Aluminum Copper Alloy
MSCI 300 – Thermodynamics of Materials
Alexandre de Freitas Silveira
December 18th, 2012.
Abstract: At this experiment, the composition of an alloy of Aluminum Copper was analyzed via X-Ray Fluorescence. From this, it was possible to construct a phase diagram a make some predictions about the possible phases presents at considering the 3 samples used in this experiment, the samples prepared at this experiment the sample as delivered was analyzed without any kind of treatment (sample I), the sample with slow cool was prepared melting the bulk material at a heater an letting it cools at the heater at a slow rate (sample II), finally, the sample with quick cool was made melting the bulk material and then slow cooled as the sample II, after this the sample was melted again and quickly cooled using liquid nitrogen (sample III). Those samples were analyzed by Scanning Electronic Microscopy to characterize the composition, as well as see the pattern of phases in the alloy.
Keywords: Aluminum Copper, Phase Diagram, Cooling rate, SEM, XRF.
The microstructure of the material plays a fundamental role at the mechanical properties. Thus, the comprehension of phase diagrams for system is very important. Besides, phase diagrams provide important information regarding the melting, casting, crystallization and other information .
1) Binary Systems with Partial Solid Solubility
This is the case of the alloy Aluminum and Copper, which solute atoms of another metal can be dissolved in the solvent in a solid state. In such diagrams, three single phase regions are found on the diagram: α, β, and liquid. The α phase, a solid solution rich in an atom, has also B atoms as the solute component. The β phase, a solid solution rich in B atoms, has A as the solute. Also, there are three two-phase regions found for the system: The α + L, β + L and α + β phases .
2) Principles of Scanning Electronic Microscopy (SEM)
A very thin electron beam is used to scan the sample. When the beam reaches the sample surface electron is emitted and those are responsible to form the image. The differences in the surface of the sample affect the pattern with which the electrons are scattered from this. Holes or cracks appear dark lumps and bumps appear clear, resulting in an image that seems to be three-dimensional . The great advantage of this instrument is the high depth of field, the order of 10 µm for increases about of 10,000X. Also the possibilities of combining microstructural analysis with chemical microanalysis are factors that greatly contribute to the widespread use of this technique .
3) Principles of X-Ray Fluorescence (XRF)
The basic principle for the XRF is based on the fact the materials can become ionized when they are excited with high-energy (X-rays for instance). When this primary X-ray beam excites the sample turn emits X-rays along a spectrum of wavelengths characteristic of the types of atoms present in the sample, the emitted X-rays indicate the type of atom present .
There were three different samples: as delivered (I), quickly cooled (II) and heated next to the melting point with slowly cooled (III) using a heater. Sample II was heated and rapidly cooled using liquid nitrogen. Sample III was slowly heated and then slowly cooled, both samples II and III were melted to clean the thermal historic and avoid unknown previous features on the samples.
The sectioning was used to produce samples for the XRF and for the initial melting process that was performed to clean the thermal historic of the samples. For obtaining the samples for the XRF and for the first melting, the bulk sample was cut manually using a saw. However, for the preparation of the samples for the metallography analysis the samples was cut using a cutoff machine, the samples that was cut at the cutoff machine were...