热处理对激光立体成形TC11钛合金组织的影响

Influence of Heat Treatment on Microstructure of Laser Solid Forming Ti-6.5Al-3.5Mo-1.5Zr-0.25Si Alloys

通过对TC11钛合金激光立体成形件沉积态和热处理态组织进行对比研究,探索改善TC11钛合金激光立体成形组织,提高材料高温综合性能的途径。结果表明,TC11钛合金的沉积态组织由贯穿多个熔覆层粗大柱状晶和粗大等轴晶组成,原始柱状β-Ti晶内的微观组织是由条状α和残留β组成。沉积态试样在950℃热处理后组织为等轴α、条状α和β转变基体组成的近似三态组织,晶界α大部分破碎球化消失,部分未破碎的晶界上镶嵌有α集束。粗大β晶内等轴α的产生与亚晶有关。在970℃热处理后为网篮组织,等轴α较少,α板条有粗化趋势;在1030℃再结晶后再经950℃热处理的组织是由粗大α板条组成的魏氏组织,在α边界和α内部残留有大量细小β,晶界α基本没有破碎消失。

The as-deposited microstructure and heat-treated microstructure of Ti-6.SAI-3.5Mo-1.5Zr-0.25Si alloys （TC11） by Laser Solid Forming （LSF） were compared, and approaches to improve LSF microstructure and high-temperature combination properties of TC11 alloys were researched. Results show the as-deposited microstructure of TC11 alloy consists of coarse columnar grains and equiaxed grains throughout cladding layers, and the prior columnar β-Ti grains are composed of lathlike a and residual ft. The microstructure of as-deposited samples after 950℃ heat treatment is a similar triplex mixture of equiaxed a, basketweave a lath and transformed ft. The majority of continuous prior a boundary is broken, and become spheroidized and illegible; a laths grow up to bunch on some unbroken boundary; the equiaxed a in coarse ℃ grains is related with subgrains. The microstructure after heat treated at 970℃ is a certain basketweave structure consisting of a few equiaxed-a and a laths which have coarsening tendency; the microstructure after recrystallization at 1030℃ followed by 950℃ heat treatment is typical Widmanstiitten structure consisting of coarse a laths, and lots of β-Ti is found to separate out inside a and on a boundaries without breaking basically.