Aluminum alloy metal matrix composites are a class of materials object of large and intensive research during the last years. In this study an AA2124 aluminum alloy were processed by means of mechanical alloying added by 10, 20 and 20 percent of silicon carbide (SiC) in vibratory SPEX type mill during 60 and 120 minutes. After this the composites powders obtained were characterized by means of Scanning Electron Microscopy (SEM) plus Energy Dispersive Spectroscopy (EDS) to determine the powders morphology. In order to consolidate the AA2124 aluminum alloy composites reinforced by silicon carbide (SiC) composites, the powders processed by high energy ball milling technique were hot extruded and the billets were characterized by SEM to determine the microstructure and the distribution of the reinforced ceramic phase of silicon carbide throughout the aluminum matrix and at last the microhardiness Vickers technique were used to evaluate the mechanical properties.
The main aim of this work was to study the behavior of the secondary hardening of AISI M3:2 high speed steel named Sinter 23® produced by powder metallurgy process of hot isostatic pressing (HIP). The M3:2 high speed steel Sinter 23® was submitted to heat treatment of hardening with austenitizing temperatures of 1140 oC, 1160 oC, 1180 oC and 1200 oC and tempering at 540 oC, 560 oC and finally 580 oC. The effectiveness and response of the heat treatment was determined using hardness tests (Vickers and Rockwell C hardness) and had its property of secondary hardness evaluated. The results showed that the secondary hardening peak of Sinter 23® high speed steel (tempering temperature at which maximum hardness is attained) is at 540 °C for the lower austenitization temperatures of 1140 °C and 1160 °C, and it is at 560 °C for the higher austenitizing/quenching temperatures of 1180 °C and 1200°C.
Crude petroleum storage and transportation systems suffer from constant physical stress caused by chemical attack of crude petroleum on its structure. Ceramics are materials with high chemical stability in hostile environment and therefore can be used as an inert coating material. In the present work we have produced Al2O3-Y2O3-ZrO2 composites with high mechanical strength, through thermo-mechanical processing. To evaluate the quality of materials developed and the possibility of using them as inert protective coatings, storage and transportation systems, we have studied the physic-chemical and mechanical stability of these materials in crude petroleum originated from onshore and offshore. Structural, microstructural and mechanical tests showed that 15-20wt% ZrO2 composite ceramics with 2 wt% of Y2O3 additives presented better results in terms of mechanical hardness and microstructural characteristics. The study of stability of composite ceramics in crude petroleum environment showed that ceramics did not present any additional phase except the constituent phases. Result of microscopy and Vickers hardness tests also showed that there is no visible change in these characteristics after even 90 days of submersion in crude petroleum. Thus we conclude that composite ceramics could be potential materials for inert coating in crude petroleum environment.
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