Improving intermetallic ductility and toughness
Improving intermetallic ductility and toughness The intermetallic compound Ni/sub 3/Al has reasonable high-temperature strength, a high elastic modulus and is strongly resistant to oxidation and corrosion. Another intermetallic Mg/sub 17/Al/sub 12/, has both high strength and a low density. However, in common with many intermetallics, these two compounds in polycrystal-line form are brittle at ambient temperature, rendering them inappropriate for many structural applications. Factors which may lead to the brittle failure of intermetallics include a limited number of easy slip systems, a large slip vector, restricted cross-slip and difficulty of transmitting slip across grain boundaries. These considerations are intrinsic to the often complex crystal structures and are simultaneously the source of their strength. Thus, it would be undesirable to disorder an ordered alloy to improve the ductility if, in so doing, the alloy's strength was also greatly diminished. The various techniques to improve ductility or toughness can be loosely-placed in four categories: microalloying, macroalloying, microstructural control through processing and fiber strengthening/toughening.
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