Qiang Yu
, Guli Riziwan, Pengfei Qi, Ruixin Gong, Qian Zhang, Wentao Qu
J. Min. Metall. Sect. B-Metall., 62 (2) (2026) 243-255. DOI:10.2298/JMMB260306018Y
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Available online 14 September 2026
(Received 06 March 2026; Accepted 28 July 2026)
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This work examines how post-annealing temperature affects the thermal-energy storage behavior of the Ni49.5Ti38.5Zr12 phase-change alloy, with the aim of mitigating heat loss and electronic failures that often occur in insulation bottles due to structural imperfections or inadequate heat-storage capability. Specimens were heat-treated over a range of temperatures, and their transformation characteristics, microstructural evolution, and thermophysical performance were systematically evaluated. The results indicate that with increasing heat-treatment temperature, the transformation enthalpy rises initially and then declines. This trend is associated with the progressive morphological change of the precipitated λ1 phase-from fine bubble-like features to sheet-like structures-together with a grain size variation that also increases first and subsequently decreases. In addition, thermal conductivity shows an overall upward tendency, which can be explained by enhanced atomic motion in the crystal lattice at elevated temperatures. After annealing at 600 °C, the alloy exhibits a transformation enthalpy of 29.8 J·g−1, a transformation start temperature (As) of 72.97 °C, a finish temperature (Af) of 119.81°C, a thermal conductivity of 15.3 W·g−1·K−1, and a microhardness of 355.147 HV. Moreover, the material retains good thermal stability after repeated thermal cycling. These outcomes provide theoretical support for employing NiTiZr-based materials in downhole insulation bottles. An annealing window of 500-700 °C is recommended to improve transformation stability and thermophysical properties, enabling suitability for high-temperature service environments such as downhole tools in the petroleum industry.
Keywords: NiTiZr alloy; Heat treatment; Microstructure Phase change characteristics; Thermal cycling stability
Correspondence Address:
Wentao Qu,
School of Mechanical Engineering, Xi’an Petroleum University, Xi’an, Shaanxi, China;
email: wtqu@xsyu.edu.cn
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