C.E. da Costa

P/M aluminum matrix composites: an overview

Abstract This paper reviews the state of art concerning powder metallurgy (P/M) aluminum matrix composites. Among all the metal matrix composites (MMCs) aluminum could be the most widely used metal as matrix due to its low density coupled with high stiffness. There are different manufacturing methods which can be applied for this composite. From these, P/M could be remarked as a highly effective and economic method compared with other alternatives.

Wear and thermal behaviour of M2 high-speed steel reinforced with NbC composite

This work studies a high speed steel composite reinforced with NbC and using Cu3P as sintering activator. High speed steels can be used as cutting material and their cutting capability could be improved if hardness, and as a consequence, wear behaviour is increased. One way for increasing these properties is to reinforce them with hard particles. NbC have been demonstrate like one good option, but with the problem of its low interaction with the HSS matrix. One way for solving this low reactivity is to add a sintering activator that interacts with the matrix and increases the joint with the reinforcement. The thermal behaviour has been studied in order to optimize the sintering parameters, as well the best heat treatments conditions. This behavior has been determined through differential dilatometry. The wear behaviour has been studied through a pin on disk test using Al2O3 of high hardness as countermaterial. Finally, mechanical properties and complete metallographic study have been performed.

Corrosion Resistance of 2014 Aluminium Matrix Composites Reinforced with Atomised Ni3Al

The corrosion resistance of 2014 aluminium matrix composites has been evaluated. The base alloy was manufactured through mechanical alloying, and reinforced with Ni3Al (manufactured through atomisation). Composite materials were manufactured according to the following procedure: mixing, cold uniaxial compacting, and hot extrusion. All materials were tested as extruded and heat treated (T6 condition). Corrosion tests were carried out following ASTM standard methods G69 (measurement of corrosion potentials) and G110 (evaluation of intergranular corrosion). The influence that the intermetallic and T6 heat treatment have on the corrosion resistance of 2014 aluminium alloy has been studied. Results show that atomised Ni3Al improves the intergranular corrosion resistance of base aluminium by a mechanism of cathodic protection. T6 heat treatment is also favourable.

Tribological behaviour of borided H13 steel with different boriding agents

Abstract Solid boriding thermochemical treatment was carried out on AISI H13 steel. Two boriding agents were used: Ekabor 1-V2 commercial powder and a mixture of 73·26 wt-% borax, 24·06 wt-%SiC, 1·22 wt-%NH4Cl and 1·46 wt-%NaCl. Pin on disc wear tests were carried out to investigate tribological behaviour. After the wear tests, samples were cut in cross-section to evaluate the thickness and morphology of the boride layer by scanning electron microscopy (SEM) and Vickers microhardness. Wear mechanisms were evaluated by SEM. A large improvement in wear resistance was observed for borided samples compared with samples that had been quenched and tempered. The thickness of the borided layer was higher for samples borided with Ekabor powder than those borided with the mixture. In comparison with quenched and tempered samples, borided samples had a higher incidence of cracks, which favours spalling and reduction of grooves formed by abrasive wear.

Sinterability and wear behaviour of P/M M2 high speed steel reinforced with NbC composite

Abstract Using an M2 grade as matrix, this work studies the thermal and wear behaviour of the reinforced with NbC composites. The thermal behaviour has been studied through a dilatometric approach and the wear performances through a ‘pin on disk’ instrumented test.

Fracture analysis of aluminium matrix composite materials reinforced with (Ni3Al)p

This paper studies the influence of Ni3Al intermetallic particles on the fracture behaviour of aluminium matrix (2014) composite materials. Intermetallics were obtained by mechanical alloying and by atomisation. The composite materials were manufactured by mixing, uniaxial compacting of a preform, and subsequent extrusion without canning or degassing. The study considered materials in extruded state and after T6 heat treatment. Assessments were made from the viewpoint of microstructure (by means of optical and scanning electron microscopy), and studying the reactions between the matrix and the reinforcement. These reactions produce a highly copper-enriched interphase. The influence of the reinforcement and state of the alloy on the fracture behaviour of the composite materials was studied through scanning electron microscopy.

Influence Of The Ni3AI Intermetallic Reinforcement On Intergranular Corrosion In Aluminium Metal Matrix Composite

M etal matrix com po ites (MMC ) h ave been widely d e veloped during the las t two decades driven by the fea sibili ty of obtaining properties therwise impo sible to obtain in a wrought material. They offer attractive physical and mechanica l properti e which combine metallic and ceramic properti e with va rious c.ombinati on of ti ffnes and strength [ 1,2]. Amo ng all matrices tud ied aluminum is one of the most pro m· ising and several material have been suggested as rein forcement in order to optimize compo ite properti e and to obta in materials fo r wea r re i ra nee and tructural applicatio n . Different reinfo rcements have been tud ied e.g. ilicon carbide, alumina, boron o r graphite, but in recent year intermetallics have appeared as a viable optio n d ue to their excellent strength and oxidation prope rtie [3 ,4,51. H owever, mo re info rmation is needed about the corr io n p ropertie of metal matrix compo ite . Vari ous studi es had bee n conducted in thi fie ld , mainly studying rainless steel 16,7,81 and alu min u m matrixcompo ite. o rro io n tudie on alu min um MM have been focused o n ilicon carbide, alu mi na and boron re in ~ r ements and they dem· nstrate that the performa n e of the comp ite material depend n the c rro ion phenomena tudie L ilic n arb ide additi ns d not affect the intergran ular o rro ion resi ta nee of the alumi·