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Different formation routes of pore structure in aluminum powder metallurgy alloy
Get PDFIn powder metallurgy (PM), severe plastic deformation (SPD) is a well-known technological solution to achieve interesting properties. However, the occurrence of pores in the final product may limit these properties. Also, for a given type of microstructure, the stereometric parameters of the pore structures, such as shape (represented by Aspect and Dcircle) and distribution (fshape, and fcircle), decisively affect the final properties. The influence of different processing routes (pressing, sintering and equal channel angular pressing (ECAP)) on pore structures in an aluminum PMalloy is discussed. The nature of porosity, porosity evolution and its behavior is explored. The correlation between pore size and morphology is also considered. The final pore structure parameters (Aspect, Dcircle, fshape, and fcircle) of studied aluminum alloys produced by different processing routes depends on the different formation routes
The Porosity Evaluation during ECAP in Aluminium PM Alloy
No full textThe main aim of this paper is to show porosity evolution during application of various processing conditions including pressing, sintering and equal channel angular pressure. An aluminium based powder (AlMgSiCuFe) was used as investigated material. After applying dierent pressing pressures (400 and 600 MPa), specimens were dewaxed in a ventilated furnace at 400◦C for 60 min. Sintering was carried out in a vacuum furnace at 610◦C for
30 min. The specimens were processed by single equal channel angular pressure pass. A signicant disadvantage of powder metallurgy processing methods is the presence of porosity. Pores act as crack initiators and, due to
their presence, the distribution of stress is inhomogeneous across the cross-section and leads to reduction of the effective load bearing area. The equal channel angular pressure process, causing stress distribution in deformed
specimens, made the powder particles to squeeze together to such an extent that the initially interconnected pores transform to small isolated pores. The proposed safety diagram includes the combined effect of stress and strain behaviour during equal channel angular pressure. The safety line eliminates and quanties the effect of large pores as a potential fracture initiation sites with respect to the mechanical viewpoint
Wear Resistance of chromium pre-alloyed sintered steels
No full textThis paper deals with the influence of the processing conditions on the material properties and wear characteristics of chromium pre-alloyed sintered steels. Three different processing conditions were used, involving different cooling rates from the sintering temperatures of 1180°C and 1240°C. A conventional (slow) cooling condition and a new progressive condition, siinter hardening, were examined. The results showed that the typical microstructure characteristics of sintered steels represent an important parameter affecting their wear behaviour
Investigation of Fracture Surfaces of Soft Magnetic Materials
No full textThe present paper focused on the analysis of the fracture surfaces of a new development insulated iron powder compound with the addition of the aluminium alloy in order to improve the mechanical properties. Results show that in the pressed state, mainly pores act as crack initiators and due to their presence the distribution of stress is inhomogeneous across the cross-section and leads to the reduction of the effective load bearing area. Investigation of fracture surfaces concluded that improvements in bonding during the pressing process and heat treatment can be helpful in the development of soft magnetic materials to give a suitable combination between pressing pressure, annealing temperature and time as well as magnetic properties
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