Using DSC for the detection of diffusion-controlled phenomena in Cu-based shape memory alloys
Using DSC for the detection of diffusion-controlled phenomena in Cu-based shape memory alloys
复制标题
使用 DSC 检测铜基形状记忆合金中的扩散控制现象
DOI：
10.1007/s10973-016-5926-4
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发表时间：
2016
影响因子：
4.4
通讯作者：
L. Bujoreanu
中科院分区：
文献类型：
--
作者：
N. Lohan;B. Pricop;L. Burlacu;L. Bujoreanu
热致可逆无扩散马氏体相变是形状记忆合金（SMA）的主要相变机制，在差示扫描量热法（DSC）曲线上可以通过热流随温度的闭合变化曲线方便地描述。冷却诱导的直接（向前）马氏体形成导致放热最大值，而马氏体回复，加热，是与吸热峰。扩散控制的现象的发生强调的热流变化的不连续性，如在Cu-Zn-Al SMA的情况下观察到的，经历热弹性马氏体相变。当加热时，在DSC曲线上观察到4个固态相变：（1）马氏体回复到母相的吸热极小值，（2）贝氏体转变的吸热极小值，（3）马氏体相变的吸热极小值。（3）对应于平衡α相沉淀的最大放热峰和（4）代表α相的级-母相的无序转变。第一个转变是无扩散的，而其他三个是扩散控制的。利用DSC装置研究了热处理温度、形变热处理次数和热循环对Cu-Zn-Al形状记忆合金发生扩散控制固态相变温度范围的影响，并与光学显微镜（OM）和透射电子显微镜（TEM）结果进行了对比。
The thermally induced reversible diffusionless martensitic transformation, that governs the mechanism of shape memory alloys (SMAs), can be conveniently illustrated, on differential scanning calorimetry (DSC) curves, by a close variation loop of heat flow with temperature. Cooling-induced direct (forward) martensitic formation causes an exothermic maximum, while martensite reversion, on heating, is associated with an endothermic peak. The occurrence of diffusion-controlled phenomena is emphasized by discontinuities of heat flow variations, such as those observed in the case of Cu–Zn–Al SMAs, experiencing thermoelastic martensitic transformation. When heating such a martensitic Cu–Zn–Al SMA, four solid-state transitions were observed on DSC curves, under the form of: (1) an endothermic minimum ascribed to martensite reversion to parent phase; (2) an endothermic minimum associated with transitory formation of bainite; (3) an exothermic maximum corresponding to the precipitation of equilibrium α-phase and (4) an endothermic peak representing the order–disorder transition of parent phase. The first transition is diffusionless, while the other three are diffusion-controlled. The DSC equipment was used to investigate the effects of: (1) heat treatment temperature, (2) number of cycles of thermomechanical treatment and (3) thermal cycling within the temperature range where diffusion-controlled solid-state transitions occur in a Cu–Zn–Al SMA, the results being corroborated with that obtained by optical (OM) and transmission (TEM) electron microscopy.