【作者】 廖军；

【导师】 宫晨利；

【作者基本信息】 合肥工业大学 ， 材料学， 2007， 硕士

【摘要】 热弹性马氏体相变是形状记忆合金系统最重要的特征，它对形状记忆合金的形状记忆效应、超弹性和高阻尼等力学行为有着关键的作用。研究形状记忆合金的力学弛豫行为对于揭示热弹性马氏体相变过程，拓展其应用领域具有重要意义。由于热弹性马氏体相变是一种特殊的马氏体相变，其弛豫行为必然具有特殊性。本实验采用Cu-Al-Ni-Mn-Ti等合金作为实验材料，测量合金在热弹性马氏体相变时的力学弛豫与温度、变温速率、应变振幅、振动频率、等温时间的关系。实验主要采用强迫振动模式，了解合金在不同测量条件下的力学弛豫特性，研究力学弛豫的演化规律以及弛豫峰的分解，揭示不同弛豫过程与相变的关系，重点研究相变的滞弹性行为。实验发现通常测得的马氏体相变内耗峰实质上由低温内耗峰和高温内耗峰叠加而成，低温内耗峰和高温内耗峰对应于不同的相变机制，说明热弹性马氏体相变是多个机制相互耦合的过程。高温内耗峰的峰高与振动频率的倒数呈线性关系，随应变振幅的增加而降低，峰位与振动频率无关，表明它与相界面法向运动产生的体积变化有关。低温内耗峰的峰高与对数振动频率呈对称的峰形函数关系，几乎不随应变振幅发生变化，在温度谱上随着频率的增加，低温内耗峰向高温方向移动，出现一定程度的频移现象，说明它与相界面切向粘滞性运动有关，从而证实热弹性马氏体相变中有滞弹性弛豫的存在。更多还原

【Abstract】 Thermoelastic martensitic phase transformation (MT) is one of the most important features of shape memory alloy (SMA) system, which plays a crucial role in shape memory effect, super-elasticity and high damping capacity of SMA. It is important to study the mechanical relaxation behaviors of SMA for revealing the thermoelastic MT and developing its applied fields.Cu-Al-Ni-Mn-Ti alloy, etc. were adopted as experimental materials to measure the relationship of the mechanical relaxation to temperature, strain amplitude, oscillation frequency and isothermal time. In the dynamic experiments, the forced vibration mode was taken to determine the mechanical relaxation characteristics under different measured conditions, to study the evolvement and decomposition of the relaxation peak, and still to reveal the relation between the heterogeneous relaxation processes and the MT, particularly the anelastic behaviors during the MT.It has been experimentally found that the internal friction (IF) peak measured in general MTs is actually composed of two independent peaks, i.e. low-temperature and high-temperature peaks, which correspond to different mechanisms, indicating that the thermoelastic MT is a process coupled by multiple mechanisms. The height of high-temperature peak is directly proportional to reciprocal frequencies and decreases as strain amplitudes increase, however its location at temperature spectra is unvaried with vibration frequencies. These facts show that the high-temperature peak is only associated with the volume change caused by the normal motion of phase interfaces. The maximum of low-temperature peak gives a symmetrical peak-like function against logarithmic frequencies and is almost independent of strain amplitudes, but the low-temperature peak shifts a few degrees in temperature spectra towards high temperatures with increasing the frequencies, exhibiting it is associated with the transversal viscous motion of phase interfaces. All the aspects prove that there exists the anelastic relaxation in the thermoelastic MT.更多还原