激光焊接TiB_(w)/TA15复合材料组织结构演变

Structure evolution of laser welding of TiB_(w)/TA15 composites

研究了不同激光焊接功率焊接后TiB_(w)/TA15复合材料的显微组织结构及相组成,分析了焊缝中TiB增强相的演变机制。对TiB_(w)/TA15复合材料分别进行了单级退火及固溶-时效热处理,探究了不同热处理工艺处理后复合材料内部显微组织和增强相的演变及相结构的变化。结果表明,激光焊接TiB_(w)/TA15复合材料组织由TiB和α′马氏体两相组成,β晶晶粒显著细化,焊缝中TiB回熔后在β柱状晶晶界以网状形式重新析出,尺寸细小且存在明显偏聚现象。热处理后α′马氏体发生分解转变为平衡态α+β相,组织中出现块状硼化物,β单相区较高温度固溶后,块状硼化物中析出细小高长径比TiB,局部初生TiB粗化,长径比明显增加。焊接后TiB网状结构的形成与凝固过程中B原子在β晶界处的聚集有关;热处理过程中TiB的转变与激光焊接过程中快速冷却导致的局部B元素扩散不充分和不均匀有关。

The microstructure and phase composition of TiB_(w)/TA15 composites after laser welding with different welding power were studied,and the evolution mechanism of TiB reinforced phase in the weld was analyzed.The microstructure evolution,reinforced phase evolution,and phase structure variation of TiB_(w)/TA15 composites in different heat treatment processes were investigated by single annealing and solution-aging heat treatment.Results show that the microstructure of laser-welded TiB_(w)/TA15 composites was composed of TiB andα′martensite,andβgrains were significantly refined.After remelting,TiB was reprecipitated at theβcolumnar grain boundary in a network form with small size and obvious segregation phenomenon.After heat treatment,α′martensite decomposed into equilibriumαandβphases,and massive borides appeared in the microstructure.After high-temperature solid solution inβphase region,fine TiB with high aspect ratio was precipitated from massive borides,local primary TiB was coarsened,and the aspect ratio increased obviously.The formation of TiB network-like structure was related to the aggregation of boron atom at theβgrain boundary during solidification process.The transformation of TiB during heat treatment was related to the insufficient and uneven diffusion of boron caused by rapid cooling during laser welding.