Micro-Mechanical Response of an Al-Mg Hybrid System Synthesized by High-Pressure Torsion

Abstract

This paper summarizes recent efforts to evaluate the potential for the formation of a metal matrix nanocomposite (MMNC) by processing two commercial bulk metals of aluminum and magnesium alloy through high-pressure torsion (HPT) at room temperature. After significant evolutions in microstructures, successful fabrication of an Al-Mg hybrid system was demonstrated by observing unique microstructures consisting of a multi-layered structure and MMNC. Moreover, the evolution of small-scale mechanical properties was examined through the novel technique of nanoindentation and the improvement in plasticity was estimated by calculating the strain rate sensitivity of the Al-Mg hybrid system after HPT. The present paper demonstrates that, in addition to conventional tensile testing, the nanoindentation technique is exceptionally promising for ultrafine-grained materials processed by HPT, where the samples may have small overall dimensions and include heterogeneity in the microstructure.

Micromechanical Response of Additively Manufactured 316L Stainless Steel Processed by High‐Pressure Torsion

“…[44] Shorter displacements (curve moves to the left) correspond to increased hardness and reduced ductility, whereas less broadening/deviation among a set of P-h curves indicates a reasonably consistent mechanical response and better plastic stability. [39,49] Therefore, Figure 4 shows a series of representative indentation curves (load P vs displacement h) for as-received and HPT-processed disks both at the center and at the edge of the disks through various revolutions at a constant strain rateε of 1.25 Â 10 À1 , obtained from 15 individual indentations at each location. Two observations could be made based on these curves.…”

“…This indicates the improved plastic stability of HPTprocessed disks, possibly due to increasingly homogeneous microstructural distributions with higher HPT revolutions. [39,49] Figure 5 shows the average P-h curves for as-received and HPT-processed disks at the center and edge locations. The shorter displacements of the P-h curves for N ¼ 1/4, 1/2, and 1 revolution at the edge (Figure 5b) in contrast with that at the center of the disks (Figure 5a) indicate rapid increase in hardness at the peripheral area compared with the central region of the HPT-processed disks during the earlier deformation stages.…”

“…To assess the practicality of UFG and NG AM 316L SS for future applications, the micromechanical response, i.e., the mechanism of plastic deformation due to HPT processing, has to be evaluated. [39] 316L SS is of particular interest because it is an important engineering material that has been widely used in a broad range of applications, e.g., oil, nuclear, and biomedical industries, due to its high corrosion and oxidation resistance, and excellent weldability. [40,41] However, so far no attempt was made to monitor the evolution of the plastic deformation mechanism at RT during HPT processing of AM 316L SS.…”

Synthesis of Hybrid Nanocrystalline Alloys by Mechanical Bonding through High‐Pressure Torsion

“…[76] In practice, nanoindentation was applied for a wide variety of metallic materials processed by different SPD techniques to understand their micromechanical responses by measuring and computing hardness and strain rate sensitivity of the nanostructured materials. [75] A series of nanoindentation measurements were reported at the disk edges [35,38] and centers [77] on mechanically bonded Al-Mg systems after HPT up to 20 turns. As was expected from the increased hardness at the disk edges of the Al-Mg system, whose strengthening mechanisms were explained in an earlier section, the results taken by nanoindentation demonstrated the increased hardness but reduced plasticity by computing the decreased strain rate sensitivity, m, with increasing numbers of HPT turns.…”

“…A series of nanoindentation measurements were reported at the disk edges and centers on mechanically bonded Al–Mg systems after HPT up to 20 turns. As was expected from the increased hardness at the disk edges of the Al–Mg system, whose strengthening mechanisms were explained in an earlier section, the results taken by nanoindentation demonstrated the increased hardness but reduced plasticity by computing the decreased strain rate sensitivity, m , with increasing numbers of HPT turns.…”