Gamma-phase influence on shape memory properties in Ni-Mn-Co-Ga-Gd high-temperature shape memory alloys
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The effect of γ-phase on two-way shape memory effect (TWSME) of polycrystalline Ni56Mn25-x Co x Ga18.9Gd0.1 alloys was investigated. The results show that an appropriate amount of ductile γ-phase significantly enhances the TWSME. The largest TWSME of 1.4% without training is observed in Ni56Mn21Co4Ga18.9Gd0.1 alloy, and this value is increased to 2.0% after thermomechanical training. The as-trained TWSME decays over the first five thermal cycles and then reaches a stable value as the number of cycles further increasing. Only the degradation of 0.2% is observed after 100 thermal cycles. The better TWSME and thermal stability are ascribed to the stable extra stress field formed by the plastically deformed γ-phase.
KeywordsShape memory alloys Ni–Mn–Ga alloys Thermomechanical training Second phase Two-way shape memory effect
This work was supported by the National Natural Science Foundation of China (No. 51601126), the Student’s Platform for Innovation and Entrepreneurship Training Program (No. 201710060118) and China Postdoctoral Science Foundation (No. 2016M601271).
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