Stoichiometry splitting of β phase in Ni-Al-Mn, Ni-Al-Co and Ni-Al-Fe ternary systems

The stoichiometry of the ternary beta phase in the Ni-Al-Mn, Ni-Al-Co and Ni-Al-Fe systems has been studied through the measurements of hardness and lattice parameter. It is shown that two stoichiometry lines are observed in the beta phase region of the Ni-Al-Mn ternary system. The first stoichiometry line is located on the composition line connecting NiAl and MnAl. whereas the second stoichiometry line is located on the composition line connecting NiAl and NiMn. fn the Ni-Al-Co ternary system. there is a single stoichiometry line, which starts from NiAl and terminates at CoAl. In the Ni-Al-Fe system, there are also two stoichiometry lines. One starts from NiAl and ends at FeAl, and the other directs toward from NiAl to the Fe corner. The stoichiometry line of the ternary beta phase in the Ni-Al-X system is either a single or a plural type, which is basically determined by the relative magnitudes of the Ni-X. Al-X and NI-AI bonding forces. The concentration dependence of solid solution strengthening or defect strengthening is greatly varied depending on ternary elements in the beta phase in the Ni-At-Mn, Ni-Al-Co and Ni-Al-Fe ternary systems.