Effects of Fe addition on rolling and age-hardening behavior in Al-Si-Mg alloys are investigated in this paper. Microstructure evolution of rolled Al-Si-Mg based alloys was observed using an optical microscope and field emission scanning electron microscope. The chemical compositions of Fe intermetallic compounds (Fe-IMCs) were analyzed by energy dispersive spectrometer (EDS). Fe-IMCs were finely fragmented with the size of around 300 nm and well distributed in the Al matrix through cold rolling process. Heat treatments were carried out to understand the effects of Fe-IMCs on the age-hardening behavior. The peak hardness of Fe-free, 0.5% Fe and 1.0% Fe alloys during aging at 250 degrees C appeared at 1.8, 1.2 and 0.6 ks, respectively. The age-hardening is accelerated at the initial stage during aging at 250 degrees C, while the degree of hardness difference decreased with increasing the Fe contents.

본 연구에서는 Inconel 713C 스크랩을 원료로 아르곤-산소 탈탄 공정을 이용하여 니켈계 초내열합금을 재활용 하였다. 아르곤-산소 탈탄 공정에서 아르곤은 1,000 sccm으로 지속적으로 주입되었고 산소는 100, 250, 500 sccm의 유량으로 10, 20, 30 분씩 주입되었다. 산소 주입 초기 단계에서는 산소 양이 증가하면서 Al, Cr, 및 Mo 함량은 증가하였고 탄소 함량은 감소하였다. 그리고 Al 함유량은 탄소의 반응이 끝난 후 Al, Cr 등의 원소와 산화가 일어났기 때문에 첨가원소와 탄소의 반응에 의해 감소하였다. 결과적으로, Al 함유량이 감소하였기 때문에 ${\gamma}^{\prime}$상이 줄어들었으며 이는 Al이 ${\gamma}^{\prime}$을 형성하는 주요 원소이기 때문이다. 또한, 탄소의 양이 줄어들면서 탄화물도 줄어들었으며 산소가 과잉 공급된 시료의 기계적인 물성(강도, 경도 등)은 감소하게 된다. In this study, the Ni base superalloy was recycled by Argon oxygen decarburization(AOD) process using an inconel 713C scrap. During AOD process, argon gas was continuously injected 1,000 sccm and oxygen gas was injected into 10, 20 and 30 minutes of 100, 250 and 500 sccm.. In early stage of oxygen injection, the oxygen dose increased with increasing Al, Cr, and Mo content and decreasing C content. And Al content was decreased by carburization with added elements in late stage Because of oxidation was occurred with Al, Cr etc. after the reaction of carbon has been finished. From the results, the ratio of ${\gamma}^{\prime}$ phase reduced due to decreasing of Al content for that reason Al is the main element to form the ${\gamma}^{\prime}$ phase. Also carbide reduced owing to decreasing of C content so the mechanical properties of the specimens excessively injected by excess $O_2$ gas were decreased.

HA (hydroxyapatite)/beta-TCP (tricalcium phosphate) biomaterial (BCP; biphasic calcium phosphate) is widely used as bone cement or scaffolds material due to its superior biocompatibility. Furthermore, NH4HCO3 as a space holder (SH) has been used to evaluate feasibility assessment of porous structured BCP as bone scaffolds. In this study, using a spark plasma sintering (SPS) process at 393K and 1373K under 20MPa load, porous HA/beta-TCP biomaterials were successfully fabricated using HA/beta-TCP powders with 10 similar to 30 wt% SH, TiH2 as a foaming agent, and MgO powder as a binder. The effect of SH content on the pore size and distribution of the BCP biomaterial was observed by scanning electron microscopy (SEM) and a microfocus X-ray computer tomography system (SMX-225CT). The microstructure observations revealed that the volume fraction of the pores increased with increasing SH content and that rough pores were successfully fabricated by adding SH. Accordingly, the cell viabilities of BCP biomaterials were improved with increasing SH content. And, good biological properties were shown after assessment using Hanks balanced salt solution (HBSS).

