Selective Electron Beam Melting of TiAl Alloy: Metallurgical Defects, Tensile Property, and Determination of Process Window

Abstract

Selective electron beam melting (SEBM) is a promising method to manufacture complex titanium aluminide (TiAl) alloy parts. Herein, the effects of beam current, scanning speed and energy density on surface appearance, porosity, and Al loss of Ti–47Al–2Cr–2Nb alloy samples fabricated by SEBM are investigated systematically. The porosity decreased initially and then increased, and Al loss increased gradually with an increase in beam current. The porosity increased continuously and the Al loss decreased gradually with an increase in scanning velocity. The tensile strength decreased when the porosity of SEBM‐produced TiAl alloy increased. The processing window for Ti–47Al–2Cr–2Nb alloy fabricated by SEBM is determined from the energy density and scanning speed, and the formation mechanisms of small pores and B2 phase precipitation around partially melted powder are explained in detail. The findings provide a valuable reference for fabricating Ti–47Al–2Cr–2Nb alloy by SEBM with a desired surface appearance, porosity and Al loss.

Influence of Electron Beam Powder Bed Fusion Process Parameters at Constant Volumetric Energy Density on Surface Topography and Microstructural Homogeneity of a Titanium Aluminide Alloy

“…Several studies have demonstrated that different combinations of beam power, scan velocity, and distance between adjacent hatch lines in powder bed fusion processes at an overall constant energy input level can lead to significantly different outcomes in terms of surface morphology, [18,21,23,54] microstructure, [35,54] and mechanical properties. [18,35,36,54] Most of these investigations focussed on PBF-LB, [32][33][34][35][36]54,55] while only few addressed the influence of different parameter combinations at constant energy density in PBF-EB [18,21] . In this study, the effect of varying beam current, scan velocity, and line offset at constant E V on the resulting surface topography, microstructure, and aluminum evaporation in PBF-EB of TNM-B1 was systematically investigated.…”

“…which additionally considers the line offset l offset as the distance between adjacent hatch lines and the layer thickness t. [18] In many cases, a higher E V was found to be associated with a reduction in part porosity. [19][20][21] A correlation between process energy input and further component properties, such as surface morphology, [22][23][24][25] microstructure, [4,26,27] or evaporation of alloying elements, [28][29][30] was also observed by several authors. It is generally accepted that insufficient energy density results in small melt pool dimensions and low melt pool temperatures, [23,31] which in turn lead to unmelted powder particles [16] and lack-of-fusion defects [13] between the individual layers.…”

“…In contrast, other parameter combinations with a similar E V produced equiaxed microstructures. Yue et al [21] outlined that the use of different scan velocities at the same energy density leads to different beam return times, which in turn affects the thermal boundary conditions. The beam return time t R is defined as the time required for the electron beam to return to the same point in the adjacent line and can be calculated according to Equation (3) as the ratio of the scan length L and the scan velocity v scan [22] t…”

Deformation Behavior of 3D‐Printed High‐Entropy Alloys: A Critical Review

“…This is also referred to as powder pushing, smoke, and powder blowing. [71,72] The preheating process can alter the phase composition in the fabricated HEAs, as demonstrated by the first study on the SEBM-fabricated HEAs. [73] It was observed that although the powdered raw material had a single-phase BCC structure, the SEBM-fabricated AlCrFeCoNi HEA consisted of a dual-phase FCC-BCC structure.…”

Numerical Study of Temperature Field and Melt Pool Properties during Electron Beam Selective Melting Process with Single Line and Multiple Line Scanning

“…The research found that high scanning speeds can result in insufficient melting of the sample, leading to increased surface roughness and decreased forming quality. Yue [21] et al studied the effects of electron beam current, scanning speed, and energy density on the surface appearance, porosity, and Al loss of Ti-47Al-2Cr-2Nb alloy samples through experiments. The results showed that with increasing scanning speed, the porosity continuously increased while Al loss gradually decreased.…”