高能球磨工艺对B4C/Al复合粉体结构演变及分布均匀性的影响

制备B4C增强Al基复合材料存在的难点主要是B4C颗粒在Al基体中的均匀分布及界面结合。本研究采用卧式搅拌高能球磨法制备了B4C/Al复合粉体,研究了搅拌轴转速和球磨时间对B4C/Al复合粉体结构演变及分布均匀性的影响。结果表明,随搅拌轴转速的提高,复合粉体受磨球碰撞时所获能量增大,增强体颗粒瞬间被破碎同时使Al粉发生较大的塑性变形,随球磨时间的延长,破碎的B4C颗粒逐渐在Al基体中分散均匀并与基体焊合,利于粉体实现均匀分布和良好的界面结合。球磨过程中B4C沿颗粒棱边脆性断裂,在Al粉的冷焊变形过程中被嵌入,形成一种片状化的Al粉基体包裹B4C增强相的复合粉体。在搅拌轴转速为600/800r/min(交变转速,交变频率为1min),球磨时间为2h时,B4C/Al复合粉体的粒度得到细化,B4C颗粒在Al基体中分布均匀、界面结合紧密。

Effect of Ball Milling Technics on Structural Evolution and Uniform Distribution of B4C/Al Composite Powder

The main difficulties of preparing the B₄C reinforced Al matrix composite are uniform distribution and interfacial bonding of B₄C particles in Al matrix. In this study, the composite powder of B₄C/Al was fabricated by high-energy ball milling. The effects of rotational speed and milling time on structural evolution and uniform distribution of B₄C/Al composite powder were investigated. The results indicate that as the rotational speed up, the composite powder gain more energy from collision with the ball. In addition, the reinforced particles are broken instantly, which lead to large plastic deformation of Al matrix. With the extension of mil-ling time, the broken B₄C particles are gradually uniformly distributed in Al matrix and bond with the matrix. This is conducive to uniform distribution and interfacial bonding of the powder. During process of milling, brittle fracture of B₄C particles happen along the edge. When the shape of Al powder change from spherical to lamella, B₄C particles are embedded in Al matrix, forming a composite powder where B₄C reinforcements are wrapped in the flaky Al matrix powder. When the rotational speed is 600/800 r/min (alternating speed with alternating frequency of 1 min) and the milling time is 2 h, the size of B₄C/Al composite powder is refined, and B₄C particles are uniformly distributed in Al matrix with strong interfacial bonding.