Damping Characteristics of Ti_(50)Ni_(49.5)Fe_(0.5) and Ti_(50)Ni_(40) Cu-(10) Ternary Shape Memory Alloys

摘要

The damping characteristics of Ti-(50)Ni-(49.5)Fe_(0.5) and Ti-(50)Ni_(40)Cu_(10) ternary shape memory alloys (SMAs) have been systematically studied by resonant-bar.testing .and internal friction (IF) measurement. The damping capacities of the B19' martensite and the 52 parent phase for these ternary alloys are higher than those for the Ti-(50)Ni_(50) binary alloy. The lower yield stress and shear modulus of these ternary alloys are considered to be responsible for their higher damping capacity. For the same ternary alloy, the B19/B19' martensite and R phase also have a higher damping capacity than does the 52 parent phase. In the forward transformations of 52 - > R, R - > b19', and 52 - > B19' for Ti5ONi5o and Ti_(50)Ni_(49.5)Fe_(0.5) alloys, the damping capacity peaks appearing in the resonant-bar test are attributed to both stress-induced transformation and stress-induced twin accommodation. The lattice-softening phenomenon can promote the stress-induced transformation and enhance the damping capacity peaks. The Ti_(50)Ni_(40)Cu-(10) alloy had an unusually high plateau of damping capacity in the B19 martensite, which is considered to have arisen from the easy movement of twin boundaries of B19 martensite due to its inherently very low elastic modulus. The peaks appearing in the IF test for the Ti_(50)Ni-(40)Cu_(10) alloy are mainly attributed to the thermal-induced transformation due to f T not = 0 during the test.