日本金属学会誌

J. Japan Inst. Metals, Vol. 59, No. 9 (1995),
pp. 939-946

Creep Properties of Alumina Short Fiber Reinforced 6061Al Alloy Composites

Kazuhiro Hongo, Jun Akaike,Norio Matsuda and Keisuke Matsuura

Department of Mechanical Systems Engineering, Faculty of Engineering, Yamagata University, Yonezawa

Abstract:

Creep tests were carried out at temperatures from 573 to 773 K on the 6061Al matrix composites reinforced with 11 vol% and 18 vol% alumina short fibers to examine the effect of short fibers reinforcement on the creep rate and the creep curve shape, and their stress and temperature dependences. Furthermore, the density change by creep deformation was measured to examine the formation of cavities during creep of the short fiber reinforced composites.
Creep curve shape changed with stress as follows: In the low stress range, the tertiary creep occurred after small extent of the primary stage, so that the creep curve was dominated by the tertiary creep without being related to the occurrence of necking in the specimen. With increasing the stress, the extent of primary and secondary stages became large and occupied a large part of the creep curve in the high stress range at low temperature.

The higher the creep temperature and the lower the creep stress, the larger was the density change by creep deformation. It showed that the tertiary creep was associated with the formation of cavities, especially at the fiber/matrix interface and at the grain boundaries at high temperature (773 K).

The θ-projection method was useful in describing the creep curve shape of the short fiber reinforced composites and it's variation with stress and temperature. It was found that rate parameters θ2 and θ4 describing the primary and tertiary creep were about equal, at least at 573 and 673 K, as proposed by Maruyama et al.

These results were compared with the creep behaviour of Al matrix composite reinforced with the same short alumina fibers as the present composites and the effect of matrix alloy on creep was discussed.


(Received May 24, 1995)

Keywords:

alumina short fiber, 6061aluminum matrix composite, creep curve, minimum creep rate, θ-projection, density change, creep cavity


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