Using high-pressure torsion for metal processing: Fundamentals and applications

Recent progress made in biomaterials and their clinical applications is well known. In the last five decades, great advances have been made in the field of biomaterials, including ceramics, glasses, polymers, composites, glass-ceramics and metal alloys. A variety of bioimplants are currently used in either one of the aforesaid forms. Some of these materials are designed to degrade or to be resorbed inside the body rather than removing the implant after its function is served. Many properties such as mechanical properties, non-toxicity, surface modification, degradation rate, biocompatibility, and corrosion rate and scaffold design are taken into consideration. The current review focuses on state-of-the-art biodegradable bioceramics, polymers, metal alloys and a few implants that employ bioresorbable/biodegradable materials. The essential functions, properties and their critical factors are discussed in detail, in addition to their challenges to be overcome.

https://www.mdpi.com/2079-4983/8/4/44/pdf

Biodegradable Materials and Metallic Implants-A Review.

Influence of stacking-fault energy on microstructural characteristics of ultrafine-grain copper and copper-zinc alloys

Ab initio modeling of dislocation core properties in metals and semiconductors

An overview of tailoring strain delocalization for strength-ductility synergy

Biological behavior of titanium processed by severe plastic deformation

Mechanical properties and TEM microstructure studies have been carried out of nanocrystalline titanium, TilONblOTa and Ti10Nb obtained by various technological routes, including: powder metallurgy (ball milling and hot pressing), Equal Channel Angular Pressing (ECAP), hydroextrusion (HE) and high pressure torsion (HPT). The HE processed material in the form of 20 mm rods was extruded at a strain rate of 2.5 × 10 2 s -1 to a diameter of 3 mm, which corresponds to the true strain of 3.8. Resulting Yield Strength (YS) at the crystal size below 80 nm exceeded 1000 MPa, i.e. attained a value of 3 times more than the initial material. Equal-Channel Angular Pressing (ECAP) at 723 K was applied to produce nanostructured titanium. Grain refinement was observed already after one pass (considerable number of grains with d < 100 nm was noted). It was accompanied by a growth of strength and slight decrease in the elongation. ECAP processing up to 4 passes resulted in further slight growth of strength and further slight loss of elongation. The titanium powder prepared by ball milling in a high energy mill decreased its crystal size down to 10 nm and reached microhardness HV 20 = 1000. The additions of Nb and Ta resulted in a similar grain refinement but lower hardness. Uniaxial hot pressing at 650 °C, followed by vacuum annealing resulted in similar microhardness as for powders. TEM studies performed using quantitative metallography allowed to estimate mean grain size at 150 nm. HPT technique at the pressure of 5 GPa resulted in finest grain size as compared to other preparation techniques leading to nanoscale grain refinement in Ti samples. The mean crystal size was estimated at about 30 nm.

Microstructure and mechanical properties of nanocrystalline titanium and Ti–Ta–Nb alloy manufactured using various deformation methods

The study is concerned with the bimetallic plate composed of the Ti6Al4V and Inconel 625 alloys. The alloys were joined together using the explosive method with the aim to produce a bimetallic joint. The structure and the mechanical properties of the as-received raw Ti6Al4V and Inconel 625 alloys, the Ti6Al4V/Inconel 625 joint, and the joint after annealing (600 °C for 1 h) were examined. The samples observations were performed using a light microscope and a scanning electron microscope. The mechanical properties were estimated by microhardness measurements, tensile tests, and three-point bending tests. Moreover, the deformation strengthening of the metals and the strength of the joint were analyzed. The explosive process resulted in a good quality bimetallic joint. Both sheets were deformed plastically and the joint surface between the alloys had a wavy shape. In the area of the joint surface, the hardness was increased. For example, the annealing at 600 °C for 1 h resulted in changes of the microhardness in the entire volume of the samples and in changes of the morphology of the joint surface. In three-point bending tests, the samples were examined in two opposite positions (Ti6Al4V on the top or Inconel 625 on the top). The results indicated to depend on the position in which the sample was tested.

/pdf/microstructure-and-properties-of-the-ti6al4v-inconel-625-3wbwwuisqg.pdf

Microstructure and Properties of the Ti6Al4V/Inconel 625 Bimetal Obtained by Explosive Joining

This paper reports on the corrosion behavior of Titanium Grade 2 when subjected to non-contact laser functionalization. Direct Laser Interference Lithography (DLIL) was used to create periodic topography with two different surface patterns on pre-modified titanium. Corrosion resistance was measured in physiological saline at 37 °C. Electrochemical Impedance Spectroscopy data (EIS) and potentiodynamic polarization curves were correlated with the characteristics of the passive films through analysis of the topography, chemical composition, and thickness of oxides formed on the titanium after surface modifications. The corrosion tests showed that laser-textured surfaces have a beneficial impact on titanium corrosion resistance in a physiological saline solution 0.9% NaCl. Moreover, the passive layer on DLIL-modified samples is more stable and less susceptible to growth in the corrosive environment. The results highlight the local interaction of DLIL treatment of the titanium surface after it had been shot-peened and acid-etched. The improved corrosion resistance in DLIL samples derives mainly from changes in the surface topography, chemical composition, and thickness of oxide films obtained after laser processing.

Corrosion behavior of titanium modified by direct laser interference lithography

Summary

The paper presents the results of investigations of the microstructures and properties of the aluminium coatings deposited by vacuum evaporation and magnetron sputtering. These coatings generally have a very refined microstructure with elongated nano-grains. However, the surface topography of the aluminium coating deposited by vacuum evaporation is more developed, its microstructure is less homogeneous and more porous. The residual tensile stresses in the aluminium coating deposited by magnetron sputtering are close to 130 MPa, and the texture is relatively pronounced. Vacuum evaporation does not induce residual stresses in the coatings and the texture is very weak. The results obtained indicate that the aluminium coatings produced by magnetron sputtering are more suitable for the diffusive Ti-Al intermetallic layers.

Halina Garbacz

Papers

Biological behavior of titanium processed by severe plastic deformation

Microstructure and mechanical properties of nanocrystalline titanium and Ti–Ta–Nb alloy manufactured using various deformation methods

Microstructure and Properties of the Ti6Al4V/Inconel 625 Bimetal Obtained by Explosive Joining

Corrosion behavior of titanium modified by direct laser interference lithography

Studies of aluminium coatings deposited by vacuum evaporation and magnetron sputtering.