• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 춘계학술대회 논문집
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• pp.221-222
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• 2009

AZ31 마그네슘 합금에 AC 전류를 인가하여 MAO(micro-arc oxidation) process로 양극산화 할 때 알카리 전해액에 첨가되는 sodium silicate(Na2SiO3)의 농도에 따라 형성되는 양극 피막의 구조와 부식특성을 평가하였다. 전해질의 조성은 10g/1 KOH와 4g/1 KF 혼합 전해액에 sodium silicate를 (5, 10, 20, 40, 80)g/1로 달리하여 첨가한 후 $40mA/cm^2$의 전류밀도로 20분간 MAO 처리한 후 양극피막의 조직을 SEM, XRD, EPMA를 이용하여 분석하였고 동전위 분극시험으로 부식 거동을 평가하였으며 micro-vickers 경도계를 이용하여 단면의 경도를 측정하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.128-131
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• 2004

Magnesium alloys are being extensively used in weight-saving applications and as a potential replacement for plastics in electronic and computer applications. Magnesium alloy has some good characteristics, EMI shielding property and high specific strength. Nevertheless their high brittleness make it uneasy to process the magnesium. Magnesium alloys are extruded like aluminium alloys. The present work was done to find a characteristic of magnesium alloy(AZ31) changing the extrusion ratio 8.5, 19.1, 49 respectly and changing the die half angle $30^{\circ},\;45^{\circ},\;60^{\circ}$. Here this present done by the hydrostatic extrusion in the hot condition, $310^{\circ}$. The higher the extrusion ratio goes, the higher the extrusion force goes.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.193.2-193.2
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• 2016

본 연구에서는 탄산이온이 포함된 수용액에서 규산나트륨의 농도가 AZ31 마그네슘 합금의 플라즈마전해산화 피막형성에 미치는 영향에 대해 알아보았다. 다양한 농도의 규산나트륨 용액에서 DC와 펄스전류를 인가하여 플라즈마전해산화피막을 형성하였으며, 형성된 피막의 surface roughness와 thickness를 분석하였다. 탄산 이온이 포함된 수용액에서 플라즈마전해산화 피막의 형성전압은 규산나트륨의 농도가 높아질수록 높아지는 것으로 나타났다. 하지만 탄산이온이 존재하지 않은 규산나트륨 용액에서의 플라즈마전해산화 피막 형성전압보다 더 낮은 값을 나타내었다. 탄산 이온이 포함된 수용액에서 규산나트륨의 농도가 높아질수록 플라즈마전해산화 피막의 surface roughness와 thickness는 증가하였으며, DC와 펄스전류 모두에서 더 밝은 색상의 균일한 산화피막을 형성할 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• 제32권4호
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• pp.570-577
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• 2008

Magnesium alloys are potentially useful as structural materials due to higher strength/weight ratio, heat conductivity and recyclability compared to other alloys. These alloys have attracted the interest of modern manufacturing such as the automobile, computer, communication and consumer electronic appliances industries. Hence welding techniques are required to be developed for these applications. Laser are known to be an excellent tool for them. This paper presents the laser weldability of AZ31 magnesium alloy with CW Nd:YAG laser. The low viscosity and surface tension of the melt pool make magnesium more difficult to weld than steel. As a result of this study, optimal process parameters could be obtained without weld defects. Also it was certain that cutting methods had influence on butt weldability.

• 자원리싸이클링
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• 제3권1호
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• pp.25-31
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• 1994

AZ91 마그네슘합금 절분 및 스크램외 재활용을 목적으로 절분 및 스크랩을 상온가압하여 빌렛을 얻었다. 이 압출용 벨렛을 압축비율 25:1로 고정하고, 압출온도를 $300~380^{\circ}C$로 변화시켜 가면서 시편을 제조하였으며, 비교재로 마그네슘합금 주조재도 열간압출을 행하였다. 마그네숨합금 절분 및 스크랩을 열간압출함에 따라 매우 미세한 재설정 조직을 얻었으며, 인장강도 및 연산률은 각각 330 MPa, 10%로 주조재를 열간압층한 재료와 거의 비슷한 기계적 특성을 나타내었다.

