Abstract
Both nickel aluminide and iron aluminide intermetallic matrix composites (IMC), Ni 3 Al and Fe 3 Al matrix with either 5 or 10 vol. pct α-Al 2 O 3 , were successfully synthesized through a multistage sintering approach from the elemental powders of Ni, Fe, Al and oxide of α-Al 2 O 3 . The entire process comprises steps involving preparing a powdery starting material, sealing it within a metal sheath or can, compacting or cold deforming, preliminarily heating the compacted material at a relatively low temperature, executing a pore-elimination process to eliminate the pores resulting from the preceding heating step and sintering the material at a relatively high temperature to develop a transient liquid phase to heal or to eliminate any micro-cracks, or collapsed pores from the previous steps as well as transform the material into the final phase structure. Most of all, it is important to develop an intermediate phase for the metal matrix during the preliminarily heating stage. The employed intermediate phases in present study are Ni 2 Al 3 and Fe 2 Al 5 for the nickel aluminide and iron aluminide IMC, respectively. These new phases are brittle materials with the low melting points (1135°C and 1169°C for Ni 2 Al 3 and Fe 2 Al 5 , respectively). They are important in preventing any significant cracks during the pore-eliminating process and in developing a transient liquid phase during the followed 1200°C sintering stage. This investigation demonstrates the feasibility to prepare the IMC products with a stress-free sintering process, hence, the expansive HIP or HP facilities are avoided.