• 한국레이저가공학회지
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• 제14권3호
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• pp.12-16
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• 2011

In automotive industry, because of the consideration of fuel economy, lightweight alloys have been adopted and are expected to be extensively used in the future. Magnesium alloys are among the promising materials, due to their lightweight and good mechanical properties. This study is related to the laser weldability of AZ31B magnesium alloy, an all-purpose wrought alloy with good strength and ductility. A 4kW Nd:YAG laser was used to join AZ31B sheet, and the effects of welding parameter on the quality of lap-welded joints were investigated. As a result of this study, the optimal condition was obtained, and the effect of gap distance was also revealed on the porosity control.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.70-73
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• 2007

The forming characteristics of cup-rod combined extrusion process were investigated with process parameter change. Simultaneous forward rod extrusion and backward cup extrusion was conducted with magnesium alloy, AZ31B. Process parameters such as forward extrusion ratio, backward extrusion ratio, and working temperature were controlled in a specific region and the effects of the parameter change were examined. Surface crack was developed in a certain state of the process parameters combination. The crack-free forming limit of the alloy in the combined process was disclosed by the parameter study. The microstructures of the initial and extruded workpieces were observed.

• Journal of Mechanical Science and Technology
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• 제20권8호
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• pp.1209-1216
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• 2006

An AZ31 magnesium alloy was tested at constant temperatures ranging from 423 to 473 K (0.46 to 0.51 Tm) under constant stresses. All of the creep curves exhibited two types depending on stress levels. At low stress (${\sigma}/ G < 4 {\times}10^{-3}$), the creep curve was typical of class A (Alloy type) behavior. However, at high stresses (${\sigma}/ G > 4 {\times}10^{-3}$), the creep curve was typical of class M (Metal type) behavior. At low stress level, the stress exponent for the steady-state creep rate was of 3.5 and the true activation energy for creep was 101 kJ/mole which is close to that for solute diffusion. It indicates that the dominant deformation mechanism was glide-controlled dislocation creep. At low stress level where n=3.5, the present results are in good agreement with the prediction of Fridel model.

• 한국기계가공학회지
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• 제11권6호
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• pp.16-21
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• 2012

Magnesium alloy has been focussed as lightweight material owing to its high strength even though low density with aluminum alloy, titanium alloy and plastic material. Friction stir welding technique was performed by rotating and plunging a shouldered tool with a small diameter pin into the joint line between two butted plates and useful to join magnesium alloy. In this paper, the experiments of friction stir welding were done to investigate the joint characteristics of AZ31 magnesium alloy. For its evaluation, the orthogonal array method$(L_{27}(3^{13}))$ was applied with four factors of pin diameter, shoulder diameter, travel speed and rotation speed of tool and also three levels of each factor. Nine tools were worked through shoulder diameter of 9, 12, 15mm and pin root diameter of 3, 4, 5mm. In addition tensile tests were excuted for the assessment of mechanical properties for joint conditions. From the results, pin diameter, shoulder diameter, and rotating speed of tool influenced on the tensile strength meaningful, but welding speed did not influence on that by the variance analysis. Beside of that, optimum condition of tensile strength was estimated as following ; shoulder diameter:15mm, welding speed:200mm/min, rotating speed:200rpm.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.98.2-98.2
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• 2017

본 연구에서는 다양한 농도의 수산화나트륨 수용액에서 AZ31 마그네슘 합금의 양극산화 거동에 미치는 인가 전류밀도의 영향에 대해 알아보았다. 다양한 크기의 DC 전류를 인가하여 양극산화 거동을 확인하였으며, 형성된 피막의 표면구조를 optical microscope, confocal scanning laser microscope 등을 이용하여 관찰하였다. 연구결과, 인가 전류밀도에 따라 세 가지 유형의 voltage-time curve를 얻을 수 있었으며, voltage-time curve의 유형에 따라 서로 다른 피막 색상과 표면구조를 형성함을 발견하였다. 수산화나트륨 전해액에서 AZ31 마그네슘 합금의 플라즈마 전해산화 피막은 0.6 M 이상의 농도를 가진 수산화나트륨 용액에서 임계값 이상의 전류밀도를 인가하였을 경우에만 형성됨을 확인하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2015년도 추계학술대회 논문집
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• pp.186-186
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• 2015

본 연구에서는 플라즈마 전해산화 처리된 AZ31 마그네슘 합금의 내식성에 봉공처리가 미치는 영향에 대해 알아보았다. 플라즈마 전해산화 공정에 의해 형성된 피막에 대하여 증류수 및 알칼리 수용액에서 봉공처리를 실시하였으며, 개회로 전위 측정, 동 전위 분극실험 및 염수분무실험을 통해 내식성을 평가하였다. 실험 결과 증류수 및 알칼리 수용액에서 모두 봉공처리를 함에 따라 내식성이 향상되었으며, 봉공처리 시간을 증가시킴으로써 AZ31 마그네슘 합금의 내식성을 크게 향상 시킬 수 있었다.

