Cause for on heat explosion during ISM of TiAl

Heat explosion often takes place during ISM of intermetallics and the spout of molten metal from the crucible endangers the normal composition of alloy and the safety of furnace as well. The study on the pore surface composition and appearance characteristics of TiAl ingot left in the cold crucible after heat explosion indicates that the surface composition of the pore left in the heat explosion ingot is rich in Al, and the ratio of Al/Ti varies between 2.62 and 3.49, much higher than the nominal ratio of 1, which means that the driving pressure of explosion comes mainly from Al vapor. Calculated results show that the domain temperature can reach 2245.6-2284.68 K due to the heat of reaction between Ti and Al at 933 K. The vapor pressure of Al in this area can go up to 1005-3366 Pa for consideration of activity coefficient of Al in Ti-Al melt. The happening of heat explosion depends on the relative value between the vapor pressure of Al and the melt static pressure which is determined by the position of Al piece in the crucible. Consequently, the relative position of Al piece in the crucible is an important parameter which can be used to prevent heat explosion. An optimal position, 2.7 cm beneath the free surface, was suggested.