Characterization of solid-phase welds between Ti6A12Sn4Zr2Mo0.1Si and Ti13.5A121.5Nb titanium aluminide

Linear friction welding of Ti-6Al-4V: Processing, microstructure, and mechanical-property inter-relationships

“…[14] At the weld center, where the temperature was the highest, the presence of a microstructure consisting of prior-beta grains then suggests that complete transformation of the alpha phase occurred. This finding is consistent with previous work on linear friction welding of titanium alloys that has indicated peak temperatures exceeding the beta transus at the weld interface, [1,3,15] as well as work on Ti-6Al-4V that has determined temperatures in excess of 1100°C at the joint periphery using a two-color pyrometer. [16] The morphology of the transformed microstructure within the prior-beta grains of Widmanstätten ␣-␤ (with some lamellar regions), as shown in Figure 9(b), is then a result of the cooling conditions after linear friction welding.…”

“…This increase in hardness, as compared to the parent material, may be attributed to the phase-transformation and grain-refinement characteristics in the weld center. [15] Specifically, in Ti-6Al-4V, Ivasishin and Lütjering have shown that the transformed beta grain structure with a Widmantstätten appearance has a yield strength that is a function of both the cooling rate and grain size. [29] During cooling from the betatransus temperature of 995°C, increasing the cooling rate from 15°Cиs Ϫ1 to 150°Cиs Ϫ1 increased the tensile yield strength in Ti-6Al-4V from 930 to 1100 MPa and from 1050 to 1280 MPa for a microstructure with a prior-beta grain size of 600 and 50 m, respectively.…”

Microstructure Evolution and Mechanical Properties of Linear Friction Welded Ti‐5Al‐2Sn‐2Zr‐4Mo‐4Cr (Ti17) Titanium Alloy Joints

“…The profile of the hardness curve in the TMAZ presents a concave shape with a higher value near the weld center. This is very different to other LFW titanium alloy joints, such as Ti-6242, [12] Ti64 [14,15] and Ti-6246. [4] The microhardness at the weld center zones in these joints was highest and it gradually decreased to that of the parent metals.…”

“…This approach is more cost-effective than machining blade/ disc (blisks) assemblies from solid billets. LFW has been used successfully to join a range of materials including titanium alloys, [3][4][5][10][11][12][13][14][15] superalloys, [16] steel, [17,18] intermetallic materials, aluminum, nickel, copper, and even dissimilar material combinations with the greatest emphasis on aircraft-engine alloys. [19] MTU is currently adapting this technique for use on a high-pressure compressor blisk with an IN718 nickel alloy.…”

“…The previous studies have shown that a sound weld of titanium alloys (e.g., Ti-64, [10,11,[13][14][15]20] Ti-6242, [12] Ti-6246 [4,5] ) with refined microstructure can be obtained by LFW. The weld also presents a much-higher hardness, [4,12,14,15] and comparable or slightly better tensile properties [14,15] than the parent titanium alloys, owing to the refined structure. In addition, it is clear that the mechanical properties of the welds, especially their fracture toughness, must be high enough for critical applications like blisks.…”