Abstract

Four component Cr_0.21Fe_0.20Al_0.41Cu_0.18 medium entropy alloy (Quaternary, 4C-MEA) and six component Cr_0.14Fe_0.13Al_0.26Cu_0.11Si_0.25Zn_0.11 high entropy alloy (sexinary, 6C-HEA) were designed and developed in non-equiatomic ratio to attain improved mechanical properties. These 4C-MEA, and 6C-HEA were synthesized via mechanical alloying (MA), and consolidated by hot pressing (HPing) at 723 K. For comparison, the same atomic ratio of four and six components of coarse grain alloys (4C-CGA and 6C-CGA) were also manufactured by conventional blending method. Nanocrystallite size powders of 27 ± 5.20 nm and 38 ± 3.7 nm were achieved for 4C-MEA and 6C-HEA respectively after 20 h MA. The phase evolutions, structural properties, and powder surface morphologies were characterized using X-ray diffraction and several electron microscopes. The 4C-MEA has possessed more quantity of body centred cubic (BCC) and less amount of face centred cubic (FCC) phases due to the more solid dissolution of 4 components. However, 6C-HEA exhibited more quantity of FCC and a small amount of BCC phases due to the incorporation of more FCC components compared to 4C-MEA and less solid dissolution due to more atomic radius difference among the mixing elements (atomic radius of Cr = 166 pm, Fe = 156 pm, Al = 118 pm, Cu = 145 pm, Si = 111 pm and Zn = 142 pm). The HPed samples produced ultra-fine crystallite size of 177 nm and 499 nm for 4C-MEA and 6C-HEA respectively. Further, 4C-MEA and 6C-HEA exhibited the ultimate compressive strength (UCS) of 365 MPa and 456 MPa respectively due to dissolution and lattice distortion of mixing elements. Also, 6C-HEA possessed Vickers hardness strength of around 1.97 GPa which was 2 times higher than 4C-MEA. The theoretical background of various strengthening mechanisms, various physicochemical, thermodynamic parameters, and four core effects behind the improved properties in entropy alloys was discussed and reported. The dislocation strengthening and solid solution strengthening were the major factors in exhibiting more UCS in 4C-MEA and 6C-HEA than 4C-CGA and 6C-CGA.

Graphic Abstract

摘要

四组分Cr _0.21 Fe _0.20 Al _0.41 Cu _0.18中熵合金（第四元，4C-MEA）和六组分Cr _0.14 Fe _0.13 Al _0.26 Cu _0.11 Si _0.25 Zn _0.11以非等原子比设计和开发了高熵合金（精制6C-HEA），以提高机械性能。这些4C-MEA和6C-HEA是通过机械合金化（MA）合成的，并通过在723 K下热压（HPing）固结。为进行比较，粗晶粒合金（4C-CGA）的四种和六种成分的原子比相同和6C-CGA）也通过常规共混方法制造。在20 h MA后，分别针对4C-MEA和6C-HEA获得了27±5.20 nm和38±3.7 nm的纳米微晶粉末。使用X射线衍射和几台电子显微镜对相演化，结构性质和粉末表面形态进行了表征。由于4种组分的固溶程度更高，因此4C-MEA具有更多的体心立方（BCC）和更少的面心立方（FCC）相。但是，与4C-MEA相比，由于掺入了更多的FCC成分，因此6C-HEA表现出更多的FCC量和少量的BCC相，并且由于混合元素之间的原子半径差更大（Cr的原子半径= 166 pm，Fe = 156 pm，Al = 118 pm，Cu = 145 pm，Si = 111 pm，Zn = 142 pm）。HPed样品分别对4C-MEA和6C-HEA产生177 nm和499 nm的超细微晶尺寸。此外，由于混合元素的溶解和晶格畸变，4C-MEA和6C-HEA分别显示出365 MPa和456 MPa的极限抗压强度（UCS）。同样，6C-HEA的维氏硬度约为1。97 GPa，是4C-MEA的2倍。讨论并报道了各种强化机理，各种理化，热力学参数以及改善熵性能背后的四个核心效应的理论背景。位错强化和固溶强化是在4C-MEA和6C-HEA中显示比4C-CGA和6C-CGA更多的UCS的主要因素。

图形摘要