Abstract

The effect of holmium addition to the Al-Si system has been experimentally studied, as the isothermal section at 500?C. The constitution of the alloys has been determined by means of scanning electron microscopy (SEM), electron microprobe analysis (EDXS) and X-ray powder diffraction. The knowledge of the phase relationships in the R-Al-Si ternary systems (R: rare earths element) is essential to deeply understand the technological properties of the Al-Si based alloys, that are useful in different industrial fields. In the system investigated have been identify nineteen ternary fields and twelve two phase fields. Three ternary compounds have been found in this ternary section: τ2-Ho2Al3Si2 (mS14-Y2Al3Si2), τ4-Ho2AlSi2 (oI10-W2CoB2) and τ5-Ho6Al3Si (tI80-Tb6Al3Si). The results obtained can be useful compared with the other known R-Al-Si systems also for predictive purposes.

Highlights

  • The Al-Si alloys, both in the as cast and after thermal treatment conditions, have been recognized as interesting materials for the industries

  • The knowledge of the phase relationships in the R-Al-Si ternary systems (R: rare earths element) is essential to deeply understand the technological properties of the Al-Si based alloys, that are useful in different industrial fields

  • 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)

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Summary

Introduction

The Al-Si alloys, both in the as cast and after thermal treatment conditions, have been recognized as interesting materials for the industries (e.g. 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 weld ability, high wear resistance and temperature strength, good corrosion re-. 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, especially in planning and develop new materials. Taking into account the aforementioned considerations, investigations of a number of R-Al-Si systems have been carried out by our research group

Boundary Binary Systems
R-Al-Si Ternary Systems
Experimental Techniques
Results and Discussion
Ternary Isothermal Section
Ternary Compounds
Binary Compounds

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