• Title/Summary/Keyword: Mg-alloy

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Determination of trace boron in steels by prompt gamma-ray activation analysis (즉발감마선방사화분석법에 의한 철강시료 중의 붕소 측정)

  • Kim, I.J.;Cho, K.H.;Paul, R.L.
    • Analytical Science and Technology
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    • v.22 no.4
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    • pp.302-306
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    • 2009
  • A trace amount of boron in steel significantly influences its mechanical and physical properties. A prompt gamma ray activation analysis (PGAA) method is used to measure boron in low alloy steel samples of KRISS 101-01-C21~C26. NIST SRMs of 362, 364, 1761 and 1767 serve as the control standards to validate the measurement method. The measured values of the NIST SRMs are consistent with their certified values within the expected uncertainties, except for that of NIST SRM 362. Experimental uncertainties are evaluated according to the guidelines given by the International Organization for Standardization (ISO). The expanded uncertainties are calculated with a coverage factor of 2, at approximately 95% confidence level. The calculated relative expanded uncertainties of boron mass fractions are between 3% and 7% at the mg/kg level. The results are compared with the results measured by the solvent extraction-inductively coupled optical emission spectrometry (ICP/OES) method.

Si and Mg Coatings on the Hydroxyapatite Film Formed Ti-29Nb-xHf Alloys by Plasma Electrolyte Oxidation

  • Park, Seon-Yeong;Choe, Han-Cheol
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2017.05a
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    • pp.152-152
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    • 2017
  • Titanium and its alloys have been widely used for biomedical applications. However, the use of the Ti-6Al-4V alloy in biomaterial is then a subject of controversy because aluminum ions and vanadium oxide have potential detrimental influence on the human body due to vanadium and aluminum. Hence, recent works showed that the synthesis of new Ti-based alloys for implant application involves more biocompatible metallic alloying element,such as, Nb, Hf, Zr and Mo. In particular, Nb and Hf are one of the most effective Ti ${\beta}$-stabilizer and reducing the elastic modulus. Plasma electrolyte oxidation (PEO) is known as excellent method in the biocompatibility of biomaterial due to quickly coating time and controlled coating condition. The anodized oxide layer and diameter modulation of Ti alloys can be obtained function of improvement of cell adhesion. Silicon (Si) and magnesium (Mg) has a beneficial effect on bone. Si in particular has been found to be essential for normal bone and cartilage growth and development. In vitro studies have shown that Mg plays very important roles in essential for normal growth and metabolism of skeletal tissue in vertebrates and can be detected as minor constituents in teeth and bone. Therefore, in this study, Si and Mg coatings on the hydroxyapatite film formed Ti-29Nb-xHf alloys by plasma electrolyte oxidation has been investigated using several experimental techniques. Ti-29Nb-xHf (x= 0, 3, 7 and 15wt%, mass fraction) alloys were prepared Ti-29Nb-xHf alloys of containing Hf up from 0 wt% to 15 wt% were melted by using a vacuum furnace. Ti-29Nb-xHf alloys were homogenized for 2 hr at $1050^{\circ}C$. The electrolyte was Si and Mg ions containing calcium acetate monohydrate + calcium glycerophosphate at room temperature. The microstructure, phase and composition of Si and Mg coated oxide surface of Ti-29Nb-xHf alloys were examined by FE-SEM, EDS, and XRD.

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A study on the Mechanical Properties of $Al_2O_{3(p)}$/LXA Composites by Melt-stirring Method (용탕교반법에 의한 $Al_2O_{3(p)}$/LXA복합재료의 기계적 성질에 관한 연구)

  • 이현규;공창덕
    • Journal of the Korean Society of Propulsion Engineers
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    • v.4 no.1
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    • pp.65-73
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    • 2000
  • Casting of metal matrix composites is an attractive process since it offers a wide selection of materials and processing conditions. Among the casting methods, melt-stirring technology is much attractive route in industrial application because it is more simple and inexpensive compared to squeeze casting or powder metallurgy. In the present work, effects of particle size, volume fraction of particles and mg addition on mechanical properties and thermal expansion coefficients of $\alpha$ -$Al_2O_{3(p)}$/LXA composites were studied. It is shown that $\alpha$ -$Al_2O_3$ particles formed at the interface of $\alpha$ -$Al_2O_3$ particles and matrix made an important role on mechanical properties. Ultimate tensile strength of most composite materials was not increased. But in the case of 5vol% addition of 16$\mu\textrm{m}$ $\alpha$ -$Al_2O_3$ Particle, Ultimate tensile strength of composite materials with 3wt.% Mg was increased. Volume fraction of reinforcements and mg content were thermal expansion coefficients of composite materials were decreased.

