Effect of Cold Rolling Pre-strain on Microstructure and Phase Transformation of Polycrystalline Cu-Al-Ni Alloy

ZHANG Zhengjie; CHEN Chen; CHEN Yulin; ZHANG Jian

doi:10.3969/j.issn.1674-6457.2026.09.018

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Journal of Netshape Forming Engineering ›› 2026, Vol. 18 ›› Issue (9) : 176-183. DOI: 10.3969/j.issn.1674-6457.2026.09.018

Copper Alloy Forming

Effect of Cold Rolling Pre-strain on Microstructure and Phase Transformation of Polycrystalline Cu-Al-Ni Alloy

ZHANG Zhengjie, CHEN Chen, CHEN Yulin, ZHANG Jian^*

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Abstract

The work aims to investigate the regulation mechanism of cold rolling pre-strain on the thermoelastic martensitic transformation behavior of the polycrystalline Cu-Al-Ni shape memory alloy, with focus on clarifying the process of stress- induced martensite evolution and the internal mechanisms by which induced defects stabilize martensite, so as to provide a theoretical basis for optimizing the alloy’s service temperature range. The polycrystalline Cu-Al-Ni alloy was cold-rolled at room temperature from 0% to 5%. Microstructural evolution and phase transformation characteristics were analyzed in detail using OM, SEM, XRD, and DSC. Results showed that increasing deformation caused a stepwise evolution of β₁→β₁’→γ₁’, with the microstructure refining from coarse laths to needles. At strain levels of 3.5%-5%, deformation of the γ₁’ phase caused intergranular/phase-boundary deformation incompatibility, which in turn prompted the accumulation of geometrically necessary dislocations within the crystal to coordinate the deformation. This microstructural evolution resulted in stage-dependent differences in the phase transformation behavior. Compared with the low-strain stage without induced γ₁’, the formation of γ₁’ phase and the combined effect of dislocation proliferation significantly enhanced the pinning effect on the phase interface, resulting in a noticeable increase in the martensitic stabilization effect. In conclusion, pre-strain significantly alters the phase transformation behavior of the polycrystalline Cu-Al-Ni alloy by introducing γ₁’ martensite and geometrically necessary dislocations. Deformation incompatibility and dislocation multiplication associated with the β₁’→γ₁’ transformation substantially increase the energy barrier to the reverse transformation, thereby improving martensite stability and widening the hysteresis. This research demonstrates that cold rolling, as a defect-engineering method, can effectively control the phase transformation temperature range and the alloy's hysteresis characteristics.

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Cu-Al-Ni shape memory alloy / polycrystalline / cold-rolling pre-strain / microstructure / phase characteristics

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ZHANG Zhengjie, CHEN Chen, CHEN Yulin, ZHANG Jian. Effect of Cold Rolling Pre-strain on Microstructure and Phase Transformation of Polycrystalline Cu-Al-Ni Alloy[J]. Journal of Netshape Forming Engineering. 2026, 18(9): 176-183 https://doi.org/10.3969/j.issn.1674-6457.2026.09.018

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