Effects of PEO Conditions on Surface Properties of AZ91 Mg Alloy

Vol. 17, No. 3, p. 71-77. 2010

PEO ▾ዒ↖֚Ỷ ๖ኞ ዮܞ੊ᮾ ⺏ܮ AZ91⁾ ⶂ᎚⯟ᩗᗦ⽺Ỷ ئ⺂ ἖ڒ

ᔻף⋪Á℻ᎫῶÁₚ⃒⽞

⽳ₛద⹿ٶ ᰆ⃒᪲؛⹿آ

Effects of PEO Conditions on Surface Properties of AZ91 Mg Alloy

Kyeong-Jin Park, Myung-Won Jung and Jae-Ho Lee

Dept. of Materials Science and Engineering, Hongik University 72-1 Sangsu-dong, Mapo-gu, Seoul 121-791, Korea (2010੪ 9Ὼ 17₢ ℷᬾ : 2010੪ 9Ὼ 28₢ ⃒ֲ⽻℻)

☮ ᆃ: ዮܞ੊ᮾ ⺏ܮ⁦ ৔⁦ ᔦ೪ኢ Ԧ⋦஺ ⃋ℶ ₚ῏⹾ἒ ₶೿╎ , ⺓؛ , ₚ೿K⽺ , ⠚⸎⩖ ทỶ ዴₚ Ḗₚ؆ ₮⁢া

ݖת℧ Ի೪Ԧ ৔؆ ৚ᚦᰃᩗₚ ↱⋦ ṰṪ ᧒῏ₚ ⅂⺂ാỮఊ . ዮܞ੊ᮾ ⺏ܮ ⶂ᎚Ỷ ৚ᰃᩗ ᧖⽺❛ ⼻ᩗ⹾ݖ ‪⹾ἒ ⽾

ף ➂⽺℧₞ K⺚ ⸲Ⴂ⊮ዮ ᧖⽺ᖻ (PEO)  ἖ڒỶ ᧒῏⹾ἦఊ . PEO ᖻ⁦ ᬾ῏ẇ ∷Ỷᩂ ⸲Ⴂ⊮ዮኢ ᕂᨃᰂ⡂ Kݖ⽺⹿℧

᧖⽺ዯ ⼻ᩗᰂ⧊஺ ᕏᖻₚఊ . ₞ԦKṻآ KቾԦ ᧖⽺⹢ዯỶ ᔞ❾஺ ἧ⻋Ỷ ద⹾ἒ ؆╖⹾ἦఊ . ༶⺂ , ⋧ቾὦ ⲪᯊKቾ ኢ ᧒῏⹾ἒ זآኢ ᚪᩃ⹾ἦఊ . ⲪᯊKቾኢ ᧒῏⹾؆ ℻Kቾᖻ ᧒῏⺂ ףῖỶ ❾ᔦ⺂ ᧖⽺ዯ ỡ ᬾ ₮Ữఊ . ᚦᰃ⯟

ᩗ ᚪᩃ ‪⹾ἒ ặܟ᧖⽺ᚪܟᕏᖻ ₚ῏⹾ἦఊ . ⶂ᎚⁾ Ի೪஺ ▾ዒK⁾ AZ91D Ỷ ᝪ⹾ἒ 5 ᕖ ₚ᧧ ⋃Ԧ⹾ἦఊ .

Abstract: Mg alloys have been used in automobile industry, aerospace, mobile phone and computer parts owing to low density. However, they have a restricted application because of low mechanical and poor corrosion properties. Thus, improved surface treatments are required to produce protective films. Environmental friendly Plasma Electrolytic Oxidation(PEO) was used to produce protective films on magnesium alloys. PEO process is combined electrochemical oxidation with plasma treatment in the aqueous solution. In this study, the effects of applied voltage and applied current on the surface morphologies were investigated. Also, the effects of Direct Current(DC) and Pulse Current(PC) were compared. PC and constant current control gave the dense coating on the Mg alloy. The potentiodynamic polarization tests were carried out for the analysis of corrosion properties of specimens. The surface hardness was 5 times higher than that of untreated AZ91D.

Keywords: PEO, Magnesium Alloy, Pulse Current, Polarization, Surface Hardness

1. ᩂ ᆆ

⚂ܢ ชỚ ずద῏ K₶ݖݖỶ ద⺂ ᬾᾺԦ ᝪả℧⁢ᆂ

⋃ద⹾؆ ₮ఊ . ^{ずద⹾ݖ ԪⳞ⹾؆ ᑚᩆ⫛ᰆₚ ῏ₚ⹾ֲ}

⹾ݖ ‪⹾ἒ ⠦ₚᯊ⁾ ⶂ᎚▾ዒԦ ∷Ὰ⹾᎖ ݖ↚Ỷ஺ ؆ ף೪ ܮ᪳೪ܮₚ ⹾ἦ⁢া ⚂ܢ ชỚ ዮܞ੊ᮾ ずద῏

K₶ݖݖỶ ᧒῏⺎Ỷ ๖Ⴂ ዮܞ੊ᮾ ⶂ᎚▾ዒỶ ద⺂ ئ ᰒₚ સṪ⋦؆ ₮ఊ . ^{ዮܞ੊ᮾ⺏ܮ⁦ ᧧῏ܮ᪳ ∷ Ԧ⃋}

৔⁦ ᔦ೪ኢ ⋦௮ᓦᆂ ₶೿╎᧖ừ , ^⺓؛᧖ừ , ^{ずద῏ K}

₶ݖݖ ⠦ₚᯊ ทỶ ਸ਼ዒ ₚ῏ാỚ⅞ ὺఊ .

ዮܞ੊ᮾ⁦ Ԧᗳ؆ , ^{ῖᬾ⺂ ᝪԻ೪ኢ ⋦௮؆ ₮⁢᎖} ,

ῖᬾ⺂ ἚK೪೪ , ^{KݖK೪೪} , ^{K₶ⰲ ╎⳶ோ ⋦௲ఊ} .

