MACROSEGREGATION DIAGRAM FOR DRY BLENDING PARTICULATE METAL-MATRIX COMPOSITES

In the manufacture of metal-matrix composites (MMC) via the powder met allurgy (P/M) route, blending of matrix and reinforcement materials is a critical operation which has received little attention in P/M proce ssing. Past investigations have generally focussed on studies of mixin g in uniform sized and large scale systems (particles with diameters i n the millimetre size range) and inferred segregation behavior of powd ers. This work describes the development of a macro-segregation diagra m which delineates clearly the effects of material, design and operati ng variables on the macro-mixing of a powder blend. This diagram aids in assessing both the mixing mechanisms and the contributions of gravi tational 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.