Assessment of diffusion mobility for the bcc phase of the Ti–Al–Cr system

In this work, the mechanochemical synthesis method was used for the first time to produce powders of the nanocrystalline Nd1.1Fe10CoTi compound from Nd2O3, Fe2O3, Co and TiO2. High-energy-milled powders were heat treated at 1000 °C for 10 min to obtain the ThMn12-type structure. Volume fraction of the 1:12 phase was found to be as high as 95.7% with 4.3% of a bcc phase also present. The nitrogenation process of the sample was carried out at 350 °C during 3, 6, 9 and 12 h using a static pressure of 80 kPa of N2. The magnetic properties Mr, µ0Hc, and (BH)max were enhanced after nitrogenation, despite finding some residual nitrogen-free 1:12 phase. The magnetic values of a nitrogenated sample after 3 h were Mr = 75 Am2 kg–1, µ0Hc = 0.500 T and (BH)max = 58 kJ·m–3. Samples were aligned under an applied field of 2 T after washing and were measured in a direction parallel to the applied field. The best value of (BH)max~114 kJ·m–3 was obtained for 3 h and the highest µ0Hc = 0.518 T for 6 h nitrogenation. SEM characterization revealed that the particles have a mean particle size around 360 nm and a rounded shape.

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Understanding the Links between the Composition-Processing-Properties in New Formulations of HEAs Sintered by SPS

Metals ◽

10.3390/met11060888 ◽

2021 ◽

Vol 11 (6) ◽

pp. 888

Author(s):

Paula Alvaredo-Olmos ◽

Jon Molina-Aldareguía ◽

Alvaro Vaz-Romero ◽

Estela Prieto ◽

Jesús González-Julián ◽

...

Keyword(s):

High Hardness ◽

Processing Parameters ◽

Heating Rates ◽

High Entropy ◽

Plasma Sintering ◽

Mechanical Study ◽

Spark Plasma ◽

Processing Properties ◽

Bcc Phase ◽

Hardness Values

This work presents two new compositions of high entropy alloys (HEAs) that were designed with the aim of obtaining a body-centered cubic (BCC) phase with high hardness values and a moderate density. Sintering was performed using Spark Plasma Sintering (SPS) with different heating rates to determine the influence of the processing parameters on the phase formation. The microstructural study revealed that the presence of Ni in the composition promoted phase separation, and the mechanical study confirmed a clear influence on the mechanical properties of both the composition and heating rate. The combination of microscopy with compression and nanoindentation tests at room and high temperature made it possible to advance our understanding of the relationships between the composition, processing, and properties of this emerging group of alloys.

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Solubility and vacancy-mediated inter-diffusion in the Zr-Nb-Cr system

Journal of Nuclear Materials ◽

10.1016/j.jnucmat.2021.152867 ◽

2021 ◽

Vol 548 ◽

pp. 152867

Author(s):

Vidur Tuli ◽

Antoine Claisse ◽

Luca Messina ◽

P.A. Burr

Keyword(s):

Cr System

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Design of Low-Cost and High-Strength Titanium Alloys Using Pseudo-Spinodal Mechanism through Diffusion Couple Technology and CALPHAD

Materials ◽

10.3390/ma14112910 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2910

Author(s):

Chaoyi Ding ◽

Chun Liu ◽

Ligang Zhang ◽

Di Wu ◽

Libin Liu

Keyword(s):

Diffusion Couple ◽

Titanium Alloys ◽

High Throughput ◽

Volume Fraction ◽

Raw Materials ◽

Low Cost ◽

High Strength ◽

High Yield ◽

Α Phase ◽

Cr System

The high cost of development and raw materials have been obstacles to the widespread use of titanium alloys. In the present study, the high-throughput experimental method of diffusion couple combined with CALPHAD calculation was used to design and prepare the low-cost and high-strength Ti-Al-Cr system titanium alloy. The results showed that ultra-fine α phase was obtained in Ti-6Al-10.9Cr alloy designed through the pseudo-spinodal mechanism, and it has a high yield strength of 1437 ± 7 MPa. Furthermore, application of the 3D strength model of Ti-6Al-xCr alloy showed that the strength of the alloy depended on the volume fraction and thickness of the α phase. The large number of α/β interfaces produced by ultra-fine α phase greatly improved the strength of the alloy but limited its ductility. Thus, we have demonstrated that the pseudo-spinodal mechanism combined with high-throughput diffusion couple technology and CALPHAD was an efficient method to design low-cost and high-strength titanium alloys.

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