Lisa Rodrigue

Nanoindentation Study of Intermetallic Phases in Al-Cu Bimetallic System

Nanoindentation hardness testing device was used to determine the mechanical properties of intermetallic phases in Al-Cu bimetallic system formed by thermal annealing the Al-Cu bimetallic coupon in air at 460degC. The nanoindenation tests were carried out at 200 mN load. The results of nanoindenation tests were found to be somewhat different from those obtained by the Knoop hardness test. Plausible explanations for the observed difference are discussed. Using the Oliver-Pharr method, the nanoindenation data were used to determine the elastic modulus of the intermetallic phases formed.

Nanoscale Mechanical Properties of Intermetallics in Lead-Free Systems

Bimetallic couples formed between commercially available lead-free alloys and selected contact materials were subjected to diffusion annealing using thermal gradients. Following diffusion annealing and aging, the contact interfaces were subjected to a detailed metallographic, scanning electron microscope (SEM), and energy dispersive X-ray (EDX) analyses. In addition, electrical resistance was used for electrical characterization of the intermetallics formed at the contact interfaces, whereas the nanoindentation technique was used to determine the nanoscale mechanical properties. An attempt was made to correlate the observed nanoindentation data with the microstructures of the intermetallic phases formed and electrical resistivity.

Improvement in the Characterization of the 2099 Al-Li Alloy by FE-SEM

This paper describes how state-of-the-art Field-Emission Scanning Electron Microscopy (FE-SEM) can contribute to the characterization of the 2099 aluminum-lithium alloy, and metallic alloys in general. Investigations were carried out on bulk and thinned samples. BSE imaging at 3kV and STEM imaging at 30kV along with highly efficient microanalysis permitted to correlate experimental and expected structures. Although our results confirm previous studies, this work points out possible substitutions of Mg and Zn with Li, Al and Cu in the T1 precipitates. Zinc and magnesium are also present in “rice grain” shaped precipitates at the grain boundaries. The versatility of the FE-SEM is highlighted in that it can provide information at the macro and micro scales with relevant details. Its ability to probe the distribution of precipitates from nano-to micro-sizes throughout the matrix makes Field-Emission Scanning Electron Microscopy a suitable technique for the characterization of metallic alloys.