The influence of different heat-treatment conditions on microstructure and mechanical properties of TC4 - DT alloy at room temperature was examined in this paper. Results show that in contrast on duplex microstructure, the sample with lamellar microstructure has better fracture toughness, but the yield stress and ductility decrease; the width of a lamellar is varied by controlling cooling rates from the β phase field heat - treatment, temperature and cooling rates of secondary heat - treatment, the microstructure by air cooling with the primary crand fine secondary a, and the microstructure by furnace cooling with the coarse a lamellar; as the microstructure of martensite obtained by water quenching from the β phase field was annealed at the (a +)8) phase field, the primary a can not completely transform into β phase, in the same way, the a lamellar is directly decomposed from martensite instead of secondary a transformed from β . The integrated matching of tensile properties and fracture toughness duo to the fine secondary a lamella can be obtained for the samples with lamellar microstructure after multi heat-treatment 1 015℃/1 h/AC +955℃/1.5 h/AC + 550℃/6 h/AC.%研究了几种热处理制度对TC4 - DT钛合金板材显微组织和力学性能的影响.结果表明:等轴或双态组织具有好的拉伸性能,片层组织能够有效提高材料的断裂韧性；控制单相区固溶的冷却速度以及第二重热处理的温度和冷却速度,可以获得不同尺寸的片层组织；单相区固溶后空冷,再经两相区第二重热处理,空冷的组织中含有粗的初生α片层和细小的次生α片层,炉冷的组织中α片层变厚,单相区固溶后水冷得到马氏体组织,在两相区热处理保温时,马氏体组织直接分解成粗的α片层.采用1 015℃/1 h/AC +955℃/1.5 h/AC+ 550℃/6 h/AC多重热处理,可以获得粗细相间的片层组织,具有更好的强度-塑性-断裂韧性的综合匹配.
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