ᔾ᎚ ዮܞ੊ᮾ⁦ ৔⁦ ⧪ᩗתᬾ , ^{⅂⺂ൂ ৯ԪԦ؛آ ₞}

ᩗ , ^{સ⁦ ⽺⹿ ᔾ⁷ᩗ} , ^{✎ả⺂ ᚦᰃ Ω⺓ᩗ ท⁾ ᑞ⅂ᆂ}

₞⺚ ᧒῏Ỷ ⅂ả ᕁֲ ൂఊ . ^{⯟ギ ዮܞ੊ᮾ ᔵ ዮܞ੊}

ᮾ ⺏ܮ⁦ ᚦᰃỶ ✎ả⹾ᓦᆂ ᚦᰃ⯟ᩗ ⻋᧧ᰂ⧊ݖ ‪

⹾ἒ ዮܞ੊ᮾ ⶂ᎚Ỷ ᧖⽺⹢ዯ ⼻ᩗₚ Ὰڒൂఊ . ^ₚ▾ᄢ

ܮ᪳Ỷ K⺚᧖⽺▾ዒኢ ⹾஺ ֩ Ṫઞఊₚ⋻ (anodizing)

ₚႢ؆ ⺂ఊ . ^{ݖ↚⁾ ἒᄒ ↫ቾ⁾ Ṫઞఊₚ⋻⁦ ዮܞ੊ᮾ}

ⶂ᎚Ỷ ఊ؛ᩗ⁾ ᬾ᧖⽺⹢ዯ ⼻ᩗᰂ⧊ᓦᆂ ᚦᰃᕏ⋦

ᔵ ዮᏎΩ⺓ᩗₚ ↱⋦ Ṱఊ . ^{⚂ܢỶ ⽾ף➂⽺℧₞} PEO (Plasma Electrolytic Oxidation) ^{▾ዒԦ ዮܞ੊ᮾ⺏ܮỶ ਸ਼}

ዒ ἖ڒാ؆ ₮ఊ .

PEO ^{▾ዒ஺ Ṫઞఊₚ⋻⁾ ⺂ ↫ቾ}

ᆂ સ⁦ ₷೿KṻỶ ⁾⺚ ݖ↚⁾ Ṫઞఊₚ⋻آ ڒᗪൂఊ . PEO ^{▾ዒ஺ ᬾ῏ẇ ৚Ỷᩂ Kݖ⽺⹿℧ ᧖⽺ὦ ⸲Ⴂ⊮ዮ}

▾ዒ⁾ ז⺏⁢ᆂ ₚሎỚ⋪ఊ . PEO ^{▾ዒ஺ ᧖⽺❛ ⼻ᩗ} , dielectric breakdown, ^{ݖ ⼻ᩗൂ ᧖⽺❛⁾ ῏⺚} , ^Ԧᯊᕏ⛂

ทₚ ೿ᰂỶ ₢Ớা஺ ᘛ⃇⺂ آ℻⁢ᆂ ⋪⺯ൂఊ .

PEO

▾ዒ ᰂ ₞ԦKṻₚ breakdown voltage ^{ᘚఊ સֲ ാ᎚ ݖ}

⼻ᩗൂ ᧖⽺⹢ዯ❛ ࿑؆ ⸲Ⴂ⊮ዮԦ ᕂᨃ⹾ֲ ാ᎖ , ^῏

⺚ൂ ܮ᪳ₚ὎آ K⺚ẇ⁾ Kݖᚪ⺚Ỷ ⁾⺂ ܮ᪳ₚ὎ₚ ⶂ᎚Ỷᩂ ؛ܯാ஺ ᧖᪲ὦ ᔾ⁷⹾ἒ ᧖⽺⹢ዯ❛ₚ ⼻ᩗ

†

Corresponding author

E-mail: [email protected]

ാֲ ൂఊ . PEO ^{▾ዒ ᰂ ఎ‪ᰂᇲ ⶂ᎚ ⫛⺚ ₚ೿ാ஺}

♃ K⹾ὦ ⋧ℷ℧⁢ᆂ ئᅎൂ Kቾᔦ೪஺ ᧖⽺❛ ⼻ᩗỶ

∷Ὰ⺂ ἓ⺆ ᬾ⺯⺂ఊ . ^{༶⺂ ᰂᇲ⁾ K◚ⶂ᎚Ỷᩂ⁾ ặ}

ܟKቾ⁾ ᚪᕖ஺ ᧖⽺❛⁾ ൶߾⁾ ܆₢೪ ᔵ ⶂ᎚⯟ᩗỶ ז℻℧₞ ἓ⺆ ⋦௲ఊ .

ᘞ ἖ڒỶᩂ஺ PEO ^{▾ዒ ᰂ Ṯ℻℧₞ ᧖⽺⹢ዯ ⼻}

ᩗ⺆ ᬾ ₮஺ ᰂᯊ⪂ ⅂₷⹾ἦఊ . ^{₞ԦKṻ⁦ ⋧ቾK}

ቾὦ ⲪᯊKቾ ൶ Ԧ⋦ኢ ₚ῏⹾ἒ ܞ ⯟ᩗ ᝪٶ⹾ἦ

⁢᎖ ᧖⽺❛⁾ ז℻ᩗ ᔵ ⽺⹿↖ᩗỶ ద⺚ ؆╖⹾ἦఊ .

⚂↫℧⁢ᆂ ݖת℧ ⯟ᩗₚ ῖᬾ⹾؆ ৚ᰃ⯟ᩗₚ ⻋᧧ൂ

ዮܞ੊ᮾ ᧖⽺ ⹢ዯ ᨃᩗ ↖֚ ⽻ዣ⹾ἦఊ . 2. ᰊ⻾ᕏᖻ

PEO ^{ᰂᯊ⪂⁦ K⺚↖ὦ ؆Kṻ ؆Kቾ Kῶ؛ܯݖ} (Xantrex, XDC600-10), ^৯೿ݖ (Lab Companion, RW-

1025G), ^{ᯊ⩲₞ዒᯊԻ Ἒٶ⽾ݖ} , ^Ⲳ⸪ , ^{K⺚ẇ ዒΩᖪᆂ}

ڒᩗാỚ ₮⁢᎖ Fig. 1 ^⁦ PEO ^{ᰂᯊ⪂⁾ Ꮞᰃ೪ₚఊ} .

