Micro-toughened titanium-based intermetallics for high-temperature service. CRADA final report

摘要

This Cooperative Research and Development Agreement (CRADA) report deals with the composition development, processing parameter development, microstructural evaluation, and mechanical properties development of the (beta) TiAl alloys. Two series of alloy compositions were identified. The first series consisted of four alloys, and the second series consisted of three alloys. The powders were packed in titanium cans, evacuated, and sealed. The titanium cans were hot extruded at 1150, 1250, and 1400(degrees)C to an area reduction ratio of 16:1. The extruded bars were heat treated between 800 and 1320(degrees)C, and their microstructure characterized in the extended and heat-treated condition by optical, scanning, and transmission electron microscopy (TEM). The microstructural features such as colony size, width of colony boundary (beta) layer, interlamellar spacing, (alpha)(sub 2)-(alpha)(sub 2) spacing, (beta)lamellar width, and (alpha)(sub 2)-(beta) layer ratio were quantified. Tensile bars were prepared from the extruded bars by electrodischarge machining followed by grinding. Tensile tests were conducted from room temperature to 1000(degrees)C. Three-point-bend tests were used to measure the fracture toughness at both room temperature and 800(degrees)C. The effect of long-term annealing at 800 and 1000(degrees)C on one of the alloys was measured at room temperature. Tensile properties of the alloys of this study were compared with the data reported in literature.