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The Effect of Warm Multi -directional Forging on Microstructure and Strength of 2024 Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Kazeminezhad, Mohsen (Supervisor)
Abstract
The 2024 aluminum alloy is deformed by two passes of multi-directional forging at room temperature, 180 oC, 250 oC, 320 oC and 380 oC with initial state of solid solution. Microstructure, mechanical properties and the state of precipitates are investigated via optical and scanning electron microscopies, hardness test, shear punch test and differential scanning calorimetry. Fragmentation and distribution of the precipitates are observed after straining at different temperatures. Dynamic precipitation of GPB zones at room temperature and 180 oC are studied by DSC analysis. The increase of both hardness and strength and the formation of shear bands are related to the presence of GPB zones....
Nanoparticle enhanced solders for increased solder reliability
, Article Materials Research Society Symposium Proceedings, 28 November 2011 through 2 December 2011, Boston, MA ; Volume 1424 , 2012 , Pages 115-120 ; 02729172 (ISSN) ; 9781605114019 (ISBN) ; Roshanghias, A ; Ashayer, R ; Kotadia, H. R ; Khomamizadeh, F ; Kokabi, A.H ; Clode, M. P ; Miodownik, M ; Mannan, S. H ; Sharif University of Technology
2012
Abstract
Due to environmental concerns traditional eutectic tin-lead solder is gradually being replaced in electronic assemblies by "lead-free" solders. During this transition, nanoparticle technology is also being investigated to see whether improvements in joint reliability for high temperature applications can be made. Nanoparticles can be used to harden the solder via Zener pinning of the grain boundaries and reduce fatigue failure. This paper explores the effects of adding Silica nanoparticles to SnAgCu solder, and how the mechanical properties induced in the solder vary with temperature. It is found that above 100°C the mechanical response and microstructure of the normal and nanoparticle...
Disabling of nanoparticle effects at increased temperature in nanocomposite solders
, Article Journal of Electronic Materials ; Volume 41, Issue 7 , 2012 , Pages 1907-1914 ; 03615235 (ISSN) ; Roshanghias, A ; Ashayer, R ; Kotadia, H. R ; Khomamizadeh, F ; Kokabi, A. H ; Clode, M. P ; Miodownik, M ; Mannan, S. H ; Sharif University of Technology
2012
Abstract
The use of nanoparticles to control grain size and mechanical properties of solder alloys at high homologous temperature is explored. It is found that silica nanoparticles in the 100 nm range coated with 2 nm to 3 nm of gold can be dispersed within solders during the normal reflow soldering process, and that these particles are effective in hardening the solder and restricting dynamic grain growth during compression testing at low homologous temperature. As the homologous temperature increases towards 0.75, the effects of the nanoparticles on both mechanical properties and dynamical grain growth reduce, and by homologous temperatures of 0.86 the effects have completely disappeared. This...