David StJohn

Prof. David StJohn

orcid

Research Focus & Metrics

Academic Career Length

37Years (1990-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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9 January 2020 in Nature Communications
Verified
Journal Article
Open access
PDF file
CTC. J. Todaro
C. J. Todaro
MEMark Easton
Mark Easton
DQDong Qiu
Dong Qiu
DZD. Zhang
D. Zhang
MBM. J. Bermingham
M. J. Bermingham
MQMa Qian
Ma Qian
Additive manufacturing (AM) of metals, also known as metal 3D printing, typically leads to the formation of columnar grain structures along the build direction in most as-built metals and alloys. These long columnar grains can cause property anisotropy, which is usually detrimental to component qualification or targeted applications. Here, without changing alloy chemistry, we demonstrate an AM solidification-control solution to printing metallic alloys with an equiaxed grain structure and improved mechanical properties. Using the titanium alloy Ti-6Al-4V as a model alloy, we employ high-intensity ultrasound to achieve full transition from columnar grains to fine (~100 µm) equiaxed grains in AM Ti-6Al-4V samples by laser powder deposition. This results in a 12% improvement in both the yield stress and tensile strength compared with the conventional AM columnar Ti-6Al-4V. We further demonstrate the generality of our technique by achieving similar grain structure control results in the nickel-based superalloy Inconel 625, and expect that this method may be applicable to other metallic materials that exhibit columnar grain structures during AM.

1 October 1997 in Corrosion Science
Verified
Journal Article
Closed access
GSG. Song
G. Song
Andrej AtrensAndrej Atrens
Andrej Atrens
DSDavid StJohn
David StJohn
XWX. Wu
X. Wu
JNJ. Nairn
J. Nairn

1 April 2019 in Acta Materialia
Verified
Journal Article
Closed access
MBM.J. Bermingham
M.J. Bermingham
DSDavid StJohn
David StJohn
JKJ. Krynen
J. Krynen
STS. Tedman-Jones
S. Tedman-Jones
MDMatthew Dargusch
Matthew Dargusch

1 July 2011 in Acta Materialia
Verified
Journal Article
Closed access
DSDavid StJohn
David StJohn
MQMa Qian
Ma Qian
MEMark Easton
Mark Easton
Peng CaoPeng Cao
Peng Cao

1 June 1999 in Metallurgical and Materials Transactions A
Verified
Journal Article
Closed access
PDF file
MEMark Easton
Mark Easton
DSDavid StJohn
David StJohn

1 November 2000 in Metallurgical and Materials Transactions A
Verified
Journal Article
Closed access
PDF file
YLY. C. Lee
Y. C. Lee
ADA. K. Dahle
A. K. Dahle
DSDavid StJohn
David StJohn