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The processing, structure and properties of deformed metals and alloys with a structural scale from the micrometer to the nanometer dimensions has been the subject of a recent viewpoint set []. The present paper will focus on deformed metals and alloys with a structural scale from 5 nm to 100 nm, concentrating on materials processed by high pressure torsion (HPT), surface mechanical attrition treatment (SMAT) and sliding. A detailed microstructural characterization has been followed by an analysis of the relationship between structural features and processing parameters. In this analysis, some general approaches have been applied for example scaling of the evolution of the boundary spacing. This analysis is the basis for a brief discussion of the relationship between the microstructural parameters and the strength. [ABSTRACT FROM AUTHOR]

The thermal stability of two-phase (α + γ) lamellar microstructure in Ti-Al-Mo PST (polysynthetically twinned that has single colony) crystals, containing C or Si, was investigated. In addition, the variation of α-phase volume fraction in Ti-Al-Mo-(C,Si) systems was investigated at several temperatures. Ti-46Al-1.5Mo-0.2C and Ti-46Al-1.5Mo-1.0Si alloys did not recrystallized (‘stable’ in this paper) during heat treatments at various heating rates and temperatures. Moreover, the α-phase volume fractions of Ti-46Al-1.5Mo-0.2C and Ti-46Al-1.5Mo-1.0Si alloys which were stable compositions, changed less than those of Ti-47Al and Ti-46Al-1.5Mo alloys which were unstable compositions. The instability of the latter alloys was caused by their relatively higher variation of α-phase volume fraction during heating. Therefore, it is suggested that the variation of α-phase volume fraction is an important factor in controlling the thermal stability of lamellar microstructure. [ABSTRACT FROM AUTHOR]

In this article, the effects of the enhanced solution treatment (EST) and high-temperature pre-precipitation (HTPP) on the microstructures, mechanical properties, and stress corrosion cracking resistance of an Al–Zn–Mg alloy have been investigated. The results indicated that EST and HTPP can substantially affect the microstructures of the alloy. The width of the continuously distributed grain boundary precipitates decreases after the EST, while the continuous grain boundary precipitation changes to a discontinuous precipitation structure after both the EST and HTPP. The yield strength, tensile strength, elongation, and fracture toughness of the specimens after the EST are much higher than those of the specimens only after traditional solution treatment, since the EST substantially decreases the size and volume fraction of the constituents. The stress corrosion cracking resistance of the specimens after both the EST and HTPP has been greatly improved due to the discontinuous distribution, and high Cu and low Mg concentrations of the grain boundary precipitates. [ABSTRACT FROM AUTHOR]

Microstructures of dynamically undercooled (melt spun) Fe-base alloys characterized by a post-dendritic needle-like growth morphology were shown to be essentially identical to those of bulk undercooled samples with Δ T > 190–200 K. Nonequilibrium crystallization is accompanied by the formation of internal stresses and defects which can lead to relaxation processes (polygonization, recrystallization) during the cooling procedure changing the asquenched microstructure. The mechanism and degree of these transformation processes are determined by the level of frozen-in microstresses, the cooling rate in the solid state, and the lattice structure of the alloys. [ABSTRACT FROM AUTHOR]

Room temperature tensile properties of polycrystal Ti–47Al–2Mn–2Nb alloy with near lamellar (NL) microstructures were investigated at the strain rates between 10−5 and 1000 s−1 using a self-designed Split-Hopkinson tensile bar setup with a rotating disk and conventional testing machine. It was found that tensile ductility varies within a narrow range with the strain rate, while dynamic strengths (σd) of the alloy are obviously higher than static strengths (σs). There exists linear relationship between σs and the logarithm of the strain rate (ln έ), and between σd and the strain rate itself (έ). Fractography analysis indicates that the alloy fractures in a mixed mode of predominant transgranular cleavage and minor intergranular cracking under static and dynamic strain rates. Environmental effect is excluded from the main cause for the room temperature brittleness of the investigated alloy. [ABSTRACT FROM AUTHOR]