Kz Nakazawa1, Masahiko tsuka2 and S kichi Umekawa3
1Research Laboratory of Precision Machinery and Electronics, Tokyo Institute of Technology, Tokyo. Present address: National Research Institute for Metals, Tokyo
The effects of annealing and subzero treatment on thermal dilatation of the W-fiber Cu composite were studied in relation to the residual stress and matrix yielding.
For the composite annealed at 600°C for 1 hr, the heating curve forms a hysteresis loop with the cooling curve on the test up to 300°C, and a small region of inflection is observed on each curve.
By the subzero treatment at -196°C for 10 min the inflection temperature on heating is lowered, but on cooling, it remains unchanged and no hysteresis loop is formed.
In the temperature range which reaches the inflection region on heating and cooling tests, the fiber and the matrix undergo elastic deformation. The matrix begins to yield at the inflection. On the heating curve of the subzeroed composite, the inflection region is observed near room temperature corresponds to the matrix yielding.
The temperature dependencies of expansion and contraction within the temperature range from the start to the inflection on heating and cooling tests below 300°C become smaller with increasing volume fraction of fiber (Vf). The coefficient can be simply estimated by the stress condition.
The expansion coefficient beyond the temperature, at which the matrix starts the yielding, is independent of Vf and corresponds to the coefficient of the fiber. The average of the coefficient up to 300°C becomes smaller with the increase of Vf and coincides with the calculated value.
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