Fabrication of TiC-Reinforced Composites by Vacuum Arc Melting: TiC Mode of Reprecipitation in Different Molten Metals and Alloys

TiC crystals were developed and grown through a melt dissolution and reprecipitation mechanism, in different alloy matrices (pure Fe, 316L, Fe-22 at.%Al, Ni-25at.%Al, and pure Co) through the use of Vacuum Arc Melting (VAM) process. The TiC surfaces exhibit a characteristic faceted mode of growth which is explained in terms of classic nucleation and crystal growth theories and is related with the well-known Jackson factor of crystal growth. Different morphologies of the finally solidified TiC grains are observed (dendritic, radially grown, isolated blocky crystals, particle clusters), the establishment of which may be most likely related with solidification progress, cooling rate, and melt compositional considerations. An initial, rough and qualitative phase identification shows a variety of compounds, and the attempts to define specific phase crystallographic-orientational relationships led to rather random results.     

Evaluation of the Microstructural Aspects,Mechanical Properties and Dry Sliding Wear Response of MoTaNbVTi Refractory High Entropy Alloy

Metals and Materials International - MoTaNbVTi refractory high entropy alloy was synthesized by the vacuum arc melting technique in its equi-atomic composition. The modification of its...     

Microstructure and sliding wear assessment of Co–TiC composite materials

Monolithic Co and Co based composites reinforced by TiC precipitates were fabricated by vacuum arc melting process. The ratio of hexagonal to cubic phase cobalt was affected by the presence of the TiC precipitates. The microstructure of the produced materials was also associated with the presence of TiC crystals. The TiC primary precipitates are characterised by a strong faceted morphology which is explained in terms of Jackson’s theory of crystal growth. The solidification progress was altered by the presence of the TiC crystals. The sliding wear behaviour of the produced composites was assessed in terms of wear track and debris examination and compared to that of Co29Cr5Mo alloy.     

Sliding wear and solid particle erosion response of aluminium reinforced with tungsten carbide nanoparticles and aluminide particles

In the present effort, aluminium matrix composites (AMCs) were produced by the addition of submicron‐sized WC particles of low (up to 2.5 vol%) content into a melt of Al1050. Casting was assisted by the use of K₂TiF₆ as a wetting agent and mechanical stirring in order to limit particle clustering. Particle distribution was reasonably uniform comprising both clusters and isolated particles. Various different reinforcing particles' phases were identified, both in situ (Al‐W, Al‐Ti, and Al‐W‐Ti intermetallic phases) and ex situ (WC particles) of various morphologies shapes and sizes. Increase of the reinforcing particle content led to an increase of the tendency for clustering. The wear properties of the composite were examined by dry sliding wear. The worn surfaces and the produced debris were examined by SEM‐EDX, and an effort to correlate the wear response of the produced materials with the matrix and the reinforcing phase characteristics was attempted. In general, the increase of the reinforcing phase content led to an improvement of the sliding wear response. Solid particle erosion experiments were carried out for impact angles of 30°, 60°, and 90°. Τhe eroded surfaces were examined with SEM‐EDX, and possible erosion mechanisms were proposed based on morphological and other material characteristics. Intensive particle clustering seemed to deteriorate the erosion resistance of the systems. Medium concentrations of the reinforcing particles (1.0‐1.5 vol% WC) are proposed as a recipe for optimum sliding wear and solid particle erosion resistance behavior.     

用于RFID接收器的基带电路——设计要点381

引言射频识别(RFID)技术采用辐射和反射RF功率来识别和跟踪各种目标。典型的RFID系统由一个阅读器和一个转发器(或标签)组成。一个RFID阅读器包含一个RF发送器、一个或多个天线以及一个RF接收器。RFID标签就是一个带天线的唯一标识IC。     

Development of a Cast Al-Mg2Si-Si In Situ Composite: Microstructure, Heat Treatment, and Mechanical Properties

An Al-11Mg₂Si-Si in situ composite was prepared by a modified investment casting technique that employs sub-pressure for castability improvement and immersion of ceramic shell molds in fluidized beds of silica sand and iron particles for heat extraction improvement. The microstructure of the as-cast composite is explained according to the pseudoeutectic Al-Mg₂Si phase diagram. The positive effect of a decreased number of mold investment layers and cooling assisted by immersion of the mold in a metallic bed on the tensile strength and hardness of the heat treated composite is noted. A minor presence of Fe in the master alloys constitutes an essential factor for the brittleness of the composite. Solution treatment notably improves the tensile strength of the composite; however, prolonged treatment deteriorates its ductility. The effect of time and temperature of the aging treatment on the hardness of the composite is investigated. The positive influence of cooling assisted by a metallic fluidized bed on the effectiveness of the aging treatment is noticed.     

Effect of Destabilization Heat Treatments on the Microstructure of High-Chromium Cast Iron: A Microscopy Examination Approach

A 18.22 wt.% Cr white iron has been subjected to various destabilization heat treatments. Destabilization at 800 °C caused gradual precipitation of M₂₃C₆ secondary carbide particles with time leading to a gradual increase in the bulk hardness. At 900, 1000, and 1100 °C, an initial sharp increase in bulk hardness with time occurred, reaching a plateau that was followed by a slightly decreasing trend. The combination of martensite formed, stoichiometry, and morphology of the secondary carbides present (mostly M₇C₃) are responsible for the obtained values of hardness. At 1100 °C, severe dissolution of the secondary carbides and consequent stabilization of the austenitic phase took place. Maximum hardness values were obtained for destabilization at 1000 °C. The correlation between bulk hardness and microstructural features was elaborated.     

Solidification behaviour of ceramic particle reinforced Al-alloy matrices

Novel metal matrix composites have been produced by cast production route. TiC and WC ceramic reinforcing particles have been successfully introduced into Al 6060, Al 319, Al 356, Al–7Si–5Mg, Al–20Cu and Al 2007 alloys. Refined grain structure and various intermetallic phase formation have been observed. Particle–melt and particle–solidification front interactions, solidification sequence and particle–matrix interfacial characteristics have been examined by means of metallography, SEM examination and EDX analysis. Particle distribution, intermetallic phase formation and location and grain structure are discussed in terms of ceramic-melt wetting characteristics, alloying element interfacial segregation and particle–solidification front thermal behaviour.