• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제40회 동계학술대회 초록집
• /
• pp.322-322
• /
• 2011

White gold는 아름다운 광택과 손쉬운 가공성의 장점 때문에 장신구를 비롯한 다양한 분야에서 그 활용 가치가 매우 높다. 본 연구에서 우리는 열처리를 통한 white gold의 hardness강화 및 품질향상을 위하여 다양한 열처리 조건별 기계적 특성변화를 비교 관찰 하였다. 열처리 전 white gold alloy의 구성성분을 조사하기 위하여 EPMA와 ICP-MS를 사용하여 분석 후 그 값을 수치화 하였다. 14K, 18K White gold alloy 총 32개의 시료를 사용하여 $750^{\circ}C$, 30 min의 조건에서 solid treatment 및 quenching 후 $200^{\circ}C{\sim}350^{\circ}C$ 온도 범위에서 $50^{\circ}C$ 간격으로 age-hardening을 실시하였다. 열처리 전과 후 각 조건별 hardness 변화는 Vicker's hardness tester를 사용하여 측정하였다. 또한 age-hardening 후 모든 시료는 optical microscope (OM)을 사용하여 각 열처리 조건 별 grain 들의 배열 및 size의 변화를 관찰하였다. 열처리 전 14K, 18K white gold alloy의 hardness의 평균값은 각각 162 Hv와 196 Hv를 나타내었다. solid treatment 후 그 수치가 146 Hv, 172 Hv로 감소하였고, age-hardening 후에는 hardness 값이 점차 증가하여 14K는 $260^{\circ}C$에서 226 Hv, 18K는 $270^{\circ}C$에서 268 Hv의 가장 높은 수치를 나타내었다. 또한 14K 및 18K는 각각 $260^{\circ}C$, $270^{\circ}C$ 이상에서는 over-aging 현상을 나타내었다. OM 분석 결과 열처리 전 불균일했던 grain들의 배열이 solid treatment 및 quenching 후 다소 균일해짐을 확인할 수 있었고, grain size 또한 열처리 전에 비해 증가함을 알 수 있었다. Solid treatment 후 모든 시료의 hardness값이 전반적으로 감소하였다가 age-hardening을 통해 grain들의 배열이 점차 안정화 되면서 hardness가 증가 하였고, over-aging 구간에서는 급격히 감소하는 경향을 나타내었다. 이 결과들로부터 우리는 14K, 18K white gold alloy 에 대한 age-hardening 최적조건을 도출하였고, 각 열처리 조건별 grain 배열 상태의 변화를 관찰 할 수 있었다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.283-283
• /
• 2013

Because of beautiful glossy and color, the value of gold leverage is very high in Europe. To improve the quality of gold alloys, we performed heat treatment on 14 K white gold alloys by variously changing age-hardening conditions. Age-hardening behavior and the related phase transformation changes were studied to elucidate the hardening mechanism of 14 K white gold alloy. For solid solution treatment [ST], casted gold alloy specimens were treated at high temperature ($750^{\circ}C$) for 30 minutes, and the specimens dropped to water to quench them. For Age-hardening treatment [AT], the specimens were treated at various temperatures ($250{\sim}300^{\circ}C$). After the heat treatment, we observed the phenomenon to increase hardness from 126 Hv to 166 Hv by Vicker's hardness tester. Through electron probe micro-analysis (EPMA) mapping analysis, we investigated that irregular particles were changed uniformly. In the SEM and OM images, two phases of matrix and particle-likestructures were observed, and the precipitation of these elements from the matrix progressed during age-hardening. By transmission electron microscope and X-ray diffraction observation, it was revealed that the formation of the Au3Cu superstructure contributed to the age-hardening at $270^{\circ}C$ in the gold alloy. After the heat treatment, this analysis shows that casted gold alloys were to improve hardness and to moderate surface defects at specific temperatures and duration.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2012년도 춘계학술발표대회
• /
• pp.107.1-107.1
• /
• 2012

