• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2011.05a
• /
• pp.116-116
• /
• 2011

AZ31과 AZ80의 마그네슘합금 소재를 이용하여 분극곡선과 전기화학적 임피던스를 측정하였고, 다른 금속과 접촉하여 대기환경에 노출시킨 부식시험을 하였다. 그 결과 AZ31보다는 AZ80의 부식저항이 더 큰 것을 확인할 수 있었고, 마그네슘 모재가 이종금속과 접촉된 상황에서 Cu>Fe>Al의 접촉재 순으로 부식이 진행되었다.

• Korean Journal of Materials Research
• /
• v.31 no.1
• /
• pp.38-42
• /
• 2021

In this study, high temperature wetting analysis and AZ80/Ti interfacial structure observation are performed for the mixture of AZ80 and Ti, and the effect of Al on wetting in Mg alloy is examined. Both molten AZ80 and pure Mg have excellent wettability because the wet angle between molten droplets and the Ti substrate is about 10° from initial contact. Wetting angle decreases with time, and wetting phenomenon continues between droplets and substrate; the change in wetting angle does not show a significant difference when comparing AZ80-Ti and Mg-Ti. As a result of XRD of the lower surface of the AZ80-Ti sample, in addition to the Ti peak of the substrate, the peak of TiAl3, which is a Ti-Al intermetallic compound, is confirmed, and TiAl3 is generated in the Al enrichment region of the Ti substrate surface. EDS analysis is performed on the droplet tip portion of the sample section in which pure Mg droplets are dropped on the Ti substrate. Concentration of oxygen by the natural oxide film is not confirmed on the Ti surface, but oxygen is distributed at the tip of the droplet on the Mg side. Molten AZ80 and Ti-based compound phases are produced by thickening of Al in the vicinity of Ti after wetting is completed, and Al in the Mg alloy does not affect the wetting. The driving force of wetting progression is a thermite reaction that occurs between Mg and TiO2, and then Al in AZ80 thickens on the Ti substrate interface to form an intermetallic compound.

• Journal of the Korean Society for Heat Treatment
• /
• v.33 no.2
• /
• pp.49-56
• /
• 2020

Magnesium alloy is a metal with high specific strength and light weight, and is attracting attention as a next generation metal for environmentally friendly automobiles and transportation equipment. However, magnesium alloys have a problem of degrading formability due to the basal texture developed during processing, and their application is limited. Although active researches on the control of textures have been conducted in order to minimize this problem, there is a lack of research on the formation of microstructures and textures according to elemental differences. In this study, AZ61 and AZ80 magnesium alloys were selected to investigate the effects of aluminum addition on the microstructure development of magnesium alloys. This research has proven that the increase of the rolling rate results in the decrease of the average grain size of the two alloys, the increase of the hardness, and the increase of the fraction of twins. As shown on this research below, the basal texture developed strongly as the rolling ratio increased. On the other hand, this research also has proven that the two alloys exhibited different texture strength and distribution tendencies, which could be due to the effects of aluminum addition on work hardening, grain size, and twin behavior.

• Advances in materials Research
• /
• v.7 no.2
• /
• pp.105-118
• /
• 2018

Magnesium and its alloys are attracted towards all engineering applications like automotive, marine, aerospace etc. due to its inherent high strength to weight ratio. But, extensive use of Mg alloys is limited to the current scenario because of low wear and corrosion resistance behavior. However, equal channel angular press is one of the severe plastic deformation technique which has been effective method to improve the wear and corrosion resistance by achieving fine grain structure. In this study, the effect of grain refinement on wear and corrosion resistance of AZ80 Mg alloys were investigated. The wear behavior of the coarse and fine-grained Mg alloys was examined through $L_9$ orthogonal array experiments in order to comprehend the wear behavior under varies control parameters. It was shown that ECAPed alloy increased the wear and corrosion resistance of the Mg alloy through the formation of fine grain and uniform distribution of secondary ${\beta}-phase$. Also, the performance of AZ80 Mg alloy for these changeswas discussed through SEM morphology.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.6
• /
• pp.263-268
• /
• 2017

A hot forming process is required for Mg alloys to enhance the formability and plastic workability due to the insufficient formability at room temperature. Mg alloy undergoes dynamic recrystallization (DRX) during the hot working process, which is a restoration or softening mechanism that reduces the dislocation density and releases the accumulated energy to facilitate plastic deformation. The flow stress curve shows three stages of complicated strain hardening and softening phenomena. As the strain increases, the stress also increases due to work hardening, and it abruptly decreases work softening by dynamic recrystallization. It then maintains a steady-state region due to the equilibrium between the work hardening and softening. In this paper, an efficient optimization process is proposed for the material model of the dynamic recrystallization to improve the accuracy of the flow curve. A total of 18 variables of the constitutive equation of AZ80 alloy were systematically optimized at an elevated forming temperature($300^{\circ}C$) with various strain rates(0.001, 0.1, 1, 10/sec). The proposed method was validated by applying it to the constitutive equation of AZ61 alloy.

