• 한국재료학회지
• /
• 제11권9호
• /
• pp.745-750
• /
• 2001

Ni-33.3at%Si elemental powder mixtures were mechanically alloyed by a high-energy ball mill, followed by CIP (cold isostatic pressing) and HIP (hot isostatic pressing) for different processing conditions. Only elemental phases (Ni and Si) were observed for the 15 min mechanically alloyed (MA 15 min) powder. but $Ni_2$Si and elemental phases were observed to coexist for the 30 min mechanically alloyed (MA 30 min) powder. Elemental Ni and $Ni_2$Si phases were observed for the HIPed compact of MA 15 min powder at 100 and 150 MPa for 2 hr at $800^{\circ}C$. Only the $Ni_2$Si phase was, however, observed for the HIPed compacts of MA 30 min powder. For the HIPed compacts, the highest sintered density was obtained to be 99.5% of theoretical density by a HIP step at $1100^{\circ}C$ at 150MPa for 2hr. The hardness values of the HIPed $Ni_2$Si compacts at $1100^{\circ}C$ at 100/150 MPa for 2 hr were higher than HRC 66. The densification and mechanical property of HIPed $Ni_2$Si compacts were found to depend on more HIP temperature than HIP pressure.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 1994년도 추계학술대회강연 및 발표대회 강연및 발표논문 초록집
• /
• pp.26-26
• /
• 1994

• 한국분말재료학회지
• /
• 제17권1호
• /
• pp.13-22
• /
• 2010

The unique features of spark plasma sintering process are the possibilities of a very fast heating rate and a short holding time to obtain fully dense materials. $\beta$-SiC powder with 0, 2, 6, 10 wt% of $\alpha$-SiC particles (seeds) and 4 wt% of Al-B-C (sintering aids) were spark plasma sintered at $1700-1850^{\circ}C$ for 10 min. The heating rate, applied pressure and sintering atmosphere were kept at $100^{\circ}C/min$, 40 MPa and a flowing Ar gas (500 CC/min). Microstructural development of SiC as function of seed content and temperature during spark plasma sintering was investigated quantitatively and statistically using image analysis. Quantitative image analyses on the sintered SiC ceramics were conducted on the grain size, aspect ratio and grain size distribution of SiC. The microstructure of SiC sintered up to $1700^{\circ}C$ consisted of equiaxed grains. In contrast, the growth of large elongated SiC grains in small matrix grains was shown in sintered bodies at $1750^{\circ}C$ and the plate-like grains interlocking microstructure had been developed by increasing sintering temperature. The introduction of $\alpha$-SiC seeds into $\beta$-SiC accelerated the grain growth of elongated grains during sintering, resulting in the plate-like grains interlocking microstructure. In the $\alpha$-SiC seeds added in $\beta$-SiC, the rate of grain growth decreased with $\alpha$-SiC seed content, however, bulk density and aspect ratio of grains in sintered body increased.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
• /
• pp.1091-1092
• /
• 2006

Silicon nitride - silicon carbide composite was developed by using an abrasive SiC powders as a raw material. The composites were prepared by mixing abrasive SiC powder with silicon, pressing and sintering at $1400^{\circ}C$ under nitrogen atmosphere in atmosphere controlled vacuum furnace. The proportion of silicon in the initial mixtures varied from 20 to 50 wt%. After sintering, crystalline phases and microstructure were characterized. All composites consisted of ${\alpha}-Si_3N_4$ and ${\beta}-Si_3N_4$ as the bonding phases in SiC matrix. Their physical and mechanical properties were also determined. It was found that the density of the obtained composites increased with an increase in the $Si_3N_4$ content formed in the reaction.

• 한국분말재료학회지
• /
• 제21권6호
• /
• pp.460-466
• /
• 2014

Al-Si-SiC composite powders with intra-granular SiC particles were prepared by a gas atomization process. The composite powders were mixed with Al-Zn-Mg alloy powders as a function of weight percent. Those mixture powders were compacted with the pressure of 700 MPa and then sintered at the temperature of $565-585^{\circ}C$. T6 heat treatment was conducted to increase their mechanical properties by solid-solution precipitates. Each relative density according to the optimized sintering temperature of those powders were determined as 96% at $580^{\circ}C$ for Al-Zn-Mg powders (composition A), 97.9% at $575^{\circ}C$ for Al-Zn-Mg powders with 5 wt.% of Al-Si-SiC powders (composition B), and 98.2% at $570^{\circ}C$ for Al-Zn-Mg powders with 10 wt.% of Al-Si-SiC powders (composition C), respectively. Each hardness, tensile strength, and wear resistance test of those sintered samples was conducted. As the content of Al-Si-SiC powders increased, both hardness and tensile strength were decreased. However, wear resistance was increased by the increase of Al-Si-SiC powders. From these results, it was confirmed that Al-Si-SiC/Al-Zn-Mg composite could be highly densified by the sintering process, and thus the composite could have high wear resistance and tensile strength when the content of Al-Si-SiC composite powders were optimized.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
• /
• pp.1071-1074
• /
• 2006