Because of beautiful glossy and color, the value of gold leverage is very high in Europe. For improve the quality of white gold, we performed heat treatment on 14K white gold alloys at various age-hardening conditions. Age-hardening behavior and the related phase transformation changes were studied to elucidate the hardening mechanism of 14K white gold alloys. For solid solution treatment [ST], casted 14K white gold alloy specimens were treated at high temperature ($750^{\circ}C$) during 30 minute, and the specimens dropped to water for quenching immediately. For Age-hardening treatment [AT], the specimens were treated at various temperatures ($250^{\circ}C{\sim}300^{\circ}C$). After the heat treatment, we observed increased hardness from 144 Hv to 214 Hv by Vicker's hardness tester. Variation of the grain size measured by optical microscopy (OM) and scanning electron microscopy (SEM) images. By electron probe micro-analysis (EPMA) mapping analysis, we investigated that irregular particles were changed uniformly. After heat treatment, 14K white gold alloys showed improved hardness and became uniformity of grain size by age-hardening treatment.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 추계학술발표대회
• /
• pp.38.1-38.1
• /
• 2011

Yellow gold는 아름다운 광택과 손쉬운 가공성의 장점 때문에 장신구를 비롯한 다양한 분야에서 그 활용 가치가 매우 높다. 본 연구에서는 yellow gold의 hardness 강화 및 품질향상을 위하여 다양한 열처리 조건 별 기계적 특성 변화를 비교 관찰 하였다. 열처리 전 yellow gold alloy의 구성성분을 조사하기 위하여 EPMA와 ICP-MS를 사용하여 정성분석 및 정량분석 결과를 수치화 하였다. 총 44개의 14K yellow gold를 사용하여 $750^{\circ}C$, 30 min 의 조건에서 solid solution treatment 후 $200{\sim}350^{\circ}C$ 온도 범위에서 $50^{\circ}C$ 간격으로 age-hardening을 실시하였다. 또한 열처리 전과 후 grain 들의 배열 및 size 변화를 관찰하기 위해 식각을 실시하였다. 식각된 시료는 optical microscope (OM)을 통해 각 열처리 조건에 따라 전 후 변화를 관찰 하였다. 열처리 전 14K yellow gold의 hardness의 평균값은 120.6 Hv를 나타내었다. Solid solution treatment 후 hardness는 95.7 Hv로 평균값이 감소하였고, age-hardening 후에는 14K yellow gold는 $260^{\circ}C$에서 159.8 Hv, $270^{\circ}C$에서 170.2 Hv로 열처리 전에 비해 약 41% 증가된 결과를 나타내었다. 하지만 $270^{\circ}C$ 부터는 over-aging 현상을 나타내었다. OM 분석 결과 열처리 전 불균일했던 grain들의 배열이 solid solution treatment 및 quenching 후 다소 균일해 짐을 확인할 수 있었고, grain size 또한 열처리 전에 비해 증가함을 알 수 있었다. Solid solution treatment 후 모든 시료의 hardness 값이 전반적으로 감소하였다가 age-hardening을 통해 grain들의 배열이 점차 안정화 되면서 hardness가 증가 하였고, over-aging 구간에서는 급격히 감소하는 경향을 나타내었다. 이 결과로 우리는 14K yellow gold에 대한 age-hardening 최적조건을 도출 하였고, 각 열처리 조건 별 grain 배열 상태의 변화를 관찰 할 수 있었다.

• 한국표면공학회지
• /
• 제43권2호
• /
• pp.86-90
• /
• 2010

In this study, we conducted heat treatment on 14K, 18K yellow gold alloy at various temperature conditions for improving their hardness and moderating their surface defects. Also after the heat treatment we used EPMA (Electron Probe Micro Analyzer), XRF (x-ray Fluorescence spectroscopy) for qualitative analysis and OM (optical microscope), SEM (scanning electron microscope) to investigate the changes of surface grain boundary. We used Vickers hardness tester to verify the changes of hardness. After the heat treatment, 14K, 18K gold alloys showed improved hardness and moderated surface defects at specific temperatures and duration.

