Sintering to full density enables powder metallurgy products to compete with castings and forgings. Subsieve powders with high inherent sinterability provide one means to attain densification, but at a substantial cost penalty when compared with readily available coarse compaction grade powders. Unfortunately, for large powders the sintering stress that causes densification is small and often insufficient to overcome the inherent compact strength that resists densification. In such cases, only slow diffusion controlled densification occurs. This study examines sintering densification by comparing the sintering stress and component strength during heating. Rapid densification occurs when the in situ strength is reduced to levels comparable to the sintering stress. Based on this concept, alloys are identified for full density sintering using thermal softening concepts borrowed from casting alloys.
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