Additive manufacturing of Ti6Al4V alloys via laser powder bed fusion (L-PBF) has demonstrated superior tensile strength compared to conventional methods. However, challenges remain in enhancing ductility and tailoring mechanical properties for specific applications. In this work, we show a feasible method to regulate the mechanical properties of additively manufacturing Ti alloys. Ti6Al4V alloys with different Nb content (1, 3, and 10 wt.%) were fabricated through laser powder bed fusion (L-PBF) in situ alloying using the mixture of Ti6Al4V and Nb powders. The powder mixture shows good printability, and dense Ti6Al4V-xNb alloys are obtained. Although the distribution of Nb is highly heterogeneous, no solidification cracks or secondary intermetallics were detected in both the Nb-rich and Nb-lean regions. The microstructure is gradually refined with the increase in Nb addition, mainly due to the heterogeneous nucleation caused by the partially melted Nb particles. The L-PBF-fabricated T6Al4V-xNb alloys are mainly in α’ martensite phase, even with the addition of 10 wt.% Nb, due to the low content of Nb solute in the matrix. The presence of β phase is suggested around the Nb particles, since a small region with graded Nb content is formed around the Nb particles. The ultimate tensile strength increases from 1050 to 1181 MPa with the addition of 3 wt.% Nb, and the total elongation increases slightly from 8.8% to 10.5%. With the addition of 10 wt.% Nb, the total elongation increases largely to 15.6%, while maintaining a high strength of 1135 MPa. Moreover, the elastic modulus decreases from 105 to 80 GPa with the increase in Nb content to 10 wt.%. The results of this work suggest that L-PBF in situ alloying is a promising approach to optimize the mechanical performance of Ti6Al4V alloys.

Objective:By studying the local effects of a new type of injectable cosmetic filler implanted into the animal to explore the mechanism of remodeling and cosmetic effect of this kind of product. Method: Take 12 rabbits and select 4 implantation points on both sides of the spine, respectively, and implant the test sample (PLLA) and negative control sample (HDPE) into the subcutaneous tissues on both sides. In the same way, take another 12 rabbits and implant the marketing control sample (cross-linked sodium hyaluronate) and negative control sample (HDPE) into the subcutaneous tissues on both sides. The animals were executed at 1 week, 4 weeks, 13 weeks and 52 weeks respectively, and Hematoxylin-Eosin staining, Masson trichrome staining and immunofluorescence staining were performed to characterize the local effects in vivo and the expression of type I collagen (Col. I), type III collagen (Col.III) and matrix metalloproteinase 9 (MMP-9). Result: Good histocompatibility of the test sample and the marketing control sample were found. The foreign body reaction of marketing control sample was more intense than that of the test sample after 13 weeks. The foreign body reaction of testing sample was more intense after 52 weeks, while that of the marketing control sample was more stable. With the process of tissue repair, the collagen fibers of test samples and marketing control samples gradually increased after implantation. Type I collagen was mainly found inside the fiber capsule, while type III collagen was mainly found outside. The positive expression of matrix metalloproteinase 9 gradually increased, the positive expression of test samples increased significantly after 52 weeks, while that of marketing control samples did not change significantly. Conclusion: Good histocompatibility of PLLA filler is found. Matrix metalloproteinase 9 participates in foreign body reaction and collagen formation, which can reflect the process of tissue remodeling.