• Title/Summary/Keyword: Base metal alloys

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Effect of Si Content and RE Addition on Molten Salt Corrosion and High Temperature Oxidation of the Austenite Alloys (오스테나이트 합금의 용융염부식 및 고온산화에 미치는 Si 농도와 RE 첨가의 영향)

  • Jo, Su-Haeng;Jang, Jun-Seon;O, Seung-Cheol;Sin, Yeong-Jun;Park, Seong-Won
    • Korean Journal of Materials Research
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    • v.12 no.1
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    • pp.3-9
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    • 2002
  • The corrosion behavior of alloys in a molten salt was investigated along with the oxidation characteristics in the air. The basic composition of alloys in the study was Fe-25Ni-7Cr with Si and RE(rare-earth metal) as additives. The corrosion rate of the alloys was low in a molten salt of LiCl while the rate was high in the mixed molten salt of LiCl and $Li_2O$. When Si is added to the base alloy of Fe-25Ni-7Cr, corrosion resistance was improved as the Si content is increased up to 3%, however, it was observed that the corrosion resistance was getting worse as the Si content is increased. The base alloy with 2.43% of Si and 0.9% of RE(KSA-65), showed higher corrosion rate compared to that of KSA-63 alloy with an equivalent amount of only Si. The corrosion resistance of KSA-65 was similar to that of the base alloy(KSA-60). The oxidation resistance of KSA-65 alloy was greatly increased even at $850^{\circ}C$ for a long term exposure.

A Study on How Cyclic Casting of Base Metal Alloy for Dental Ceramic Crown May Effects upon Its Mechanical Properties and Microstructure (치과 도재용착 주조관용 비귀금속 합금의 반복주조가 기계적 특성 및 미세조직에 미치는 영향)

  • Choi, Un-Jae;Shin, Moo-Hak;Chung, Hee-Sun;Koh, Myoung-Won
    • Journal of Technologic Dentistry
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    • v.25 no.1
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    • pp.9-20
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    • 2003
  • Using a nickel-chrome casting alloy called 'Rexillium V' which is also available as base metal alloy for dental ceramic crown, 4 types of mixtures(A, B, C, D) with old and new metal were prepared for cyclic casting. The results of cyclic casting can be outlined as follows: 1. For Vickers hardness after casting, specimen A and D tended to have lower hardness in the course of cyclic casting, while specimen B and C tended to higher hardness. 2. The results of X-ray diffraction analysis showed that major crystal phase contained nickelchrome compounds and carbide. 3. The observation results of SEM photographs after cyclic casting show that there was a significant tendency to have similar structures among experimental groups. 4. The results of EDX analysis after cyclic casting showed that there were little differences in chemical composition between parent metal and base metal alloy. Although industrial nickel-chrome cast alloy did not show any significant change in material properties even through cyclic casting over several times, it is recommended that more there be more in-depth studies on how to detect any potential corrosion, discoloration and toxication of dental ceramic crown implanted in patient's oral cavity.

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A Study on the Thermal Behavior of Friction Stir Welding in hi 6061 Alloys (Al 6061합금의 마찰교반접합시 접합부의 열거동에 관한 연구)

  • 방한서;김흥주;고민성;김규훈
    • Journal of Welding and Joining
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    • v.20 no.4
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    • pp.534-537
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    • 2002
  • In the various industry such as shipbuilding and automobile, etc., Al-alloys are used to reduce weight and improve economical efficiency, and they are mainly utilized in the process of Friction Stir Welding (FSW). A number of studies have been carried out on the metallurgical characteristics of friction stir welding In Al-alloys. However, research on the thermal behavior of FSW by using numerical analysis is not sufficient in the domestic and abroad. In this paper, therefore, numerical simulation was used to find out thermal behaviour of FSW by finite element method. We considered heat source that occurred by friction between tool shoulder including pin and base metal. To confirm the result of simulation, macrostructure is examined and compared after welding. The result of numerical simulation shows that Al-alloy is welded under a melting point of Al around pin by FSW.

