• Korean Journal of Materials Research
• /
• v.7 no.1
• /
• pp.50-56
• /
• 1997

급냉응고법을 이용하여 고용한도 이상으로 Mn량을 첨가할 때 Mn량에 따른 인장특성의 변화와 시효특성을 조사하였다. 원심분무법으로 AI-4.7%Zn-2.5%Mg-0.2%Zr합금에 Mn량을 각기 달리 첨가한 급냉응고 분말을 제조 하였다. 이 분말을 냉간압축, 진공 탈가스처리를 한 후 15:1로 압출하여 봉상 시편을 만들었다. 분말의 미세조직은 $\alpha$-AI수지상과 수지상간 편석부로 이루어져 있으며 Mn첨가에 따라 조직의 변화는 관찰되지 않았다. 빠른 냉각속도로 인하여 2.0%Mn을 첨가한 경우에도 초정 Mn상을 발견할 수 없었다. 압출재의 미세조직은 아결정립으로 이루어져 있으며 약간의 제2상들이 관찰되었다. 대부분의 Mn 분산상은 압출후 용체화처리 과정에서 형성되었으며 시효경화량은 Mn양에 관계없이 일정하였다. 46$0^{\circ}C$에서 1시간 용체화처리하고 12$0^{\circ}C$에서 24시간 시효처리한 경우 최대의 시효경도값을 나타내었다. 인장강도는 Mn첨가량에 따라 증가 하였는데 이것은 Mn분산상의 밀도증가에 의한 것으로 확인되었다. 2.0%Mn을 첨가한 합금의 시효후 인장강도는 590MPa, 연산율은 4%를 보였다.

• Korean Journal of Materials Research
• /
• v.9 no.9
• /
• pp.905-912
• /
• 1999

Tensile properties of powder metallurgy (PM) processed Cu-7.5Ni-5Sn alloys, either as-received or additionally solution heat treated, were examined as a function of aging time. It was found that the as-received Cu-7.5Ni-5Sn alloys showed an abrupt increase in tensile strength after aging at $350^{\circ}C$ for 20 minutes, due to the metastable ${\gamma}$\\` precipitation and a marginal Spinodal decomposition. The resolutionized PM Cu-7.5Ni-5Sn alloys, on the other hand, showed a gradual increase in tensile strength from the very early stage of aging. The overall tensile strength of resolutionized PM Cu-7.5Ni-5Sn alloys, however, was lower than that of the as-received and aged counterparts, due to the grain growth during resolutionization. Afterprolonged aging for the as-received PM Cu-7.5Ni-5Sn alloys, a considerable amount of discontinuous precipitates formed along the grain boundaries. The formation and growth kinetics of such discontinuous precipitates appeared to be dependent on the heat treatment conditions, and affect the mechanical properties greatly.

• Journal of the Microelectronics and Packaging Society
• /
• v.14 no.4
• /
• pp.15-20
• /
• 2007

Growth kinetics of intermetallic compound (IMC) at various interface in Cu pillar bump during aging have been studied by thermal aging at 120, 150 and $165^{\circ}C$ for 300h. In result, $Cu_6Sn_5\;and\;Cu_3Sn$ were observed in the Cu pillar/SnPb interface and IMC growth followed parabolic law with increasing aging temperatures and time. Also, growth kinetics of IMC layer was faster for higher aging temperature with time. Kirkendall void formed at interface between Cu pillar and $Cu_3Sn$ as well as within the $Cu_3Sn$ layer and propagated with increasing time. $(Cu,Ni)_6Sn_5$ formed at interface between SnPb and Ni(P) after reflow and thickness change of $(Cu,Ni)_6Sn_5$ didn't observe with aging time. The apparent activation energies for growth of total $(Cu_6Sn_5+Cu_3Sn),\;Cu_6Sn_5\;and\;Cu_3Sn$ intermetallics from measurement of the IMC thickness with thermal aging temperature and time were 1.53, 1.84 and 0.81 eV, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2012.10a
• /
• pp.695-696
• /
• 2012

• Journal of the Korean Society for Nondestructive Testing
• /
• v.22 no.3
• /
• pp.267-274
• /
• 2002

This research is described on the applicability of a electrochemical techniques for evaluating nondestructive material degradation with various polarization characteristics for Cr-Mo-V steel. The applied electrochemical technique is anodic polarization test which are widely used to evaluate the corrosion rate and/or sensitization at depleted zone of strengthening elements mainly caused by thermal experience for stainless steels. The evaluation of material degradation is performed by small punch test which has been well known as micromechanics test method using specimen size of $10{\times}10{\times}0.5mm$. The 1,000hrs aged material at $630^{\circ}C$ shows the highest material degradation$({\Delta}[DBTT]_{SP})$, but the 2,000hrs and 3,000hrs aged materials show the decrease of ${\Delta}[DBTT]_{SP}$ as aging time increases. It is observed that the difference of current density $({\Delta}I_{FP}\;and\;{\Delta}I_{SP})$.

