Isamu Igarashi, Gorô Ôhira and Takeo Horigome
The authors investigated the solidification process of Fe-C alloy experimentally comparing with that of Al-Si alloy. The results obtained are as follows:
(1) When the hypo-eutectic Fe-C alloy was slowly cooled,primary dendrites of austenite were formed at first,then at eutectic temperature the austenite named SASANOHA structure, which were super-saturated with carbon,developed from the primary dendrites.
The super-saturated carbon crystallized out on the axes of SASANOHA as cementite,which immediatly graphitized to so-called flaky graphite. Besides, the linkes of cementite remained on the grain boundaries of austenite and in a few cases it happened that the blocks of cementite were closed in the austenite,and they turned into chain-like graphite and block graphite with the lapse of time.
(2) As to the hypo-eutectic of Al-Si alloy,the primary dendrites of Al were formed at first, then SASANOHA solid solution of Al developed followed by the separation of Si on the axes of SASANOHA. The final structure was the eutectic Si-needles which corresponded to the flaky graphite in Fe-C alloy.
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