Microstructure And Mechanical Properties Of A High Temperature Alloy For Short-term Use At700℃

The ingot of Ti-Al-Sn-Zr-Mo-Nb-W-Si high temperature alloy was prepared byinduction skull melting(ISM) in a water cooler copper crucible. The pancake andsheet were obtained by forging and rolling, respectively. This research involves thesolidification, forging and rolling of the alloy. Microstructures and properties arealso emphasized and systemically discussed. Some results are shown as thefollowing.The typical microstructure of the ingot is thick widmanstatten. The tensile testsat room and high temperature showed that the strength reach to1026MPa、616MPaand492MPa at the room temperature650℃and700℃, the elongation reach to4.7%、5.2%and8.8%. The high-temperature oxidation test showed that the surfaceoxides were mostly TiO2and a small amount of Al2O3, the oxidation kinetic curvesconform the parabolic law. Over time, the gradual thickening of oxide layer wascrazed and dropped.The basket weave is refined after forging, and the original β grains weredisappeared. The tensile test at room temperature show that the strength reach to1138MPa and the elongation reach to6.3%. Compared with casting, after forging,the alloy has a better strength and elongation in high temperature. The strength andthe elongation reached752MPa and549MPa,11.7%and15.8%at650℃and700℃, respectively. In the two-phase region, with the solution temperatureincreasing, α phases of the alloy reduce, but basket weave’s size increase; in thesingle β-phase region, it is the acicular widmanstatten.The alloy sheets were obtained by different craft rolling. The structure of1150℃/50%sheet is acicular basket weave. The strength reached to1188MPa, butthe elongation only reached to3.4%at the room temperature tensile test. At650℃and700℃, the alloy got the best strength and elongation, reached768MPa and585MPa,17%and32.4%. The structure of1050℃/60%sheet is equiaxial β grains,and has the best room temperature tensile properties. The strength and theelongation reached1193MPa and9.6%. Respectively, the double basket weaves andbimodal microstructur were obtained after solution in the two-phase region. Basketweaves were obtained after solution in β phase region.