PEO ^{Ỷ ᧒῏ൂ ዮܞ੊ᮾ ⺏ܮ⁦} AZ91(9 wt% Al, 1 wt%

Zn) ^ 20 ^× 20 mm ^{⁾ ⦒ݖᆂ ⰶ᧧⁢ᆂ ⅂₷⹾ἒ ặܟ⁢ᆂ}

᧒῏⹾ἦఊ . ^{⁲ܟ⁢ᆂ஺ ᯊ⩲₞ዒᯊԻ ጃ ᧒῏⹾ἦఊ} .

Kቾᔦ೪஺ ặܟآ ⁲ܟ᧒ₚ⁾ ֖ዒὦ ặܟ⁾ K , ^⿪᎚

Ỷ ๖Ⴂ ╎ₚԦ াᓦᆂ , ^{ᰂᇲ K ⶂ᎚Ỷ ؆ኞ ᧖⽺⹢ዯ❛}

 ⼻ᩗ⹾ݖ ‪⹾ἒ ᯊ⩲₞ዒᯊԻ ጃ ೪ܮ↖ ৚᎚Ỷ K

◚℧⁢ᆂ ൾᄒ ⁲ܟ⁢ᆂ ᧒῏⹾ἦఊ . ^{K⺚ẇ⁾ ڒᩗ⁦ ݖ}

ᘞ℧⁢ᆂ sodium hydroxide 2 g/ ^lὦ sodium silicate 10 g/ ^l

⁾ ↖ᩗỶᩂ ᧒῏⹾ἦఊ . PEO ^{▾ዒ ᰂ ᕂᨃ⹾஺} micro- arc ^{⁾ ∷ᰒᚦ ὎೪஺} 2200

C ^{ₚ᧧⁢ᆂ ⚺℻ൂఊ} . ^ₚᄒ⺂

micro-discharge ^{Ỷ ⁾⺂ Ἒ ᕂᨃ⁢ᆂ ₞⹾ἒ K⺚ẇ⁾ ὎}

೪஺ ᰂԪₚ ⋦৆ᬾᆃ ᧧ᯟ⺂ఊ . ^{K⺚ẇ⁾ ὎೪Ԧ સṪ}

⋦᎚ ⹢ዯ❛⁾ ᔦ╏ᩗₚ Ω⹾ാ؆ ᧖⽺⹢ዯ❛⁾ ℧❛ₚ

↱⋦ ṰṪ ᚦᰃ⯟ᩗₚ াឆ⋦ֲ ൂఊ . ^{K⺚ẇ⁾ ὎೪ኢ}

20~30

C ^{ᆂ ⁆⋦⹾ݖ ‪⹾ἒ ᯊ⩲₞ዒᯊԻ Ἒٶ⽾ݖኢ}

╪⨃⹾ἒ K⺚ẇ ὎೪⁾ ⁆⋦⹾ἦఊ .

Fig. 1 ^{آ Կ⁦ ᭂ⽾ڒ↖஺ K⺚ẇ ὎೪⁾ Ṯ℻⽺᣶ዲ Ṫ}

௮Ⴂ ᧖⽺⹢ዯ⁾ ᔦ╏ᩗ ⻋᧧ᰂ⡂∦ఊ . PEO ^{▾ዒ ೿}

ṮỶ ặܟỶᩂ ఊჯ⁾ ᧖᪲ԦᯊԦ ᕂᨃ⹾஺ಖ ᧖᪲ Ԧᯊ Ԧ ⶂ᎚Ỷ ⋦᪳℧⁢ᆂ ょ╏⹾ֲ ാ᎚ ܞ ᚦ‪Ỷ஺ ᧖⽺

⹢ዯ❛ₚ ⼻ᩗാ⋦ Ṱݖ ๲ᑞỶ ᚮ܆₢⺂ ఊݖ؛ᩗ ⹢ዯ

⼻ᩗ⁾ ῶ₞ₚ ൂఊ . ^{ᘞ ᰊ⻾ ᰂᯊ⪂Ỷᩂ஺ ⚺Ԧ℧₞ ٶ}

ᔾ ⃋❾ Ửₚ Իᅋ⺂ Ⲳ⸪⁾ ぶኪ⁢ᆂ ᧖᪲ Ԧᯊኢ ⅂֖

⹾ἦఊ . ^{K⺚ẇ ዒΩᖪỶᩂ Ⲳ⸪Ỷ ⁾⺚ ؛ܯാ஺ ╎ԦῚ}

K⺚ẇ⁾ ؛ܯᚦኢ ᰂᇲ⁾ ‪❾Ỷ ጄ⚺Ớ ᩊת⹾ἦఊ . ^؛

ܯാ஺ ⁆◚⁾ ᕏ⻋آ ⳯⺯⹾ֲ ᰂᇲԦ ‪❾⹾᎚ , ^ⶂ᎚Ỷ

ょ╏⺂ ᧖᪲ Ԧᯊኢ K⺚ẇ⁾ KఎᅋỶ ⁾⹾ἒ ⅂֖⹾ἦ

ఊ . PEO ^{▾ዒൂ ᰂⳞ⁾ ఎ᎚آ ↖ᩗ⁦} FESEM (Field

Emission Scanning Electron Microscopy) ^آ EDS (Energy Dispersive Spectroscopy) ^{ኢ ₚ῏⹾ἒ ᚪᩃ⹾ἦ⁢᎖} EG&G 273A (Potentiostat/Galvanostat) ^{ኢ ₚ῏⹾ἒ ᚪܟ؇ᩆ ᚪ}

ᩃ⹾ἦఊ .

3. זآ ᔵ ؆╖

PEO ^{▾ዒኢ ⹾ἦ ๲ ₞Ԧ KṻỶ ๖Ⴂ ᧖⽺⹢ዯ❛}

ₚ Ớໆ⺂ ⯟ᩗ Լֲ ാ஺⋦ ئ╖⹾ݖ ‪⹾ἒ ⋧ቾ ↖

֚⹾Ỷᩂ Kṻ ᗦ⽺ᰂ⡂ PEO ^{▾ዒኢ ⹾ἦఊ} . ^K⺚ẇ

 15.2 L/min ^{⁾ ᪳೪ᆂ ᭂ⽾ᰂ⡖ఊ} . PEO ^{▾ዒ ᰂԪ⁦ ⹢}

ዯₚ ਮᑚ ൶ߢῲ⋦஺ ֩ ᕏ⋦⹾ݖ ‪⹾ἒ 30 ^ᚪ⁢ᆂ

؆℻⹾ἦ؆ ᰂⳞỶ ₞Ԧ⹾஺ Kṻ 400V, 450V, 500V ^ᆂ

ᗦ⽺ᰂ⡖ఊ . Fig. 2 ^{஺ ℻Kṻ ⹾Ỷᩂ} PEO ^{▾ዒൂ ᰂⳞช}

Fig. 1. The schematics of PEO experimental system.