Fusion Zone Characteristics of Dissimilar Aluminum Alloys Joining (이종 알루미늄 합금 용접의 용융부 특성 연구)

  • Park, Seon-Hong;Park, Byeong-Cheol;Kim, Yeong-Gi;Baek, Ung-Ryul
    • Proceedings of the KWS Conference
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    • 2007.11a
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    • pp.141-143
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    • 2007
  • Increasing demand of using low weight materials in recent automotive trends has been the challenge to develop a sound welding of aluminum alloys. A heat treatable AA6082-T6 and a non-heat treatable AA5083-0 aluminum alloys were joined in this study. Investigations revealed that about 60 UTS will be reduced due to welding process. Fracture happened in the interface between fusion zone and base metal of top specimen where penetration is shallow. Therefore, lower welding torch angle produced the better strength which allows deeper penetration to the top specimen. PWHT at $560^{\circ}C$ for 2 hours can be used to return the original UTS of the specimens.

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The Effects of Welding Conditions on the Joint Properties of the Friction Stir Welded AZ31B-H24 Mg Alloys (마찰교반용접한 AZ31B-H24 마그네슘 합금의 용접특성에 미치는 용접조건의 영향)

  • 이원배;방극생;연윤모;정승부
    • Journal of Welding and Joining
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    • v.20 no.5
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    • pp.87-92
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    • 2002
  • Weldability of Friction Stir Welded(FSW) AZ31B-H24 Mg alloy sheet with 4m thick was evaluated by changing welding speed. The sound welding conditions mainly depended on the suffiicient welding heat input during the process. The insufficient heat input resulted in the void like defect in the weld zone. Higher welding speed caused a larger inner void or lack of bonding. The defects were distributed at the stir zone or the transition region between stir zone and thermo-mechanical affected zone (UE). The size of defects slightly increased with increasing welding speed. These defects had a great effect on the joint strength of weld zone. The weld zone was composed of stir zone, TMAZ and heat affected zone. The stir zone was cosisted of fine recrystallized structure with $5-8\mu\textrm{m}$ in the mean grain size. The hardness of weld zone was near the 60HV, which was slightly lower than that of base metal. The maximum joint strength was about 219MPa that was 75% of that of base metal and the yield strength was also lower than that of base metal partly due to the existance of defects.

Effect of Welding Parameters on the Friction Stir Weldability of 5052 Al alloy (5052 알루미늄 합금 마찰교반접합부 특성에 미치는 접합인자의 영향)

  • 이원배;김상원;이창용;연윤모;장웅성;서창제;정승부
    • Journal of Welding and Joining
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    • v.22 no.3
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    • pp.69-76
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    • 2004
  • Effects of friction stir welding parameters such as tool rotation speed and welding speed on the joints properties of 5052 Al alloys were studied in this study. A wide range of friction stir welding conditions could be applied to join 5052 AA alloy without defects in the weld zone except for certain welding conditions with a lower heat input. Microstructures near the weld zone showed general weld structures such as stir zone (SZ), thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ). Each zone showed the dynamically recrystallized grain, transient grain and structure similar to base metal's, respectively. Hardness distribution near the weld zone represented a similar value of the base metal under wide welding conditions. However, in case of 800 rpm of tool rotation speed, hardness of the stir zone had a higher value due to the fine grain with lots of dislocation tangle, a higher angle grain boundary and some of Al3Fe particles. Except joints with weld defects, tensile strength and elongation of the joints had values similar to the base metal values and fracture always occurred in the regions approximately 5mm away from the weld center.

Evaluation of effect of galvanic corrosion between nickel-chromium metal and titanium on ion release and cell toxicity

  • Lee, Jung-Jin;Song, Kwang-Yeob;Ahn, Seung-Geun;Choi, Jung-Yun;Seo, Jae-Min;Park, Ju-Mi
    • The Journal of Advanced Prosthodontics
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    • v.7 no.2
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    • pp.172-177
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    • 2015
  • PURPOSE. The purpose of this study was to evaluate cell toxicity due to ion release caused by galvanic corrosion as a result of contact between base metal and titanium. MATERIALS AND METHODS. It was hypothesized that Nickel (Ni)-Chromium (Cr) alloys with different compositions possess different corrosion resistances when contacted with titanium abutment, and therefore in this study, specimens ($10{\times}10{\times}1.5mm$) were fabricated using commercial pure titanium and 3 different types of Ni-Cr alloys (T3, Tilite, Bella bond plus) commonly used for metal ceramic restorations. The specimens were divided into 6 groups according to the composition of Ni-Cr alloy and contact with titanium. The experimental groups were in direct contact with titanium and the control groups were not. After the samples were immersed in the culture medium - Dulbecco's modified Eagle's medium[DMEM] for 48 hours, the released metal ions were detected using inductively coupled plasma mass spectrometer (ICP-MS) and analyzed by the Kruskal-Wallis and Mann-Whitney test (P<.05). Mouse L-929 fibroblast cells were used for cell toxicity evaluation. The cell toxicity of specimens was measured by the 3-{4,5-dimethylthiazol-2yl}-2,5-diphenyltetrazolium bromide (MTT) test. Results of MTT assay were statistically analyzed by the two-way ANOVA test (P<.05). Post-hoc multiple comparisons were conducted using Tukey's tests. RESULTS. The amount of metal ions released by galvanic corrosion due to contact between the base metal alloy and titanium was increased in all of the specimens. In the cytotoxicity test, the two-way ANOVA showed a significant effect of the alloy type and galvanic corrosion for cytotoxicity (P<.001). The relative cell growth rate (RGR) was decreased further on the groups in contact with titanium (P<.05). CONCLUSION. The release of metal ions was increased by galvanic corrosion due to contact between base metal and titanium, and it can cause adverse effects on the tissue around the implant by inducing cytotoxicity.

