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演 講 人:Prof. Dr. Mingxing Zhang
演講題目:Additive manufacturing of titanium alloys with exceptionally uniform mechanical properties

服務單位/職 稱:

School of Mechanical and Mining Engineering University of Queensland / Professor

2024/4/15 上午10點20分-12點10分
演講摘要(Summary of speech):
Additive manufacturing (AM), which creates metallic parts by successive addition of material, is shaping the future of manufacturing. However, owing to the layer-wise build fashion of AM, metallic alloys produced by AM often develop spatially dependent phases through solid-state phase transformations under the intrinsic thermal cycling. This leads to heterogeneous phase distribution, and inhomogeneous mechanical properties, presenting substantial risks to applications involving multiaxial stress states. Although post-AM heat treatment is often performed to homogenize the microstructure, it unfortunately lengthens the production cycle and, more importantly, cannot completely eliminate the mechanical inhomogeneities due to the site-specific thermal history in the as-fabricated part. Here, based on titanium − 6% aluminium − 4% vanadium (Ti−6Al−4V, in weight per cent) − the workhorse in the titanium industry − which typically exhibits spatial variation of phases along the building direction while being additively manufactured, we demonstrate a self-stabilization strategy in which we introduce commercially pure titanium (CP−Ti) powders as the main additive and iron oxide (Fe2O3) nanoparticles as the trace additive to Ti−6Al−4V feedstock powder via a surface engineering approach. Decreasing V content by increasing CP-Ti addition whilst introducing Fe through Fe2O3 in the alloy encourages in-situ decomposition of the metastable, brittle phase − which is usually distributed on the top surface of the AM fabricated part − into stable phases similar to those in the lower region, yet without the need of additional heat treatment. Our alloys with uniform self-stabilized constituent phases not only achieve uniform tensile properties, but also stand out among the conventionally and additively manufactured Ti−6Al−4V with outstanding combinations of strength and ductility. This work provides a pathway for eliminating the mechanical inhomogeneity associated with thermal cycling that is inherent to the AM process and should help to guide the design and tailoring of new alloys specifically for AM with uniform mechanical properties.

Keywords: Additive manufacturing, titanium alloy, pure titanium, property homogeneity.

個人學經歷(Education & Research Experience):

Current Employment:
Professor in Materials Science and Engineering
Discipline Leader for Materials Engineering
Director for the School's International Engagement Committee
School of Mechanical and Mining Engineering, The University of Queensland, Australia.

Education and Qualifications
2000 – 2001 Part-time Graduate Diploma in Information Technology
                     Queensland University of Technology, Australia
                     Graduate Diploma in Information Technology was awarded in February 2002.
1994 – 1997 PhD in Materials Science and Engineering
                     The University of Queensland, Australia
                     PhD in Materials Science and Engineering was awarded on 12 November, 1997.
1984 – 1987 Masters in Materials Science and Engineering
                     Northwestern Polytechnical University, China
                     Masters degree in Engineering was awarded in March 1987.
1980 – 1984 Bachelor Degree in Engineering
                     Inner Mongolian University of Science and Technology, China
                     Bachelor degree in Engineering was awarded in July 1984.