In order to investigate the influence of inter-fiber spacing on proof stress in Al-Al3Ni eutectic composites,
the microstructures were observed in detail, and the tensile and compressive 0.2% proof stresses
were measured in the specimens unidirectionally solidified at various rates.
The tensile and compressive proof stresses are not coincident with each other. This difference is thought to be caused by residual stress. The proof stress depends on inter-fiber spacing and cell density. The inter-fiber spacing effect is larger than the cell density effect.
The residual stress estimated from the proof stress and rule of mixtures is found to depend on the interfiber spacing. It is suggested that the dependence of proof stress on inter-fiber spacing relates to the dependence of residual stress which has been accumulated during cooling process after solidification. Therefore, it is not adequate to understand the inter-fiber spacing dependence of proof stress in the composites in terms of Orowan's by-pass theory, applied directly without considering the residual stress.
(Received January 29, 1988)
Keywords: eutectic composites, yield stress, inter-fiber spacing, residual stress, rule of mixtures, aluminum-nickel system, tensile test, compression test
* Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 724, Japan.
** Faculty of Engineering, Hiroshima University, Higashi-Hiroshima. Present address: Government Industrial Research Institute, Shikoku, Japan.