Preparetion, Microstructure And Mechanical Properties Of Tial Based Alloy Sheet

TiAl based alloys are extensively investigated in recent years because of theirlow density, high strength, excellent oxidation and creep resistance. TiAl sheetscan be used not only as structure materials but also as function materials. Withthe development of TiAl based alloys application, it is urgent to fabricate TiAlsheets. However, the major factors limiting structural applications of thismaterial are their ambient temperature brittleness and poor workability. In thispaper TiAl sheets are obtained with a new method,which involve preparing ingot,caned forging and hot-pack rolling. The property of the TiAl based alloy sheetproduced was test.The ingots were prepared by Induction Skull Melting(ISM). The resultsindicate that the as-cast alloy consists ofα2,γ, B2 and YAl2 phases. Thecrystalline grains of as-cast alloy are coarse lamellar structure. Element V existsin B2 phase, and of element Y exist in YAl2phase. The mechanical property testsshowed that the plasticity of as-cast alloy is very low. At room temperature,σsandσb are 419.5MPa and 510.6 MPa, respectively, andδis 0.5%. At 700℃,σsandσbare 342.6MPa and 442.7MPa,respectively, andδis 5.7%.TiAl based alloy pancake is prepared by caned forging. The as-forged alloyconsists ofα2,γ, B2 and YAl2 phases. Microstructure observation indicated thatthe amout of lamellar structure reduces apparently, the grain size is finer, and Y-rich phases are broken up or elongated as strap shape after deformation andrecrystallization.At room temperature,σsandσbreach 551.2MPa and 613.8 MPa,respectively, andδis 1%.By using hot-pack rolling, the TiAl base alloy sheets wereprepared with asizeof 340×(65~110)×2mm. After rolling, the Y-rich phase disperses in the matrixmore uniformly.The as-rolled structure is coarser than the as-forged structure. Atroom temperature,σs andσb are 509.1MPa and 611.7 MPa, respectively, andδis1.2%. At 700℃,σs andσb are 414.6MPa and 488.8 MPa, respectively, andδis7.9%.