Enhanced Mechanical Properties of Nano/Meso Hybrid Structure Materials Produced by Hot Roll Sintering Process

Abstract

SUS316L stainless steel and commercially pure titanium powders are processed by Mechanical Milling (MM) which is one of Severe Plastic Deformation (SPD) process. These MM powders are sintered by Hot Roll Sintering (HRS) process. Microstructure of materials produced by HRS process consists of a shell and core hybrid microstructure, that is, a shell structure with nano grains and a core structure with workhardened coarse grains. All of the HRS materials demonstrate not only superior strength but also good elongation. The mechanical properties are strongly influenced by the shell/core microstructure. The nano/meso hybrid microstructure by HRS process has been proved to be very effective to improve mechanical properties.

Application of Harmonic Structure Design to Biomedical Co–Cr–Mo Alloy for Improved Mechanical Properties

“…These observations indicate that the plastic deformation during milling was mostly limited to the areas near the surface of the milled powders. Similar morphological changes have also been reported for the powders of other materials milled under controlled conditions 15,16) wherein it was observed that such a controlled mechanical milling leads to the formation of a severely deformed layer, consisting of nano-sized crystallites, near the surface of the powders. Therefore, each milled powder particle represents a CoreShell microstructure wherein the coarse grained inner part of the powder is surrounded by a severely deformed layer with sub-micron sized grains.…”

“…A similar observations have been made also for harmonic structured pure Ti and SUS316L. 12,16) Therefore, the mechanical properties of the harmonic materials appears to be strongly dependent on the shell volume fraction, and an optimum set of strength and ductility can be achieved by controlling the shell volume fraction in the compacts.…”

Obtaining Copper with Harmonic Structure for the Optimal Balance of Structure-Performance Relationship

“…13,14) It is essentially a structure having bimodal grain size distribution. However, in addition to be bimodal, the term "harmonic" signifies that this structure has a specific topology: "fine" and "coarse" grains in it are positioned in a periodic, or the "harmonic" order.…”

Application of High Pressure Gas Jet Mill Process to Fabricate High Performance Harmonic Structure Designed Pure Titanium

“…7,11,15) Hence, the controlled mechanical milling via the jet mill proved extremely effective in achieving controlled severe plastic deformation, limited to the sub-surface regions of the fine size powder particles, in the form of a featureless "shell" region. As a result, jet milling successfully created a bimodal microstructure in the milled powder particles, i.e.…”