Keywords: 
• Zr55 Cu30 Al10 Ni5块体非晶合金 /
• 激光立体成形 /
• 退火处理 /
• 粉末状态

Abstract: Laser solid forming (LSF) is a viable and promising manufacturing technique for preparing bulk metallic glasses (BMGs) without size limitation. Owing to the structural heredity of alloy melts, the crystallization characteristic of the powder has an important influence on that of the deposit during LSF process. In this work, the as-prepared Zr55Cu30Al10Ni5 (Zr55) alloy powder and the Zr55 alloy powder annealed at 1000 K are used for LSF of Zr55 BMGs. The influence of the crystallization characteristic of Zr55 alloy powder on the crystallization behavior of the remelted zone (RZ) and heat affected zone (HAZ) in the deposit are investigated. It is found that the as-prepared Zr55 powder prepared by plasma rotating electrode process (PREP) is composed of the amorphous phase and Al5Ni3Zr2 phase. When the heat input of laser is low, there exist some Al5Ni3Zr2 residual phases in the amorphous matrix in the RZ, and there appear some Cu10Zr7, CuZr2 and NiZr2 phases besides the Al5Ni3Zr2 phase in the HAZ for the deposit fabricated by as-prepared Zr55 powders. With the increase of the heat input of laser, the RZ remains the amorphous state since the Al5Ni3Zr2 phase is completely remelted, while there are a large quantity of Al5Ni3Zr2 phases and some other crystallization phases precipitated in the HAZ because the heating and cooling rate decrease in the HAZ during LSF. Fabricated by the fully crystallized annealed powder, the deposit is mainly of the amorphous phase, and almost no Al5Ni3Zr2 phase is found even if the incident laser power is low. It is shown that the crystallization of the deposit fabricated by the annealed powder at the low heat input does not change remarkably with the increase of the deposited layers. The Zr55 deposit with five deposited layers could still keep large volume fraction of amorphous phase. This is mainly because the powder experiences the structure relaxation entirely during the annealing treatment, and the volume fraction of the short/medium-range ordered structure associated with the Al5Ni3Zr2 phase in the powder is reduced. Therefore, the volume fraction of the Al5Ni3Zr2 clusters in re-solidified amorphous RZ in the deposited layer decreases during LSF, which is conducible to the increase of the thermal stability of the already-deposited layer. In result, the area of the HAZ in the subsequent deposition decreases and the precipitation of Al5Ni3Zr2 phase is suppressed. In conclusion, increasing the heat input of laser aggravates the crystallization of the deposited layers, and the Al5Ni3Zr2 cluster in the powder has an important influence on the crystallization behavior of the Zr55 deposited layers.