| The effect of Fe addition on Ni-Aluminide intermatallics was studied in order to improve the mechanical properties, especially the room temperture ductility and the high temperature strength. It was found that the Fe addition in the two phase alloy of (NiAl＋Ni₃Al) gives significant improvement in the room temperature ductility. The high ductility of Ni-Al-Fe alloy at room temperature seems to be caused by the mobile dislocations formed at NiAl which occurred by the accumulated dislocations in Ni₃ Al. The strength improvement, especially at high temperature, was tried by micro-alloying and hot forming. When the micro-alloying of B, Cr, Ti and Zr was tried the optimum condition in strength and elongation was obtained from the addition of 1 at % Ti in Ni-20Al-27.5Fe. When the alloy is hot-formed, the Zr addition gives significant improvement in the high temperature strength, that is to say, the maximum strength at high temperature range was obtained from the hot extruded bars of Ni-20Al-27.5Fe-1Ti-0.5Zr. It is believed that the microstructure is consisted of fine grains and precipitates by the hot extrusion, which is accentuated by the Zr compounds. |
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