• Journal of the Korean Society for Heat Treatment
• /
• v.33 no.4
• /
• pp.180-184
• /
• 2020

The crystallographic texture plays an important role in both the plastic deformation and the macroscopic anisotropy of magnesium alloys. In previous study for AZ80 magnesium alloy, it was found that the main texture components of the textures vary with the deformation conditions at high temperatures. Also, the basal texture was formed at stress of more than 15-20 MPa and the non-basal texture was formed at stress of less than 15-20 MPa. Therefore, in this study, uniaxial compression deformation of AZ80 magnesium alloy was carried out at high temperature (stress of 15-20 MPa). The uniaxial compression deformation is performed at temperature of 723 K and strain rate 3.0 × 10^-3s^-1, with a strain range of between -0.4 and -1.3. Texture measurement was carried out on the compression planes by the Schulz reflection method using nickel filtered Cu Kα radiation. EBSD measurement was also conducted in order to observe spatial distribution of orientation. As a result of high temperature deformation, the main component of texture and its development vary depending on deformation condition of this study.

• Transactions of Materials Processing
• /
• v.21 no.4
• /
• pp.240-245
• /
• 2012

With the increasing demand for light-weight materials to reduce fuel consumption, the automobile industry has extensively studied magnesium alloys which are light weight metals. The intrinsic poor formability and poor ductility at ambient temperature due to the hexagonal close-packed (HCP) crystal structure and the associated insufficient number of independent slip systems restricts the practical usage of these alloys. Hot working of magnesium alloys using a forging or extrusion enables net-shape manufacturing with enhanced formability and ductility since there are several operative non-basal slip systems in addition to basal slip plane, which increases the workability. In this research, the thermomechanical properties of AZ80 Mg alloy were obtained by compression testing at the various temperatures and strain rates. Optical microscopy and EBSD were used to study the microstructural behavior such as misorientation distribution and dynamic recrystallization. The results were correlated to the hardening and the softening of the alloy. The experimental data in conjunction with a physical explanation provide the optimal conditions for net-shape forging under hot or warm temperatures through control of the grain refinement and the working conditions.

• Journal of the Korean institute of surface engineering
• /
• v.46 no.2
• /
• pp.80-86
• /
• 2013

Magnesium alloys of AZ31 containing (0.5, 1, 1.5) wt.% of initially added CaO particles were cast in air, and their oxidation behavior was studied at $450-650^{\circ}C$ in air. The initially added CaO particles either decomposed to dissolve in the ${\alpha}$-Mg matrix or precipitated as $Al_2Ca$ along the grain boundaries of the matrix during casting. The ignition temperatures were $565.4^{\circ}C$ for AZ31, $608.6^{\circ}C$ for AZ31+0.5 wt.%CaO, and $689.7^{\circ}C$ for AZ31+1 wt.%CaO. No ignition occurred for AZ31+1.5 wt.%CaO up to $700^{\circ}C$, displaying good oxidation resistance. The CaO-rich oxide scales that formed on the surface of the AZ31+(0.5, 1, 1.5) wt.%CaO alloys improved the oxidation resistance of AZ31 alloys.

• Korean Chemical Engineering Research
• /
• v.53 no.3
• /
• pp.282-288
• /
• 2015

A new energetic thermoplastic elastomer based on the azidated polybutadiene(Az-PBD)/ethylene vinyl acetate copolymer (EVA) blends was prepared, and structure and properties of the blends were invetigated by SEM, DSC, DMA, tensile testing and combustion test. The Az-PBD was synthesized via a two-step process involving the addition reaction of commercially available 1,2-PBD with $Br_2$ and subsequent nucleophilic substitution reaction of the brominated PBD with $NaN_3$. EVA/Az-PBD with 90/10, 80/20, 70/30 (wt/wt) was prepared by a solution blending. SEM, DSC, and DMA results revealed that the blends are partially compatible and Az-PBD is dispersed in continuous EVA matrix. Tensile test showed that modulus and tension set increased while elongation-at-break of the blends decreased with increasing Az-PBD content in the blends, but all the blends showed a elongation at break as high as 700% and a tension set of less than 5%, indicating that the blends are typically elastomeric. Combustion test showed that, with increasing Az-PBD content in the blend, higher energy can be released.

• Journal of the Korean institute of surface engineering
• /
• v.44 no.6
• /
• pp.233-238
• /
• 2011

The friction and wear characteristics of CrN and TiN coatings on SKD61 which is mold material using for extrusion of AZ80 magnesium alloy were investigated. The coatings were deposited by the arc ion-plating method, and the thickness were about $3.59{\mu}m$ and $3.28{\mu}m$, respectively. Reciprocating friction wear tests were conducted by varying pin load and temperature of counter substrate at un-lubricated condition. The pin loads were 11, 15 and 19 kgf, and the substrate temperatures were room temperature and $120^{\circ}C$. CrN coating which has a lower friction coefficient and a smaller adhesive wear with AZ80 magnesium alloy showed better wear resistance than TiN coating.