Development of New B2 Type Shape Memory Alloys end theirs Application for Multi-functional Devices.

形状记忆材料是一种典型的智能材料，具有温度传感器和执行器的双重功能。虽然SM器件比铁电器件产生更大的功率和位移，但它们存在对输入信号的响应太慢的非常严重的问题，因为SM器件中的热导率是一个速率决定过程。近年来，在Ni-Mn-Ga系中发展了一种可在磁场作用下工作的铁磁形状记忆合金。本论文研究了新型的具有B2 bcc有序结构的Co-Ni-Al合金。（1）相变温度：用DSC和VSM测量了马氏体相变温度Ms和居里温度Tc。一些合金在室温以上的相对高温区域中具有Ms和To。这一结果表明Co-Ni-Al合金是一种很有前途的FSMA的候选材料。(2)晶体结构：母相和马氏体相分别具有B_2和L_1_0结构。L1_0相的c/a比为0.81。(3)形状记忆和力学性能：与γ相共存改善了合金的延展性，并且可以通过训练处理获得完美的形状记忆。(4)磁性：使用单晶测定奥氏体和马氏体相的磁各向异性，并检测到约0.3%的磁致伸缩。(5)FSM线材，具有0.5至1.0mmf的FSM线材可以通过常规的轧制和拉拔技术生产。所获得的线显示出伪弹性行为。

Shape memory (SM) material which possesses double functions of thermo-sensor and actuator is one of the typical smart materials. Although the SM devices yield larger power and displacement than the ferroelectric one, they have a very serious problem in which the response for input signal is too slow, because the thermal conductivity in the SM devices is a rate determining process. Recently, ferromagnetic Shape memory (FSM) alloys that can be operated by magnetic field have been developed in the Ni-Mn-Ga system. In the present study, new type of FSMAs, Co-Ni-Al alloys with B2 bcc ordered structure were investigated.. The details of results obtained by the present work are as follows:(1) Transformation temperatures: Martensitic transformation temperature (Ms) and Curie temperature (Tc) were determined by DSC and VSM measurement. Some alloys have Ms and To in relatively high temperatures region over room temperature. This result means that the Co-Ni-Al alloys can be a candidate of the promising FSMA.(2) Crystal structure: The parent and martensits phases have B2 and Ll_0 structures, respectively. The c/a ration of the Ll_0, phase is 0.81.(3) Shape memory and mechanical properties: Coexistence with γ phase improves the ductility of alloys and a perfect SM can be obtained by a training treatment.(4) Magnetic properties: Magnetic anisotropies of austenite and martensite phases were determined using single crystals, and magnetostriction of about 0.3% was detected.(5) FSM wire, FSM wire with 0.5 to 1.0mmf could be produced by conventional techniques of rolling and drawing. The obtained wire showed a pseudoelastic behavior.