The Effects Of Alloy Elements On The Microstructures And Properties Of The Rapidly Solidified NiAl-34Cr Alloy

The microstructure and high temperature properties of the NiAl-34Cr eutectic alloycontaining small amount of Zr, Nb, Ti elements were studied by means of optical microscope,scanning electron microscope, XRD and Gleeble-1500thermal simulation test machine.The microstructure of the button cast NiAl-Cr-Zr alloy is typically eutectic and with theHeusler （Ni₂AlZr） phase at the cell boundary. The microstructure of NiAl-Cr-Zr alloy iscomposed of the black gray NiAl matrix and grey white lamellar Cr phase. The microstructureof NiAl and Cr does not basically change after heat treatment. But the Heusler phasesdisappear partly or totally. With the content of Zr increasing, the hardness of the castNiAl-Cr-Zr alloy decreases. The microstructure of the suction cast alloy is the same as thebutton cast alloy. However, the microstructure of the suction cast alloy is much thinner thanthat of the cast alloy. The hardness and the compressive yield strength of the suction cast alloyare superior to the cast alloy.The microstructure of the button cast NiAl-Cr-Nb alloys is the cellar dendrite with theLaves（NiAlNb） phase at the cell boundary. The microstructure of NiAl-Cr-Nb alloy iscomposed of the black gray NiAl matrix and grey white lamellar Cr phase. The microstructureof NiAl and Cr does not basically change after heat treatment. With the content of Nbincreasing, the hardness of the cast NiAl-Cr-Nb alloy increases. The microstructure of thesuction cast alloy is the same as the button cast alloy; however the microstructure of thesuction cast alloy is much thinner than that of the cast alloy. The hardness and thecompressive yield strength of the suction cast alloy are superior to the cast alloy.The microstructure of the button cast NiAl-Cr-Ti alloys is typically eutectic and with theHeusler （Ni₂AlTi） phase at the cell boundary. The microstructure of NiAl-Cr-Ti alloy iscomposed of the black gray NiAl matrix and grey white lamellar Cr phase. With the contentof Ti increasing, the hardness of the cast NiAl-Cr-Ti alloy decreases. The microstructure ofthe suction cast alloy is the same as the button cast alloy; however the microstructure of thesuction cast alloy is much thinner than that of the button cast alloy. The hardness of suctioncast alloy is higher than that of the cast alloy.The effect of the same content Zr, Nb, Ti elements on the hardness and the compressiveyield strength of the NiAl-Cr alloy do not appear the real law, however, the hardness andcompress yield of the suction cast NiAl-Cr-1.0Nb alloy is higher than that of the same contentof Zr or Ti suction alloy.