Al含量对激光沉积(CoCrFeNi)-Al高熵合金晶粒形貌的影响

Effect of Al Content on Grain Morphology of Laser Deposited(CoCrFeNi)-Al High Entropy Alloys

激光沉积技术有望成为制备高熵合金的理想方法,但其制备的高熵合金易产生粗大柱状晶组织,限制了其在高熵合金制备中的广泛应用。利用激光沉积制备了(CoCrFeNi)1-xAlx(x=0,0.10,0.15,0.20)高熵合金,研究了不同Al含量下激光沉积(CoCrFeNi)1-xAlx高熵合金物相及晶粒形貌的演变规律,利用差热分析法对不同Al含量下高熵合金的凝固行为进行了分析。结果表明:随Al含量的增加,激光沉积(CoCrFeNi)1-xAlx高熵合金物相由面心立方(FCC)单相转变为FCC和体心立方(BCC)双相结构,不同Al含量下高熵合金中BCC相含量分别为3vol%(x=0.10)、24vol%(x=0.15)和52vol%(x=0.20);激光沉积高熵合金组织形貌也随Al含量增加由粗大柱状晶转变为细长晶粒,晶粒尺寸由116μm(x=0)显著降低至40μm(x=0.20)。这主要是由于Al含量的增加可降低(CoCrFeNi)1-xAlx高熵合金形核过冷度(ΔTN),并提高合金的生长限制因子(Q),从而产生更为显著的成分过冷,大幅促进了形核行为。

Laser deposition technology is expected to be an ideal method for preparing high entropy alloys(HEAs).However,the HEAs prepared by laser deposition prefer to present the microstructure of coarse columnar grains,which limits the wide application of laser deposition in preparing HEAs.(CoCrFeNi)1-xAlx(x=0,0.10,0.15,0.20)HEAs were prepared by laser deposition.The evolution of phase and grain morphology of laser deposited(CoCrFeNi)1-xAlx HEAs were studied.The solidification behavior of the HEAs was analyzed by differential thermal analysis.The results show that with the increase of Al content,the phase of laser deposited(CoCrFeNi)1-xAlx HEAs changes from face centered cubic(FCC)single phase to FCC and body centered cubic(BCC)dual phase structure.The content of BCC phase in the HEAs with different Al contents is 3vol%(x=0.10),24vol%(x=0.15)and 52vol%(x=0.20),respectively.With the increase of Al content,the grain morphology of the laser deposited HEAs also changes from coarse columnar grains to fine elongated grains,and the grain size decreases significantly from 116μm(x=0)to 40μm(x=0.20).This can be owing to the decrease in nucleation undercooling(ΔTN)and the increase of growth restriction factor(Q)of(CoCrFeNi)1-xAlx caused by the increase of Al content,which can promote more significant constitutional undercooling and boost the nucleation behavior.