• 한국주조공학회지
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• 제23권5호
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• pp.251-256
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• 2003

Effects of Ca addition on grain refinement, microstructure and mechanical properties of AZ31 Mg alloy were investigated. Due to Ca addition to Mg alloy (AZ31), the microstructure was refined, the quantity of $Mg_{17}Al_{12}$phase was reduced, and new $Al_2Ca$ phase was formed. The tensile property of AZ31 was increased with the minor addition of Ca, but was decreased rapidly over 0.2 wt.% of Ca content. The $Al_2Ca$ phase was considered to be detrimental to the mechanical property of AZ31 Mg alloy.

• 한국기계가공학회지
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• 제19권6호
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• pp.9-16
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• 2020

This study aims to assess the effects of specimen thickness (ST) on fatigue crack growth in the early stages of crack propagation and near failure in magnesium alloys. The analysis of variance (ANOVA) method was adopted because fatigue crack propagation in magnesium alloys exhibits statistical behavior. The equality of variance test and residual diagnostics were performed on the grown cracks to confirm the validity of ANOVA by verifying the normal distribution and mutual independence of the residuals and their homoscedasticity. ANOVA confirmed that ST heavily impacts crack growth; i.e., when ST is smaller, cracks grow faster in the early crack propagation stage and break more quickly before the formation of larger cracks. We found that ST significantly affects fatigue crack growth in the early crack propagation stage and near the failure stage in magnesium alloys. The regression model was also used to predict crack formation near the failure stage.

• 한국자동차공학회논문집
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• 제21권4호
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• pp.77-82
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• 2013

In this paper, the design of experiment with two-way factorial design was adopted and from that, optimum values of welding variables including the welding speed and rotation speed were found to improve the strength of AZ31 magnesium alloy sheets joined by the friction stir technique. Tool with shoulder diameter of 12 mm and pin diameter of 3.5 mm was used. Also the welding direction was aligned with the material rolling direction, and dimensions of the AZ31 magnesium alloy sheets were $100{\times}100{\times}2mm$. Conditions of rotation speed were 1000, 1100 and 1200 rpm and those of welding speed were 200, 300 and 400 mm/min. As far as this work is concerned, the optimal conditions for friction stir joint were predicted as the rotation speed of 1200 rpm and welding speed of 200 mm/min.

• Journal of Welding and Joining
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• 제22권5호
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• pp.53-57
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• 2004

Friction stir weldability of AZ31B-H24, AZ61A-F and AZ91C-F Mg alloys were studied using microstructural observation and mechanical tests. The microstructure of stir zone(SZ) was coarse in AZ31B-H24 alloy whereas it was very fine both in AZ61A-F and AZ91C-F alloys. The hardness of SZ was remarkably increased by very fine recrystallized grains both in AZ61A-F and AZ91C-F alloys. On the other hand, the hardness of SZ was decreased in AZ31B-H24 due to the coarse microstructure. In SZ, AZ91C-F alloy showed very high hardness values because of dispersion hardening of $Mg_{17}$Al$_{12}$($\beta$ phase) and Al solid solution hardening. Because of more $Mg_{ 17}Al_{12}($\beta$ phase)$ intermetallic compounds, Mg alloy with high Al content showed poor mechanical properties.s.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 추계학술발표대회 개요집
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• pp.256-258
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• 2003

Hot-rolled and Extruded plates of AZ type magnesium alloys were successfully joined by friction stir welding(FSW). AZ31B-H24 and AZ61 plates with the thickness of 4mm were used, and the microstructural development in the stir zone were investigated using optical and scanning electron microscopes. The grain size of base metal and stir zone were investigated using the line-intersecter method. Hardness of the stir zone was remarkably increased due to very fine recrystallized grain structure both in AZ3l and AZ6l alloys. Tensile strengths of the FS welded Mg alloys AZ31 and AZ61 were strongly affected by formation of the intermetallic compounds, ${\beta}$-Al$\sub$12/Mg$\sub$17/.