Effect of rare earth element (La,Nb) on hardness of Ti15Cu15Ni filler metal and shear strength of TC4 joint

The effect of rare earth on the Ti15Cu15Ni brazing filler alloys and the properties of joints brazed with the widely-used TC4 was studied by adding small-amount of LaNd to Ti15Cu15Ni. The results indicate that RE phases are distributed on the boundaries between α-Ti and intermetallic phases, which improves the hardness of brazing filler alloys by hindering the movement of dislocations. When the content of RE is 1%, the hardness reaches to the maximum of 40 HRC. The RE content has large effect on the shear-strength, when the content of RE is under 0.5%. The strength increases with the increase of RE, when the content of RE is higher than 0.5%. The strength decreases with the increasing of RE. When the content of RE is exactly 0.5%, the shear-strength reaches a maximum of 244.55 MPa.