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75wt.% Ag-25wt.% Pd 합금의 Ta첨가에 따른 미세조직변화와 기계적성질에 관한 연구
정호년,김명호,백승호,김경남,백홍구 대한치과기재학회 1996 대한치과재료학회지 Vol.23 No.1
In study, mechanical properties and microstructures of 75wt.%Ag-25wt.Pd alloys with different amount of Ta additions from 0.1 to 1.0wt.% are investigated. With increasing Ta content grain size is reduced and tensile strength is increased. When 0.2wt.% Ta is added, reduction of the grain size is remarkable, and maximum tensile strength is achieved. With 0.6wt.% addition of Ta, fine primary crystals are found at the grain boundary after casting and tensile strength is slightly decreased. There is no significant microstructual changes at all heat treatment conditions. TEM, EPMA, and XRD analysis reveal that fine primary crystals are Pd₃Ta with tetragonal crystal structure. No apparent change of tensile strength is observed with different heat treatments. Experimental results shows that Ta intermetallic particles formed in the melt of Ag-Pd alloy act as nucleation sites for solidification which results in the grain refinement. Addition of Ta more than 0.6wt.% reduces the tensile strength of the alloy by forming coarse Pd₃Ta in the melt. The Optimum amount of Ta addition on Ag-Pd alloy is 0.2wt.%, which reduce grain size about 42% and improve tensile strength up to 20% in comparison with Ag-Pd binary alloy without Ta.
이원재,이상혁,정호년,김명호,임범순 대한치과재료학회 2011 대한치과재료학회지 Vol.38 No.3
수열처리법에 관한 연구는 많이 있지만, 본 연구에서는 복잡한 과정의 수산화인회석 코팅법의 대체법으로 RBM 처리한 cp-Ti를 증류수에서 수열처리하여 티타늄 표면에 수산화인회석(HA) 나노 결정상을 석출시키는 방법에 관하여 알아보고자 하였다. 디스크 형태의 cp-Ti(grade 4) 표면을 HA(hydroxyapatite)와 TCP(tricalcium phosphate)를 혼합한분말로 RBM처리한 후 스테인레스 강 챔버에 넣고 증류수를 적정량 채우고 다양한 온도와 시간(200, 250 및 300℃에서 1, 3 및 5시간) 동안 수열처리를 실시하였다. 수열처리한 티타늄 표면을 SEM/EDS, XRD 및 접촉각 측정기로 분석하였다. 티타늄 표면에 형성된 수산화인회석 나노 결정상은 RBM(resorbable blasted media) 처리 후 티타늄 표면에박힌 TCP 입자에서 용출된 칼슘이온과 인 이온에 의해 수산화인회석 핵이 생성되고 성장하여 생성된 것으로 보였다. 수열처리온도가 증가할수록 균일하고 밀도가 높은 수산화인회석 결정시 석출되었으며, 수열처리시 포화된 증기압이 수산화인회석 나노 결정상 형성에 중요한 역할을 하는 것으로 보였다.
Au-Pt-Cu계 합금의 미세구조 및 기계적 특성에 미치는 첨가원소 Indium 효과에 관한 연구
이상혁,도정만,정호년,민동준 대한의용생체공학회 2003 의공학회지 Vol.24 No.3
인듐함량에 따른 Au-Pt-Cu 삼원계합금의 미세조직 및 기계적 특성을 광학현미경, 시차주사열분석기, SEM, XRD, EPMA 그리고 미소경도계를 이용하여 조사하였다. 인듐함량이 0.5 wt% 인 Au-Pt-Cu-0.5In 사원계 합금을 온도범위 150~95$0^{\circ}C$에서 열처리한 결과 55$0^{\circ}C$/3O분 열처리한 시료의 경도 값이 가장 높게 나타났고, 55$0^{\circ}C$에서 시효시간을 증가시킴에 따라 30분에서 최고 경도치에 도달된 후 거의 일정하게 유지되었다 또한, 55$0^{\circ}C$에서 30분 동안 시효 처리한 Au-Pt-Cu 삼원계합금의 미세조직은 인듐 함량이 증가함에 따라 결정립이 미세화 되었다. XRD, EPMA을 이용하여 Au-Pt-Cu-In 사원계 합금에 존재하는 석출상을 분석한 결과 모상은 fcc구조를 갖는 Au-Pt-Cu 고용체, 석출상은 Ll$_2$구조를 갖는InPt$_3$ 석출물로 판명되었다. 이러한 연구결과로부터 인듐 함량에 따른 Au-Pt-Cu-In 합금의 경도증가는 결정립 미세화에 의한 강화 효과와 InPt$_3$ 형태의 석출물에 의한 석출강화 효과에 기인하는 것으로 해석된다. The effect of indium on the microstructure and hardness of a Au-Pt-Cu ternary alloy was investigated using optical microscopy, differential scanning calorimeter, scanning electron microscopy x-ray diffractometry, electron probe microanalizer and vickers hardness tester. A hardness of the solution floated Au-Pt-Cu-0.5In quarternary alloy with 0.5 wt.% was reached a maximum value (162 Hv) in 30 min at 550$^{\circ}C$ in the range of 150 to 950$^{\circ}C$ but that of the alloy was rapidly increased until 30 min with increasing aging time at 550$^{\circ}C$ and after that was remained almost constant value. Also, the microhardness of the matrix Au-Pt-Cu ternary alloy aged at 550$^{\circ}C$ for 30 min was continuously increased with indium contents and the grain size of Au-Pt-Cu ternary alloy decreased as increased indium contents. Analyses of EPMA and XRD revealed that the matrix Au-Pt-Cu-In quarternary alloy is composed of fcc structure and intermetallic InPt$_3$ precipitate with Ll$_2$ structure. Based on this investigation, it can be concluded that an increase in microhardness of Au-Pt-Cu-In quarternary alloy is due to precipitation hardening InPt$_3$ and grain size refinement.
