Effect of Cu Doping on Phase Transition, Thermal Strain, and Thermal Expansion Property in Polycrystalline Ni 50 Mn 23− x Cu x Ga 27 Alloys

• Published in: Physica status solidi. A, Applications and materials science Vol. 220; no. 19
• Main Authors: Wei, Shengxian, Hu, Fene, Deng, Liping, Yue, Bao, Cao, Yiming, He, Xijia, Zhang, Yuanlei, Kang, Yanru, Xu, Kun, Li, Zhe
• Format: Journal Article
• Language: English
• Published: 01-10-2023
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.202300348

The influence of Cu doping on phase transition, thermal strain, and thermal expansion property of polycrystalline Ni
50
Mn
23−
x
Cu
x
Ga
27
(
x
 = 1, 3, 5, 6 and 7) alloys is investigated. The results show that with increasing Cu concentration, martensitic transformation gradually gets close to Curie transition. A magnetostructural transition (MST) is observed in samples with
x
 = 6 and 7. Such MST can enhance magnitude of transformation strain. Besides, Ni
50
Mn
23−
x
Cu
x
Ga
27
alloys possess an isotropic, recoverable, and thermally stable thermal strain. Excitedly, Cu doping can effectively tune the phase transition, thermal strain, and thermal expansion properties of Ni
50
Mn
23−
x
Cu
x
Ga
27
alloys. Adjustable coefficients of thermal expansion from positive to negative are obtained by Cu‐doped Ni
50
Mn
23−
x
Cu
x
Ga
27
alloys. The average linear expansion coefficient (
α
) between −140.44 and −207.70 ppm K
−1
is observed in samples with
x
 = 6 and 7 for a narrow temperature span of 11–14 K. When the temperature span is about 72 K (
x
 = 6) and 73 K (
x
 = 7), which is the largest temperature span observed in Ni–Mn–Ga‐based alloys recently, the α values decrease to about −36 ppm K
−1
. These findings are beneficial for manipulating the thermal expansion property of Ni–Mn–Ga–Cu alloys and their multifunctional applications.