• 대한치과기공학회지
• /
• 제28권1호
• /
• pp.27-41
• /
• 2006

The physical property and phase transformation in a commercial dental casting high gold alloy was investigated as a function of ageing temperature and time using microvickers hardness tester, X-ray diffraction, optical and electron microscopy and EPMA analyser. 1. With increasing ageing time, the hardness of solution-treated gold alloys increased slowly at the initial stage of ageing treatment at an ageing temperature of $300{\sim}400^{\circ}C$, and it reached a maximum value of hardness at the medium stage. Finally, it decreased gradually during further ageing. The maximum value of hardness at was similar with that of the conventional materials and suitable for using as the crown & bridge. 2. During isothermal ageing at a temperature range of $300{\sim}400^{\circ}C$, three phases consisting of the Au-rich ${\alpha}_1$phase with a face-centered cubic structure, the Pt3Zn ${\alpha}_2$phase with an ordered AuCu3(L12) type(f.c.c.) and the Pt-rich ${\alpha}_3$phase with face-centered cubic structure in solution-treated gold alloys were transformed into different three phases consisting of the ${\alpha}_1$phase, the ${\alpha}_3$phase and the PtZn $\beta$phase with an ordered AuCu I(L10) type. 3. The hardening of gold alloys was attributed to the lattice strains of the matrix resulting from the transformation of the ${\alpha}_2$phase to the $\beta$phase. 4. The softening of gold alloys during over-ageing was attributed to the coarsening of the nodules consisting of the $\beta$phase and ${\alpha}_1$matrix.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
• /
• pp.238-238
• /
• 2012

현재 국내 주얼리(gold alloy) 제품을 생산함에 있어 주조 방법은 크게 대기 중 주조(흡입주조) 방법과 진공주조 방법으로 나누어진다. 국내 주얼리 제조업체의 약 90%이상이 대기 중에서 주조하는 흡입주조방법을 통해 제품을 제작하고 있고, 국외의 경우, 대다수 진공주조방법을 통해 제품을 제작하고 있다. 본 연구에서는 주얼리 제품을 생산할 때 사용되는 합금재료(master alloy)가 동일한 조건에서 주조방법을 달리하여 각각 24개씩 총 48개의 14K yellow gold alloy 제품을 제작한 후 열처리를 통해 각각의 기계적, 물리적 특성분석을 비교 분석하였다. EPMA (Electron Probe Micro Analysis)분석을 통해 합금재료 및 제품의 구성성분을 조사하였고, ICP-MS (Inductively Coupled Plasma Mass Spectroscopy)를 사용하여 성분에 대한 정량분석을 실시하였다. 용체화처리(solid solution treatment)는 $700^{\circ}C$, 30분의 조건으로 실시하였고, 시효경화처리(age-hardening)는 $200{\sim}300^{\circ}C$의 온도범위에서 $50^{\circ}C$ 간격으로 실시하였다. 열처리 전과 후 시료의 grain 들의 배열 및 size 변화를 관찰하기 위해 식각 후 OM (optical microscope) 및 SEM (Scanning Electron Microscope)를 통해 분석하였다. 열처리 전 제품의 경도측정결과 대기 중 흡입주조방법 및 진공 주조방법을 통해 제작된 제품이 각각 119 Hv, 126 Hv로 나타났고, 용체화 처리 후 98 Hv, 92 Hv로 감소하였다. 시효경화 처리 후의 경도변화는 대기 중 흡입주조 및 진공주조방법을 통해 제작된 제품 모두 $270^{\circ}C$에서 각각 154 HV, 166 HV로 가장 높은 경도 값을 나타내었고, $270^{\circ}C$ 이상에서는 과시효(over aging)현상으로 인해 경도 값이 다시 감소하는 경향을 나타내었다. EPMA mapping 분석을 통해 주조방법에 따라 각각 제품의 구성성분분포도를 확인하였다. 이를 통해 열처리 전 다소 불균일하게 분포되었던 성분들이 열처리 후 균일해짐을 확인할 수 있었다.

• 대한의용생체공학회:의공학회지
• /
• 제15권4호
• /
• pp.389-394
• /
• 1994

The age-hardening behavior and the structural changes in a commercial dental Au-Ag-Cu-Pd alloy were investigated by means of hardness test, optical and scanning electron microscopic observation, energy dispersive spectroscopy and X-ray diffraction study. The drastic reduction in hardness by prolonged aging occurred after a rapid increase in hardness at the initial stage by the isothermal aging at $350^{\circ}C$. This softening was due to the broad precipitates formation of the lamellar structure which was composed of the f.c.t. AuCu I ordered f.c.t. phase containing Pd and the f.c.c. Ag-rich $\alpha$1 solid solution f.c.c.phase containing Au.

