Abstract

Ribbons of alloys of the quasi-binary TiNi–TiCu system with 25, 30, 35, and 40 at % copper were fabricated by planar flow casting at a cooling rate of 10⁶ K/s. The thickness of the ribbons was 30–50 μm, and their width was 10–20 mm. The structure and phase transformations of alloys were studied using electron microscopy, X-ray diffraction, and differential scanning calorimetry. It was found that the alloys with 25 and 30 at % Cu in the initial state have an amorphous-crystalline structure, which undergoes one-stage polymorphic crystallization of the amorphous state with the formation of austenitic phase B2 under heating in a calorimeter. When cooled to room temperature, phase B2 undergoes a martensitic transformation to orthorhombic phase B19. It was demonstrated that the alloys with 35 and 40 at % Cu become amorphous when quenched and undergo two-stage (primary and eutectic) crystallization under heating. The resulting structure is two-phase (tetragonal phase B11 (TiCu) with a small fraction of phase B2). An increase in the concentration of copper leads to a reduction in the onset temperature of crystallization.

中文翻译：

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高浓度铜非晶态TiNiCu合金的结晶细节

摘要

通过以10 ⁶ K / s的冷却速率进行平面流铸来制造含25％，30％，35％和40％的铜的准二元TiNi–TiCu系统的合金带。色带的厚度为30–50μm，宽度为10–20 mm。使用电子显微镜，X射线衍射和差示扫描量热法研究了合金的结构和相变。发现在初始状态下具有25和30原子％的Cu的合金具有非晶态晶体结构，该非晶态晶体结构在非晶态下经历一阶段的多晶型结晶，并在热量计中加热形成奥氏体相B 2。当冷却至室温时，相B 2发生马氏体转变为正交相B19.证明了具有35和40原子％的Cu的合金在淬火时变成非晶态并且在加热下经历两阶段（一次和共晶）结晶。所得的结构为两相（四方相B 11（TiCu）和一小部分的相B 2）。铜浓度的增加导致结晶开始温度的降低。