The advantages and limitations of the arc-casting method for producing metallic molybdenum and its alloys are discussed. The general properties of unalloyed cast molybdenum are described and curves are presented to show the room temperature tensile properties, hardness, and notched-bar values after annealing at various temperatures, the effect of testing temperature on hardness, and the transition temperatures for various types of impact tests.

The need for addition of alloying elements is discussed. Preliminary selection of appropriate alloying elements was based on their vapor pressures and known or expected solid solubility limits. Curves are presented showing the solid solubility limits of silicon, aluminum, iron, cobalt, and nickel in molybdenum at various temperatures as determined by the measurement of lattice parameters of arc-cast samples, and the effects of beryllium, aluminum, silicon, titanium, vanadium, chromium, iron, cobalt, nickel, zirconium, columbium, tantalum, and tungsten on the hardness of molybdenum at various temperatures.

Molybdenum containing a small amount of beryllium can be hardened by quenching and softened by slow cooling.

Regardless of which alloying element is used, there appears to be a limit to the increase in hardness that can be tolerated without causing difficulty in hot-working by the techniques applied so far.

The effects of several of the alloying elements on the rate of work-hardening and on the temperatures of softening and recrystallization were studied using a series of alloys which were extruded.

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