EFFECT OF CERTAIN ELEMENTS ON THE PLASTICITY OF NICKEL AT HIGHER TEMPERATURES (VLIYANIE NEKOTORYKH ELEMENTOV NA PLASTICHNOST NIKELYA PRI POVYSHENNYKH TEMPERATURAKH),
FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO
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The strongest modifying agent for nickel was found to be lithium 0.1 Li by batch completely eliminates the zone of columnar crystals and reduces the size of the grain by approximately five times in comparison with unalloyed nickel. Additions of Ti, Ce, Ca, Zr, and Mg reduce the average dimension of grains by approximately two times and also cause over distribution of columnar zones and equiaxial crystals in the ingot. The remaining investigated additions cause no noticeable pulverization of the micrograin of the casted nickel structure. In this way, alloying of nickel with Mg, Ca, Sr, Ti, Zr, Hf, B, La, Ce, and Pr sharply raises plasticity at 400 -900C. The surplus quantities of these elements with exception of titanium appear to be harmful and embrittle nickel. The effect of the mentioned additions on plasticity of nickel is best explained on the basis of ideas concerning the binding of harmful admixtures into stable ones, into high melting compounds. The effect of surface active elements, such as boron, apparently, is connected with the change in grain boundary energy and with the prevention in this connection of the formation of solid continuous formations of low melting admixtures over the boundaries.