Papers by Author: H. Y. Rahman

Abstract: This paper presents the development of FeCuAl powder compacts through uniaxial die compaction process. Iron powder ASC 100.29 was mechanically mixed with other elemental powders, i.e., copper (Cu), and aluminum (Al) for 30 minutes at a rotation of 30 rpm. The feedstock was subsequently shaped at three different temperatures, i.e., 30°C, 150°C, and 200°C through simultaneous upward and downward axial loading of 325 MPa. The as-pressed samples termed as green compacts were then sintered in argon gas fired furnace at 800°C for three different holding times, i.e., 30, 60, and 90 min at a rate of 10°C/min. The sintered samples were characterized for their relative density, electrical resistivity, and bending strength. The microstructure of the sintered samples was also evaluated through scanning electron microscopy (SEM). The results revealed that the sample formed at 150°C and sintered for 30 min obtained the best final characteristics, i.e., higher relative density, lower volumetric expansion and electrical resistivity, and higher bending strength. Microstructure evaluation also revealed that the sample formed at 150°C and sintered for 30 min obtained more homogeneous distribution of grains and less interconnected pores compared to the other samples.

Abstract: The strength of a green compacts formed through warm powder compaction route is strongly dependent on the forming load and temperature. As the forming load increases, the powder particles move from its initial position by sliding among them and die wall. This movement results in new arrangement and packing order of the particles. However, due to this movement, pores among the particles are generated that affects the mechanical properties of the green compacts. Having pores in green compacts lead to strain intensification at ligaments between pores during sintering at later stage, hence serve as areas for crack initiation. Therefore, as the powder forming relates directly to the load and temperature, strength to porosity relationship has to be analyzed based on those parameters. This paper presents the effect of porosity to the strength of green compacts formed at different load and temperature (70 kN to 130 kN; 30°C to 200°C). The bending strengths of green compacts are measured while Scanning Electron Microscopy is used for porosity evaluation. It has been found from the results that porosity and strength are related to each other at all forming parameters. In addition, high forming load and temperature give better strength due to porosity reduction.