铸态Ti-46Al-6(Cr, Nb, Si, B)合金的高温流变行为及其组织演变

High Temperature Flow Behavior and Microstructural Evolution of As-cast

摘要:

以3次真空自耗熔炼的Ti-46Al-6 (Cr, Nb, Si, B) (at%) (以下简称G4合金)合金为对象，采用恒温等应变速率热模拟压缩试验研究G4合金在1050～1250 ℃及0.001~1 s-1应变速率下的高温流变行为和组织演变。结果表明，在高温变形过程中，G4合金呈现先硬化后软化的流变行为特征，组织由粗大的铸态γ+γ/α2近片层组织演变为细小的近等轴γ+α2组织；造成G4合金流变软化和组织演变的主要原因是动态再结晶(DRX)。变形温度和应变速率是影响G4合金高温流变和组织演变的2个主要因素。铸态G4合金在高温下的变形机制以γ/α2层片晶团的扭折、弯曲、球化和DRX以及γ晶粒的拉长、破碎和DRX为主，孪生变形也起到了一定的辅助作用。其最佳高温塑性变形温度为1150 ℃，应变速率应不大于0.1 s-1

Abstract:

The samples of Ti-46Al-6(Cr,Nb,Si,B) (at%), G4 alloy for short, were hot compressed in the temperature range of 1050-1250 oC at constant strain rate from 0.001~1 s-1 for high temperature flow behavior and microstructural evolution study. The results show that G4 alloy displays a flow characteristic of hardening followed by softening during hot compression. The microstructure of G4 alloy evolves from as-cast big size γ+γ/α2 to small size near-equiaxed γ+α2. Dynamic recrystallization (DRX) is the main reason that results in flow softening and macro- and micro-structure evolution of G4 alloy. Temperature and strain rate are the two main factors that influence flow softening behavior and microstructure evolution of the G4 alloy during high temperature deformation. The main transformation mechanism of the G4 alloy at elevated temperature is kinking, curving, globalizing and DRX of γ/α2 lamellae, and elongating, breaking and DRX of γ grain, with twining as an auxiliary deformation mode. The optimum temperature for hot forming of cast near lamella G4 alloy is 1150 oC, and the strain rate should not exceed 0.1 s-1