Combustion synthesis of Al-Ni alloys by a pseudo-HIP process

Several Al–Ni alloys containing 20 to 80 at% nickel are produced from a mixture of aluminum and nickel powders by a combustion synthesis method using a pseudo-HIP (Hot Isostatic Pressing) process. All the powder mixtures exothermically react and produce intermetallic compounds. The change in the exothermic temperature resulting from the composition of the powder mixture seems to be similar to the change in the melting temperature of the alloy. When the nickel content of the powder mixture is below 30 at% or above 70 at%, the multiphase structure including the elemental phase is formed. When an intermetallic compound phase has a relatively wide concentration range, the monophase structure of the compound is formed. The Vickers hardness of the synthesized alloy which include the elemental phase is 100 to 200 at room temperature. The hardness of Ni2Al3 is above 700. The hardness of NiAl changes with the nickel content; it decreases from 400 to 300 as the nickel content increases from 46 to 50 at%, but it increases to 400 as the nickel content increases from 50 to 56 at%