Title of dissertation: FLEX CRACKING AND TEMPERATUREHUMIDITY-BIAS EFFECTS ON RELIABILITY OF MULTILAYER CERAMIC CAPACITORS Mohammadreza Keimasi, Doctor of Philosophy, 2007 Dissertation directed by: Professor Michael Pecht Department of Mechanical Engineering Multilayer ceramic capacitors (MLCCs) are known to be susceptible to cracking when subjected to excessive printed circuit board (PCB) flexu...

Single-crystal (SX) nickel aluminide alloys have potential for structural applications where hightemperature strength and oxidation resistance are required. In this work, SX deposits of the Ni3Albased IC221W alloy were produced on a SX Ni-base superalloy substrate by means of the laser-engineered net shaping (LENS) process. The microstructure of the deposits was characterized. The effects of pr...

FeCrAl alloys were prepared with TiC additions to act as hydrogen traps and improve resistance to hydrogen cracking. Weldability results showed that alloys with up to 20 wt% Al and 11 wt% Cr could be prepared crack-free with relatively small TiC additions of ~ 4 wt%. Thermogravimetric analysis of Fe-10Al-5Cr corrosion coupons with and without TiC has shown that the corrosion resistance is not s...

High entropy CoCrFeNiCux alloys with a Cu molar ratio of x ≈ 0, 0.5, 1, 1.5 and 2 were arc welded. Solidification cracking occurred in the fusion zones 1 1.5. Cu-rich material was observed around cracks, increasing quantity content. Liquation partially melted zone next to zone, it propagated into as solidification cracking. A recently proposed index for susceptibility tried, i.e., |dT/d(fS)1/2|...

Metallic cast components inevitably contain defects such as shrinkage cavities which are inherent to the solidification process. Those defects are known to significantly alter the fatigue life of components. Yet very little is known, quantitatively, on the dangerosity of internal casting defects compared to surface ones. In this study, fatigue specimens containing controlled internal defects (s...

Cracking is a major concern in welding aluminum alloys. Although weld solidification cracks can be eliminated through the addition of filler metal, the additives modify the alloy or base metal constituents and may not always be desirable. High-energy beam processes, such as electron beam welding, that result in minimal heat input reduce crack sensitivity, but their high cost limits their applic...

The causes of liquation cracking in the heat-affected zone (HAZ) of a cast Mar-M004 superalloy weld were investigated. X-ray diffraction (XRD), electron probe microanalyzer (EPMA), and electron backscatter diffraction (EBSD) were applied to identify the final microconstituents at the solidification boundaries of the cast alloy. Fine borides and lamellar eutectics were present in front of some γ...

The current work was carried out to characterize welding of AISI 310 austenitic stainless steel to Inconel 657 nickel-chromium superalloy. The welds were produced using four types of filler materials; the nickel-based corresponding to Inconel 82, Inconel A, Inconel 617 and austenitic stainless steels 310. Of the two joints involved, this paper describes the choice of welding consumables for the...