Equiaxial grains

Nickel—Iron and Cobalt—Iron Alloys. Selenium improves the machinabifity of Ni—Ee and Co—Ee alloys which are used for electrical appfications. Neither sulfur nor tellurium are usefiil additives because these elements cause hot britdeness. The addition of 0.4—0.5% selenium promotes a columnar crystal stmcture on solidification, doubling the coercive force of cobalt—iron-titanium alloy permanent magnets produced with an equiaxial grain stmcture. 

The structure formed under those conditions consists of polyhedral and virtually equiaxial grains and is referred to as nondendritic one. Ingots with the nondendritic structure can be obtained under industrial conditions for most of the high-alloyed aluminum alloys. 

Figure 5.64 Fracture surface showing equiaxial grains (19).

Figure 11.43 Microstructures of sintered AI2O3. (A) undoped material showing pore-grain boundary separation and abnormal grain growth (B) MgO-doped material showing high density and equiaxial grain structure. (From Ref. 81.)...

Positive influence of scandium has a complex character. Thus, the additions of Sc not only increase the yield stress and the ultimate tensile strength, but improve also the workability of alloy and its production ductility, decrease the grain size in as-cast condition, eliminate the dendrite structure and lead to the formation of a fine-grained equiaxial structure, sharply increase the recrystallization temperature (Tab.2), improve metal weldability and raise its corrosion resistance. 

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