Pure Cu compacts were fabricated by spark plasma sintering (SPS) process for sputtering target application. For the fabrication of the Cu compacts, conditions such as temperature, pulse ratio, pressure, and heating rate were optimized during the sintering process. The final sintering temperature required to fabricate the target materials with high density, and the heating rate up to the final temperature, were 800 degrees C and 80 degrees C/min, respectively. The heating directly progressed to 800 degrees C without any holding time. Sputtering target materials with high relative density of 99.7% were fabricated in a uniaxial pressure range of 60 MPa at a sintering temperature of 800 degrees C, without any significant change in the grain size. Also, the shrinkage displacement of the Cu target materials was found to considerably increase with increasing pressure at sintering temperatures up to 800 degrees C.

The effect of heat treatment on the microstructure and mechanical properties of cast Ti-6%Al-4% V alloy was investigated. Heat treatment of cast Ti-6Al-4V alloy was conducted by solution treatment at 950 degrees C for 30 min; this was followed by water quenching and then aging at 550 degrees C for 1 to 1440 min. The highest hardness of the heat-treated specimens was obtained by solution treatment and subsequent aging for 5 min due to precipitates of fine a that formed from retained beta phase. The tensile strength of this alloy increased without dramatic decrease of the ductility due to microstructural refinement resulting from the decomposition of alpha' martensite into fine alpha and beta phases, and also due to the fine alpha phase formed from the retained beta phase by aging treatment for 5 min. In addition, this strengthening might be caused by the transformation induced plasticity (TRIP) effect, which is a strain-induced martensite transformation from the retained beta phase during deformation, and which occurs even after aging treatment at 550 degrees C for 5 min.

Production of casting titanium alloys has been increased due to a significantly high competitive price rather than processed products (e.g. forging, extrusion and rolling). Therefore, advanced casting skills have been developed to manufacture titanium alloys with high quality. However, as-cast titanium alloys have a limit to improve their properties because of lower mechanical properties than forged alloys. In this study, Ti-6Al-4V alloy was fabricated by vacuum arc re-melting (VAR); it is a commercial casting’s method. Heat treatment is useful method for improving mechanical properties of the casting parts through microstructure’s evolution. The main aim of this work is to study relationship between heat treatment, microstructure and mechanical properties have been investigated. Solution treatment was performed at 950°C for 0.5h followed by water quenching. After that, the samples were aged at 450, 550 and 650°C. Hardness and tensile tests (at RT and high temperature) were conducted. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the microstructure as well. The hardness slightly increased with increasing aging time. In addition, tensile properties at high temperature (400°C) by aging treatment were improved.

Biomaterials of ceramics are useful as implant materials in orthopedic surgery. In this study, porous HA(hydroxyapatite)/β-TCP(tricalcium phosphate) composite biomaterials were successfully fabricated using HA/βTCP powders with 10-30wt% NH4HCO3 as a space holder (SH), 2wt%TiH2 as a foaming agent (FA) and as binder of 1wt% MgO powder. The HA/β-TCP powders were consolidated by spark plasma sintering (SPS) process at 1000 °C under 20MPa pressure. The effect of SH content on the pore size and distribution of the HA/β-TCP composite was observed by scanning electron microscopy (SEM) and micro-focus X-ray computer tomorgraphy system(SMX225CT). These microstructure observations revealed that the volume fraction of pores increased with increasing SH content. The pore size of the HA/β-TCP composites is about 400-500μm. The relative density of the porous HA/βTCP composite increased with decreasing SH content. The porous HA/β-TCP composite fabricated with 30%SH exhibited similar elastic modulus to cortical bone, but compression strength of this composite is higher than that of cortical bone.

