The effects of solution-aging treatment on the microstructures, mechanical properties and internal friction of Ti- 55.06%Ni-0.3%Cr （mole fraction） alloy were investigated by means of tensile test, dynamic mechanical analysis （DMA） and spherical aberration electron microscopy （SAEM）. The results show that the aged alloys with Cr3Ni2 phase always exhibit higher tensile strength and hardness than those of solution-treated alloy without Cr3Ni2 phase, and the aging peak temperature presents at 375 ℃. It is also found that the internal friction peak （tan 6） value decreases with increasing the frequency. There are two internal friction peaks corresponding to the B2（austenite）→R and R→M（martensite） transformations upon cooling, but only one corresponding to the reverse M→B2 transformation upon heating in both solution-treated and 375 ℃-aged alloys, due to the superposition of Mand R phase transformation. Besides, the position of internal friction peaks in the alloy after aging at 375 ℃ shifts to higher temperature. This is attributed to the decrease of Cr and Ni content, and the decline of lattice deformation and transformation resistance, all of which are related to the precipitation of Cr3Ni2 phase in the solution-aged alloys.