이상혁,도정만,정호년 대한치과기공학회 2003 대한치과기공학회지 Vol.25 No.1
The microstructure and hardness of a porcelain fused Au-Pt-Cu-In alloy was investigated usingoptical microscopy, secondary electron microscopy, electron probe microanalyzer, transmissionelectron microscope, and vickers hardness. The hardness of the heat-treated Au-Pt-Cu-Inquartenary alloy reached a maximum value in 30 min at 550in the range of 150 to 950. In theaged Au-Pt-Cu-0.5In alloy at 550, the hardness of the alloy rapidly increased until 30min withincreasing aging time and after that it was remained nearly constant value. Based on above results, glazing and final aging of the porcelain fused Au-Pt-Cu-0.5In alloy wereperformed at 920 and 550, respectively. The hardness of Au-Pt-Cu-0.5In alloy glazed at 920was 90 Hvand that of the alloy aged for 30 min at 550increased to 160 Hv. This indicates that aceramic-metal crown with high strength can be manufactured using the glazing at 920andfollowed final aging at 550for 30 min.
Ag-Pd-In 삼원계합금의 시효처리에 따른 기계적 성질변화와 미세상의 석출거동
백홍구,도정만,정호년,김명호,김경남 大韓齒科器材學會 1995 대한치과재료학회지 Vol.22 No.1
The effects of aging on the microstructures and mechanical properties of a 75wt.%Ag-25wt.%Pd alloy with various indium additions were studied. Tensile strength and hardness of the alloy increased with increasing aging temperature and time in the temperature range of 350 to 450℃. Similar trends were observed with increasing amount of In addition and precipitated InPd₃phase. Such features indicated that the alloy system considered in the study was age hardenable. In₂O₃oxide layers were observed to form at the outer surface of the specimen during heat treatment procedure. Based on the experimental observation, cracks were observed to form outer surface of the specimen followed by crack propagation along the grain boundary of the matrix, resulting in some decrease in the tensile strength.
Ni-Cr-W-Al-Ti 계 초내열합금 (KM 1557) 의 크리프특성
최주,허성강,백홍구,도정만,정호년 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.7
The creep-rupture properties of a Ni-Cr-W-Al-Ti superalloy(KM 1557) have been investigated in the temperature range of 750℃ and 1000℃. In the stress and temperature ranges studied, the inverse of the rupture life(strain rate) exhibited power law dependence on the applied stress. The stress exponents for this alloy were between 5 and 12, and the activation energy for the creep was determined to be approximately 115 ㎉/mole. Precipitate free zones formed by grain boundary migration or sliding and the accommodation of sliding by the dislocation motion, were observed from the creep-ruptured specimens. Cracks were nucleated at the grain boundary or triple point, and propagated along the grain boundary containing PFZs. The shape of grains remained unchanged for the samples tested at low temperatures of 750 and 800℃. On the contrary, highly elongated grain shape was observed along the direction of applied stress when tested at high temperatures of 850, 900, 950, and 1,000℃.
75wt.%Ag-25wt.%Pd합금의 Zr첨가에 따른 미세조직변화와 기계적성질에 관한 연구
백홍구,김혜성,김명호,정호년,김경남 大韓齒科器材學會 1995 대한치과재료학회지 Vol.22 No.2
The effects of Zr addition on the microstructures and mechanical properties of 75wt.%Ag-25wt.%Pd alloy was studied. Grain size of the alloy was diminished with increasing amount of Zr addition, and it was notable when 0.2wt.% of Zr was added. when 0.6wt.% of Zr was added, coarse Pd₃Zr intermetallic compound(hexagonal, ??, ??) was precipitated in the matrix, and fine Pd₂Zr intermetallic compound(body centered tetragonal, ??, ??) could be seen by aging treatment at 450℃. Ultimate tensile strength of the alloy was increased with decreasing grain size until 0.2 wt.% Zr addition, but when an excess of Zr was added, ultimate tensile strength of the alloy was somewhat diminished despite of decreasing grain size. So, we concluded that the grain size of the 75wt.%Ag-25Wt.%Pd alloy was diminished by the Zr addition and mechanical properties were increased with decreasing grain size, and the optimum amount needed for hardening was 0.2 wt.%.