Tham khảo tài liệu 'handbook of materials for product design part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 3 a b Figure a As-cast Ti-47Al-2Nb-2Cr at exhibiting coarse a2 p lamellar structure and b heat-treated Ti-47Al-2Nb-2Cr at showing refined a2 p lamellar colonies HT 1420 C 20 min WQ cyclic heat treatment described in . patent tures of a cast Ti-47Al-2Nb-2Cr at alloy before and after heat treatment. The HT applied to this material involves 1420 C 20 min WQ cyclic heat treating. The refined lamellar structure will yield a better balance between room-temperature tensile properties and high-temperature creep resistance in comparison with coarse cast lamellar structure or cast duplex structure derived from conventional heat treatment at 1010 C 50 hr . Examples of cast Y-TiAl components have been produced ranging from turbocharger rotors and engine valves for the automobile engines compressor and turbine blades casings and other structural components for turbine engines but widespread applications have been slow to take hold. GE has built and tested a turbine engine with a low-pressure turbine rotor that was fitted with Y-TiAl power turbine blades but there are still no reports of these alloys being used in commercial engine applications. Table shows some data comparing the cast Y-TiAl with two commonly used cast nickel based alloys. From these data it is clear that although the creep and fatigue properties of Y-TiAl have been improved significantly engine manufacturers are still looking for an increase in these properties that would allow them to have the same service life as the nickel alloys that are the current alloys of choice. Titanium TABLE Comparative Property Data for Nickel Alloys and Cast Y-TiAl Property Alloy IN100 IN713LC XD alloy Density ib cu. in. UTS ksi 140 129 69 to 96 Specific UTS ksi ib cu. in. 500 446 480 to 668 Yield strength ksi 112 102 36 to 69 Specific yield strength ksi lb cu. in. 400 353 250 to 480 Young s modulus X 107 X 107 X 107 Specific creep properties Time to 1 creep strain 43
