Molten Cu-13AI and Cu-13AI-4Ni (mass fraction) alloys have been investigated using X-ray diffraction method. A distinct pre-peak has been found in the structure factors. The pre-peak increases its intensity with decre...Molten Cu-13AI and Cu-13AI-4Ni (mass fraction) alloys have been investigated using X-ray diffraction method. A distinct pre-peak has been found in the structure factors. The pre-peak increases its intensity with decreasing temperature and addition of Ni. The structural unit size corresponding to the pre-peak equals to magnitude of (111) planar distance of phase. The appearance of a pre-peak is due to existence of clusters with -phase-like structure in melt. Quantity and size of clusters increase with decreasing temperature but their structural unit size remains constant. Cu-13AI-4Ni shape memory alloy ribbons can be fabricated by rapid solidification technique. Order degree of martensite and temperature of the reverse martensitic transformation increase with decreasing liquid quenching temperature. phase particles develop from incorporating and growing of the clusters during solidification, thus result in the correlation between liquid structure and solid transformation.展开更多
The mechanical behavior of shape memory alloys （SMAs） is closely related to the formation and evolution of its microstructures. Through theoretical analysis and experimental observations, it was found that the stres...The mechanical behavior of shape memory alloys （SMAs） is closely related to the formation and evolution of its microstructures. Through theoretical analysis and experimental observations, it was found that the stress-induced martensitic transformation process of single crystal Cu-based SMA under uniaxial tension condition consisted of three periods： nucleation, mixed nucleation and growth, and merging due to growth. During the nucleation, the stress dropped rapidly and the number of interfaces increased very fast while the phase fraction increased slowly. In the second period, both the stress and the interface number changed slightly but the phase fraction increased dramatically. Finally, the stress and the phase fraction changed slowly while the number of interfaces decreased quickly. Moreover, it was found that the transformation could be of multi-stage： sharp stress drops at several strains and correspondingly, the nucleation and growth process occurred quasi-independently in several parts of the sample.展开更多
基金This work was supported by the National Natural Science Foundation of China (No.50071028) and the Shandong Natural Science Foundation of China (No. L2000F01).
文摘Molten Cu-13AI and Cu-13AI-4Ni (mass fraction) alloys have been investigated using X-ray diffraction method. A distinct pre-peak has been found in the structure factors. The pre-peak increases its intensity with decreasing temperature and addition of Ni. The structural unit size corresponding to the pre-peak equals to magnitude of (111) planar distance of phase. The appearance of a pre-peak is due to existence of clusters with -phase-like structure in melt. Quantity and size of clusters increase with decreasing temperature but their structural unit size remains constant. Cu-13AI-4Ni shape memory alloy ribbons can be fabricated by rapid solidification technique. Order degree of martensite and temperature of the reverse martensitic transformation increase with decreasing liquid quenching temperature. phase particles develop from incorporating and growing of the clusters during solidification, thus result in the correlation between liquid structure and solid transformation.
基金the National Natural Science Foundation of China(Nos.10372033 and 10672042)Pujiang Scholar Program and Natural Science Foundation of Shanghai(No.06ZR14009).
文摘The mechanical behavior of shape memory alloys （SMAs） is closely related to the formation and evolution of its microstructures. Through theoretical analysis and experimental observations, it was found that the stress-induced martensitic transformation process of single crystal Cu-based SMA under uniaxial tension condition consisted of three periods： nucleation, mixed nucleation and growth, and merging due to growth. During the nucleation, the stress dropped rapidly and the number of interfaces increased very fast while the phase fraction increased slowly. In the second period, both the stress and the interface number changed slightly but the phase fraction increased dramatically. Finally, the stress and the phase fraction changed slowly while the number of interfaces decreased quickly. Moreover, it was found that the transformation could be of multi-stage： sharp stress drops at several strains and correspondingly, the nucleation and growth process occurred quasi-independently in several parts of the sample.