⁾ ⶂ᎚⼻᧧ SEM ^{⁢ᆂ ئ╖⺂ ₚᔞ⋦ₚఊ} . ^{᧖⽺⹢ዯ❛}

ⶂ᎚⁦ ᚮ܆₢⺂ ఊ؛ᩗ⁾ ⼻᧧ₚఊ . ^{₷೿Kṻₚ સᬾ}

ᆃ ᚮ܆₢೪ὦ ݖ؛⁾ ⦒ݖ஺ ⠊ⅲఊ . ^{ⶂ᎚Ỷᩂ ئ╖ാ}

஺ ݖ؛ช⁦ PEO ^{▾ዒ ᰂ ⶂ᎚Ỷᩂ ዮₚ⦒ᆂ Ṫ⦒Ԧ ᕂ}

ᨃ⺆ ๲ ⺎߾ ᕂᨃ⹾஺ ᧖᪲ݖⴒ⁾ ⴒ⾳Ỷ ⁾⺂ ֩ₚఊ .

⸲Ⴂ⊮ዮ⁾ ⦒ݖ஺ Kቾ⁾ ⦒ݖỶ ᝪᅦ⹾ᓦᆂ ₷೿Kṻ ₚ સᬾᆃ ݖ؛⁾ ⦒ݖԦ ⠊⋦ֲ ൂఊ . ^{᧖⽺⹢ዯ⁾ ᚮ}

܆₢⺂ ᩗ⃋ⱎ⩚آ ᩗ⃋آ℻Ỷᩂ ᧖᪲ݖⴒ⁾ ⴒ⾳⁦ ᩞ Ⴂᔟ❛Ỷ ਹ⁦ ݖ؛❛ₚ ⼻ᩗാ஺ ῶ₞ₚ ൂఊ .

PEO

▾ዒ ᰂỶ ᕂᨃ⹾஺ ዮₚ⦒ᆂ Ṫ⦒⁾ ⦒ݖ஺ KṻᩞݖỶ

⋧ℷ℧⁢ᆂ ᝪᅦ⹾ݖ ๲ᑞỶ ݖ؛ ⦒ݖ೪ ܞỶ ๖Ⴂ ᝪ ᅦ⹾ֲ ൂఊ . ^{⸲Ⴂ⊮ዮԦ ᕂᨃ⹾᎖ ᩗ⃋⺂ ᧖⽺❛⁾ ൶}

߾ኢ ئ╖⹾ݖ ‪⺚ FESEM ^{⁢ᆂ ♒ἧ⺂ ᰂⳞ⁾ ఎ᎚᧒}

⋪ Fig. 3 ^{Ỷ া⧦৚Ữఊ} .

᧖⽺❛⁾ ൶߾஺ ԧ 5 ^µ m, 20 ^µ m, 90 ^µ m ^ᆂ PEO ^▾ዒ

ᰂ ₞Ԧ⹾஺ Kṻ⁾ ᩞݖԦ ⋃Ԧ⺆ᬾᆃ ⼻ᩗാ஺ ᧖⽺❛

⁾ ൶߾Ԧ ൶ߢῲ⋪ఊ . ^ܞዒ؆ 450 V ^{Ỷᩂ ▾ዒൂ ᰂᇲ⁾}

᧖⽺❛⁾ ൶߾஺ 400V ^{Ỷᩂ ▾ዒൂ ᧖⽺❛⁾ ả} 4 ^ᕖἦ؆ ,

500V ^{Ỷᩂ ▾ዒൂ ᰂᇲ⁾ ᧖⽺❛⁾ ൶߾஺} 450 V ^{Ỷᩂ ▾}

ዒൂ ᰂᇲ⁾ ᧖⽺❛⁾ ả 4.5 ^ᕖἦఊ . ^ₚ஺ PEO ^{▾ዒ ᰂ}

Ỷ ⶂ᎚Ỷ ぶኚ஺ KቾԦ Kṻ⁾ ᩞݖỶ ᝪᅦ⹾ἒ ⋃Ԧ

⹾⋦ Ṱ⁲ া⧦৞ఊ . ^{༶⺂ ₷೿Kṻₚ સᬾᆃ ⸲Ⴂ}

⊮ዮ⁾ Ի೪Ԧ ౺ સṪᩂ ዴ⁦ ặ⁾ ᰂᇲԦ ⶂ᎚⁢ᆂᚦ

⩖ ῏⺚ാỮ؆ , breakdown voltage ^{ኢ ᧧⾲⹾஺ Kṻᩞݖ}

ᆂ ₞⹾ἒ ⃋ᰂԪ೿Ṯ ⦖ ዮₚ⦒ᆂ Ṫ⦒Ԧ ⋦᪳ാỮఊ .

Fig. 4 ^஺ PEO ^{▾ዒൂ ᰂᇲช⁾ ᚦᰃΩ⺓ᩗ ⳯Ԧ⹾ݖ}

‪⺂ ᚪܟ؇ᩆ া⧦৞ ܞႾ⸪ₚఊ . ^{ᚦᰃ⽾ף⁦ ᔺఝᑢ}

⁾ ↖ᩗآ ⁆᧒⺂ 5% NaCl ^{῏ẇ ৚Ỷᩂ ᚪܟ؇ᩆ ❇}

℻⹾ἦఊ . ^{ᚪܟ؇ᩆ ܞႾ⸪ኢ ᧚Ⳛᘚ᎚ ₷೿Kṻ⁾ ᩞݖ}

ὦ ᚦᰃK‪⁾ ᧧ئئתኢ Ꭻ⽻ギ ╤ ᬾ஺ Ử⋦ዲ ద

◚℧⁢ᆂ PEO ^{▾ዒኢ ⺂ ᰂⳞ⁾ ᚦᰃK‪஺ ▾ዒ K ᰂ}

ⳞỶ ᝪ⹾ἒ 0.3 V ^{ₚ᧧ ᧧ᯟ⹾ἦ؆ ᚦᰃKቾ஺} 1/10 ^ₚ⹾

ᆂ Զ᪲⹾ἦఊ .

