The effect of interlayer thickness of niobium on the microstructure and mechanical properties of the interface in multimaterial additive manufacturing components made of NiTi-Ti6Al4V

A niobium interlayer approximately 50 micrometres thick produced a crack-free interface in multimaterial laser powder bed fusion components combining NiTi with Ti6Al4V under the study’s optimized processing conditions of 400 watts and a scan speed of 800 millimetres per second. In the comparison with a roughly 150-micrometre, three-layer interlayer, the thinner design formed a graded Ti₂Nb/β-Ti(Nb)/α-Ti transition zone and a continuous high-hardness band with a peak of 465.0 HV. It also achieved a compression shear strength of 90 MPa and showed quasi-cleavage fracture, while only minor micropores were observed.

The study examined interfacial cracking as a limitation on the application of multimaterial laser powder bed fusion for NiTi/Ti6Al4V composite components. Researchers introduced niobium between the two alloys and directly compared two interlayer designs: one deposited layer, approximately 50 micrometres thick, and three deposited layers, approximately 150 micrometres thick. The one-layer interlayer created a graded transition across the interface rather than the coarse brittle regions observed in the thicker design. The researchers reported that this structure suppressed brittle Ti₂Ni precipitation and accompanied a continuous high-hardness band, providing a quantitative indication that the thinner interlayer supported more consistent interfacial conditions under the tested conditions.

The thicker interlayer produced a markedly different microstructure. Its central region contained severe unmelted niobium particles and coarse brittle bands, together with a pronounced hardness gradient spanning 170.0–243.8 HV. These features were accompanied by pervasive cracking and mechanically unreliable performance. By comparison, the single-layer specimen reached a maximum hardness of 465.0 HV, well above the highest value reported for the central region of the three-layer interlayer. The contrast indicates that increasing the amount of niobium did not improve the interface in this comparison: the approximately 150-micrometre design retained unmelted material, developed coarse brittle bands and cracked extensively, whereas the approximately 50-micrometre design yielded the reported crack-free interface and higher measured mechanical performance.

The results apply to the study’s comparison of two niobium-interlayer thicknesses in multimaterial laser powder bed fusion components made from NiTi and Ti6Al4V, with the principal results obtained at 400 watts and 800 millimetres per second. The supplied findings do not establish how the interfaces would perform under other machines, scan parameters, geometries or interlayer compositions, and they do not provide evidence about long-term service behavior. Within the reported experimental scope, however, the single approximately 50-micrometre niobium layer was identified as the critical tested thickness for reliable metallurgical bonding. Its graded Ti₂Nb/β-Ti(Nb)/α-Ti transition zone, limited Ti₂Ni precipitation, continuous high-hardness band and 90 MPa compression shear strength distinguished it from the three-layer design, whose unmelted particles, brittle bands, hardness gradient and pervasive cracking were associated with unreliable mechanical performance.

Subject of Research: Niobium interlayer thickness and interface performance in laser powder bed fusion of NiTi–Ti6Al4V

Article Title: The effect of interlayer thickness of niobium on the microstructure and mechanical properties of the interface in multimaterial additive manufacturing components made of NiTi-Ti6Al4V

Article References: Ge, H., Li, X., Niu, Z., Xu, J., Zhou, S., Shi, J., Gao, X., Liu, F., & Chen, H. (2026). The effect of interlayer thickness of niobium on the microstructure and mechanical properties of the interface in multimaterial additive manufacturing components made of NiTi-Ti6Al4V. Journal of Materials Science, 61(41), 32023-32040. https://doi.org/10.1007/s10853-026-13653-4

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13653-4

Keywords: niobium interlayer, laser powder bed fusion, multimaterial manufacturing, NiTi, Ti6Al4V, interfacial microstructure, interface cracking, metallurgical bonding, hardness, compression shear strength, effect, interlayer