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Presents a statistical analysis of the evolution of polygranular segment lengths during high-temperature annealing of Al(Cu) thin-film interconnects with quasi-bamboo microstructures. Preparation of the samples; Microstructural modification by post-pattern annealing; Distribution of longest polygranular segments.

A study was carried out to observe a heat-affected zone (HAZ) in a deformed Fe–Cr–Ni system containing α[sup ′] martensite using high-T[sub c] superconducting quantum interference device (SQUID) microscopy. Microstructure and remanent magnetization images were studied by an optical microscope and a SQUID microscope, respectively. The HAZ, in which only the face-centered-cubic austenite phase exists, could be visualized by the SQUID microscope. It was also found that the SQUID images were consistent with the results from the microstructural analysis. It was concluded that a simple SQUID measurement may serve as an effective method for a nondestructive evaluation of ferromagnetic steel phases by correlating remanent magnetization images to microstructural characteristics. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The article discusses the developments of microstructure and brittle failure of steels in the generation of structural steels which is the workhorse of infrastructure. Researchers have focused on thermal or thermomechanical processes that produce desirable microstructures in low-alloy steels or combine alloying and thermomechanical treatments to achieve high strength and toughness. Stronger and tougher steels are needed to reduce weight and improve safety in transportation, enhance architectural flexibility in construction, and improve performance in heavy machinery. The Yoffee diagram suggests two ways to suppress the ductile-brittle transition by raising the brittle fracture stress and lowering the effective yield stress.

Recent experimental studies of the microstructure of dislocated martensite in low-carbon steel have shown that its superficially complex microstructure is, in fact, a simple hierarchical pattern whose basic element is a composite block containing two Kurdjumov-Sachs variants of the α' phase that share the same Bain axis. The blocks are plates with interfaces generally parallel to {011}α planes that can be stacked into four crystallographically distinguishable packets. When the prior austenite grain contains all four packets its transformation can be a simple dilatation that involves no net shear. In the present paper we use the crystallographic theory of dislocated martensite to show that the stackable composite martensite plate is the simplest transformed plate that can be constructed that preserves a close-packed plane ({011}α||{111}&#947) and has an invariant {111}&#947 habit plane, as the experimental results require. The 12 distinct variants of this plate can be configured into a microstructure that duplicates the patterns and pole figures found experimentally. The results suggest that there is no single-variant martensite plate that can be stacked in this way without substantial strain, though the theory does predict the single-variant plates with {557}α habit planes and Greninger-Troiano orientation relations that are found in alloys with large fractions of retained austenite. [ABSTRACT FROM AUTHOR]