PEO ^{▾ዒᆂ ⼻ᩗൂ ᧖⽺⹢ዯ❛⁾ ז℻᧧ ᚪᩃ⹾ݖ}

‪⹾ἒ Kṻ ᗦ⽺⹾ἒ PEO ^{▾ዒ⺂ ൶ ᰂⳞỶ ద⹾ἒ}

XRD ^{ⱎ⩚ ❇℻⹾ἦఊ} . Fig. 5 ^{஺ ⋧ቾKቾᆂ ▾ዒൂ}

AZ91 ^⁾ XRD ^{ⱎ⩚ া⧦৞ఊ} . ^❇℻זآ peak ^⁾ intensity

Fig. 2. Surface morphologies of AZ91 after PEO treatment using DC for 30 min (a) 400 V (b) 450 V, and (c) 500 V.

Fig. 3. Cross sectional view of AZ91 after PEO treatment using DC for 30 min (a) 400 V (b) 450 V, and (c) 500 V.

Fig. 4. Potentiodynamic polarization curves of AZ91 after PEO

treatment. (Solution: 5% NaCl solution, Scan rate: 2 mV/s,

Temp: 25

C).

⁾ ╎ₚ஺ ₮Ữ⁢া ೿₢⺂ ז℻᧧ₚ া⧦া஺ ֩ Ṳ

ᬾ ₮Ữఊ .

PEO ^{▾ዒ ೿ṮỶ ఊặ⺂ ፺⠊௮⊾⁢ᆂ ᧖⽺⹢ዯ❛Ỷ} MgO, Mg

SiO

, MgAl

O

⁾ ᩞԦ⋦ ᩞႢᔟ᧧ₚ ⼻ᩗൂఊ .

ₚᄒ⺂ ז℻᧧ ڒᩗ⹾஺ ῶ᪲ช⁦ ᰂᇲ⁾ ῏⺚ , ^ặܟỶ

ᩂ⁾ ᧖᪲Ԧᯊ ᕂᨃ , ^{K⺚ẇ⁾ Kݖᚪ⺚} , ^{ᑢ⁾ Ԧᬾᚪ⺚}

ท⁾ ⼪᧧⁢ᆂ ₚ὎⽺ാ؆ , ^{ἒᄒ Ԧ⋦ ᔾ⁷ ⫛⺚ ᩞႢ}

ᔟ ᧧ ڒᩗ⺂ఊ . ^{ԧ ᩞႢᔟ᧧⁾ ⼻ᩗ ፺⠊௮⊾⁦ ఊ⁲}

آ Կఊ . MgO ^{⁾ ⼻ᩗ ፺⠊௮⊾⁦ ݖ↚⁾ Ṫઞఊₚ⋻ ݖ}

ᭆآ ⁆᧒⹾ఊ . (1) ^{آ Կ⁦ ᔾ⁷Ỷ ⁾⺚} Mg

^{Ԧ ᰂᇲᆂᚦ}

⩖ ᧖⽺❛ / ^{K⺚ẇ ת᎚⁢ᆂ⁾ ₚ೿⹾؆ K⺚ẇ⁢ᆂᚦ⩖}

ᰂᇲ / ^{᧖⽺❛ ת᎚⁢ᆂ} O

^{Ԧ ₚ೿⹾ἒ ᧖⽺❛} / ^{K⺚ẇ ת}

᎚آ ᰂᇲ / ^{᧖⽺❛ ת᎚Ỷᩂ ೿ᰂỶ} MgO ^{Ԧ ⼻ᩗൂఊ} .

:

Mg

+ O

= MgO (1)

Mg

SiO

஺ SiO

⁲ₚ὎ₚ ᬾ᧖⽺ݖὦ⁾ ᔾ⁷ ⫛⺚

ₚሎỚ⋪ఊ . ^{K⺚ẇ৚⁾} sodium silicate ^{஺ ᮣֲ Ԧᬾ ᚪ⺚}

ാỚ Si(OH)

ኢ ᨃᩗ⹾া Si(OH)

஺ OH

^{ὦ ᔾ⁷⹾ἒ} SiO

ኢ ⼻ᩗ ⿪ Mg

^{ὦ ᔾ⁷⹾ἒ} Mg

SiO

Ԧ ⼻ᩗൂఊ .:

AZ91 ^{ዮܞ੊ᮾ ⺏ܮ⁦ Ṳሎᔞப ⴒ⺎⹾ᓦᆂ Ṯ℻⺂}

MgAl

O

஺ ᚦ೿⨂⼪᧧ Ի⽺ᰂ⧎ఊ .

₞ԦKṻỶ ๖Ⴂ ᧖⽺⹢ዯ❛ ⼻ᩗ آ℻ ᧚Ⳛᘚ᎚ , ^⋧

ቾKቾ ↖֚Ỷᩂ஺ ܮ᪳ₚ὎ₚ ἖᪳℧⁢ᆂ ટṪাὊ᎖

᧖⽺❛ₚ ೿ᰂỶ ⼻ᩗാ⋦ዲ , ^{ⲪᯊKቾ ↖֚Ỷᩂ஺} on- time ^{Ỷ ܮ᪳ₚ὎ₚ ટṪাὊ᎚ᩂ ᧖⽺❛ₚ ⼻ᩗാ؆} off- time ^{೿Ṯ ܮ᪳ₚ὎⁾ ؛ܯ⁦ ∷ఎാ؆ ݖ⼻ᩗൂ ᧖⽺❛}