Influences of Coatings and Solution Corrosivity on Cathodic Protection of Metallic Materials

  • Yoo, Y.R.;Chang, H.Y.;Jin, T.E.;Kim, Y.S.
    • Corrosion Science and Technology
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    • v.5 no.3
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    • pp.106-111
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    • 2006
  • Painting has protected metallic stack but the paint films may be degraded and corrosion problem can be arisen. To protect the painted metal stack, cathodic protection can be applied. If cathodic protection is applied to bare metal, only small area may be protected. However, if cathodic protection is applied to painted metal surface, large area can be protected and the lifetime of paint films can be extended. High corrosion resistant alloys were corroded at a Flue Gas Desulfurization (FGD) facility of power plant within a short period and thus cathodic protection can be used to protect these metals. On the base of computer simulation, if cathodic protection is applied to bare metal in a FGD environment, it was estimated that applied current could almost be spent to protect area near the anode. However, if cathodic protection is applied to high resistant-coated metal, the much larger area from the anode could be effectively protected.

A Study of Dissimilar Weldability of Incoloy 825 with Mild Steel (Incoloy 825합금 및 탄소강의 이종강종간 용접특성 연구)

  • Kim, Hui-Bong;Lee, Chang-Hui
    • Korean Journal of Materials Research
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    • v.7 no.2
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    • pp.162-170
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    • 1997
  • This study has evaluated the dissimialr weldability of Incoloy 825 Ni base alloy with a mild steel(SS41). Further a compatibility study of wrveral Ni base filler metals with the dissimilar joint between the two alloys was also included. The dissimilar weldability of Incoloy 825 with mild steel is strongly dependent upon the type of the filler metal used. Among the filler metals, ENiCrFe which has a chemical comosition similar to that of Incoloy 825 was found to be most compatible to the joint. In addition, a filler metal which showed a good cracing resistance in one dissimiar alloy combination was not necessarily graranteed to other combination. Microstructural examination with SEM, TEM and Auger revealed that the solidification cracking resestance of the dissimilar joint. between Incoloy 835 and SS41 was closely with the Ti+Nb content and with the content of a low melting eutectic phase of Laves relatibve to that of MC type phase.

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Control of Grain Size on Friction Stir Welded AZ31 and AZ91 (AZ31과 AZ91의 마찰교반용접부 결정립 크기 제어)

  • Gwon, Gi-Su;Lee, Chang-U;Kim, Mok-Sun;Sato, Yutaka S.;Kim, Jeong-Han
    • Proceedings of the KWS Conference
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    • 2007.11a
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    • pp.328-331
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    • 2007
  • It was carried out to evaluate microstructure and mechanical properties of friction stir welded(FSW) on magnesium alloys. Two types magnesium alloy was used in this work, AZ31 wrought and AZ91 cast magnesium alloy. Microstructure near the weld zone showed general weld structures such as stir zone(SZ), thermo-mechanically affected zone(TMAZ) and heat affected zone(HAZ). In the AZ91 alloy, the SZ had a fine grain size and $\beta$ phase particles which were well distributed in matrix. It was characterized to redistribute by partial or full re-solution of the $\beta$ phase which is coarse in base metal during FSW processing. The hardness of the SZ slightly increase than the base metal in AZ31 Mg alloy.

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