Microstructure And Properties Of High-temperature Castings Ti6242 Alloy

Ti6242 nearly α titanium alloy provided by Shanghai Institute of precision instruments. The alloy has a small density, high strength, high temperature resistance, corrosion resistance, good fatigue properties and other excellent features.Studied alloys T(α + β) means this paper by means of optical microscopy, X-ray diffraction, scanning electron microscopy, mechanical properties and thermal simulation tests / β phase transition temperature, hot isostatic pressing and heat treatment on the behavior of the alloy room temperature, high temperature mechanical properties and microstructure effects. The main conclusions are as follows:(1) Ti6242 alloy castings organization widmanstatten, yield strength and elongation after Ti6242 gravity casting alloys increased by 23.1% and 1.3%(2) Hot isostatic processing eliminates generated when casting Shrinkage defects such as grain refinement, α slice thickness and slice of cluster size, organization into uniform widmanstatten, thus significantly improving mechanical properties, in particular mechanical properties at room temperature. After hot isostatic pressing ultimate tensile strength 852 MPa, the maximum tensile strain of about 6.32%.(3) Ti6242 alloy at a temperature in the range of 825℃~ 965℃solution treatment, as the solution temperature increases, and the organization of lamellar microstructure wherein the α sheet thickness thicker yield strength and maximum tensile strength of liters high trend, when the solution temperature is higher than 910℃, yield strength and elongation did not change significantly.(4) Different changes in the cooling rate leads to tissue and secondary α/β phase structure varies. Ti6242 alloy solution treatment faster rate obtained with more residual β transformation structure and organization of these β transformation subsequent heat treatment will be converted to the secondary α phase. The high proportion of fine secondary particle α phase can block dislocation movement and further increasing the strength of Ti6242 alloy, reducing its ductility. yield strength and elongation α / β obtained by heat treatment with α Ti6242 alloy sheet thickness variation Ti6242 alloy obey Hall-Peck relationship.(5) βA heat, βB heat, βC have enhanced heat the raw material yield strength and elongation. βA lamellar heat treatment, elongation of 54%. βB heat treatment basketweave, enhance the yield strength of about 15%. βC heat treatment to obtain coarse basketweave, improved 6.4% yield strength, elongation, improved 78%.(6) βC heat treatment Ti6242 alloy has the best overall tensile properties, which is due to the organization after the heat treatment of the obtained cluster as a small, coarse α sheets basket structure.(7) at an elevated temperature, the yield strength and maximum tensile strength decreases with increasing temperature, ductility and increased with increasing temperature. After βC mechanical properties of high temperature heat treatment has the best(823K down), then the yield strength of 458.7MPa, elongation of 15.3%.