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Comprehensive characterizations and evaluations were conducted on the relationship between process parameters and density in the Inconel 718 (IN718) alloy fabricated by selective electron beam melting (SEBM). Additionally, the microstructure and anisotropy of tensile properties were evaluated in both the as-built state and after solution treatment and aging (STA). During different stages of energy density, the primary contributors to the porosity rate transitioned from the lack of fusion (LF) pores to the inclusion of spherical and shrinkage pores, resulting in a maximum relative density of 98.95 %. The as-built parts displayed notable parallel texture to the building direction, and a significant tensile anisotropy supported by the Taylor factor. The matrix of these parts consisted of δ, γ', γ″, and carbonitrides, with a considerable presence of δ precipitation leading to a reduction in γ″ content and lower strength. After heat treatment, the δ dissolved, and γ″ precipitated extensively, while the carbonitrides and texture were retained. However, unique tensile results contradicting the predictions made by computational modeling were observed, we propose a new insight attributed to the presence of shrinkage pores along the build direction and use finite element analysis to support this view. • The as-built parts contain elements and precipitates that segregate in a unique striped pattern along the build direction. • The unique δ distribution gives tensile specimens varying strain hardening capabilities in different directions. • Along with grain and precipitates, shrinkage pores arranged along the build direction affect the anisotropy of specimens. [ABSTRACT FROM AUTHOR]

A refractory high entropy alloy (RHEA) NbHfTiV was selected as the master alloy and carbon element was introduced to synthesize the novel NbHfTiVC x RHEAs (x = 0, 0.1, 0.2, 0.3), which perform outstanding strength and excellent ductility simultaneously. Phase identification, microstructure evolution, and mechanical properties were systematically analyzed. The results show that the primary MC-type carbides and nano-precipitate carbides are generated in the BCC matrix phase with the addition of carbon. The primary carbides evolve from solid spheroid (x = 0.1) to sandwich-like pattern (x = 0.2, 0.3), and grain size is significantly refined from 537 µm (x = 0) to 25 µm (x = 0.3). Compressive tests show that the yield strength increases from 958 MPa to 1115 MPa, and the fracture mechanism is changed from ductile fracture to ductile and brittle mixed fracture with carbon content increasing. Meanwhile, the atomic size mismatch and elastic mismatch of the matrix phase reduce with carbon content increasing, which could decrease the lattice distortion degree and soften the matrix phase. [Display omitted] • Carbides (FCC-MC) are generated in BCC matrix with the addition of carbon. • After adding carbon, the grain size is greatly refined from 537 to 25 µm. • Increasing carbon content release severe lattice-distorted and soften the matrix. • Yield strength of NbHfTiVC x RHEAs increase from 958 (C 0) to 1115 MPa (C 0.3). [ABSTRACT FROM AUTHOR]

In the present study, the effect of C micro-alloying on microstructure evolution and properties of metastable immiscible Cu-20Fe alloy was comprehensively investigated. Experimental results indicate that the microstructure of Cu-Fe alloy is extremely sensitive to the C content. It was found that obvious liquid-liquid phase separation (LLPS) behavior is observed in Cu-20Fe alloy after C micro-alloying, and the tendency of LLPS is enhanced with increasing C content. The calculation of ΔScc(0) suggests that C atoms preferentially pair with free Fe atoms to form new Fe (C) atomic clusters, thus resulting in the enhancement of bonding of the like-atom pairs. In addition, the quasi-binary phase diagram calculation further reveals the existence of a stable miscibility gap for C-containing alloys, and the temperature interval of miscibility gap is significantly enlarged with increasing C content. Meanwhile, the interface energy between two liquids formed by LLPS also slightly increases as C content increasing. These above reasons should be responsible for the microstructure evolution of Cu-20Fe-xC alloys. In addition, the C micro-alloying deteriorates the soft magnetic properties of Cu-Fe alloys to a certain extent, whereas improves its corresponding wear-resistance. • The microstructure evolution and solidification behavior of Cu-20Fe-xC alloys were clearly elucidated. • The calculation of ΔScc(0) indicates that C atoms preferentially pair with free Fe atoms to form new Fe(C) atomic cluster. • Phase calculation indicates that the metastable miscibility gap of Cu-20Fe alloy is stabilized by the introduction of C. • The addition of appropriate amount C enhances the wear-resistance of Cu-20Fe alloy. [ABSTRACT FROM AUTHOR]