Evolution of Two Types of α Plates in Tri-modal Microstructure of TA15 Alloy under Varying Processing Conditions

摘要:

为了通过组织设计获得优异的性能，揭示TA15钛合金三态组织中的 2 种片层α相（次生片层α和转变β基体中细α条）的演化至关重要。采用等温压缩（在950，965和975 ℃），结合双重热处理（在压缩温度以下10~40 ℃进行第 1 次热处理，然后在810 °C进行第2次热处理），研究了2种片层α相的演化规律。结果表明，在低于等温压缩温度以下10 ℃进行第1次热处理，可以获得单独分布的厚片层α相和细α条，这种细α条在第1次热处理后空冷具有集束的形态，而在第1次热处理后水冷具有针状形态。在低于等温压缩温度以下25 ℃进行第1次热处理，可以获得集束和网篮状的片层α相以及细α条。在低于等温压缩温度以下40 ℃进行第 1次热处理，只能获得集束和网篮状的片层α相。另外，在第1 次热处理温度相同的条件下，不同冷却方式对次生片层α相的形态影响较小。

Abstract:

It is critical to reveal the evolution rules of two types of α platelets (secondary lamellar α and thin α lath in transformed β matrix) in the tri-modal microstructure of TA15 alloy so as to obtain exceptional properties through microstructural design. The combined effects of isothermal compression (at 950, 965, and 975 °C) and subsequent double heat treatments (a high-temperature heat treatment at 10 °C to 40 °C below the compression temperature followed by a 810 °C heat treatment) on the evolution of the two types of α platelets were studied. The results show that the isolated lamellar α and the thin α lath can be produced by first heat treatment at 10 °C below the compression temperature and the thin α lath in this structure has a colony morphology under air cooling and an acicular morphology under water quenching. Colony and basketweave lamellar α and thin α lath can be produced when the first heat treatment is at 25 °C below the compression temperature. Only the colony and basketweave lamellar α can be produced when the first heat treatment temperature is 40 °C lower than the compression temperature. Besides, the morphology of lamellar α is not substantially influenced by cooling modes after the first heat treatment at the same temperatures.