Grain-growth inhibitor

In the General Electric—Allegheny Ludlum (GE—AT,) process (18), boron and nitrogen with sulfur or selenium are used as grain-growth inhibitors. 

Although more expensive than melt fiberization, the sol processes offer advantages in fiber chemistry selection. In melt fiberization, viscosity and surface tension are gready influenced by additions of small quantities metallic oxides. In the sol process, where viscosity can be controlled independently, any number of metal salts may be added without adverse effects. These salts can serve as grain growth inhibitors, sintering aids, phase stabilizers, or catalysts. 

Although these mixed metal alkoxide complexes are a means of obtaining atomic mixing of the various metals, the stoichiometric ratio of metals may or may not be that desired for the ceramic powder. A different stoichiometric ratio, n, for the same two metals is not likely to be precipitated out just because the initial solution contains a different stoichiometric ratio. Also for many electronic ceramic compositions it is desirable to have many other metals incorporated at the ppm level into the ceramic powder as sintering aids, grain growth inhibitors, and crystal phase stabilizers. Adding these otiier metals is very difficult... 

Figure 19 shows a microstructure of Al203 sintered with 0.05 wt % Y203 and 0.05 wt % MgO above the ternary eutectic temperature. The lack of entrapped porosity reported by Rossi and Burke [5S] is confirmed. The microstructure has a distinct shift in grain size distribution if one compares this structure with Fig. 13. It is hypothesized that MgO remains an effective grain growth inhibitor in the presence of the ternary eutectic...

The following carbide powders are used in hardmetal manufacture WC-TiC, WC-TiC-TaC(NbC), TaC, TaC(l%C), as well as M02C, Cx C2, and VC (the latter are used in small concentrations as WC grain growth inhibitors). 

Some developments in grain-oriented Si-Fe alloys have used grain-growth inhibitors to enhance preferential orientation during secondary recrystallisation (Taguchi et al, 1976). The features of domain structures in grain-oriented Si-Fe have been studied by Nozawa et al. (1988). 

MgO (primarily ZrOi a grain-growth inhibitor), were swept into the residual glass regions between the crystalline monticellite grains (known as the snow-ploughing process). 

Grain-growth inhibitor in WC-cobalt hard metals In steel alloys where it forms during melting... 

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