• 한국재료학회지
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• 제15권1호
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• pp.25-30
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• 2005

The microstructural changes by hot extrusion of AZ31B magnesium alloy were observed, and the relation to the tensile property was examined. The tensile properties as oriented longitudinal(L), half transverse(HT) and long transverse(LT) to the extrusion direction were investigated at $20^{\circ}C,\;100^{\circ}C,\;200^{\circ}C,\;300^{\circ}C\;and\;400^{\circ}C$, respectively. As the results, many recrystallized small grains distributed uniformly in large banded microstructures formed along the extrusion direction. The grain size of as-extruded specimen was around $30\~150\;{\mu}m$. As increasing the test temperature the tensile and yield strength with respect to the angle between the axis of the tensile and the longitudinal direction in extrusion was decreased, but their elongation were increased and their deviation between L and LT specimens have disappeared from $300^{\circ}C$. This mechanical anisotropy was reduced at elevated temperatures and almost disappeared at $400^{\circ}C$. It was considered that the homogenization was occured by the recrystallization and the change of slip system was occurred during tensile test process in elevated temperatures.

• 대한기계학회논문집A
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• 제37권7호
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• pp.913-919
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• 2013

본 연구에서는 마그네슘 합금 AZ31을 적용한 배터리 팩 케이스를 개발하여 자체 진동 및 외부 충격으로부터 배터리를 보호하도록 하며, 기존 스틸 소재 대비 50% 이상 경량화하여 친환경 기술개발을 목적으로 한다. 또한, 제품의 복잡한 형상 및 마그네슘 소재의 특성으로 제품을 성형하기에는 힘든 측면이 많으므로 이를 해결하기 위해 마그네슘 합금소재의 온도별 최적성형조건을 제시하고자 한다. 즉 AZ31의 성형방법에 따라 상온, $230^{\circ}C$, $250^{\circ}C$ 및 $270^{\circ}C$의 4가지 조건하의 시험편으로 인장시험, 경도시험, 부식시험 및 피로시험 등을 실시하여 기계적 특성을 정량적으로 분석하였고, 또 FEM해석을 통하여 자동차 부품 배터리 팩 케이스 개발에 적용토록 하였다.

• 터널과지하공간
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• 제22권3호
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• pp.221-225
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• 2012

마그네슘 합금은 경량화 재료로서 많은 주목을 받고 있으나, 스테인레스 스틸과의 접합이 어려운 문제점이 있다. 본 연구에서는 수중충격파를 이용하여 스테인레스 스틸(SUS304)과 마그네슘 합금(AZ31)의 폭발용접을 수행하고 접합특성에 관한 분석을 수행하였다. SUS304의 두께는 0.5 mm와 1 mm를 사용하였으며, 폭약과 재료의 이격거리는 45 mm, 폭약의 설치경사는 $20^{\circ}$로 하여 실험한 결과, 두 재료의 접합면에서 중간층(resolidified interlayer)이 형성되었다. 중간층의 형성을 억제하기 위하여 폭약과 재료의 거리를 60 mm로 증가시켰으며 폭약의 경사는 $30^{\circ}$으로 변경하여 폭발용접실험을 수행하였다. 그 결과, 폭약과 재료 사이의 간격과 경사각이 증가함에 따라 중간층이 나타나지 않는 경향을 보였다. 이 중간층에 대하여 EPMA분석한 결과, 중간층은 두 금속의 재료가 혼합되어 있는 것으로 확인 되었으며, 경도는 두 금속의 평균 경도에 해당 됨이 확인 되었다.

• 대한금속재료학회지
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• 제46권4호
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• pp.189-198
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• 2008

The changes in microstructure and mechanical properties of AZ31 alloy subjected hot-rolling process were investigated. The AZ31 plates fabricated by horizontal continuous casting process were prepared and have hot-rolled from 30 mm to 1 mm in thickness under different processing conditions. At the rolling temperature of $400^{\circ}C$, little surface and side crack was observed up to 20% reduction rate. As total reduction and reduction rate increase to more than 75% and 20% pass, respectively, Grains were more uniformly refined through overall thickness, and particularly lots of shear bands were appeared to be inclined at less than $20^{\circ}C$ along the rolling direction. Average grain size of less than $5{\mu}m$ and tensile properties of YS ${\geq}$ 250 MPa, UTS ${\geq}$ 300 MPa and El. ${\geq}$ 13% were acquired for hot-rolled AZ31 sheets without post-heat treatment. Maximum intensity of (0002) pole figure was decreased with an increase in reduction rate, indicating the improvement of texture by means of high reduction rate.