Compaction Behavior and Mechanical Properties of Uniaxially Pressed Bi-W Composites

Abstract

Powder metallurgy is a useful route to forming particulate composite materials; however, the densification of hard and soft powder mixtures is usually inhibited by the more refractory phase. The Bi-W powder compacts were uniaxially pressed at room temperature and the compaction behavior and mechanical properties were evaluated. Pressing was performed in incremental steps from~1 to 540 MPa. After each step, the pressure was relieved and the thickness and sound-wave transit time were measured in situ (in the die), in order to determine the density and sound-wave velocity in the compact. The data show that the unreinforced Bi powder compacts to~98 pct density at 540 MPa. The W reinforcement inhibits the densification process, resulting in increased levels of residual porosity. The compaction behavior was evaluated using a modified Heckel equation, while the porosity dependence of the ultrasonically determined elastic modulus was described by a site percolation approach. Postcompaction sound-wave velocity and Vicker's hardness measurements show <5 pct anisotropy between the axial (pressing) and radial directions. The mechanical characterization illustrates the competing effects of the W reinforcement and the associated residual porosity.

Regulating the Electronic Structure of Bismuth Nanosheets by Titanium Doping to Boost CO2 Electroreduction and Zn–CO2 Batteries

“…According to earlier studies in the literature, Bi powder has irregular and random shape features. [ 38 ] From the linear scanning voltammetry (LSV) curves ( Figure a), it can be seen that the cathodic current density of the ultrathin TiBi NSs varies with the applied voltage. In the CO 2 saturated solution, the cathodic current density of the ultrathin TiBi NSs increases significantly from −9.8 mA cm −2 (−0.29 V vs RHE) to −338.3 mA cm −2 (−1.25 V vs RHE), while the current density of Bi NSs increases from −2.1 mA cm −2 (−0.29 V vs RHE) to –239.1 mA cm −2 (−1.25 V vs RHE), while the current density of the Bi powder increases from −1.3 mA cm −2 (−0.29 V vs RHE) to −134.4 mA cm −2 (−1.25 V vs RHE).…”

“…According to earlier studies in the literature, Bi powder has irregular and random shape features. [38] From the linear scanning voltammetry (LSV) curves (Figure 3a), it can be seen that the cathodic current density of the ultrathin Ti-Bi NSs varies with the applied voltage. In the CO 2 saturated solution, the cathodic current density of the ultrathin Ti-Bi NSs increases significantly from −9.8 mA cm −2 (−0.…”

Characterization of Tantalum Carbide Reinforced Copper Composite Developed Using Mechanical Alloying

“…It allows consolidation without a meltprocessing step, which can be advantageous for high-melting-point materials such as the refractory metals or ceramics. However, the densification of hard and soft powder mixtures is usually inhibited by the refractory phase [4]. Therefore, this present work aims to investigate the structural and properties of in-situ copper-tantalum carbide composite developed through mechanical alloying.…”