Effect of Ce Content on Properties of Al-Ce-Based Composites by Powder-in-Tube Method

Al-Ce based alloys have gained recent interest and have proven to have excellent strength without heat treatment and high thermal stability. Challenges with the production of Al-Ce samples from elemental powders arise due to the elemental material before alloying being susceptible to rapid oxidation. The methodology for making superconductive wire, powder-in-tube, was used as a consolidate Al and Ce elemental powder, and Al-8 wt % Ce-10 wt % Mg composite powder into bulk nanostructured material. Powder samples are fabricated in an inert controlled atmosphere, then sealed in a tube to avoid oxidation of powders. Therefore, most of the powder is used without much loss. We used 316 stainless-steel tubes as a sheathing material. For Al-xCe wt % (x = 8 to 14) samples of elemental powder, liquid phase sintering was used and for Al-Ce-Mg powder solid-state sintering. Characterization of the bulk consolidated material after sintering, and before and after heat treatment, was made using optical and Scanning Electron Microscope imaging, Energy Dispersive Spectroscopy, Microhardness and Rockwell Hardness test. We demonstrated that microstructure stability in Al-Ce-based specimens can be retained after thermomechanical processing. Densification was achieved and oxidation of powder was avoided in most samples. In addition, we found that Fe and Ni in the sheathing material react with Al in the process, and Ce concentration modifies the reactivity the sheath.

New functional material: spark plasma sintered Si/SiO2 nanoparticles – fabrication and properties

A bulk nanostructured material based on oxidized silicon nanopowder was fabricated using a spark plasma sintering technique.

Synthesis of Bulk Nanostructured DO22Superlattice of Ni3(Mo, Nb) with High Strength, High Ductility, and High Thermal Stability

We show that a bulk nanostructured material combining high strength, high ductility, and high thermal stability can be synthesized in a Ni-Mo-Nb alloy with composition approaching Ni3(Mo, Nb). By means of a simple aging treatment at700°C, the grains of the parent face-centered cubic phase are made to transform into nanosized ordered crystals with DO22superlattice maintaining a size of 10–20 nm after up to 100 hours of aging and corresponding room-temperature yield strength of 820 MPa and tensile ductility of 35%. Deformation of the superlattice is found to predominantly occur by twinning on{111}planes of the parent phase. It is concluded that, although the respective slip systems are suppressed, most of the twinning systems are preserved in the DO22superlattice enhancing the ductility.

Effect of Milling Time and Annealing on the Mechanical Response of Mechanically Milled Aluminium

Owing to its many exceptional properties, aluminium finds many applications in theaerospace, automotive, building and packaging industries. Enhancing its properties through alloyingor thermal treatments has been the focus of researchers’ interests for a long time. In this work, purealuminium powders were mechanically milled for up to 12 hrs and then were cold compacted andextruded to produce bulk nanostructured material. Both tensile and compressive tests wereconducted and the results compared. Post extrusion annealing treatments for up to 3 hrs wereconducted on additional samples.It was found that increasing the process control agent (PCA) content as well as the milling durationresulted in a finer microstructure and hence enhanced mechanical strength. This was accompaniedby a reduction in the ductility of the material. Moreover, compression tests revealed that thesamples are significantly more ductile in compression than in tension and that the decrease inductility with increase in milling time is less significant than in the case of tension. The differencein mechanical response is attributed to plastic instabilities. Annealing was found to enhance thetensile ductility of the samples without sacrificing strength.