Multilayered gradient titanium-matrix composites fabricated by multi-material laser powder bed fusion using metallized ceramic: Forming characteristics, microstructure evolution, and multifunctional properties

Titanium matrix composites (TMCs) have potential applications in various high-end industries because of their outstanding performances, such as high special strength, toughness, and wear resistance. Multi-material laser powder bed fusion (LPBF) technology was adopted to fabricate the multilayered gradient TMCs samples with metallized TiB2 ceramic. The process-structure-performance relationships of multi-material LPBF-processed multilayered gradient TMCs were investigated. A suitable laser linear energy density for composite layers enabled high-density multilayered TMCs to obtain smooth surfaces, stable molten pools, and good interlayer bonding. The in-situ generated TiB whiskers exhibited a transition from submicron whiskers to nano-whiskers as the scan speed increasing. The mechanical and thermal performances of LPBF-processed multilayered TMCs could be adjusted by various grain sizes and porosities, which were determined by laser processing parameters. The microhardness and bending strength reached 469 HV0.5 and 1940 MPa under the effects of grain refining and dispersion strengthening. Besides, the thermal conduction mechanisms of multi-material LPBF-processed multifunctional TMCs indicated that the thermal boundary resistance induced by multilayered structure and grain refinement had an impact on the thermal conductivity. These LPBF-processed multifunctional TMCs with high and tailorable mechanical and thermal performances are expected to be utilized in integrated thermal- and load-bearing structures in the aerospace industry.