A B S T R A C TThe possibility to reuse the metal powder wasted in Laser Material Deposition (LMD) process has been evaluated and a simple procedure developed. LMD uses metal powder which is fed through a nozzle into the focal point of a laser, where it melts the powder and the substrate material. During the process, a high ratio of particles hits against an unmelted area and directly bounces off the deposited area. The efficiency ratio of deposition can drop to 40% depending on the configuration and spot size. This work deals with the design of a procedure to recollect and reuse the wasted powder of a nickel based superalloy IN718. After usage, powder is recollected, undesired fractions are magnetically segregated and aggregates are removed by sieving. The particles are mixed again and ready for reuse. In order to study the effectiveness of the process, no new powder has been added to the recovered fraction, and this procedure has been repeated five times. Experimental tests show that deposited material present similar properties than those obtained with new powder grains. But, after 3 reuses, the porosity content increases consequently and the rupture strain decreases strongly. The implementation of this process allows the improvement of the final efficiency, reducing costs and decreasing the hazardous powder amount.

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Titanium diboride (TiB 2 ) particles have traditionally been added to aluminium melts incorporated into Al-Ti-B master alloys for grain-refining purposes. The addition of only 0.15 wt% is enough to have a significant influence on the grain refinement. Moreover, the addition of TiB 2 particles provides further advantages, since the average size of the pores gets lower and the remaining porosity is more evenly distributed. However, TiB 2 particles that have not participated in nucleation events tend to be pushed by the solidification front and lie at grain boundaries where they create aggregates that may impair the properties of the alloys. Due to its inertness and good wetting behaviour with aluminium, TiB 2 can also be used as a reinforcing phase in metal matrix composites (MMCs). [1][2][3][4][5][6] When the amount of TiB 2 incorporated is increased in order to reinforce the materials, other solidification-related phenomena appear. In particular, TiB 2 particles are insoluble in aluminium and do not react chemically with it, but it has been observed that some solidification characteristics of the alloy are affected by the addition of TiB 2 : solidification events start earlier due to the lower undercooling required and the solidification time is reduced. [4] These phenomena have also been reported in other MMC systems. SiC-reinforced composites have been the most studied, but, in the case of TiB 2 -reinforced alloys, not much data on solidification aspects are available: some studies have focused on Al/TiB 2 composite alloys, [1,3,4] and Youssef et al. [4] recorded a reduction of the latent heat and solidification time, which was related to microstructural aspects of the materials.The present study deals with the analysis of the cooling curves of two aluminium alloys reinforced with 6 wt% of TiB 2 particles and produced by plaster casting. This lost wax variant used to produce the different samples is characterized by a low solidification rate due to the low thermal conductivity of the plaster that is used to build the moulds. Notice that the amount of 6 wt% of TiB 2 greatly exceeds the level necessary for grain refining. The aim was that the particles improve the properties of the alloys following the patterns shown by other particle-reinforced aluminium matrix composites (AMCs): mainly wear resistance, Young's modulus and high-temperature strength.The solidification curves of the reinforced and nonreinforced materials are studied and the effect of the presence of TiB 2 particles on the main solidification parameters, such as the maximum temperature of primary a-aluminum growth, the temperature and time difference between the maximum and minimum of the liquidus recalescence and the precipita-COMMUNICATION [*] Dr. A. Veille`re, Dr.Two aluminium alloys with 6 wt% TiB 2 particles are studied for applications where increased wear resistance and mechanical strength at high temperature are required. The incorporation of hard ceramic particles has a strong influence on the microstructure and properties of the alloys. T...

Please cite this article as: Barcena, J., de Cortazar, M.G., Seddon, R., Lloyd, J.C., Torregaray, A., Coleto, J., Effect of the incorporation of interfacial elements on the thermophysical properties of Cu/VGCNFs composites, Composites Science and Technology (2010), doi: 10.1016/j.compscitech.2010 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. and addition of metal nanoparticles (Ti) to Cu matrix deposited by electroless plating. The effect of the incorporation of these metallic elements on the microstructure and thermophysical properties is discussed. B and Ti lead to higher interaction at the Cu/C interface over Ni and Co. ACCEPTED MANUSCRIPTThis allows the reduction of the coefficient of thermal expansion but regarding the thermal conductivity it was not possible to obtain a value higher than that of copper.

The present work deals with aspects related to the solidification and properties of an Al-Si10Mg/SiC 20p alloy cast in plaster moulds. Several strategies were followed to shorten its solidification time such as embedding copper tubes into the mould to make circulate cooling fluids immediately after the casting step. The analysis of cooling curves provided valuable information on the effect of the particles on solidification events. The precipitation of different phases of the MMC takes place at higher temperatures and earlier than in the case of the non reinforced alloy. Particles affect the solidification pattern of the alloy and play a noticeable role in the precipitation of the phases. This fact should be taken into account to design the filling and feeding systems correctly and for modelling and processing parameters as well as in thermal treatments. Eventually samples were obtained under the highest solidification rate conditions to analyse the microstructure and tensile properties of the MMC material.Keywords: F3S.20S, MMCs, lost wax, plaster casting, solidification Praca przedstawia aspekty związane z krzepnięciem i właściwościami stopów Al-Si10Mg/SiC20p odlewanych w formach gipsowych. Aby skrócić czas krzepnięcia stopu testowano kilka strategii, takich jak osadzanie rur miedzianych w formie aby umożliwić obieg cieczy chłodzących natychmiast po odlaniu stopu. Analiza krzywych chłodzenia dostarczyłacennych informacji na temat wpływu cząstek na proces krzepnięcia. Wydzielanie różnych faz w kompozytach metalowo-ceramicznych odbywa się w wyższych temperaturach i wcześniej, niż w przypadku nieumacnianego stopu. Cząstki wpływają na schemat krzepnięcia stopu i odgrywają zauważalną rolę w wydzielaniu faz. Fakt ten powinien być brany pod uwagę przy projektowaniu prawidło-wego systemu zalewania formy, modelowaniu parametrów procesu, jak również obróbki cieplnej. Na koniec pobrano próbki otrzymane przy najwyższej szybkości krzepnięcia do analizy mikrostruktury i właściwości wytrzymałościowych kompozytu metalowo-ceramicznego.