Properties Of Compressible Flow Research Articles

An evidence of pseudo-elasticity in a caliber rolled Ti[sbnd]6Al[sbnd]4V alloy and its effect on tension-compression flow asymmetry

The tensile and compressive flow properties, microstructure evolution and fracture behavior at room temperature were investigated in a Ti6Al4V alloy, caliber rolled at 750 °C. While pseudo-elastic behavior is exhibited in compression test, the same is not exhibited in the tension test. Pseudo-elasticity is ascribed to the formation of twins and martensite, which also cause a deep and elongated dimple fracture, unlike the conventional dimple fracture in tension. Electron back scatter diffraction studies reveal texture evolution in the compression test but not in the tension test. The tension-compression flow asymmetry and fracture behavior are thus attributed to the difference in microstructure and texture evolution in the two modes of deformation.

Effect of Solid Die Equi-Channel Pressing Angle on β-Mg17Al12 Phase Morphology and Mechanical Behavior of AZ80 Mg alloy

The effects of die channel angle (Φ) in hot (~623 K) equi-channel angular pressing (ECAP) on microstructure, and tensile and compressive flow properties of AZ80 Mg alloy were investigated. Two solid ECAP dies, having Φ of (1) dual 60° and 120° in a single die and (2) 90° in another die, were designed for this purpose. Grain refinement with more than 40% reduction in average grain size along with submicron size second-phase β-precipitates was achieved after single-pass ECAP. A great variation in β-Mg17Al12 phase morphology with increasing flow stresses in tension and compression are found with decreasing value of angle Φ. There found an increasing effect on strain to failure with decrease in porosity and second-phase precipitate modification. However, there appears flow asymmetry between tension and compression with the latter exhibiting greater flow stress and strain to failure.

Grain Growth and β-Mg17Al12 Intermetallic Phase Dissolution During Heat Treatment and Its Impact on Deformation Behavior of AZ80 Mg-Alloy

Microstructure evolution after solutionizing and ageing treatment of cast AZ80 Mg alloy were investigated using optical and scanning electron microscopy. Effect of these treatments on grain size, β-Mg17Al12 intermetallic phase, mechanical behavior, and flow asymmetry were investigated. The initial continuous network of β-phase found to be reduced after solutionizing. The dissolution of β-phase and simultaneous grain growth are found to be interrelated. Mechanical properties including yield strength, maximum strength (ultimate compressive strength), and maximum strain attainable in compressive found almost twice than the corresponding values obtained in tension. The asymmetry in compressive and tensile properties is found to decrease with grain size at certain solutionizing duration. Particular heat treatment found to offer best combination of tensile compressive flow properties in AZ80 Mg alloy. Aging under certain conditions found to minimize the strength asymmetry.

Mechanical properties of Nb 25Mo 25Ta 25W 25 and V 20Nb 20Mo 20Ta 20W 20 refractory high entropy alloys

Two refractory high entropy alloys with compositions near Nb 25Mo 25Ta 25W 25 and V 20Nb 20Mo 20Ta 20W 20, were produced by vacuum arc-melting. Despite containing many constituents, both alloys had a single-phase body-centered cubic (BCC) structure that remained not only stable after exposure to 1400 °C, but also disordered, as confirmed by the absence of superlattice reflections in neutron diffraction data. Compressive flow properties and microstructure development of these alloys were determined from room temperature up to 1600 °C. Limited compressive plasticity and quasi-cleavage fracture at room temperature suggest that the ductile-to-brittle transition for these alloys occurs above room temperature. At 600 °C and above, both alloys showed extensive compressive plastic strain. The yield stress of both alloys dropped by 30–40% between room temperature and 600 °C, but was relatively insensitive to temperature above 600 °C, comparing favorably with conventional superalloys.

High-temperature deformation behavior of Ti-TiBw in-situ metal-matrix composites

In developing titanium-based materials for high-performance structural applications, the focus has been on discontinuously reinforced titanium-matrix composites that are based on the in-situ creation of TiB whiskers. This article presents the elevated-temperature compressive flow properties of Ti-TiBw composites as a function of temperature (from 973 K to 1,273 K), strain rate (from 10−5 to 10−3s−1), and the TiB whisker content (commercially pure titanium and composites with 30 to 86 vol.% TiBw). In both the commercially pure titanium and the TiB-whisker-containing titanium composites, flow stress increases with increasing strain rate and decreasing test temperature. In this study, flow stress increased with increasing volume fraction of TiB at a given temperature and strain rate. The composite containing 86% TiBw showed significantly higher elevated-temperature strength when compared to the other composites. The composites exhibit systematic trends in the variation of work-hardening behavior (in terms of work-hardening exponent, n, and work-hardening rate, dσ/dɛ) and the strain-rate dependence.

Aggregation Effects on the Compressive Flow Properties and Drying Behavior of Colloidal Silica Suspensions

The influence of aggregation phenomena on the compressive flow properties and drying behavior of nonaqueous and aqueous silica (SiO2) suspensions of varying electrolyte (NH4Cl) concentrations were studied. Compressive rheology measurements, including sedimentation and centrifugal consolidation, were first conducted to investigate consolidation behavior in the absence of solvent evaporation. The volume‐fraction‐dependent osmotic pressure and compressive yield stress were determined for dispersed and flocculated SiO2 suspensions, respectively. Consolidation behavior then was studied in situ by simultaneously measuring stress evolution and solvent loss as a function of drying time. The observed drying stress histories of the films were complex, consisting of several characteristic regions. First, there was an initial period of stress rise to a maximum drying stress. These measured stress values exhibited good agreement with the osmotic pressure and compressive yield stress at equivalent SiO2 volume fractions for the dispersed and flocculated systems, respectively. Beyond the maximum drying stress there was a subsequent region of stress decay, which coincided with the draining of liquid‐filled pores. No residual drying stress was detected for films prepared from salt‐free SiO2 suspensions, whereas salt‐containing films exhibited residual drying stresses likely due to salt‐bridging effects. Microstructural characterization of dried films prepared from aqueous SiO2 suspensions revealed nonuniformities in the spatial distribution of colloidal particles and precipitated salt, with the highest concentrations located at the outer edges of the films. Such features result from capillary‐induced transport of these species during drying, and they have important implications on colloidal processing of ceramic thick films and bulk forms.