The Al-Si alloys, both in the as cast and after thermal treatment conditions, have been recognized as interesting materials for the industries (eg automotive, heat exchanger, etc). The addition of a rare earth element, at a very low concentration, can modify the property of the alloys, improving some useful characters as low density and thermal expansion coefficients, good casting performance and weldability, high wear resistance and temperature strength, good corrosion resistance [1-4]. All of the above leads to an increasing interest in the study of R-Al-Si based alloys (R being a trivalent rare earth element). The knowledge of the phase equilibria and the transformations that take place during the solidification pathway of foundry aluminum based alloys are crucial, expecially in planning and develop new materials. The industrially relevant R-Al-Si alloys have usually a concentration lying near the binary Al-Si eutectic composition and mischmetal (alloy of rare earth metals, whose typical composition includes approximately 50% Ce, 25% La and smaller small amounts of Nd and Pr) is often added. 

Moreover, owing to the definition of pseudo-lanthanide [5] it is possible to predict the behavior of an intermetallic phase not prepared yet, when experimental data are available for the adjacent members of this series. Taking into account the aforementioned considerations, investigations of a number of R-Al-Si systems have been carried out by our research group. 

To our best effort literature data on R-Al-Si systems isothermal sections (in the whole range of concentrations) and liquidus projections mainly deal with the following, reported in figure 1 and figure 2 respectively: La-Al-Si (0-33at%La) [6], Ce-Al-Si [7], Pr-Al-Si [8,9], Nd-Al-Si [9], Sm-Al-Si [9 and refs therein,10], Eu-Al-Si [11], Gd-Al-Si, Al-Si-Tb and Al-Si-Dy [9 and refs therein], Ho-Al-Si (0-33 at%Ho) [12], Er-Al-Si [13] and Y-Al-Si (0-33 at% Y) [14]. In this work will be presented the results obtained in the experimental study of the whole Ho-Al-Si isothermal section at 500°C, in comparison with the R-Al-Si systems previously studied (R: Pr, Nd, Sm, Eu, Gd, Tb ,Dy and Er as concern the isothermal sections; Pr, Nd and Sm as concern the liquidus projections in the Al rich corner). The experimental techniques used have been scanning electron microscopy (SEM), electron microprobe analysis (EDXS), X-ray powder diffraction (PXRD) and differential thermal analysis (DTA). 

By comparing the different ternary isothermal sections, fig.1, some points can be highlighted. All the sections are characterized by the presence of intermediate phases with R content up to 60 at% rare earth. The number of phases decreases on going from the light (Pr, Nd, Sm) to the heavy rare earths (Gd, Tb, Dy, Er). Only the RAl2Si2 compounds form along the whole lanthanides series and these phases are point compounds. At low R content the three-phase equilibrium: (Al) / (Si) / RAl2Si2, common to all the R-Al-Si ternary systems, occurs. Many R-Si and R-Al compounds extend in the ternary system forming solid solutions at a constant R-content. 

As the liquid projections in figure 2, the investigated systems (R= Pr, Nd, Sm) show the Al-rich ternary eutectic equilibrium L (Al) + (Si)+ RAl2Si2 at the temperatures: Pr- 567°C, Nd- 561°C, Sm- 567°C. Near the boundary R-Al binary systems, the primary crystallization regions, common to these systems, are (Al), (Si), RAl2Si2 and RAlSi. Moreover, further primary crystallization regions have been found for R= Pr and Sm (SmAl3 and Pr3Al11 respectively).

Borned in Genova in 1962, degree in chemistry in 1987 at the Genova University, Phd in chemistry in 1991. Researcher at the University of Genova -Department of Chemistry and Industrial Chemistry- since 1992. Member of the Italian Chemical Society. The research fields of interest are: phase equilibria and thermodynamic properties of metallic alloys, in binary and ternary systems formed by rare earth elements, with metals as Al, Mg, Cu, Mn, Si, Zn. The research activity mainly pertains the effects of a rare earth addition on the properties of binary light alloys, as Al-Si, focusing both on the phase diagram of the ternary system and on the correlation between thermodynamic technologically interesting properties. Experimental measurements of the enthalpy of formation at 300K of binary and ternary alloys and intermetallic compounds, particularly according to the following reaction in the solid state: (1-x)RE(s) + xAl(s) RE(1-x)Alx(s) . 

More recently she has undertaken the study of possible chemical and biochemical methods for the recovery of precious metals and rare earths from waste, with particular attention to electronic waste. The experimental techniques used are: direct calorimetry, differential thermal analysis, thermogravimetric analysis, X-ray diffraction, optical and scanning electron microscopy. Furthermore another area in which she is involved regards some spread of science activities.