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Gas Absorption and Release Properties of Zn(BH4)2 and MgH2-Zn(BH4)2-Ni-Ti-Fe Alloy

  • Kwak, Young Jun;Kwon, Sung Nam;Song, Myoung Youp
    • Korean Journal of Materials Research
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    • v.25 no.1
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    • pp.43-47
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    • 2015
  • $Zn(BH_4)_2$ was prepared by milling $ZnCl_2$ and $NaBH_4$ in a planetary ball mill in an Ar atmosphere, and XRD analysis, SEM observation, FT-IR analysis, DTA, and TGA were performed for synthesized $Zn(BH_4)_2$ samples. 90 wt% $MgH_2$+1.67 wt% $Zn(BH_4)_2(+NaCl)$+5 wt% Ni+1.67 wt% Ti+1.67 wt% Fe (named $90MgH_2+1.67Zn(BH_4)_2(+NaCl)$+5Ni+1.67Ti+1.67Fe) samples were also prepared by milling in a planetary ball mill in an $H_2$ atmosphere. The gas absorption and release properties of the $Zn(BH_4)_2(+NaCl)$ and $90MgH_2+1.67Zn(BH_4)_2(+NaCl)_2(+NaCl)$+5Ni+1.67Ti+1.67Fe samples were investigated. An FT-IR analysis showed that $Zn(BH_4)_2$ formed in the $Zn(BH_4)_2(+NaCl)$ samples prepared by milling $ZnCl_2$ and $NaBH_4$. At the first cycle at $320^{\circ}C$, $90MgH_2+1.67Zn(BH_4)_2(+NaCl)$+5Ni+1.67Ti+1.67Fe absorbed 2.95 wt% H for 2.5 min and 4.93 wt% H for 60 min under 12 bar $H_2$, and released 1.46 wt% H for 10 min and 4.57 wt% H for 60 min under 1.0 bar $H_2$.

MicrostructuraL Characteristics During Hydrogen Desorption of Mechanical Milled TiH2 (기계적 합금화된 TiH2의 수소방출에 따른 미세조직 특성)

  • Jung S.;Jung Hyun-Sung;Ahn Jae-Pyoung;Park Jong-Ku
    • Journal of Powder Materials
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    • v.13 no.3 s.56
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    • pp.199-204
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    • 2006
  • We manufactured the metal hydrides of $(Ti_{0.88}Mg_{0.12})H_2$ using a very easy and cheap way that Ti-12%Mg blending powder was mechanically milled with liquid milling media such as isopropyl alcohol ($C_3H_8O$, containing oxygen) and hexane ($C_6H_{14}$, no oxygen) as hydrogen source. The $(Ti_{0.88}Mg_{0.12})H_2$ synthesized in isopropyl alcohol contained the high oxygen of 11.2%, while one in hexane had the low oxygen content of 0.7%. Such a difference of oxygen content affected the dehydriding behavior, phase transformation, and microstructural evolution at high temperature, which was investigated through X-ray diffraction and DSC measurements, and electron microscope observations.

Microstructural Characterization of Hot Extruded Al-Zn-Mg-Cu Alloys Containing Sc (Sc을 첨가한 Al-Zn-Mg-Cu 합금 압출재의 열처리에 따른 미세구조 변화)

  • 이혜경;서동우;이상용;이경환;임수근
    • Transactions of Materials Processing
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    • v.13 no.1
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    • pp.53-58
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    • 2004
  • The microstructural changes of Al-Zn-Mg-Cu alloy containing Sc during hot extrusion and post heat treatment were investigated. Two kinds of Al-Sc alloys with different alloying elements (B1, B2) were hot extruded to make T-shape bars at extrusion temperature of $380^{\circ}C$, then the bars were solution treated at $480^{\circ}C$ for 2hrs followed by artificial aging at $120^{\circ}C$ for 24hrs. The interior microstructure of as extruded bar consisted of elongated grains, however, fine equiaxed grains were also observed around surface. The microstructural gradient suggested that different restoration process could proceed during the hot extrusion. For B1 and B2, different grain growth behaviors were found around the surface during the post heat treatment. Rapid grain growth behavior was observed for B1 around the surface, however, it was not observed for B2. Orientation pinning, which was related with the evolution of preferred orientation, and precipitation were thought to be responsible for the rapid grain growth.

