Effect of Rolling Temperature on the Structural Refinement and Mechanical Properties of Dual-Phase Heterostructured Low-Carbon Steel

Warm rolling at temperatures ranging from 25 °C to 500 °C was conducted on the dual-phase heterostructured low-carbon steel to investigate the effect of deformation temperature on the structural refinement and mechanical properties. Defying our intuition, the grain size and strength of the rolled steels do not deteriorate with the increase in deformation temperature. Warm rolling at 300 °C produces a much finer lamellar structure and higher strength than steels rolled at both room temperature and elevated temperature. It is supposed that the enhanced interactions between carbon atoms and defects (interfaces and dislocations) at 300 °C promote dislocation accumulation and stabilize the nanostructure, thus helping with producing an extremely finer structure and higher strength than other temperatures.

Development of a Novel Low-Silver Cu-P Brazing Filler Metal Bearing Sn

The flame brazing of H62 brass using a novel, low-silver Cu-P brazing filler metal was investigated in this study. The effect of the addition of a trace amount of Sn on the microstructure and properties of Cu-7P-1Ag filler metals was analyzed by means of X-ray diffractometer, scanning electron microscopy and energy dispersive spectrometer. The addition of trace Sn led to a decrease in the solidus and liquidus temperatures of Cu-7P-1Ag filler metals. Meanwhile, the spreading performance of the filler metals on a H62 brass substrate was improved. The microstructure of the low-silver, Cu-P brazing filler metal was mainly composed of α-Ag solid solution, α-Cu solid solution and Cu3P; an increase of Sn content led to the transformation of the microstructure of the joints from a block to a lamellar structure. When the Sn content was 0.5 wt. %, the shear strength of the joint at room temperature reached 348 MPa, and the fracture morphologies changed from a cleavage to a quasi-cleavage structure.

Особенности фазового состава и структуры доэвтектоидной стали, проявляющиеся в поведении намагниченности вблизи магнитного насыщения

Investigation of the temperature evolution of magnetization curves near magnetic saturation makes it possible to extract new information on the features of the phase composition and structure of hypoeutectoid steel. It is shown that the main contribution to the magnitude and the temperature behavior of the energy density of the local magnetic anisotropy of hypoeutectoid steel is due to the lamellar structure of pearlite. The peculiarity of the temperature behavior of the energy of the magnetic anisotropy, along with the behavior of the paraprocess, indicates the formation of Mn-substituted cementite in the studied steel sample. The observation of the crossover of power-law regularities in the approximation of magnetization to saturation indicates the formation of two-dimensional nano-inhomogeneities of the local axis of easy magnetization in the plates of alpha iron, which are part of the pearlite.

Characterization of the Naked Mole Rat Incisors: Chemical Composition, Microstructure and Mechanical Properties

The naked mole rat incisors (NMRI) exhibit excellent mechanical properties, which makes it a good prototype for design and fabrication of bionic mechanical systems and materials. In this work, we characterized the chemical composition, microstructure and mechanical properties of NMRI, and further compared these properties with the laboratory rat incisors (LRI). We found that (1) Enamel and dentin are composed of organic matter, inorganic matter and water. The ratio of Ca/P in NMRI enamel is higher than that of LRI enamel. (2) The dentin has a porous structure. The enamel has a three-dimensional reticular structure, which is more complex, regular and denser than the lamellar structure of LRI enamel. (3) Enamel has anisotropy. Its longitudinal nano-hardness is greater than that of transverse nano-hardness, and both of them are higher than that of LRI enamel. Their nano-hardness and elastic modulus increase with the increment of distance from the enamel-dentin boundary. The nano-hardness of dentin is smaller than that of enamel. The chemical composition and microstructure are considered to be the reasons for the excellent properties of NMRI. The chemical composition and unique microstructure can provide inspiration and guidelines for the design of bionic machinery and materials.

Microstructural Evolution and Tensile Testing of a Bi–Sn (57/43) Alloy Processed by Tube High-Pressure Shearing

Tube high-pressure shearing (t-HPS) processing was performed on a eutectic Bi–Sn (57/43) alloy for 0.25, 1, 5 and 20 turns. The selected samples were stored at room temperature for up to 56 days to examine the strain weakening and self-annealing behavior of the alloy. The results showed that t-HPS processing gradually refined the microstructure and led to decreasing of microhardness, but microhardness increased slowly during the subsequent storage at room temperature. Shear localization of the eutectic structure during t-HPS processing was observed as large amounts of narrow dense lamellar zones were visible in the deformed microstructures. The Bi–Sn (57/43) alloy processed by t-HPS exhibited significantly enhanced superplastic properties with elongations up to >1800% in a sample after t-HPS processing for 20 turns. This high elongation is attributed to the breaking of the lamellar structure and the very small grain size.

Dissimilar Brazing of Ti–15Mo–5Zr–3Al and Commercially Pure Titanium Using Ti–Cu–Ni Foil

Dissimilar brazing of Ti–15Mo–5Zr–3Al (Ti-1553) to commercially pure titanium (CP-Ti) using Ti–15Cu–15Ni foil was performed in this work. The microstructures in different sites of the brazed joint showed distinct morphologies, which resulted from the distributions of Mo, Cu, and Ni. In the brazed zone adhered to the Ti-1553 substrate, the partitioning of Mo from the Ti-1553 into the molten braze caused the formation of stabilized β-Ti without Ti2Cu/Ti2Ni precipitates. In the CP-Ti side, the brazed joint displayed a predominantly lamellar structure, composed of the elongated primary α-Ti and β-transformed eutectoid. The decrease in the Mo concentration in the brazed zone caused the eutectoid transformation of β-Ti to Ti2Cu + α-Ti in that zone. The diffusion of Cu and Ni from the molten braze into the CP-Ti accounted for the precipitation of Ti2Cu/Ti2Ni in the transformed zone therein. The variation in the shear strength of the joints was related to the amount and distribution of brittle Ti2Ni compounds. Prolonging the brazing time, the wider transformed zone, consisting of coarse elongated CP-Ti interspersed with sparse Ti2Ni precipitates, was responsible for the improved shear strength of the joint.