Fibre strength selection and the mechanical resistance of fibre-reinforced metal matrix composites

For predicting the strength of fibre-reinforced metal matrix composites, the in situ fibre strength value has to be introduced in the calculations. Tension tests series have been conducted on SiC fibres (SCSO and SCS2 TEXTRON) before and after chemical interaction with a pure liquid aluminium bath and the reacted fibres have been tested before and after dissolution of the aluminium coating simulating the metallic matrix around the fibres. The results obtained for the different fibre batches show that the in situ fibre resistance may differ significantly from the strength of as-received or extracted fibres that is usually adopted in the models

PM Based Titanium Matrix Composites for Aerospace Applications: Processing, Mechanical Properties and Scale Up

The reinforcement of titanium with a hard phase is an efficient way to increase the stiffness and strength of conventional titanium alloys. The high reactivity of titanium is a critical challenge in the processing of Titanium Matrix Composites (TMCs). For this reason, Powder Metallurgy is considered a very promising route for the manufacturing of TMCs. In this work, a master alloy (Ti-TiC) was developed by combustion synthesis. This alloy was further blended with conventional titanium alloy and the final consolidation was performed by Spark Plasma Sintering. In addition to the processing details, microstructural and thermomechanical characterization is presented. Materials obtained present higher Young Modulus and strength than conventional Ti-6Al-4V, with higher thermal conductivity and maintaining similar thermal expansion coefficient (CTE). The good corrosion resistance of the material makes it a candidate for possible applications in aerospace. This work presents also the scale up of the process to obtain aerospace demonstrators.This work was carried out within the frame work of the projects: ‘‘Development and Characterization of Advanced Metal Matrix Composites (Hybrid-MMs)’’) and “Hybrid Titanium Matrix Composites (TMC) for aero engines applications (AIRTMC) both supported by ESA (European Space Agency

Space propulsion components based on Gamma TiAl based alloys by combustion synthesis + compation route

Intermetallic compounds of Ti-Al system and alloys based on such compounds are materials of rapidly growing technological importance. Such alloys have relatively high yield strength at elevated temperatures, advanced creep characteristics, and good oxidation/corrosion resistance. Several methods have been utilized in the synthesis of Ti-Al intermetallic compounds. These include conventional melting and casting processes and powder metallurgical techniques. The latter include mechanical alloying, plasma-rotating electrode processes, and inert gas atomization (which all have been recently proposed as methods of preparing titanium aluminides in powder form). In all of these approaches, a subsequent step is required to obtain products with the desired density and shape. Over past years, a search for new synthetic approaches to intermetallides (including titanium aluminide and related materials) has led, among others, also to the technique of Self-propagating High-temperature Synthesis (SHS). This is an alternative powder technique for the production of intermetallics. This process requires a large exothermic enthalpy of formation for the desired intermetallic compound. Because of a low caloricity of reaction between Ti and Al, the classical SHS reaction between these metals can be initiated only upon preliminary heating of a green mixture. For this reason, the best results in synthesis of titanium aluminides were attained by combining SHS with some kinds of internal influence, such as heating up to the ignition temperature, mechanoactivation of green mixture, SHS followed by hot isostaic pressing (HIP), SHS in electromagnetic field, etc. This work studied and optimized the SHS-densification route for the synthesis of Gamma TiAl based Intermetallic (GE alloy: 48Ti-48Al-2Cr-Nb) using two different combustion modes: forced SHS + compaction and thermal explosion + compaction. A complete metallurgical characterization of the product was done: phase analysis, density, chemical analysis, microstructure and mechanical properties (tensile strength). The developed material and manufacturing process is a potential candidate to be used as turbine blades for ARIANNE VULCANE engine.Peer reviewe

Wysokotemperaturowe badania zwilżalności i reaktywności ciekłego Mg w kontakcie z podłożem Ni

The paper focuses on the experimental investigation of high temperature wetting behaviour of liquid pure Mg during a contact heating on Ni substrate by the sessile drop method. High temperature wettability test was performed by the classical sessile drop method at T = 700°C for t = 300 s, under flowing Ar 99.999% atmosphere, by using the equipment and testing procedures that have been developed by the Foundry Research Institute. In order to suppress effects of heating and cooling histories on wetting and spreading behaviours, Mg/Ni couple was introduced inside a metallic heater already preheated up to the test temperature, while after the wettability test, it was immediately removed to the cold part of the chamber. During the wettability test, images of the couple were recorded by high-resolution high-speed CCD camera. It was observed, that the wetting phenomenon (θ ≤ 90°) takes place immediately after melting of Mg sample. The Mg/Ni system shows a good wetting at T = 700°C after t = 300 s forming the final contact angle of 18°.Praca prezentuje wyniki badań wysokotemperaturowego oddziaływania ciekłego Mg w kontakcie z podłożem Ni podczas wspólnego nagrzewania badanej pary materiałów. Wysokotemperaturowe badania zwilżalności przeprowadzono klasyczna metodą kropli leżącej w temperaturze T = 700°C i czasie t = 300 s w gazie przepływowym Ar 99,999%. Do badań zastosowano aparaturę i procedury badawcze opracowane w Instytucie Odlewnictwa. W celu eliminacji wpływu historii nagrzewania i chłodzenia na zwilżalność i rozpływność, badany układ Mg/Ni wprowadzono do gorącej części komory badawczej nagrzanej do temperatury badań. Po badaniach zwilżalności badaną parę materiałów natychmiast wprowadzono do zimnej części komory badawczej. Podczas badań zwilżalności stosowano ciągłą rejestrację obrazu badanej pary materiałów za pomocą wysokorozdzielczej kamery cyfrowej CCD. Zaobserwowano, że zjawisko zwilżania (θ ≤ 90°) zachodzi natychmiast po stopieniu próbki czystego Mg. Układ Mg /Ni wykazuje bardzo dobrą zwilżalność w temperaturze T = 700° C po t = 300 s, a końcowa wartość kąta zwilżania wynosi 18°