Effect of cooling rate upon the microstructure and mechanical properties of in-situ TiC reinforced high entropy alloy CoCrFeNi

Abstract Three types of in-situ TiC (5 vol%, 10 vol% and 15 vol%) reinforced high entropy alloy CoCrFeNi matrix composites were produced by vacuum induction smelting. The effect of two extreme cooling conditions (i.e., slow cooling in furnace and rapid cooling in copper crucible) upon the microstructure and mechanical properties was examined. In the case of slow cooling in the furnace, TiC was found to form mostly along the grain boundaries for the 5 vol% samples. With the increase of TiC reinforcements, fibrous TiC appeared and extended into the matrix, leading to an increase in hardness. The ultimate tensile strength of the composites shows a marked variation with increasing TiC content; that is, 425.6 MPa (matrix), 372.8 MPa (5 vol%), 550.4 MPa (10 vol%) and 334.3 MPa (15 vol%), while the elongation-to-failure (i.e., ductility) decreases. The fracture pattern was found to transit from the ductile to cleavage fracture, as the TiC content increased. When the samples cooled rapidly in copper crucible, the TiC particles formed both along the grain boundaries and within the grains. With the increase of TiC volume fraction, both the hardness and ultimate tensile strength of the resulting composites improved steadily while the elongation-to-failure declined. Therefore, the fast cooling can be used to drastically improve the strength of in-situ TiC reinforced CoCrFeNi. For example, for the 15 vol% TiC/CoCrFeNi composite cooled in the copper crucible, the hardness and ultimate tensile strength can reach as high as 595 HV and 941.7 MPa, respectively.

[1]  Jun Wang,et al.  Microstructure and mechanical properties of non-equilibrium solidified CoCrFeNi high entropy alloy , 2017 .

[2]  Jun Wang,et al.  Enhanced mechanical properties of a CoCrFeNi high entropy alloy by supercooling method , 2016 .

[3]  C. Zou,et al.  High-temperature tensile strengths of in situ synthesized TiC/Ti-alloy composites , 2012 .

[4]  M. Heilmaier,et al.  Microstructure Evolution in a New Refractory High-Entropy Alloy W-Mo-Cr-Ti-Al , 2016, Metallurgical and Materials Transactions A.

[5]  B. Li,et al.  The microstructure and properties of (FeCrNiCo)AlxCuy high-entropy alloys and their TiC-reinforced composites , 2014 .

[6]  Daniel B. Miracle,et al.  Microstructure and Properties of Aluminum-Containing Refractory High-Entropy Alloys , 2014, JOM.

[7]  R. Koç,et al.  TiNiFeCrCoAl high-entropy alloys as novel metallic binders for TiB2-TiC based composites , 2018, Materials Science and Engineering: A.

[8]  B. Cantor,et al.  Microstructural development in equiatomic multicomponent alloys , 2004 .

[9]  J. Yeh,et al.  Microstructure and mechanical property of as-cast, -homogenized, and -deformed AlxCoCrFeNi (0 ≤ x ≤ 2) high-entropy alloys , 2009 .

[10]  Jian Lu,et al.  Phase stability and tensile properties of Co-free Al0.5CrCuFeNi2 high-entropy alloys , 2014 .

[11]  A. Chrysanthou,et al.  TiC-TiB2 composites : A review of phase relationships, processing and properties , 2008 .

[12]  Liqun Li,et al.  Effect of TiC particle size on the microstructure and tensile properties of TiCp/Ti6Al4V composites fabricated by laser melting deposition , 2018, Optics & Laser Technology.

[13]  Xiaodong Sun,et al.  High entropy alloy FeCoNiCu matrix composites reinforced with in-situ TiC particles and graphite whiskers , 2018, Materials Chemistry and Physics.

[14]  Jien-Wei Yeh,et al.  Microstructure and Properties of Al0.5CoCrCuFeNiTix (x=0–2.0) High-Entropy Alloys , 2006 .

[15]  Dapeng Xu,et al.  Cooling rate effect on microstructure and mechanical properties of AlxCoCrFeNi high entropy alloys , 2017 .

[16]  Bin Liu,et al.  Ductile CoCrFeNiMox high entropy alloys strengthened by hard intermetallic phases , 2016 .

[17]  K. Dahmen,et al.  Microstructures and properties of high-entropy alloys , 2014 .

[18]  Jian Lu,et al.  High-entropy alloy: challenges and prospects , 2016 .

[19]  Martin Heilmaier,et al.  Microstructure and mechanical properties at elevated temperatures of a new Al-containing refractory high-entropy alloy Nb-Mo-Cr-Ti-Al , 2016 .

[20]  A. W. Wagoner Johnson,et al.  Deformation mechanisms in Ti-6Al-4V/TiC composites , 2003 .

[21]  Riping Liu,et al.  Effect of Ti on microstructures and mechanical properties of high entropy alloys based on CoFeMnNi system , 2018, Materials Science and Engineering: A.

[22]  K. Das,et al.  Microstructural and mechanical characterization of in situ TiC and (Ti,W)C-reinforced high manganese austenitic steel matrix composites , 2009 .

[23]  T. Shun,et al.  Nanostructured High‐Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes , 2004 .

[24]  M. Emamy,et al.  The effect of Li on the tensile properties of cast Al–Mg2Si metal matrix composite , 2008 .

[25]  Jiangbo Cheng,et al.  Evolution of microstructure and mechanical properties of in situ synthesized TiC–TiB2/CoCrCuFeNi high entropy alloy coatings , 2015 .

[26]  C. Liu,et al.  Precipitation hardening in CoCrFeNi-based high entropy alloys , 2017 .