Small-Scale Plastic Deformation of Nanocrystalline High Entropy Alloy

High entropy alloys (HEAs) have attracted widespread interest due to their unique properties at many different length-scales. Here, we report the fabrication of nanocrystalline (NC) Al0.1CoCrFeNi high entropy alloy and subsequent small-scale plastic deformation behavior via nano-pillar compression tests. Exceptional strength was realized for the NC HEA compared to pure Ni of similar grain sizes. Grain boundary mediated deformation mechanisms led to high strain rate sensitivity of flow stress in the nanocrystalline HEA.

Energy Absorption of Superplastic Zn-22Al Alloy Foam Manufactured through Melt Foaming Process

Closed-cell superplastic Zn-22Al alloy foams were manufactured through the melt foaming process using sodium hydrogen carbonate powder as a foaming agent. Foaming tests were carried out under different foaming temperatures, times and additive amounts of foaming agent. The porosity of Zn-22Al alloy foams were between 30 and 70%. The cell wall consisted of fine equiaxial crystal grains after solution treatment. The compressive properties of the Zn-22Al alloy foams were investigated at room temperature and high temperature. Zn-22Al alloy foams exhibited high strain rate sensitivity, which was caused by superplastic deformation of the cell wall material.

Strain-Rate Characteristic of the Brush Plated Nanocrystalline Cu

In this study, the pure nanocrystalline Cu columns were fabricated by the brush electrodeposition technique at 20°C and at different deposition current densities in the range of 200 240 mA cm-2. The columns shows high strain rate sensitivity in the room temperature compressive test. In the tested strain rate range, the strength of the nanocrystalline Cu at 2% plastic strain increases from 660 MPa to 1500 MPa. The nanocrystalline Cu exhibits obvious flow softening behavior at high strain level, and the degree of the softening is related to the strain rate.

The Effect of Strain Rate on the Tensile Behavior of Electrodeposited Nanocrystalline Ni-Co Alloy

A fully dense nanocrystalline Ni-Co alloy with 18 nm grain size exhibited high strength of about 2200 MPa and ductility of 8.19.2% at strain rates of 1.04×10-5 to 1.04 s-1 and room temperature. The alloying of Co element induces the grain refinement, solid solution hardening and decrease of stacking fault energy should contribute to the favorable combination of mechanical performance. The obvious distinctions of fracture-surface morphologies with strain rate alteration were attributed to underlying deformation mechanism transition. The high strain rate sensitivity exponent and small activation volume indicate that grain boundary activity may be expected in this alloy.