放电等离子烧结制备低密度AlTiCrNiCu高熵合金及其组织性能研究

Microstructure and Mechanical Properties Study of Low Density AlTiCrNiCu High-Entropy Alloy Prepared by Spark Plasma Sintering

摘要:

采用机械合金化和放电等离子烧结工艺制备了低密度AlTiCrNiCu高熵合金材料,重点研究了球磨时间对各元素粉末的合金化过程及烧结温度(950 ~ 1050 ℃)对高熵合金组织及力学性能的影响。结果表明：高熵合金粉末为单相BCC结构,随着球磨时间的增加,粉末粒径先变大后变小,其最终平均粒径大约为20 μm。高熵合金块体材料的相结构为BCC1(基体相)+BCC2(富Cr相)+FCC(富Cu相),密度为6.22 ~ 6.30 g/cm_³。烧结温度的升高,有利于高熵合金粉末的冶金结合,促进了高熵合金块材料的致密化。当烧结温度为1050 ℃时,AlTiCrNiCu高熵合金具有良好的综合力学性能,其屈服强度、压缩强度、塑性和显微硬度分别为1410 MPa,2000 MPa,9.13%和524 HV。分析认为高的烧结温度为各元素原子间的充分扩散提供了足够的能量。然而,TEM分析表明,高的烧结温度也促进了弥散的FCC富Cu相在晶界的聚集长大。

Abstract:

Low density AlTiCrNiCu high-entropy alloy (HEAs) powder particles and bulk HEAs were prepared by mechanical alloying and spark plasma sintering. The effects of ball milling time on the alloying process of various elemental powders and the sintering temperature (950 ~ 1050 °C) on the microstructure and mechanical properties of high-entropy alloys were investigated. The results show that the high-entropy alloy powder is a single-phase BCC structure. As the ball milling time increases, the powder particle size first becomes larger and then smaller, and the final powder particle size is about 20 μm. The phase structure of the bulk high-entropy alloy is BCC1 (matrix phase) + BCC2 (Cr-rich phase) + FCC (Cu-rich phase), and the density was between 6.22 ~ 6.30 g/cm_³. As the sintering temperature increases, the metallurgical bonding of the high-entropy alloy powder is more complete and the microstructure is more dense, which is related to increasing the sintering temperature so that there is enough energy between the atoms of the elements for sufficient diffusion. The increase of sintering temperature is beneficial to the metallurgical combination of high-entropy alloy powder and promotes the densification of the bulk high-entropy alloy materials. When the sintering temperature is 1050 °C, the AlTiCrNiCu high-entropy alloy has good comprehensive mechanical properties, and its yield strength, compressive strength, plasticity and microhardness are 1410 MPa, 2000 MPa, 9.13% and 524 HV, respectively. The analysis considers that a high sintering temperature provides sufficient energy for sufficient diffusion between the atoms of the elements. However, TEM analysis indicates that a high sintering temperature also promotes the aggregation of the dispersed FCC-rich Cu phase at the grain boundaries.