Improvement in the ductility of molybdenum alloys due to grain boundary segregation

On the fracture toughness of fine-grained Mo-3Si-1B (wt.%) alloys at ambient to elevated (1300 °C) temperatures

“…grained alloys, as well as the coarse-grained Kruzic alloy. Oxygen is known to have has a deleterious effect on the strength of grain boundaries in molybdenum alloys [53]. Free oxygen has a greater potential to weaken the grain boundaries than oxygen tied up in silica or other glassy inclusions, so the location of any oxygen impurities is vitally important to these alloys' structural performance.…”

Weldable ductile molybdenum alloy development

“…Metallographic examinations of microstructure were performed using a Murakami's etch (10 g Potassium Ferri-cyanide + 10 g Potassium Hydroxide + 100 ml water) to reveal the grain structure. Specimens from Alloys #2, #5, and #6 were characterized by atom probe tomography (APT) using the same methods used for earlier work on Mo-Zr-B alloys [4,5,27].…”

“…These include hightemperature strength, creep resistance, and relatively low coefficient of thermal expansion [1][2]. One deficiency for most applications is the decreased ductility and increased ductile to brittle transition temperature (DBTT) in the heat-affected zone (HAZ) of welded joints [1][2][3][4][5][6][7][8][9][10][11]. Molybdenum is susceptible to embrittlement when low amounts of oxygen segregates to grain boundaries during recrystallization and grain growth in the HAZ of welds.…”

“…Alloying molybdenum with small amounts of boron and zirconium has been shown to prevent this grain boundary embrittlement and resulted in improved amounts of ductility in the HAZ of welded TZM [3]. The segregation of zirconium, boron, and carbon to grain boundaries for these Mo-Zr-B alloys resulted in suppressed oxygen concentration at grain boundaries preventing embrittlement in the HAZ of these welds [4,5]. Motivation for that earlier work with Mo-Zr-B alloys was based on earlier efforts by several Russian investigators on similar boron-containing alloys TsM-6 (Mo-Zr-B) and TsM-10 (Mo-Al-B) where improved weld properties were observed [12][13][14].…”

“…The compositions of the alloys were selected to bound previous work on Mo-Zr-B alloys of 1500 ppm Zr and 6 ppm B and Mo-Al-B alloys of 30 ppm Al and 10 ppm B [3][4][5][12][13][14]. Microstructure examinations are performed using metallography, fractography, and atom probe tomography.…”