Alloy hardening and softening in binary molybdenum alloys as related to electron concentration

Decrease of yield strength in molybdenum by adding small amounts of Group VIII elements

“…At both temperatures, the yield strength tended to decrease with the increase of the Ω-value. These results are qualitatively consistent with the result of the Mo-Re, Mo-Os, Mo-Ir and Mo-Pt alloys by Stephens and Witze [17]. In addition, the yield strength demonstrated a minimum at almost the same Ω-value irrespective of the alloy element.…”

“…Stephens and Witze [17] demonstrated that the hardness of the alloy depends on the parameter Ω that is defined by the following equation:…”

“…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].…”

“…Addition of a certain amount of rhenium substantially decreases the yield strength of molybdenum, which is called rhenium softening effect [9][10][11][12][13][14]. The low-temperature ductility of the Mo-Re alloys is generally excellent [15][16][17][18][19][20][21]. 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].…”

Solid Solution Softening (Rhenium Ductilizing Effect and Bubble Strengthening in Tungsten-Rhenium Alloys

“…While there is some indication that: an extrinsic mechanism is responsible (42-48) in a couple Group V systems the overwhelming evidence is that the softening (weakening) is a result of a reduction in the Peierls stress (8,17,18,(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41) This is the same mechanism responsible for the rhenium ductilizing effect.…”