Different formation routes of pore structure in aluminum powder metallurgy alloy

In 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

Innovative Soft Magnetic Composite Materials: Evaluation of magnetic and mechanical properties

Electrical machines cover a very wide range of applications in many industrials sectors and the research to improve the performance of those applications is recently leading to the development of new solutions. Those devices are generally equipped with magnetic circuits made of laminated ferromagnetic steel, but in the last decade, new magnetic materials have been developed to realisemagnetic circuits: SoftMagnetic Composites (SMC). The Authors have investigated SMCs with organic layer obtained through the adoption of phenolic and epoxy resins; in previous research activities several mixture compositions have been produced and analysed with different percentages of binder and compacting pressures. Promising results regarding magnetic and mechanical performances have been obtained using a very low binder content. The paper aims to investigate the lower limit of the binder to be used, still keeping good mechanical properties. Appropriate magnetic tests have been performed on toroidal specimens: good magnetic characteristics have been obtained, maintaining on the other side proper mechanical strengt

Influence of cryorolling on properties of L-PBF 316l stainless steel tested at 298K and 77K

The goal of the present work is to evaluate mechanical properties and to analyse the microstructure of 316L stainless steel produced by Laser Powder Bed Fusion (L-PBF) follow by rolling with different thickness reduction under ambient and cryogenic conditions. The samples before rolling were heat treated. The static tensile test was realized at ambient and cryogenic (77K) conditions. The L-PBF powder metal production technology approved that is a key technology in the additive manufacturing (AM) area, especially for metal powder materials. Mechanical properties tested at 298K and 77K shows that the application of various thermo-deformation rolling conditions increases of strength properties. Achieved mechanical properties are comparable to conventional bulk materials. The strength properties after the rolling under ambient and cryogenic conditions were significantly increased

The Study of Local Effect of Manganese on Microstructure Development of Admixed Fe-Mn-C Sintered Steels

The present paper is focused on the effect of manganese on microstructure development of admixed Fe-Mn-C sintered steels along with diffusion characteristics of manganese in the iron matrix. Admixed systems were prepared on the base of sponge iron powder, with addition of 0.3% C and 3% Mn added as ferromanganese. Sintering at 1,023, 1,173, 1,323, 1,423 and 1,473 K for 180 s was carried out in laboratory tube furnace in an atmosphere of pure gases mixture 25% N-2 + 75% H-2 with the dew point of 243 K. The results show that admixed sintered manganese steels exhibit heterogeneity of microstructure due to the local chemical heterogeneities of these materials, in particular for those areas with a high manganese concentration. On the basis of calculation of manganese apparent diffusion coefficient and penetration depth, results reveal that diffusion-induced grain boundary migration (DIGM) is the dominant alloying mechanism in sintered manganese steels

Correlation between Microstructure/Fracture Surfaces and Material Properties

The present paper deals with the evaluation of the eect of different vacuum heat treatments on the microstructure and fracture surfaces of a low alloyed sintered Fe[1.5Cr0.2Mo]0.6C steel, in correlation with the mechanical and plastic properties achieved. The heat treatment consists of the sintering process in vacuum furnace at 1393 K for 1800 s, followed by different cooling conditions and an integrated final tempering at 473 K for 3600 s. The average cooling rates, calculated in the range of 1393 K to 673 K, were 0.1, 0.235, 3, and 6 K/s, respectively. Vacuum heat treatment is supporting the bainitic-martensitic microstructure, the higher the faster cooling rate applied. This provides a marked increase in strength coupled to a decrease in ductility. The decrease of the impact energy after heat treatment is justied by the microstructural changes, especially if a part of bainite is converted to brittle martensite. Samples with bainitic microstructure presented higher impact energies than those with martensitic microstructure. This is fully confirmed by the fracture surface analysis at higher magnication, revealing three main micromechanisms of fracture: brittle, ductile and quasi-cleavage