FoundationItem
:
Item SponsoredbyNationalNaturalScienceFoundationofChina
(
５０８０１０２１
,
５１２０１０６１
);
ProgramforYoungKeyTeachersin
HenanProvinceofChina
(
２０１１GGJSＧ０７０
);
ProgramforHenanProvinceforScienceandTechnologyInnovationExcellent
TalentsofChina
(
１４４２００５１０００１
)
Biography
:
YiXIONG
,
Doctor
,
AssociateProfessor
;
EＧmail
:
xy
_
hbdy＠１６３com
;
ReceivedDate
:
March４
,
２０１４
JOURNALOFIRON ANDSTEELRESEARCH
,
INTERNATIONAL２０１５
,
２２
(
１
):
５５Ｇ５９
MicrostructureEvolutionandMicrohardnessofUltrafineＧ
g
rainedHi
g
h
CarbonSteeldurin
g
Multi
p
leLaserShockProcessin
g
YiXIONG
１,２
,
TianＧtianHE
３
,
FengＧzhangREN
１,２
,
PengＧyanLI
１
,
LuＧfeiCHEN
１
,
AlexA．VOLINSKY
４
(
１．SchoolofMaterialsScienceandEngineering
,
HenanUniversityofScienceandTechnology
,
Luoyang４７１００３
,
Henan
,
China
;
２．HenanCollaborativeInnovationCenterofNonＧferrousMetalGenericTechnology
,
Luoyang
４７１００３
,
Henan
,
China
;
３．InstituteofMetalResearch
,
ChineseAcademyofSciences
,
Shenyang１１００１６
,
Liaoning
,
China
;
４．DepartmentofMechanicalEngineering
,
UniversityofSouthFlorida
,
TampaFL３３６２０
,
USA
)
Abstract
:
Surfacemicrostructureand microhardnessof
(
ferrite＋cementite
)
microduplexstructureoftheultrafineＧ
grainedhighcarbonsteelafterlasershockprocessing
(
LSP
)
withdifferentimpacttimeswereinvestigatedbymeans
ofscanningelectronmicroscopy
(
SEM
),
transmissionelectronmicroscopy
(
TEM
),
XＧraydiffraction
(
XRD
)
and
microhardnessmeasurements．Equiaxedferritegrainswererefinedfrom４００to１５０nm
,
andthecementitelamellae
werefullyspheroidized
,
withadecreaseoftheparticlediameterfrom１５０to１００nmastheimpacttimesincreased．
Thecementitedissolutionwasenhancedsignificantly．Correspondingly
,
thelatticeparameterofαＧFeandmicrohardＧ
nessincreasedwiththeimpacttimes．
Keywords
:
ultrafineＧgrainedhighcarbonsteel
;
lasershockprocessing
;
impacttimes
;
microstructure
;
microhardness
Lasershockprocessing
(
LSP
)
isanewsurface
modificationtechnologyforimproving metalmeＧ
chanicalpropertiesatultraＧhighstrainrates
(
１０
６
－
１０
７
s
－１
)
[１]
．ShockwavesgeneratedduringLSPorigＧ
inatefromtheplasmavolumeexpansionformedon
thematerialsurfacewhenitisirradiatedwithalaser
operatedinthenanosecondorsubＧnanosecondrange
withpowerdensitytypicallygreaterthan１０
９
W
/
cm
２
．
Thisshock wavealtersthesurface microstructure
and mechanicalpropertiesof materials
,
such as
hardness and fatigue strength
[２,３]
．The fatigue
strengthincreasesduetothesurfacecompressivereＧ
sidualstressesintroduced bytheshock waves
[４]
．
TheincreaseinhardnessandyieldstrengthisattribＧ
utedtothehighdensityarraysofdislocationsinsevＧ
eralalloys
[５]
anddeformationtwinsinsomeferrous
alloys
[６]
generatedbylasershock wave．Therefore
,
LSPhasbeen usedto hardenthesurfaceandimＧ
provethe mechanicalpropertiesofsomestructural
metalcomponentsmadefrom magnesiumalloys
[７]
,
aluminumalloys
[８]
,
copper
[９]
andtitaniumalloys
[１０]
．
Steelsare widelyusedintheindustry．LSPof
steelhasbeen extensivelystudied andreportedin
theliterature．Forexample
,
Nikitinetal
[１１,１２]
comＧ
paredthenearsurfacemicrostructurechangeandfaＧ
tiguelifeimprovementofAISI３０４stainlesssteelafＧ
terLSPanddeeprolling
(
DR
)
．HuandYao
[１３]
inＧ
vestigatedLSPofAISI１０４５steelbyfiniteelement
modeling
,
andtheresultswerevalidatedbyexperiＧ
ments．Chuetal
[１４]
comparedmicrostructure
,
hardness
andresidualstressgeneratedbyLSP
,
DRandshot
peening
(
SP
)
on Hadfield manganesesteel．Inthe
studyperformedbyChuetal．
,
it wasfoundthat
LSPresultedinalargehardnessincreaseduetothe
highdensityεＧmartensitephaseformation．Lu et
al
[５,６]
investigatedLSPofLY２ AlalloyandAISI
３０４stainlesssteelbysingleandmultiplepulses．The
effectofgrainrefinementbymultiplepulseLSPwas
superiortothatbyasinglepulse
,
revealingtheunＧ
derlyinggrainrefinementmechanism．Recently
,
traＧ