Microstructural and Mechanical Characteristics of Porous Irons Produced with Small Particle Size Corn Starch

The space holder technique was widely used in manufacturing high melting-point porous metals. Corn powders with a smaller size (11.4 μm on average) than that of iron powders (25.5 μm on average) were used as a space holder. Porous irons having microporosities between 37.9% and 48.9% were produced after sintering at 1100–1250°C for 2 h. The amount of increase in microporosity was much less than the corn volume fraction because some corn powders scattered in micropores already formed between the iron powders. The volumetric shrinkage increased with the corn addition and/or the sintering temperature. In addition, the compressive yield stress was 108 ± ± 8 MPa, 77 ± 26 MPa, and 61 ± 31 MPa for corn additions of 0, 20, and 40 vol.%, respectively. The high sintering temperature could reduce the negative effect of corn addition on the yield stress. Perfect contacts between iron powders were observed at 1250°C, indicating that a high temperature was necessary to obtain excellent mechanical properties for this kind of porous irons.