Physical and Structural Characterization of Monocrystalline Cu-13.7% Al-4.2% Ni Alloy Submitted to Thermo-Cyclical Treatments under Applied Loads

Abstract

Monocrystalline alloy with a nominal composition of Cu-13.7% Al-4.2% Ni (wt.%) that shows reversible martensitic transformations (RMTs) was studied. The alloy, manufactured by the “Memory Crystals Group” in Russia, was subjected to thermo-cyclical treatment (TCT) under tension within a range that included critical RMT temperatures. A special device was developed to perform TCTs (up to 500 cycles) and three different loads were applied: 0.11, 0.26, and 0.53 MPa. X-ray diffraction analysis, optical microscopy, differential calorimetry, and Vickers microhardness were involved in the alloy’s characterization. Under TCTs, the alloy displayed complex structural transformation, revealing the sequence of RMT, β1 ↔ R ↔ β′1 + γ′1; the involved phases were coherently precipitated but very sensitive to the experimental conditions. It was found that during TCTs (from 300 cycles) performed under optimum load (0.26 MPa), the processes of martensite reorientation, hardening, and stabilization of the structure were the most intensive thus leading to a reduction of RMT critical intervals and increased microhardness.

The Effect of Ceo2 Addition on Transformation Temperatures and Wear Resistance of Cu-Al-Ni Shape Memory Alloys

“…The transformation went to a higher temperature for each sample for the three alloys. Thermal cycling up to 200°C is well recognized for causing changes in alloy structure and composition and physical and mechanical characteristics [15]. After a suitably long aging period at 200°C, an increase in the critical transition temperatures associated with a conversion of γ ' into β`1 martensite was also identified.…”

Влияние предварительной сжимающей нагрузки на работу, производимую монокристаллами Cu-Al-Ni при взрывном восстановлении деформации памяти формы

“…В настоящей работе использовались монокристаллы сплава Cu (82.5 wt.%)−Al (13.5 wt.%)−Ni (4.0 wt.%). Этот сплав достаточно подробно исследован в плане мартенситных превращений [7][8][9]. Кристаллы были вы-ращены из расплава в форме стержней диаметром 5 mm.…”