• Journal of the Korean Ceramic Society
• /
• v.34 no.3
• /
• pp.323-329
• /
• 1997

Particle growth of BT-oxalate was investigated in aging with various additives such as glycerine, chloro-form and NaCl. Their effects on size and morphlogy of particle was examined. It can be known that particle size distributions of BT-oxalate precipitate varied with amounts of these additivies. With small amounts of these additives, particle growth of nonuniform distribution was occurred, but above 1 mole percent of those additives, uniform size distributions of about 0.4 ${\mu}{\textrm}{m}$ could be obtain. There was little difference among the effects by the kinds of additives. From the decomposition of uniform BT-oxalate, BaTiO3 powders of about 0.3${\mu}{\textrm}{m}$ could be obtained.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05c
• /
• pp.73-78
• /
• 1996

Type 316L 스테인레스강에 대한 질소첨가의 효과를 분석하기 위해 질소를 소량(0.024%)첨가한 합금과 적정량(0.15%) 첨가한 합금을 용해하여 입계부식특성 평가를 하였다. Oxalic시험 및 DL-EPR 시험 결과 적정량의 질소를 첨가한 합금이 소량 첨가한 금보다 우수한 예민화 특성을 보였다. TEM에 의한 미세구조 분석 결과 저질소 합금의 경우 비교적 짧은 열처리 시간에 M$_{23}$C$_{6}$ type의 석출물이 입계를 따라 형성되고 시효시간이 경과 할수록 그양이 급격히 증가하는 양상을 보인 반면에 적정 질소 첨가 합금의 경우 탄화물 생성이 비교적 긴 시효시간으로 늦추어져 예민화 실험 결과와 일치된 결과를 보였다. 두 합금 모두에서 탄화물 이외에 Mo의 함량이 매우 높은 석출물이 관찰되었는데 적정질소 첨가강의 경우 시효 시간의 경과에 따라 초기의 작은 cluster들의 형태에서 시작하여 얇은 박막의 형태로 입계면을 따라 성장하는 양상을 보였고, 반면에 저질소합금의 경우 입계를 따른 작은 석출물들이 cluster들로는 성장하였으나 장시간 시효가 진행됨에 따라 탄화물의 성장에 의해 박막 형태로는 성장하지 못하였다. Mo-rich 박막형상 석출물에 대한 분석 결과 20-면체 준결정상의 형태에 매우 가까운 결정구조를 보였으며 때로 η상과 매우 밀접한 회절 패턴도 관찰되었다. 이러한 상은 적정 질소첨가 합금에서의 탄화물 생성 지연과도 관련이 있을 것으로 추정되었다.

• Analytical Science and Technology
• /
• v.6 no.1
• /
• pp.141-147
• /
• 1993

The behavior of reverted austenite in Fe-Ni-Mn(Ti) maraging steels has been investigated in the temperature range from $400^{\circ}C$ to $550^{\circ}C$ using TEM equipped with EDX. Four kinds of reverted austenite appeared depending on the aging temperatures and time : Widmanstatten, granular, lath-like and recrystallized austenite. The reverted austenites are enriched in Ni and Mn due to the dissolution of precipitates and redistribution of alloying elements. Widmanstatten austenite appears unformly in the lath martensite having the K-S orientation relationship with the martensite lath, while lath-like martensites showed K-S and N relations depending on the chemistry and heat treating condition. The recrystallized austenite forms at $550^{\circ}C$ after long aging times : some becomes unstable and transforms to lath martensite on cooling.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.3
• /
• pp.275-282
• /
• 2012

In this study, tensile tests were performed using standard and notched-bar specimens under two different displacement rates and various temperatures, in order to investigate the effects of the stress and strain concentration at the notched section on the dynamic strain aging (DSA) behavior of carbon steel piping material. In addition, finite element simulations were conducted to evaluate quantitatively the stress and strain states for both types of specimen under uniaxial tensile loading. The results showed that serration and an increase in tensile strength, which are considered to be evidence of DSA in carbon steels, can be observed from tensile tests for notched-bar specimens. It was also found that the temperature region of DSA observed in the notched-bar specimens was higher than the DSA region observed in the standard tensile specimens tested under the same displacement rate. The results of finite element analysis showed that this behavior is associated with the high strain rate at the notched section, which is caused by the stress and strain concentration.

• Journal of the Microelectronics and Packaging Society
• /
• v.12 no.4 s.37
• /
• pp.301-306
• /
• 2005

Aging characteristics of newly developed Sn-1.8Bi-0.7Cu-0.6In solder was evaluated by shear strength and microstructure. Stencil printing was applied to form solder. The shear strength of Sn-1.8Bi-0.7Cu-0.6In at $150^{\circ}C$ showed the highest values through aging. Intermetallic compounds formed on the interface between solder and Au/Cu/Ni/Al UBM were $(Cu,\;Ni)_6Sn_5$ Furthermore, it was found that Spatting of Intermetallic compounds started before 500h aging at $150^{\circ}C$.