated N2O4 or NO2 due to the decomposition of Bi(NO3)3·5H2O promoted by MgSO4 should be responsible for this mechanochemical nitration.

Shadowing Effect Analyzing for Propeller-Ice Milling Condition With Peridynamics

During the research of propeller-ice contact process, we found that shadowing effect has great influence on the ice loads of propeller blade. Therefore, more study in the shadowing effect would be helpful to solve the complicated propeller-ice contact problem. A numerical simulation model is established based on the coupling of peridynamics and panel method in this paper, and ice force for the whole blade and for blade back and blade face separately are obtained through the calculation of the simulation model. The influence law to ice loads of shadowing effect would be revealed clearly by comparing the loads of blade face with the loads of blade back .On this basis, more research is carried out on the mechanism of shadowing effect. In addition, a new calculation formula for shadowing coefficient is put forward in this paper. The results show that the influence of shadowing effect on propeller loads is well predicted by the calculation result of shadowing coefficient formula.

Systematic study of the prediction methods for machined surface topography and form error during milling process with flat-end cutter

An enhanced time-domain simulation method of cutter/workpiece dynamic engagement during milling process is proposed in this article, which comprehensively considers the effect of multi-order modal characteristics of cutter system and cutter runout including offset and inclination. Based on the cutter dynamic displacement response, this article further presents the machined surface reconstruction algorithm and evaluation method for the form error. This research systematically studies and compares the calculation accuracy between the proposed method and other previous three kinds of methods. The effectiveness of the proposed method has been verified by a series of milling experiments successfully. By comparing with the other three methods, the proposed method shows a high calculation performance, especially under the milling condition with a large axial depth of cut and low damping or stiffness of cutter system. Besides, the results indicate that the form error has a strong dependence characteristic on the milling parameters, particularly on spindle speed. Additionally, cutter runout would easily cause over cut phenomenon on the machined surface and seriously deteriorate the surface roughness.