Shape memory alloys — characterization techniques
Shape memory alloys — characterization techniques
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形状记忆合金——表征技术
DOI：
10.1007/s12043-002-0229-7
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
J. Uchil
中科院分区：
文献类型：
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作者：
J. Uchil
形状记忆合金是一类具有热记忆和机械记忆功能的合金。形状记忆效应涉及的基本物理学是可逆热弹性马氏体转变。一般来说，形状记忆合金存在两个相，即高温相或奥氏体相(A)和低温相或马氏体相(M)。此外，在某些特殊情况下还存在中间R相。 M↔A 转化与约 6.5-8% 的可恢复应变相关，R↔A 转化与约 1% 的可恢复应变相关。前者的改造已广泛应用于卫星天线部署、航天联轴器、正畸弓丝、诊断和治疗导管的医用导丝以及其他工业应用。我们课题组一直重点研究R相的表征技术，使用差示扫描量热法（DSC）、电阻率探针（ER）和热机械分析仪（TMA）。人们发现 R 相具有有吸引力的特性，例如热循环稳定性、热滞后小和可忽略的应变恢复疲劳。除了确定转变温度之外，DSC 已成功用于表征可恢复应变参数。 ER 用于系统研究各个相对热处理温度的依赖性。 TMA 已被有效地用于混合相的研究。设计并制造了空间旋转平台，使用形状记忆弹簧致动器来获得受控旋转。该执行器的效率和可靠性已经过超过一百万次的热循环测试。
Shape memory alloys are the generic class of alloys that show both thermal and mechanical memory. The basic physics involved in the shape memory effect is the reversible thermoelastic martensitic transformation. In general, there exists two phases in shape memory alloys, viz., a high-temperature phase or austenitic phase (A) and a low-temperature phase or martensitic phase (M). In addition, an intermediate R phase exists in some special cases. The M↔A transformation is associated with a recoverable strain of about 6.5–8% and the R↔A transformation is associated with a recoverable strain of about 1%. The former transformation has been widely used in the applications like antenna deployment of satellite, aerospace couplings, orthodontic arch wires, medical guide wires for diagnostic and therapeutic catheters and other industrial applications. Our group has been giving emphasis to the characterization techniques for R phase, using differential scanning calorimetry (DSC), electrical resistivity probe (ER) and thermomechanical analyzer (TMA). R phase is found to have attractive features like stability against thermal cycling, a small thermal hysteresis and a negligible strain recovery fatigue. DSC has been used successfully to characterize the recoverable strain parameters, apart from the determination of transformation temperatures. ER is used, for the systematic study of the dependence of various phases on heat-treatment temperatures. TMA has been effectively employed for the study of the mixed phases. A space-rotating platform is designed and fabricated, using an actuator of shape memory spring, for obtaining controlled rotations. The efficiency and the reliability of this actuator has been tested, over a million thermal cycles.