Fabrication and investigation of composite made of graphite, SiC, mullite and aluminum as the additive are the aim of this project. Aluminum acts as an anti-oxidant. SiC is a non-metallic anti-oxidant that increases composite strength. Different compositions with influent percents of aluminum have been selected to determine product specifications by XRD, SEM and STA methods. Results show that the composition of 40wt% graphite-20% SiC- 20% mullite-20% aluminum is a more robust and occurs at elevated temperatures than other graphite combustion composites.

• 한국분말재료학회지
• /
• 제4권1호
• /
• pp.26-41
• /
• 1997

The powder metallurgy (P/M) processed 2009 and 2124 Al composites reinforced with SiC particulates were studied by focusing on the effect of consolidation temperature on the microstructural and mechanical Properties. The mechanical properties such as tensile properties and microhardness of the second phases were analysed in relation to the microstructures observed by a SEM and an optical microscope. The in situ fracture process study using SEM showed that the grain refinement and the removal of manganese-containing particles often observed in the 2124 Al-${SiC}_{p}$ composites were important for the improvement of the mechanical properties. This study offers an optimum consolidation temperature for the control of the manganese-containing particles in the 2124 Al-${SiC}_{p}$ composites that yields mechanical properties higher than those of the 2009 Al-${SiC}_{p}$ composites.

• 한국자기학회지
• /
• 제26권1호
• /
• pp.7-12
• /
• 2016

전기비저항이 높아 1 MHz 이상 고주파용 코어재료로 적합한 Fe-9%Si-2%Cr 합금분말의 열처리 온도에 따른 투자율 거동과 규칙-비규칙 전이에 대해 연구하였다. 분무과정에서 B2 규칙상의 생성이 억제되지 않았으며, $550^{\circ}C$ 이상에서 열처리 했을 경우 $DO_3$ 상의 회절선을 검출할 수 있었다. 열처리 온도가 증가할수록 격자상수와 보자력은 감소하였으나 $450^{\circ}C$에서 보자력의 갑작스런 큰 증가가 있었다. $150^{\circ}C$의 비교적 낮은 열처리 온도에서 가장 높은 투자율을 나타내었고, 이후 열처리 온도가 증가할수록 투자율은 감소하였다. 이상의 거동은 $DO_3$ 규칙상의 생성과 이에 따른 비저항의 변화로 설명할 수 있었다.

• 한국분말재료학회지
• /
• 제3권3호
• /
• pp.167-173
• /
• 1996

The effect of ball milling on the pressureless sintering of MoSi$_2$ was investigated. Ball milling was conducted at 70 rpm for 72 hours using different balls and vessels: one used tungsten carbide balls in a plastic vessel(referred as B-powder) and the other stainless steel ball in a stainless steel vessel(referred as C- powder). The powder was compacted with 173MPa and subsequently sintered at the temperature range of 1150 $^{\circ}C$ and 1450 $^{\circ}C$ in H$_2$, atmosphere. Sintered density was measured and scanning electron micrograph was observed. Over 90% of the theoretical density was attained at 1250 $^{\circ}C$ within 10 minutes for C-powders, while the similar densification required a sintering temperature of 1450 $^{\circ}C$ for B-powders. Such a difference in sinterability between B and C-powders was discussed in terms of the effect of particle size reduction and activated sintering caused by Ni and/or Fe introduced during ball milling.

• 한국분말재료학회지
• /
• 제8권4호
• /
• pp.223-230
• /
• 2001

Ti-37.5at%Si elemental powder mixtures were mechanically alloyed by a high-energy ball mill, followed by CIP (cold isostatic pressing) and HIP (hot isostatic pressing) for different processing conditions. Only elemental phases (Ti and Si) were observed for the 5 min mechanically alloyed (MA 5 min) powder, but only $Ti_5Si_3$phase was observed for the 30 min mechanically alloyed (MA 30 min) powder. $Ti_5Si_3$phase was observed for the HIPed compact of MA 5 min and 30 min powders at 150 and 190 MPa for 3 hr at $1000^{\circ}C$. For the HIPed compacts, the highest sintered density was obtained to be 99.5% of theoretical density by a HIP step at $1350^{\circ}C$ at 190MPa for 3hr. The hardness values of the HIPed $Ti_5Si_3$compacts at $1350^{\circ}C$ at 150/190 MPa for 3hr were higher than HRC 76. The densification and mechanical property of HIPed $Ti_5Si_3$compacts was found to depend on more HIP temperature than HIP pressure.