Abstract

Local canning compression is imposed on equiatomic NiTi shape memory alloy (SMA) with complete B19′ martensite. A fraction of retained nanocrytalline grains are embedded in the dominant amorphous phase. The compressed NiTi samples are annealed for 2 h at various temperatures, including 300, 450 and 600 °C. Grain size increases with increasing crystallization temperature during heat treatment. Under annealing at 300 °C, nanocrystalline grains are dominant in NiTi SMA, where there exists local amorphous zone. Under annealing at 450 °C, almost complete nanocrystalline can be obtained. Under annealing at 600 °C, grain size increases substantially, but there still exists a small amount of nanocrystalline grains. Under annealing at 300 °C, NiTi SMA exhibits extremely high elastic limit, but its plasticity is poor. Under annealing at 450 °C, NiTi SMA exhibits very high yield stress and it simultaneously keeps high plasticity. Under annealing at 600 °C, NiTi SMA exhibits relatively low yield stress, but its yield stress is still higher than that of as-received NiTi SMA and its plasticity is also high.

Graphic Abstract

中文翻译：

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等原子NiTi形状记忆合金经受局部罐头压缩和随后退火的组织和力学性能

摘要

对具有完整B19'马氏体的等原子NiTi形状记忆合金（SMA）施加局部罐头压缩。一部分保留的纳米晶晶粒被嵌入主要的非晶相中。压缩的NiTi样品在包括300、450和600°C在内的各种温度下退火2小时。热处理过程中，晶粒尺寸随着结晶温度的升高而增加。在300°C下退火时，NiTi SMA中纳米晶粒占主导地位，那里存在局部非晶区。在450°C下退火，可以获得几乎完整的纳米晶体。在600℃下退火时，晶粒尺寸显着增加，但是仍然存在少量的纳米晶粒。在300°C下退火时，NiTi SMA表现出极高的弹性极限，但可塑性却很差。在450°C下退火，NiTi SMA表现出非常高的屈服应力，并且同时保持了高可塑性。在600°C的退火条件下，NiTi SMA表现出较低的屈服应力，但其屈服应力仍高于所接受的NiTi SMA，并且其可塑性也很高。

图形摘要