ₚ ᪲זൂఊ . Fig. 6 ^{⁦ ⲪᯊKቾ ⹾Ỷᩂ ₞ԦKṻ⁾ ᩞݖ}

ኢ ఒዒ⹾ἒ PEO ^▾ዒൂ AZ91D ^{ᰂⳞช⁾ ⶂ᎚⼻᧧}

SEM ^{⁢ᆂ ئ╖⺂ ֩ₚఊ} . ^{Ⲫᯊ ∢ݖ஺ Kṻ⁾} on time ^

500 ms, off time ^ 500 ms ^{ᆂ ⹾ἒ Kṻₚ ₞Ԧാ஺ ᰂԪ}

ₚ 30 ^{ᚪₚ ാ೪ᆃ ♃} 1 ^ᰂԪ೿Ṯ PEO ^{▾ዒኢ ⹾ἦఊ} . ^ئ

╖ זآ , ^{᧖⽺⹢ዯ❛ ⶂ᎚⁦ ⋧ቾKቾኢ ₞Ԧ⺮ ๲ὦ}

ዮ╒Ԧ⋦ᆂ ఊݖ؛ᩗ⁾ ᚮ܆₢⺂ Ꮞᯛ া⧦৮ఊ . ^ܞᄒ

া ⲪᯊKቾỶᩂ ▾ዒൂ ᰂᇲ⁾ ⶂ᎚⁦ ⋧ቾKቾỶᩂ ▾ ዒൂ ᰂᇲᘚఊ ᧧ద℧⁢ᆂ ܆₢⺂ ⶂ᎚ া⧦৮⁢᎖ ݖ

؛⁾ ᬾԦ ⋧ቾKቾ₢ ๲ᘚఊ ℧Ữ؆ , 500 V ^{ኢ ₞Ԧ⺮}

๲ া⧦া౾ ⦒Ⴟₚ ⲪᯊKቾỶᩂ஺ ᘚₚ⋦ ṰṾఊ . ^⋧

ቾKቾỶᩂ஺ ⋦᪳℧₞ ᧖᪲Ԧᯊ⁾ ⴒ⾳⁢ᆂ ₞⹾ἒ ᧖

⽺⹢ዯ❛ ৚ ݖ؛⁾ ᔦ೪Ԧ સ⁦ ᔾ᎚ , ^{ⲪᯊKቾỶᩂ஺}

Ⲫᯊ∢ݖ ∷ off ^{ᰂԪ೿ṮỶ ⶂ᎚Ỷ ょ╏⺂ ᧖᪲ԦᯊԦ}

સ⁦ ⁆᪳Ỷ ⁾⺚ ⅂֖ാݖ ๲ᑞỶ ݖ؛⁾ ᔦ೪Ԧ ᧧ద

℧⁢ᆂ ৔Ṫ⋦ݖ ๲ᑞ⁢ᆂ ᧒ᇲൂఊ . ^{๖Ⴂᩂ ݖ؛⁾ ᔦ}

೪Ԧ ৔Ṫᩂ ܆₢೪Ԧ ↱⁦ ᧖⽺⹢ዯ❛ ỡݖ ‪⺚ᩂ஺

⋧ቾKቾᘚఊ ⲪᯊKቾኢ ₞Ԧ⹾஺ ֩ₚ ౺ ⁆ዒ⹾ఊ .

Kቾᔦ೪Ԧ ਮᑚ સ⁢᎚ Իᅋ⺂ ⸲Ⴂ⊮ዮԦ ᕂᨃാỚ K⺚ẇỶ ⁾⺂ ᰂᇲ⁾ ৯ԧ⿎آኢ ໎Ớ၎ᅊ ᩞႢᔟ❛⁾

Fig. 5. XRD patterns of AZ91 after PEO treatment: (a) 500 V (b) 400 V.

Fig. 6. Surface morphologies of AZ91 after PEO treatment using PC for 60 min (a) 400 V (b) 450 V, and (c) 500 V.

᪲ז ᕏ⺚⺂ఊ. ᰂⳞỶ ₞Ԧ⹾஺ Kṻₚ ₢℻⹾೪ᆃ K ṻ ⅂Ớ⹾ἦ ๲ ᧖⽺❛ₚ ᩗ⃋⺆ᬾᆃ ᰂⳞ⁾ ⶂ᎚Ỷ ぶኚ஺ Kቾ஺ Fig. 7Ỷᩂ ᘚตₚ ℶℶ Զ᪲⹾ֲ ാỚ Ớ ஶ ℻೪ ൶߾ᆂ ᧖⽺❛ₚ ᩗ⃋⹾ἦ ๲ ⶂ᎚Ỷ ぶኚ஺

Kቾ⁾ ặ⁦ ᔞᔞ⹾ֲ ൂఊ. Kṻₚ Զ᪲⹾஺ ܞႾ⸪஺

⦒ֲ ൶ ڒԪ⁢ᆂ াଲ ᬾ ₮஺ಖ ☮ݖỶ ⦖ KቾԦ ぶኚ

஺ ڒԪآ KቾԦ ܯ׏ギ Զ᪲⹾ἒ Kቾ⁾ Զ᪲Ԧ ᔞᔞ

⺂ ڒԪ⁢ᆂ াଲ ᬾ ₮ఊ. Kṻ ⅂Ớ⹾ἦ ๲ ᧖⽺❛

⁾ ᩗ⃋⁦ ᰂԪỶ ๖Ⴂᩂ ᝪᅦ⹾஺ ֩ₚ Ṫ௮Ⴂ KቾԦ

⦒ֲ ぶኚ஺ ☮ᔾỶ ᧖⽺⹢ዯ❛⁾ ⼻ᩗₚ ܯ׏⹾ֲ ₚሎ Ớ⋦஺ ֩⁢ᆂ ⰶఎ⹾؆ ₢℻⺂ KቾԦ ぶኚ೪ᆃ Kቾኢ

⅂Ớ⹾ἒ ᰊ⻾ ⹾ἦఊ.

