Effect of Cu on Amorphization of a TiNi Alloy during HPT and Shape Memory Effect after Post‐Deformation Annealing

Abstract

A ternary TiNiCu shape memory alloy is subjected to high‐pressure torsion (HPT) followed by post‐deformation annealing (PDA) to study the effect of Cu (5 at%) on amorphization after HPT processing and to investigate the microstructural evolution and shape memory effect (SME) after PDA. The results show that even after 20 revolutions the ternary alloy contains nanocrystalline areas and the microstructure is not fully amorphous. An easier martensite‐to‐austenite transformation and minor remaining austenite in the ternary alloy are responsible for suppressing amorphization. Post‐deformation annealing at 673 K provides nanocrystalline microstructures containing an R‐phase with a minor martensitic B19' phase in the ternary alloy. The SME of this alloy after PDA is not as satisfactory as that of the binary alloy processed through similar conditions because of the existence of a high volume fraction of the R‐phase. However, the total recovered strain of the ternary alloy after PDA for 30 min has a maximum value of 6.5%.

Evidence for a phase transition in an AlCrFe2Ni2 high entropy alloy processed by high-pressure torsion

“…It seems probable that at this point the steady-state concentration of second components, such as Al and Ni in the FCC solid solution, may be the same after HPT processing as in the alloy after subjecting to a long anneal at an elevated temperature. This suggests the potential for beneficially employing a post-HPT heat treatment, as used in some other research programs [73,74], in order to achieve better combinations of strength and ductility. Further experiments are necessary to more fully explore this possibility.…”

Microstructure Evolution and Mechanical Properties of AlCoCrFeNi2.1 Eutectic High-Entropy Alloys Processed by High-Pressure Torsion

“…In a word, the HPT resulted in an imbalance between strength and ductility. Therefore, in order to address this imbalance phenomenon, it was believed that heat treatment could improve ductility at the expense of some strength, as previously reported [ 54 , 55 ]. However, for AlCoCrFeNi 2.1 EHEAs, this requires further experimental verification.…”

Laser Powder Bed Fusion of Cu–Al–Ni–Mn Shape‐Memory Alloy for the Application of Active Heat Sinks: Processability, Microstructures, and Shape‐Memory Effect

“…During this heating process, the start, peak, and finish temperatures of this transformation temperature are called A s , A p , and A f , respectively. [ 56 ]…”

“…During this heating process, the start, peak, and finish temperatures of this transformation temperature are called A s , A p , and A f , respectively. [56] In order to explore the correlation between the scan speed and transformation temperatures, three samples with scan speed of 700, 900, and 1100 mm s À1 were selected and their DSC curves upon heating and cooling are shown in Figure 9a,b, respectively. Generally, the transformation temperatures showed a decreasing trend with the increase of scan speed (Figure 9c).…”