Stoichiometry splitting of beta 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 N i-Al-Fe systems has been studied through the measurements of hardness and l attice parameter. It is shown that two stoichiometry lines are observed in the beta phase region of the Ni-Al-Mn ternary system. The first stoichiomet ry line is located on the composition line connecting NiAl and MnAl. wherea s the second stoichiometry line is located on the composition line connecti ng NiAl and NiMn. fn the Ni-Al-Co ternary system. there is a single stoichi ometry 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 e nds at FeAl, and the other directs toward from NiAl to the Fe corner. The s toichiometry 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 m agnitudes of the Ni-X. Al-X and NI-AI bonding forces. The concentration dep endence 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.