Microstructural features of Sc- and Zr-modified Al-Mg alloys processed by selective laser melting

Grain refinement and performance enhancement of laser powder bed fusion in-situ processed Al-Mg alloy modified by ScH3 and ZrH2

Growth of coarse columnar grains during solidification easily leads to hot cracking during laser powder bed fusion (LPBF) of Al alloys. This work offers an alternative route to inhibit the formation of coarse columnar grains during LPBF process. The crack-free 6061Al alloy with a refined microstructure was obtained using nano-sized TiO2 modified feedstock powders. After HIPPing, a nearly defect-free sample was obtained with a fracture elongation of 19.5 ± 0.14%. After artificially peak ageing treatment, the TiO2 modified 6061Al alloy fabricated by LPBF exhibits a tensile strength of 336.1 ± 3.5 MPa and the fracture elongation is still 8.1 ± 0.92%. It is believed that the approaches used in this work are also effective for other LPBF fabrication of low-printability Al alloys.

For large-scale selective laser melting (SLM) additive manufacturing technology, three main problems severely restrict its development and application, namely the residual stress, defects, and columnar grains with anisotropy. To overcome these problems, a new method is proposed by combining SLM with ultrasonic impact treatment (UIT) technique. This study explores the feasibility of UIT assisted SLM, as well as the effect of UIT on the residual stress, defects and β grains of Ti-6Al-4V alloy sample. The results indicate that after the application of UIT during SLM, residual stress can be largely reduced and defects can be hammered flat and even eliminated. Meanwhile, the epitaxial growth of columnar grains is prevented, and fine equiaxed grains are formed due to plastic deformation and recrystallization.

Microstructure of NiTi superelastic alloy manufactured by selective laser melting

Stable superelasticity with large recoverable strain in NiTi alloy via additive manufacturing

Characterization of Inconel 625 fabricated using powder-bed-based additive manufacturing technologies

Effect of laser parameters on microstructure and mechanical properties of Al–Ni–Sc–Zr alloys fabricated by laser powder bed fusion

Grain structure and cracks behaviors of tungsten with different geometrical shapes and support structure prepared by laser powder bed fusion

Grain refinement tendency of pure Fe and Fe-X (X=5~10at%Al, 2~10at%Ti) alloys produced by laser powder bed fusion (LPBF) process was investigated. Pure Fe, Al, and Ti powders were dry mixed and cubic samples were built from the mixtures. The microstructure analysis revealed that (1) the microstructure of pure Fe consisted of equiaxed grains having an average diameter of 1.7 μm with fine iron oxide particles. (2) Fe-5 and 10at%Al alloys showed coarse columnar grains. (3) Fe-2at%Ti shows a mixture of fine equiaxed and columnar shape grains. (4) the microstructures of Fe-5at%Ti and 10at%Ti alloys are fully equiaxed, and grain refinement tendency was confirmed with increasing Ti content. Ti(N,O) oxi-nitrides are efficient in reducing the grain size because of the low lattice misfit with the ferrite matrix. Additionally, the effectiveness of Ti(N,O) particles as grain refiners was confirmed by building samples using TiN powder mixed with Fe-10at%Al and Fe-2at%Ti. While these alloys alone are coarse grained, a dispersion of Ti(N,O) particles achieved a fine-grained microstructure.

The expansion of the material library for the laser powder bed fusion (LPBF) process is essential for the further establishment of the process in areas such as the aerospace and automotive industries. In this study, we designed a high-strength and low-cost Al-Mn-Ti-Zr alloy specifically tailored to the unique conditions of the LPBF process. Gas-atomized pre-alloyed powder was prepared and used as feedstock to fabricate LPBF specimens for microstructural examination and mechanical testing. By taking advantage of the high solidification rate, unconventionally large amounts of Mn (3.7 ± 0.5 wt%) are metastably frozen within the α-Al matrix, contributing significantly to solid solution hardening (~104 MPa ≙ 37% share of yield strength). The as-built specimens exhibit a yield strength of 284 ± 3 MPa, an ultimate tensile strength of 320 ± 1 MPa, and an elongation at fracture of 16.9 ± 0.2%. This new alloy exhibits a bimodal microstructure consisting of alternately distributed fine equiaxed and coarse columnar grain regions. Further microstructural analyses reveal a high number of primary L12 cubic Al3(Tix Zr1 - x) nanoparticles within the equiaxed α-Al grains near the bottom of the melt pool. A highly coherent interface with the α-Al matrix confirms high efficiency for heterogeneous nucleation during solidification. In addition to the Al3(Tix Zr1 - x) nanoparticles, an AlxMn(Fe, Si) phase with a quasi-crystalline structure is observed along the grain boundaries and interdendritic areas.

Segregation enabled outstanding combination of mechanical and corrosion properties in a FeCrNi medium entropy alloy manufactured by selective laser melting

A Discrete Dendrite Dynamics Model for Epitaxial Columnar Grain Growth in Metal Additive Manufacturing with Application to Inconel

Mechanical property, corrosion behavior and cytocompatibility of CoCrMo for dental application: A comparative study of cast and laser powder bed fusion

Effect of bimodal microstructure on the tensile properties of selective laser melt Al-Mg-Sc-Zr alloy

Improving the processability and grain structures of additively manufactured Al-Fe-Cu-xZr alloy: Experiment and high-fidelity simulation