(西北工业大学 材料科学与工程学院，西安710072)
摘 要: 采用大变形量等温锻造、低温多向锻造、等通道转角挤压(ECAP)、形变热处理及其复合工艺，对TA15近α钛合金进行细晶和超细晶化加工研究。结果表明：高低温复合形变热处理是细化TA15合金显微组织的有效途径，单相区的高温形变热处理可获得细针状马氏体α′和亚稳态β相，两相区较低温度的形变热处理可显著细化由α′马氏体和亚稳β相分解而来的细针状α和β相。ECAP工艺通过强烈的纯剪切变形，虽可使TA15合金等轴α晶粒尺寸细化至3 μm左右，但ECAP形变热处理复合工艺可通过位错墙和孪晶交割等作用进一步获得晶粒尺寸为0.2~0.6 μm的亚微米级等轴超细晶及晶粒尺寸为20~50 nm的部分纳米晶。
关键字: 钛合金；锻造；等通道转角挤压；复合形变热处理；位错墙；孪晶交割；超细晶
（School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China）
Abstract:The fine or ultrafine grained near α titanium alloy TA15 was prepared through large deformation isothermal forging, low temperature multi-directional forging, equal channel angular pressing (ECAP), thermomechanical treatment and the ways above combined. The results indicate that high and low temperature thermomechanical treatment is an effective way to refine the microstructure of TA15 alloy. Fine acicular martensite α′ phase and metastable β phase are obtained after high-temperature thermomechanical treatment above β transus, and the needle α and β phases decomposed from martensite α′ and metastable β-phase are significantly refined after thermomechanical treatment at lower temperature in two-phase region. Though the grain size of TA15 alloy can be refined to 2-3 μm under the intense pure shear deformation effect of ECAP process, the microstructures with sub-micron grains of 0.2-0.6 μm and some nano-sized grains of 20-50 nm are obtained under the functions of dislocation walls and twins intersection through multiple processing of ECAP and thermomechanical treatment.
Key words: titanium alloy; forging; equal channel angular pressing; multiple thermomechanical treatment; dislocation walls; twins intersection; ultrafine grains
