Dendritic Arm Spacing Affecting Mechanical Properties and Wear Behavior of Al-Sn and Al-Si Alloys Directionally Solidifi
- PDF / 874,916 Bytes
- 13 Pages / 593.972 x 792 pts Page_size
- 94 Downloads / 223 Views
YS of Al-Sn are well known for having excellent tribological and mechanical properties, making this kind of alloy system suitable for engineering applications, particularly in combustion engine pistons and cylinder liners.[1–4] The solid solubility limit of Sn in Al is below 0.09 wt pct Sn (0.02 at. pct Sn). Therefore, Al-Sn alloys having Sn contents higher than 0.09 wt pct are formed by Sn particles spread over a continuous Al-rich matrix. This type of structural morphology determines the good tribological behavior of the alloy, because the tough Al-rich matrix, which is more resistant to high mechanical loads, acts in combination with the Sn particles that function as solid lubricants.[5] KLEBER S. CRUZ, formerly Doctoral Student, Department of Materials Engineering, University of Campinas, UNICAMP, Campinas, SP, Brazil, is with IM2NP, University Paul Ce´zanne Aix-Marseille III, 13397 Marseille Cedex 20, France. ELISANGELA S. MEZA, Department of Mathematics and Statistics, State University of Ponta Grossa, Ponta Grossa, PR, Brazil, is on leave of absence as a Doctoral Student, Department of Materials Engineering, University of Campinas (UNICAMP). FREDERICO A.P. FERNANDES, Doctoral Student, and LUIZ C. CASTELETTI, Professor, are with the Department of Materials, Aeronautical, and Automotive Engineering, University of Sa˜o Paulo, Sa˜o Carlos, SP, Brazil. JOSE´ M.V. QUARESMA, Professor, is with the Federal University of Para´, Bele´m, PA, Brazil. AMAURI GARCIA, Professor, is with the Department of Materials Engineering, UNICAMP, 13083-860 Campinas, SP, Brazil. Contact e-mail: [email protected] Manuscript submitted February 17, 2009. Article published online January 20, 2010 972—VOLUME 41A, APRIL 2010
Alloys of Al-Si provide the most significant part of all shaped castings manufactured. Silicon strongly improves casting properties such as mechanical properties and corrosion resistance. In general, castings varying from 5 to 7 wt pct Si are produced by slow cooling rate processes (sand, plaster, investment), from 7 to 9 wt pct Si by permanent molds and from 8 to 12 wt pct Si by die castings.[6] The Al-Si alloys are also used in engineering components that are supposed to be exposed to critical wear conditions, such as engine parts, pistons, cylinder blocks and heads, water-cooled jackets, etc.[7] The typical hypoeutectic aluminum-silicon alloys have two major microstructural components, namely primary aluminum and an aluminum-silicon eutectic. For metal/nonmetal eutectics, the growth form of the faceting phase (Si) is such as to produce a threedimensional skeletal crystal pattern rather than thin sheets. Although the silicon plates appear to be separate crystals, they are in fact interconnected. The microstructural morphology of materials causes a significant influence on the mechanical behavior of metallic alloys. In the as-cast state, an alloy may possess within individual grains a dendritic network of continuously varying solute content, second phases, and possibly porosity and inclusions, as shown in the schemati
Data Loading...
