MACROSEGREGATION DIAGRAM FOR DRY BLENDING PARTICULATE METAL-MATRIX COMPOSITES

In the manufacture of metal-matrix composites (MMC) via the powder metallurgy (P/M) route, blending of matrix and reinforcement materials is a critical operation which has received little attention in P/M processing. Past investigations have generally focussed on studies of mixing in uniform sized and large scale systems (particles with diameters in the millimetre size range) and inferred segregation behavior of powders. This work describes the development of a macro-segregation diagram which delineates clearly the effects of material, design and operating variables on the macro-mixing of a powder blend. This diagram aids in assessing both the mixing mechanisms and the contributions of gravitational and inertial forced to mixing. Scale-up parameters to achieve a macro-mixed MMC, as affected by material variables and blender size as well as the effects if gas atmosphere, are readily apparent on the macro-segregation diagram.