研究激光立体成形(Laser Solid Formed,LSF)Ti60合金热处理(双重退火980℃,2 h AC+650℃,3 h AC)前后的组织形成规律,分析其在室温和高温(600℃)下的拉伸性能.研究发现:Ti60合金在激光立体成形过程中由于熔池顶部形成的等轴晶层占有一定的比例,在熔覆新层时未被完全覆盖,在整个熔覆层中呈现出等轴晶的宏观形貌,并出现了层带组织.Ti60合金激光沉积态显微组织为魏氏组织,由大量沿原始等轴β晶界向晶内生长的α板条束和少量板条间β相组成,成形件室温和高温强度分别高于锻造件,室温塑性比锻造件低,而高温塑性超过锻态;经过双重退火后,成形件中的层带组织消失,晶界α相被打断,不连续分布在原始的β晶界处,晶内α板条粗化,并部分球化,这使得室温和高温强度略有下降,但塑性增高,综合力学性能提高.
In the present paper, the microstructore and mechanical properties of as-deposited and duplex-annealing treated laser solid formed (LSF) Ti60 alloy at room temperature and 600 ℃ were investigated. It was found that Ti60 alloy is inclined to form equiaxed grains during laser solid forming due to a high proportion of the equiaxed grains in the molten pool and uncompletely remelting when new layer was deposited on prior layer. For the as-deposited sample, the microstructure is composed of Widmanstatten a laths in prior equiaxed β grain. Through duplex-annealing treatment, the continuous prior β boundary was broken up, the α laths have an obvious tendency to coarsen and part of them were spheroidized. The ultimate tensile strength of the as-deposited LSF sample at room temperature and 600 ℃ are both higher than wrought, while the plasticity of room temperature is lower than wrought. The fractography shows toughness fracture character, and the plasticity of 600 ℃ approach those of wrought. The comprehensive mechanical properties of laser formed samples are improved obviously through duplex-annealing treatment.
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