• 대한치과보철학회지
• /
• 제19권1호
• /
• pp.17-27
• /
• 1981

This study was conducted to determine the chemical composition and the mechanical properties of four commercially available low gold-based crown and bridge alloy produced in Korea. Four dental casting gold-silver-palladium alloys, i.e., A, B, C and D (code of alloys) were selected for the evaluation of chemical composition, ultimate tensile strength, elongation. values and Vickers hardness. The chemical composition of test specimens was analyzed by both emission spectrography and wet gravitation method with a 1.5gm of low gold ingot. The tensile properties and Vickers hardness was determined with cast specimens treated in following three conditions; as-cast, softening heat treatment and hardening heat treatment. The tensile testing bars were cast in accordance with the model designed by Gettleman and Harrison (1969) which was modified from the A. D. A. Specification No. 14 for dental chromium-cobalt casting alloy. Nine tensile test specimens were made from a split silicone mold for each of the test alloys to the size of 2.5mm in diameter and a gauge length of 10mm. All four alloys were handled in accordance with conventional methods used in Type III gold alloys. Ultimate tensile strength and elongation were measured on an Instron Universal Tensile Testing Machine (Model 1125, Japan) operated at a crosshead rate of 0.1cm/min. Elongation values were measured using Digital Measuring Microscope (MS-152, FUSOH, Japan). Vickers hardness was determined with a Vickers Hardness Tester (Model VKH-l, Japan) at a 1.0kg load on a mounted tensile test specimen. The following results were obtained from this study; 1. All tested alloys were composed of Au, Ag, Pd, Cu, Zn and Fe in common. The composition rate of gold for all four alloys was found in the range of $42{\sim}47$ weight % as shown below. Alloy A; Au 45%, Ag 40.2%, Pd 5.76%, others 9.04%. Alloy B; Au 47.1%, Ag 29.03%, Pd 6.98%, others 16.92%. Alloy C; Au 45%, .Ag 26.9%, Pd 6.83%, others 21.07%. Alloy D; Au 41.8%, Ag 34.4%, Pd 6.95%, others 16.85%. 3. The ultimate tensile strength of the four alloys was in the range of $31{\sim}82kg/mm^2$. The test results were shown in the below order from the highest value; As-cast condition; D, B, C, A. Softening heat treament; B, C, D, A. Hardening heat treatment; D, B, C, A. 4. The test :results of the elongation rate for each alloy were in the range of $0.5{\sim}18%$. The test results were shown in the below order from the highest value; As-cast condition; A, D, B, C. Softening heat treatment; A, C, D, B. Hardening heat treatment; C, D, B, A. 5. Vickers hardness for each of the four alloys was in the range of $120{\sim}230$. The test results were shown in the below order from the highest value; As-cast condition; C, B, D, A Softening heat treatment; D, B, C, A. Hardening heat treatment; D, A, C, B. 6. There were no differences in the physical properties between as-cast condition and softening heat treatment.

• 대한치과기공학회지
• /
• 제31권4호
• /
• pp.9-15
• /
• 2009

The purpose of this study was to observe the change of mechanical property and microstructure in porcelain fused to gold alloy by heat treatment. PFG alloys are composed with Au-Pd-Ag alloy of the additional elements with indium, tin and copper. Specimens were tested in hardness using vicker,s micro-hardness tester and the surface micro structural changes were analysed by SEM and EDS. The results were as fellows: 1. The vickers hardness showed highest in Au-Pd-Ag alloy of the additional element with tin. 2. By hardening-oxiding result, the vicker,s hardness increased in additional element with tin but there was no significant difference in additional elements with indium and copper. 3. The surface oxide layer of Au-Pd-Ag alloy with added indium and tin increased but there was small change in additional element with copper. 4. The elements of indium and tin increased with increasing heat treatment in the surface alloy.