“…It is also pointed out that Group VIII elements such as osmium (Os), iridium (Ir) and platinum (Pt) possibly demonstrate the softening effect similar to rhenium [22]. Stephens and Witze [17] investigated the hardness change of molybdenum by adding a Group IVA element such as hafnium (Hf), a Group VA element such as tantalum (Ta), a Group VIA element such as tungsten (W), a Group VIIA element such as rhenium, or Group VIII elements such as osmium, iridium and platinum from the viewpoint of the electron configuration. They suggested that the alloy softening phenomenon is correlated with the difference in the number of (s + d)-electrons between the alloy element and molybdenum [12].…”