The Effect of Heat Treatment on the Structure and Mechanical Properties of Nanocrystalline Cu–14Al–3Ni Alloy Subjected to High-Pressure Torsion

Abstract

The effect of heat treatment on the microstructure, phase composition, mechanical properties, and microhardness of the shape-memory Сu–14 wt % Al–3 wt % Ni alloy prepared in the nanocrystalline state, which results from the severe plastic high-pressure torsion (HPT), is studied. Electron microscopy and X-ray diffraction analysis are used in combination with electrical resistivity measurements in order to obtain data on the peculiarities of thermoelastic martensitic transformations and decomposition in the HPT-processed alloy subjected to thermal actions.

Microstructure and Mechanical Behavior of Cu-Al-Ni-B Alloys with Thermoelastic Martensitic Transformation

“…In addition, precipitates are formed at temperatures below the T ED of the β 2 phase with a BCC lattice of the type B2 based on NiAl (a B2 is close to 0.289 nm) [1,8,16]. In previous studies, it was found that the quenching of alloys of the Cu-Al-Ni system from a single-phase β region of existence prevents eutectoid decomposition [10][11][12][13][14][15][16]. Additives 3, 4, and 4.5 wt% Ni reduce the diffusion mobility of copper and aluminum atoms, thereby restraining the eutectoid decomposition of the high-temperature β phase during quenching, whereas an increase in the content of aluminum leads to a decrease in the critical temperatures of the start (M s , A s ) and finish (M f , A f ) of the forward (M s , M f ) and reverse (A s , A f ) TMTs [16].…”

“…Nowadays, various methods of size refinement of a grain structure are known [10][11][12][13][14][15][16]. In order to suppress grain growth and increase the rate of formation of their nuclei during crystallization, methods such as complex microalloying, powder metallurgy [17][18][19], and rapid quenching from the melt (RQM) [20,21] are being tried out.…”

Effect of Controlled Heat Treatment and Aluminum Additions on the Strengthening of Cu–Ni-Based Alloys

“…However, due to the fact that the compression process is governed by the creation and annihilation of dislocations produced by the applied stresses, the dislocation movement can then be minimized when it crosses through the grain boundaries, reducing the dislocations mobility. Additionally, combined with the presence of precipitates, which works as an obstacle for plastic deformation, the combination of these factors produces an improvement in the yielding behavior [36]. Due to Young's modulus, [E] is the relation between the differential of the applied stress and the differential of the obtained strain, which is described as follows:…”

Design and Development of High-Strength and Ductile Ternary and Multicomponent Eutectoid Cu-Based Shape Memory Alloys: Problems and Perspectives

“…It is established that an increasingly homogeneous nano-grain martensitic structure in both of the Cu-Al-Ni alloys, characterized by a ring-wise distribution of reflections in SAED patterns, is formed as a result of HPT, with an increase in the number of revolutions from 1 to 10, and, accordingly, the degree of deformation. (c,f) the corresponding SAED pattern for the (a-c) Cu-14Al-3Ni alloy and (d-f) Cu-13.5Al-3.5Ni after its quenching from 1223 K and HPT of 10 revs [46,64].…”

“…Annealing martensite at 373 and 473 K according to SEM data did not lead to noticeable dimensional and morphological changes in the martensitic UFG structure formed as (c,f) the corresponding SAED pattern for the (a-c) Cu-14Al-3Ni alloy and (d-f) Cu-13.5Al-3.5Ni after its quenching from 1223 K and HPT of 10 revs [46,64].…”