放電融合によるダイカストアルミニウム合金への TiC/TiAl 生成複合層の形成

概要

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This paper presents a new method of surface modification to diecast aluminum alloy by electrical discharge alloying. The process proceeds to deposit and alloy with titanium powder in electrode and with carbon decomposed from hydrocarbon working fluid on aluminum alloy. Electrical discharge alloying with an electrode of Ti/36 mass % Al premixed green compact synthesizes an in situ composite layer consisted of TiC and TiAl on an ADC 12 surface, since the substances between the electrode and substrate are transferred to the substrate surface by means of the electrical discharge process. The method makes it possible not only to form in situ composite layers with an average thickness of 100 μm, but also to vary the TiC volume ratio in the layer by the process parameters. The TiC morphology shows extremely fine dendric precipitates due to rapid solidification during the process. The volume ratio of TiC decreases with a distance from the surface, which means the modified layers are composed of gradient constituents. The hardness close to the modified surface can be selected any value of HV 400-1200 by controlling the TiC ratio through the process parameters, such as pulse width and working time.
Japan Foundry Engineering Societyの論文