Al-FeCoNiCrAl high entropy alloy(HEA) composite coatings were prepared on Ti-6Al-4V via highenergy mechanical alloying(MA). The microstructures and phase composition of the coatings were studied. A continuous and dens...Al-FeCoNiCrAl high entropy alloy(HEA) composite coatings were prepared on Ti-6Al-4V via highenergy mechanical alloying(MA). The microstructures and phase composition of the coatings were studied. A continuous and dense coating could be fabricated at a ratio of 35%(weight fraction)Al-FeCoNiCrAl after 4 h milling.The results showed that the thickness of the composite coatings increased first and then decreased with the increase of milling time. And the hardness of coating increased with the increase of milling time. The phase changed during the annealing process. Part of the initial body-centered cubic(BCC)phase of the composite coatings changed into the L12 phase,(Ni,Co)3Al4 and σ phase after annealing above 550 ℃. Ordered BCC was found in the coatings after annealing above 750 ℃. Only BCC and ordered BCC appeared in coatings after annealing above 1 050 ℃. The hardness of the coatings after annealing at 550 ℃ and 750 ℃ was higher than before because of spinodal decomposition and high hardness σ phase. The hardness of the coatings after annealing at 1 050 ℃ decreased because residual stress released.展开更多
文摘由于当前具有微小孔的结构等零部件加工难度大,精度要求高,传统加工方法无法满足现有的加工精度要求,该文采用一种软性加工方法—磨粒流加工技术,实现微小孔结构精密加工。采用CFD(computational fluid dynamics)和DEM(discrete element method)相结合的方法对磨粒流加工过程进行数值分析。在数值分析过程中,考虑颗粒对壁面的碰撞作用,对不同入口速度条件下的流体和颗粒的分布状态进行对比分析,揭示磨粒流微切削作用行为,通过对材料去除机理的分析揭示颗粒对壁面的作用规律。数值模拟结果表明:随着入口速度的增大,颗粒与零件表面的摩擦与碰撞作用更为剧烈,颗粒动能转化为切削能,提高了材料的去除率;当颗粒碰撞应力小于材料极限应力时,材料只发生塑性变形,当碰撞应力大于材料极限应力时,才会发生材料去除。试验结果表明:经磨粒流加工的表面粗糙度Ra值由2.03μm降低到0.65μm,研究结果可为后续研究颗粒碰撞和颗粒微切削提供一定借鉴价值。
文摘Al-FeCoNiCrAl high entropy alloy(HEA) composite coatings were prepared on Ti-6Al-4V via highenergy mechanical alloying(MA). The microstructures and phase composition of the coatings were studied. A continuous and dense coating could be fabricated at a ratio of 35%(weight fraction)Al-FeCoNiCrAl after 4 h milling.The results showed that the thickness of the composite coatings increased first and then decreased with the increase of milling time. And the hardness of coating increased with the increase of milling time. The phase changed during the annealing process. Part of the initial body-centered cubic(BCC)phase of the composite coatings changed into the L12 phase,(Ni,Co)3Al4 and σ phase after annealing above 550 ℃. Ordered BCC was found in the coatings after annealing above 750 ℃. Only BCC and ordered BCC appeared in coatings after annealing above 1 050 ℃. The hardness of the coatings after annealing at 550 ℃ and 750 ℃ was higher than before because of spinodal decomposition and high hardness σ phase. The hardness of the coatings after annealing at 1 050 ℃ decreased because residual stress released.
