Metal matrix composites (MMC) have become important materials in many technical fields. But above all there is a high amount of failures due to alternating stresses because of temperature changes.
In this investigation the thermal fatigue behaviour of two metal matrix composites with different particle contents and their base material without particles are compared. It is shown that there are three main parameters influencing lifetime: the maximum temperature of the cycles, the particle content and the particle size. An increasing of these parameters means a decreasing of the cycle numbers before damage occurs.
The development of residual stresses and strains in the matrix material of the extruded aluminium alloy EN AW-6061-T6 both with no reinforcement and also reinforced with 15vol.% and 22vol.% α-alumina particles was investigated in thermal cycling tests and additionally by finite-element-simulation for the non-reinforced material. For this purpose cylindrical specimens were heated by a 3kW diode laser and cooled by a water quench. Residual stresses in the surface area of the laser beam and temperature distribution inside the specimen were measured. The results were used to validate the finite-element model for calculating stress and strain distributions inside the specimens.
KurzfassungDie Darstellung des Gefüges von Aluminiumlegierungen bereitet immer wieder Probleme. So kommt es z.B. häufig zu Fehlinterpretationen bei der Unterscheidung von Korngrenzen und Subkorngrenzen wegen deren unterschiedlichen Reaktionen auf die verschiedenen möglichen Ätzmittel. Aber auch die Vorbereitung durch Schleifen und Polieren kann bei nur wenig veränderten Randbedingungen zu unterschiedlichen Ergebnissen nach dem Ätzvorgang führen.In den hier beschriebenen Untersuchungen wurden die Aluminiumlegierung EN AW-6061 und zwei Aluminiummatrix-Verbundwerkstoffe auf Basis von EN AW-6061 mittels Rückstreuelektronen-Kikuchi Beugung (EBSD; electron back scattering diffraction) untersucht.Es konnte eine eindeutige Zuordnung von Groß- und Kleinwinkelkorngrenzen vorgenommen werden. So gelang eine genaue Analyse des Gefüges sowohl hinsichtlich des Einflusses der Fertigung als auch der Verstärkungsphase in den Verbundwerkstoffen.
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