Effect of Si and Ca Addition on the Strengthening Behavior of Gravity-cast AM60 Magnesium Alloys (중력주조 AM60 마그네슘 합금의 강화 거동에 미치는 Si 및 Ca 첨가영향)

  • Kim, Jae-Woo;Kim, Do-Hyang;Shin, Kwang-Seon
    • Journal of Korea Foundry Society
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    • v.18 no.4
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    • pp.364-372
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    • 1998
  • Effects of Si and Ca additions on the mechanical properties of AM60 based Mg alloys have been investigated. Hardness of the AM60 based Mg alloys reached a maximum value after aging for approximately 33 hours but the amount of hardness increase was negligible. The poor age hardening response of the alloys was due to low Al content, which implies that Al content must be >6 wt.% to observe age hardening effect. The tensile and yield strength increased with increasing Al, Si, and Ca content but elongation decreased with increasing Al and Si content. The best mechanical properties obtained in AM 40-2.5Si-0.2Ca alloy after T4 heat treatment were as follows; tensile strength 193.4 MPa, yield strength 79.2 MPa, and elongation 11.2%. High temperature property obtained from creep test was also improved by introducing $Mg_2Si$ which has high hardness, high melting temperature and low thermal expansion coefficient.

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Microstructures and Mechanical Properties of AZ31-(0~0.5%)Ca alloys (AZ31-(0~0.5)%Ca 합금의 미세조직과 기계적 성질)

  • Jun, Joong-Hwan;Park, Bong-Koo;Kim, Jeong-Min;Kim, Ki-Tae;Jung, Woon-Jae
    • Journal of the Korean Society for Heat Treatment
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    • v.17 no.5
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    • pp.299-304
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    • 2004
  • Influence of Ca addition on microstructure and room temperature mechanical properties has been studied for AZ31(Mg-3%Al-1%Zn-0.2%Mn)-(0~0.5)%Ca wrought alloys, based on experimental results from metallography, X-ray diffractometry and mechanical tests. Yield strength, ultimate tensile strength and hardness of the alloys increased remarkably with increasing Ca content, whereas elongation was deteriorated continuously. Microstructural examination revealed that Ca addition efficiently refined grains of ${\alpha}$(Mg) phase and that some of the Ca dissolved in ${\beta}(Mg_{17}Al_{12})$ precipitates. The former and the latter facts are thought to be responsible for improved strength and loss of ductility of the AZ31+Ca wrought alloys, respectively.

Microstructural Features of Al Alloy 7N01 Welded by $CO_2$ Laser - Microsturctural Features of Full Penetration Joints - ($CO_2$ 레이저 용접한 7N01 Al합금의 미세조직 특징(I) - 완전용입 용접부의 미세조직 -)

  • 윤재정;강정윤;김인배;김대업
    • Journal of Welding and Joining
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    • v.19 no.4
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    • pp.429-436
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    • 2001
  • The effect of welding condition on the microstructures of the weld metal in A7N01 welded by $CO_2$ laser was investigated. The number of ripples was increased with decreasing power and increasing welding speed. In the bead without ripple lines, the subgrain microstructures distribution from the fusion line toward the center of the bead were in the order of cellular, dendritic and equiaxed dendrite. However, in the bead with ripple lines, cellular and dendritic were formed between the fusion boundary and the ripple line. Inaddition, those structures were also observed between the ripple line. Equiaxed dendrites were formed only at the center line region. Cellular and dendritics formed near the ripple line were larger than those formed near the fusion boundary. The cooling rates estimated by the dendrite arm spacing were in the range of 200 to 1150oC/s. Cooling rate was increased with decreasing the power and increasing the welding speed. Mg and Zn segregated at the boundaries of cellulars and dendritics, Mg was segregated more than Zn. The segregation of Mg and Zn decreased with increasing cooling rate. Hardness of the weld metal was lower than that of the base metal in all welding conditions and increased as the cooling rate increased.

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A Study on the Effects of Ag Addition on the Mechanical Properties and Microstructure in Atomized Al-Zn-Mg Alloys (분무 Al-Zn-Mg 합금의 기계적 성질 및 미세조직에 미치는 Ag 첨가의 영향)

  • Shin, Hee-Sang;Jeong, Tae-Ho;Nam, Tae-Woon
    • Journal of Korea Foundry Society
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    • v.19 no.6
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    • pp.456-465
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    • 1999
  • The overall objective of this study is to investigate the effect of Ag addition on the mechanical properties and microstructure of rapid solidified 7000 Al series alloys. Al-Zn-Mg-Cu alloys with small amounts of Ag was fabricated into the powder by gas atomization. The powder was extruded after the cold compaction and degassing and then followed by T6 heat treatment. Microstructure observation, phase analysis, room and high temperature tensile test and hardness test were pursued. The tensile strength and hardness of Ag-added alloy after heat treatment was increased with increasing Ag contents. However, the elongation of extruded alloys was not increased as much as to be expected. The reason of this result seems to be related to $the{\Omega}$ phase, which contribute to the high temperature strength stability of Al-Cu-Zn alloys through the formation of eutectoid with Ag addition.

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