{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,3]],"date-time":"2026-05-03T03:17:27Z","timestamp":1777778247800,"version":"3.51.4"},"reference-count":40,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2025,11,6]],"date-time":"2025-11-06T00:00:00Z","timestamp":1762387200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["51975271"],"award-info":[{"award-number":["51975271"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Laser powder bed fusion (L-PBF) is an additive manufacturing technique that enables the fabrication of complex geometries through a layer-by-layer approach, overcoming limitations of conventional manufacturing. In this study, multiaxial low-cycle fatigue (MLCF) tests were conducted on L-PBF Ti-6Al-4V (Ti64) specimens built in four different orientations, selected based on critical plane orientations identified from rolled titanium. Under proportional strain-controlled loading, the cyclic softening behavior, mean stress response, and fracture mechanisms of the material were systematically investigated. The results show that L-PBF Ti64 exhibits a three-stage softening characteristic (continuous softening, stable, and rapid softening). Fatigue cracks primarily initiate from inner-surface lack-of-fusion defects. Crack propagation shows cleavage and quasi-cleavage characteristics with tearing ridges, river patterns, and multi-directional striations. Proposed KBMP life prediction model, incorporating \u03bb and building direction parameters, was developed. The KBMP-\u03bb model demonstrates optimal accuracy, providing a reliable tool for the design of L-PBF titanium components subjected to complex multiaxial fatigue loading with relative errors within 20%.<\/jats:p>","DOI":"10.3390\/ma18215056","type":"journal-article","created":{"date-parts":[[2025,11,6]],"date-time":"2025-11-06T10:08:51Z","timestamp":1762423731000},"page":"5056","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Proportional Multiaxial Fatigue Behavior and Life Prediction of Laser Powder Bed Fusion Ti-6Al-4V with Critical Plane-Based Building Direction Variations"],"prefix":"10.3390","volume":"18","author":[{"given":"Tian-Hao","family":"Ma","sequence":"first","affiliation":[{"name":"School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yu-Xin","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wei","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7712-1412","authenticated-orcid":false,"given":"Jian-Ping","family":"Zhao","sequence":"additional","affiliation":[{"name":"School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Chang-Yu","family":"Zhou","sequence":"additional","affiliation":[{"name":"School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,11,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"100233","DOI":"10.1016\/j.addlet.2024.100233","article-title":"Laser additive manufacturing of a carbon-supersaturated \u03b2-Ti alloy for biomaterial application","volume":"11","author":"Dong","year":"2024","journal-title":"Addit. 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