Volume 46, Issue 9

Optical metallography and electron metallography (SEM and TEM) techniques are applied to the characterization of additive-layer manufactured products and prototypes by electron beam melting (EBM) of Ti-6Al-4V atomized precursor powder. In addition, microstructure-property comparisons are made by hardness and tensile test measurements which demonstrate prospects for controlled property-performance variations by varying process parameters including temperature profiles and cooling rates in manufactured prototypes.

The purpose of the research was to illustrate a reconstruction of grains in case of selected cross-section of a precision cast turbine blade made of MAR M247 polycrystalline nickel-base superalloy using electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM) and standard methods of quantitative metallography using imaging with light microscopy. The results of measurement of the grains performed using both methods were compared with each other with the help of a statistical test.

Samples of annealed and cold rolled 70%Cu-30%Zn brass and 800H alloy were characterized using electron backscatter diffraction (EBSD) pattern analysis to determine average grain diameter, with the ability to differentiate between random high angle grain boundaries and annealing twin boundaries. Hardness measurements of both materials and minimum creep rates for the brass alloy were measured and compared to average grain diameter measurements, which had been calculated with twin boundaries both included and excluded (in accord with ASTM E 112). The present results indicate that annealing twin boundaries contribute to mechanical properties and therefore should be considered in structure-property correlations.

A new methodology, co-site microscopy, is presented and discussed through a set of case studies. Images from the same field, or set of fields, of a sample are acquired with different microscopy techniques, or from the same microscope in diverse contrast modes and/or sample conditions. The obtained data is assembled in a multi-modal database that provides better statistical accuracy than traditional quantitative metallography approaches, while tracking local changes in the sample. Case studies on automotive catalysts, a copper ore, and a cast iron are presented and discussed.