**9. References**

274 Mechanical Engineering

SiCp/AZ61 composite has good flow property, and can be used to form complicated

(a) Traditional forging workpiece (b) Thixo-forging workpiece

The microstructural structures of magnesium matrix composite were studied in three different casting processes. The results indicated that SiCp/AZ61 composites fabricated in stirring melt casting process, compared to those in fully liquid stirring casting process and in semi-solid stirring casting process, possessed fairly uniform distribution of SiC particulates and few porosity rate. It was an ideal metal matrix composites fabricated

Under the experimental conditions, the optimum processing plan of SiCp/AZ61 composites fabricated by a stirring melt casting method were the volume fraction of SiC particles 6%, stirring temperature 595℃ and stirring time 5 min. In addition, the effects of volume fraction of SiC particles on the mechanical properties of SiCp/AZ61 composites was the most important among three factors (volume fraction of SiC particles, stirring temperature and

Semi-solid isothermal heat treatment technology was used for the partial remelting of SiCp/AZ61 composites. A fine semi-solid microstructure was obtained, whose equal-area diameter size was between 60µm and 85µm, and the effective liquid volume fraction was about 31%~38%. The optimal technological parameters of SiCp/AZ61 composites were the reheating temperature of 595℃~600℃ and an isothermal holding time of 30min~60min.

Compression tests on semi-solid SiCp/AZ61 magnesium matrix composites were carried out. Influences of strain-rate, strain, temperature and volume fraction of SiC particles on flow stress were analyzed. The results show that the flow stress of semi-solid SiCp/AZ61 composites is sensitive to temperature and strain rate. Meanwhile the flow stress increases

The influence of deformation temperature, strain rate, strain, liquid volume fraction, volume fraction of reinforcement on flow stress in composites thixotropic plastic deformation process was considered. A new constitutive model of composites in thixotropic plastic

Fig. 26. Traditional forging and thixo-forging workpieces of composite

stirring time), the second were stirring time and stirring temperature.

with the increasing of the volume fraction of SiC particles.

workpiece.

**7. Conclusions** 

process.


**12** 

*Argentina* 

**Development of a Winding Mechanism for** 

Marcelo Ruben Pagnola1 and Rodrigo Ezequiel Katabian2

*1Universidad de Buenos Aires, Facultad de Ingeniería,* 

*2Universidad de Buenos Aires, Facultad de Ingeniería,* 

*INTECIN (UBA-CONICET)* 

*Laboratorio de Sólidos Amorfos (LSA)* 

*Departamento de Ingeniería Mecánica* 

**Amorphous Ribbon Used in Transformer Cores** 

In recent years, the application range of available soft magnetic materials has increased significantly due to the development of amorphous and nano-crystalized systems. Certain ferromagnetic alloys can be obtained as vitreous phases by rapid quenching techniques; some of them partially crystallize by certain heat treatments achieving structures composed by 10 to 40 nanometre long grains surrounded by a vitreous phase. One of these rapid quenching techniques is the melt-spinning, from which it is obtained amorphous metal

The later-use of the wound rolls is the conformation of electric transformer cores showing meaningful improvement in its overall outputs, as well as an increment in the efficiency and fewer environmental impacts. In the past, these cores have been produced with grainoriented and non-grain-oriented silicon steel sheets, ferrite sheets, Ni-Fe and Co-Fe alloys sheets produced by conventional casting processes, which require several mechanical and thermal processes, which some of them, have a high cost (Gelinas, 2000). The fabrication of nano-structured magnetic packages can be done, in this particular case, by the directemployment of melt-spinning´s strips into different kinds of heat treatments, where it can also be adjusted the hysteresis cycle. Furthermore, its uses can be extended to complex geometries introducing a milling stage after the melt-spinning process, obtaining refined elemental powder particles (Nowacki, 2006; Byoung et al., 2007), which its dimensions can be modified by the control of the milling stage time (Dobrzanskia et al, 2004). The connotations of using soft magnetic alloys affect not only transformer cores but also AC motors (Pagnola et al., 2009; Pagnola, 2009). These new amorphous and nano-crystalized materials are currently sold up to 3 times the price of conventional materials (Condes, 2008). Magnetic cores lose energy through two independent mechanisms: hysteresis (dissipated energy during the re-orientation cycle of magnetic domains) and Foucault current (eddy or parasitic current). These losses can rise up to 5% and 15% of the entire produced energy, which fluctuates over the manufacturing technique employed. Own research and other authors confirm that these losses can be reduced almost 80 % from those that appear in

**1. Introduction** 

strips that are, later, wound up into rolls.

