Creep behaviour of Al based Metal Matrix Composites

01.04.2007 - 31.03.2010
Forschungsförderungsprojekt
High Tech engineering applications require materials with property profiles, where light weight, stiffness, conductivity, corrosion resistance, strength up to elevated temperatures, fatigue and creep resistance are combined. The development of Metal Matrix Composites (MMCs) during the last decades has been trying to cope with these requirements providing a variety of combinations of matrix alloys and reinforcements of different types, volume fractions, shapes and architectures. MMCs exhibit significant improvements with respect to conventional alloys, but as well some disadvantages like increased cost. Al-based MMCs with discontinuous ceramic reinforcement have reached applications due to their high specific mechanical properties such as Young¿s modulus and strength and relatively moderate price. However, the behaviour of Al-based discontinuously reinforced MMCs at elevated temperatures needs further investigations to understand the heterogeneous thermal activation of the matrix offering a knowledge based potential for improvement. The creep resistance of this kind of materials depends essentially on the size, volume fraction, shape and architecture of the ceramic reinforcement. The available literature as well as own studies show that ceramic short fibres enhance the creep resistance with respect to the unreinforced matrix alloys, while particles reduce the creep resistance in some cases. Focusing on these contradictory results, the proposed project aims to achieve a basic and generally applicable understanding of the processes and parameters influencing the long-term creep behaviour of discontinuously reinforced Al-MMCs. The investigations will be carried out for model MMCs, prepared in co-operation with international partners, and MMCs resembling commercial grades: 1) an unreinforced and particle reinforced Al-Cu alloy using two different particle types with different volume fractions and reinforcement sizes. 2) unreinforced and short fibre reinforced Al-Si alloys to study the effect of short fibres as well as that of the three dimensional hybrid Si-short fibre network formed in these composites. Prior and in the course of the creep tests, the materials will be characterised by means of Young¿s modulus measurements, high temperature tensile tests, differential scanning calorimetry (DSC), dilatometry and metallographic methods in order to determine mechanical properties and microstructural features. Internal stresses and pores induced during production and their evolution during long-term creep will be studied by neutron and synchrotron diffraction as well as by X-ray and synchrotron computed tomography. These ¿non-destructive¿ techniques provide a three dimensional insight into the internal adaptation of these heterogeneous materials to long-term creep exposure. The experimental results will provide input data for the modelling of the creep behaviour of the studied matrices and composites, while the modelling results will be verified by experiments and shall provide the means for the prediction of material improvements.

Personen

Projektleiter_in

Projektmitarbeiter_innen

Institut

Grant funds

  • FWF - Österr. Wissenschaftsfonds (National) Austrian Science Fund (FWF)

Forschungsschwerpunkte

  • Composite Materials: 10%
  • Special and Engineering Materials: 5%
  • Structure-Property Relationsship: 20%
  • Computational Materials Science: 5%
  • Materials Characterization: 35%
  • Modeling and Simulation: 25%

Schlagwörter

DeutschEnglisch
Metal Matrix Verbundwerkstoffemetal matrix composites
Kurzfaservertärkte MetallenShort fibre reinforced metals
Innere SpannungenInternal Stresses
KriechenCreep
Teilchenverstärkte MetallenParticle Reinforced Metals

Publikationen