Electron Backscatter Diffraction Observations Research Articles

Copper-bearing high-strength low-alloy steels: the influence of microstructure on the initiation and growth of small fatigue cracks : Davidson, D.L., Chan, K.S. and McClung, R.C. Metallurgical and Materials Transactions A (Sept. 1996) 27A, 2540–2556

In this work, the influences of laser shock peening (LSP) on the residual stress state, microstructures and mechanical properties of Ti-6Al-4V alloy fabricated by selective laser melting (SLM) were researched. Particularly, the microstructural evolution before and after LSP was clarified using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) observations. The results showed that the residual stress was adjusted from tensile to compressive state. Furthermore, high-density dislocations and a great number of parallel nano mechanical twins (nano-MTs) were promoted in the coarse lamellar α' structures, contributing to the grain refinement. The ultimate tensile strength and elongation of the SLM-manufactured (SLMed) Ti-6Al-4V alloy increased by approximately 14.3% and 18.3% after LSP treatment, respectively. Finally, the dominant mechanism of tensile property enhancement by LSP was revealed. High levels of compressive residual stress and grain refinement of the α' structures induced by LSP realized the excellent combination of strength and ductility.

The Officers Reserve Corps.—General Orders No. 32. Issued by War Department. (Abstracts.)

Electron backscatter diffraction (EBSD) was used to examine the microstructural evolution in a one-step thermomechanically processed 304 austenitic stainless steel specimen during the thermomechanical process of grain boundary engineering. Solution-treated materials were cold-rolled to 3% reduction and subsequently annealed at 1220 K for different annealing times. The EBSD observation of the specimen showed an increase in the frequency of coincident site lattice (CSL) boundaries and a decrease in the percolation probability of random boundaries. Additionally, the specimen exhibited heterogeneous growth of clusters of grains that contained a high frequency of CSL boundaries. These clusters of grains were developed in the entire observed area by strain-induced grain growth according to the results of grain orientation spread analysis. The details of the growth of the clusters and the disconnection of random boundaries were successfully observed in situ using EBSD and a heating stage. The frequency of CSL boundaries increased with the growth of the clusters. Disconnection of random boundaries between the clusters was achieved by the formation of annealing twins through the impingement of the growing clusters during the thermomechanical process. Twin variant selection to introduce CSL boundaries into a random boundary network was observed by the in situ EBSD observation.