Fig. 8⁦ Kቾኢ ⅂Ớ⹾ἦ ๲ ᰂԪỶ ぶኪỶ ๖ኞ K ṻ⁾ ᗦ⽺ኢ ݖᆃ⺂ ܞႾ⸪ₚఊ. ⶂ᎚Ỷ஺ ₢℻⺂ Kቾ Ԧ まᄦ⁢᎖ ᰂԪₚ ぶኢᬾᆃ Kṻ⁦ ⋃Ԧ⹾஺ ֩ ᘢ

ᬾ ₮ఊ. Kṻآ ⶂ᎚⁾ ᗦ⽺஺ ⦒ֲ ᩞ Ԧ⋦ ڒἓ⁢ᆂ ئ

╖െ ᬾ ₮ఊ. ☮ᔾ 300 Vݲ⋦ Kṻₚ ܯ׏⹾ֲ ⋃Ԧ⹾஺

ڒԪỶᩂ஺ ⶂ᎚Ỷ ⸲Ⴂ⊮ዮԦ ⼻ᩗാ⋦ Ṱ؆ ᧖᪲Ԧᯊ ዲ ᕂᨃ⹾᎖ ᧖⽺❛ₚ ⼻ᩗൂఊ. ₚ ⼪᧧⁦ ☮ݖ ⌍⁦ ᰂ

Ԫ ৚Ỷᩂዲ ₚሎỚ⋦᎖ Kṻₚ ⋃Ԧ⹾ἒ breakdown voltageᘚఊ સֲ ാ᎚ ൶ ᖮ⌞ ڒԪỶᩂ ݖ ⼻ᩗൂ ᧖⽺

⹢ዯ❛ ࿑؆ ⸲Ⴂ⊮ዮԦ ᕂᨃ⹾ֲ ൂఊ. ₚ֩⁦ ₢℻

ᰂԪ ặܟ ᧖⽺ ⿪ ⹢ዯₚ ⼻ᩗാ஺ זآỶ ݖ₞ാ஺ ֩

⁢ᆂ ᧒ᇲൂఊ. ዮ⋦ዯ⁢ᆂ Kṻₚ Ṯ℻ാ஺ ڒԪỶᩂ஺

⸲Ⴂ⊮ዮԦ ⋦᪳℧⁢ᆂ ⾂ᕂギ ₢Ớা᎖ ᧖⽺⹢ዯ❛ₚ ת᪳ ᩗ⃋⺂ఊ.

Fig. 9஺ Kṻ ⅂Ớ⹾ἒ 450 VỶᩂ 20ᚪ ೿Ṯ ₞Ԧ⹾

ἒ PEO ▾ዒኢ ⺂ ᰂⳞآ Kቾኢ ⅂Ớ⹾ἒ 0.2AỶᩂ 20 ᚪ ೿Ṯ PEO ▾ዒኢ ⺂ ᰂⳞ⁾ ⶂ᎚ SEM⁢ᆂ ئ╖⹾

ἒ ᝪٶ⺂ ᧒⋪ₚ᎖, Fig. 10⁦ ఎ᎚ ᝪٶ⺂ ᧒⋪ₚఊ.

Kቾኢ ⅂Ớ⹾ἦ ףῖỶ ᧖⽺ዯ ⶂ᎚⁾ ݖ؛ₚ ᧧ద℧

⁢ᆂ ₢℻⺂ ⦒ݖኢ ᘚἦ⁢᎖ ఎ᎚ ༶⺂ Kቾኢ ⅂Ớ⹾

ἦ ףῖ ᧧ద℧⁢ᆂ ൶߾Ԧ ₢℻⹾؆ ᧖⽺ዯ ৚ ᧖᪲

Ԧ ⴒ⾳ാỚ া⧦া஺ ݖ؛ₚ ℧⁦ ֩⁢ᆂ ئ╖ാỮఊ.

Kṻ ⅂Ớ⺮ ๲ ᧖⽺⹢ዯ❛⁾ ൶߾஺ ౺ ậṾ؆ ⶂ

᎚Ỷ஺ ⦒ݖԦ ᚮ܆₢⺂ ݖ؛ₚ ዴṾఊ. ᔾ᎚ Kቾኢ ⅂ Ớ⺮ ๲ ᧖⽺⹢ዯ❛⁾ ൶߾஺ Kṻ ⅂Ớ⹾ἦ ףῖ ᘚఊ ൶߾Ԧ ܆₢⹾؆ ᧖⽺⹢ዯ❛ ৚⁾ ݖ؛ₚ ዴₚ ᕂ גാ⋦ ṰṾఊ. ༶⺂ ⶂ᎚⁾ ݖ؛⁾ ⦒ݖԦ ᧧ద℧⁢ᆂ

܆₢⹾ἦ؆ ⦒Ⴟₚ ᘚₚ⋦ ṰṾఊ. ܆₢⺂ ᧖⽺ዯ⁾ ⼻

ᩗỶ஺ Kṻ ⅂Ớ⹾஺ ֩ ᘚఊ Kቾኢ ⅂Ớ⹾஺ ֩ₚ

↱⁦ ֩⁢ᆂ ᧒ᇲൂఊ.

0.1Aᆂ ؆℻ᰂ⡂ Կ⁦ Kቾኢ ∢Ữ ๲ PEO ▾ዒ ᰂ ԪỶ ๖ኞ ⶂ᎚ ⼻᧧ SEM⁢ᆂ ئ╖⹾ἒ Fig. 11Ỷ া

⧦৚Ữఊ. PEO ▾ዒ ᰂԪₚ ⋃Ԧ⺆ᬾᆃ ᰂⳞỶ Ԧ⺚⋦

஺ Kṻₚ ⋃Ԧ⹾᎚ᩂ ᧖⽺⹢ዯⶂ᎚⁾ ݖ؛ₚ ⠊⋦஺ ֩ Fig. 7. Change of current with time at different applied voltage.

Fig. 8. Change of voltage with time at different applied current.

Fig. 9. Surface morphologies of AZ91 using PC for 20 min: (a) 450 V (b) 0.2A.

Fig. 10. Cross sectional view of AZ91 using PC for 20 min: (a)

450 V (b) 0.2A.

 Ṳ ᬾ ₮ఊ. ₚ֩⁦ ᰂԪₚ ぶኪỶ ๖Ⴂ Kṻₚ ⋦᪳

℧⁢ᆂ ⋃Ԧ⹾ֲ ാ؆, ᰂⳞ⁾ ⶂ᎚Ỷ ᕂᨃ⹾஺ ☮ݖ⁾

ᔞᩞ⺂ ⸲Ⴂ⊮ዮชₚ ⦖ ⸲Ⴂ⊮ዮᆂ ᔺलֲ ാ᎚ᩂ ܞ ᬾ

஺ ᧧ద℧⁢ᆂ ℧Ớ⋦ݖ ๲ᑞ⁢ᆂ ⰶఎൂఊ. ₷೿ᰂԪ

ఒዒ⹾ἒ PEO ▾ዒኢ ⺂ ᰂⳞช⁾ ൶߾ኢ Fig. 12Ỷ া

⧦৚Ữఊ. ᧖⽺⹢ዯ⁾ ൶߾஺ ᰂԪ⁾ ぶኪỶ ๖Ⴂ ⋧ᩆ

℧₞ ⼻⨂ᆂ ⋃Ԧ⹾஺ ֩ Ṳ ᬾ ₮ఊ. Kṻ ⅂Ớ⹾ἦ

 ףῖ, ₢℻⺂ ᰂԪ ₚ⿪ᆂ஺ ⹢ዯ⁾ ൶߾⁾ ⋃ԦԦ ᔞ ᔞ⺂ ֩آ஺ ద↖ാ஺ ⼪᧧ₚఊ. Fig. 13஺ PEO ▾ዒ ∷ ⶂ᎚Ỷ ᕂᨃ⹾஺ ⸲Ⴂ⊮ዮኢ ┳⁦ ዮ⦒ᆂ᧒⋪ₚఊ. 0.1A

⁾ Kቾᔦ೪ኢ ∢Ớ 10ᚪ ఎ‪ᆂ ئ╖ ⺂ זآ, ᰂԪₚ

⋦৆ᬾᆃ ⶂ᎚Ỷ ᕂᨃ⹾஺ ⸲Ⴂ⊮ዮ⁾ ⦒ݖ஺ ⠊⋦؆ ܞ

ᬾ஺ Զ᪲⹾ἦఊ. Fig. 11⁾ ⶂ᎚᧒⋪Ỷᩂ PEO ▾ዒ ᰂԪ ₚ ாỚ৆ᬾᆃ ᧖⽺⹢ዯỶ ↚⃒⹾஺ ݖ؛⁾ ⦒ݖԦ ⠊⋦

؆ ݖ؛⁾ ᬾ஺ ∪Ớข஺ ֩آ ₢❾⺂ఊ. PEO ▾ዒൂ

AZ91 ዮܞ੊ᮾ ⺏ܮ⁾ ⶂ᎚ף೪ኢ ❇℻⹾ἒ Fig. 14Ỷ

া⧦৚Ữఊ. ⶂ᎚ ף೪஺ ᭂᬾ ዮܞ੊ᮾₚ 40 Hv, AZ91D Ԧ 80 Hv₞ ᔾ᎚ PEO ▾ዒൂ AZ91D⁾ ⶂ᎚ף೪஺

460 Hvᆂ ᭂᬾ ዮܞ੊ᮾ⁾ 10ᕖ, AZ91 ዮܞ੊ᮾ ⺏ܮ⁾

5ᕖ ₚ᧧ ⋃Ԧ⹾ἦఊ.

Fig. 11. Surface morphologies of AZ91 at 0.1A: (a) 10 min (b) 20 min (c) 40 min (d) 50 min.

Fig. 12. Change of magnesium oxide thickness with respect to time.

Fig. 13. Evolution of micro arc on the surface with time (a) 10 min (b) 20 min (c) 30 min (d) 40 min (e) 50 min.

Fig. 14. Surface micro hardness of pure Mg, AZ91D and AZ91D

after PEO treatment.

4. ז ᆆ

PEO ᰂᯊ⪂ ⅂₷⺂ ⿪ AZ91D ዮܞ੊ᮾ ⺏ܮ ⦒

ֲ Kṻ⅂Ớ, Kቾ⅂Ớᆂ াପỚ PEO ▾ዒኢ ⹾ἦఊ.

PEO ▾ዒ זآᆂ ዮܞ੊ᮾ ⺏ܮ⁾ ⶂ᎚Ỷ ܆₢⺂ ᧖⽺

ዯ❛ₚ ⼻ᩗാỮఊ. ₷೿Kṻₚ સᬾᆃ ᧖⽺⹢ዯ ⶂ᎚

⁾ ݖ؛⁾ ⦒ݖ஺ ⠊ⅲ؆ ൶߾ ༶⺂ ⋃Ԧ⹾ἦఊ. Կ⁦ K ṻỶᩂ ▾ዒᰂԪỶ ๖ኞ ╎ₚ஺ ⦒ֲ ỬỮఊ. ⋧ቾKቾ ὦ ⲪᯊKቾỶ ๖ኞ ⦖ ╎ₚ஺ ỬỮ⁢া ⋧ቾKቾᘚఊ Ⲫ ᯊKቾỶᩂ ▾ዒ ᰂ ᧖⽺⹢ዯ⁾ ܆₢ᩗ⁦ ⻋᧧ാỮఊ. K ቾኢ ⅂Ớ⹾ἒ PEO ▾ዒኢ ⹾ἦ ๲, ₷೿ᰂԪỶ ๖Ⴂ

⋧ᩆ℧⁢ᆂ ൶߾஺ ⋃Ԧ⹾ἦఊ. ⲪᯊKቾኢ ₚ῏⹾ἒ 0.1A⁾ ↖֚Ỷᩂ ▾ዒ⺂ ףῖ ⚂℧⁾ ᧖⽺⹢ዯ ỡ ᬾ

₮Ữ⁢᎖. PEO ▾ዒ ⿪ ⶂ᎚ ף೪஺ 5ᕖ ₚ᧧ ⋃Ԧ⹾ἦ

⁢᎖ ৚ᰃᩗ⁦ 10ᕖ ₚ᧧ ⋃Ԧ⹾ἦఊ.

Զ᧒⁾ ܦ

ᘞ ἖ڒ஺ ᩂ῞ᰂ ᧖⹿἖ ⼷ᅋ᧒ừ (آ⅂ᖮ⽞ 10555)ὦ

⹿ᭆ⋪る⃒ఎ (2007-D00953)Ỷ ⁾⹾ἒ ⋦ῶᕁṾ⁢᎖ ₚ Ỷ Զ᧒ขዣ௮ఊ.

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