Microstructure and thermal properties of Mg–(3 mass% or 5 mass%) Sn–2 mass% Ca alloys as casts and extrusions have been investigated with different ram speeds and extrusion temperatures. Mg–(3 mass% or 5 mass%) Sn–2 mass% Ca alloys are composed of \(\upalpha \)-Mg, MgSnCa, and \(\hbox {Mg}_{2}\hbox {Ca}\) phases. By adding Sn content from 3 mass% to 5 mass%, the MgSnCa phase is increased and the \(\hbox {Mg}_{2}\hbox {Ca}\) phase is decreased. During hot extrusion, the average grain sizes are increased with increasing ram speed and temperature. The ultimate tensile strength (UTS) and elongation for the Mg–5Sn–2Ca alloy at \(2.3\, \hbox {mm}{\cdot }\hbox {s}^{-1}\) are 227.73 MPa and 18.43 %, respectively. With increasing extrusion ram speed, the UTS and elongation for the Mg–5Sn–2Ca alloy are remarkably decreased to 215.95 MPa, 206.33 MPa, and 14.74 %, 6.88 %, respectively. The thermal conductivity for the Mg–3Sn–2Ca alloy is dramatically improved, compared to commercialized Mg alloys such as AZ31 and AZ91 due to formation of MgSnCa and \(\hbox {Mg}_{2}\hbox {Ca}\) phases.

Mo and Nb elements have been considered as beta-stabilizer and non-toxic elements in Ti alloy. Therefore, Ti-17 wt-% Mo-10 wt-% Nb alloy was used to reduce the Young's modulus and improve the biocompatibility in this study. In addition, spark plasma sintering was used for consolidation of Ti-17Mo-10Nb milled powders by high-energy mechanical milling during 1-8 hours. Consequently, the compression strength, Young's modulus and biocompatibility could be improved by proper milling time of Ti-17Mo-10Nb powder. To investigate the microstructure, phases and mechanical properties of Ti-17Mo-10Nb alloy, scanning electron microscope, X-ray diffraction and compression test were conducted. Also the biocompatibility and corrosion resistant of this alloy was conducted by MTT (tetrazolium-based colorimetric) assay and polarization measurement, respectively. The results showed that biocompatibility of this alloy was improved by increasing milling time and Young's modulus of Ti-17Mo-10Nb alloy decreased by using 8 hours milled powder.

Ceramics biomaterials are useful as implant materials in orthopedic surgery. In this study, porous HA(hydroxyapatite)/beta-TCP(tricalcium phosphate) composite biomaterials were successfully fabricated using HA/beta-TCP powders with 10-30 wt% NH4HCO3 as a space holder(SH) and TiH2 as a foaming agent, and MgO powder as a binder. The HA/beta-TCP powders were consolidated by spark plasma sintering(SPS) process at 1000 degrees C under 20 MPa conditions. The effect of SH content on the pore size and distribution of the HA/beta-TCP composite was observed by scanning electron microscopy(SEM) and a microfocus X-ray computer tomography system(SMX-225CT). These microstructure observations revealed that the volume fraction of the pores increased with increasing SH content. The pore size of the HA/beta-TCP composites is about 400-500 mu m. The relative density of the porous HA/beta-TCP composite increased with decreasing SH content. The porous HA/beta-TCP composite fabricated with 30% SH exhibited an elastic modulus similar to that of cortical bone; however, the compression strength of this composite is higher than that of cortical bone.

The influence of yttrium addition on high-temperature performance of stress rupture property and oxidation resistance in Inconel 713C has been investigated. High-temperature stress rupture property and oxidation resistance property of Inconel 713C were dramatically improved with increasing yttrium addition content up to 0.02% yttrium, then decreased in excess of yttrium. Especially, the carbide morphology changed to discrete blocky shapes by causing improved high-temperature properties. Intermetallic compounds by excess yttrium addition made a poor stress rupture life. The high-temperature oxidation resistance of 0.02 wt-% yttrium added Inconel 713C improved more than no added yttrium Inconel 713C.

Biomaterials of titanium and its alloys are useful as implant materials in orthopaedic surgery. In this study, porous Ti-13wt% Nb-13wt% Zr biomaterials were successfully fabricated using powder metallurgy by adding 10-30 wt-% NH4HCO3 as a space holder and TiH2 as a foaming agent to mixed and milled Ti-Nb-Zr powders. The alloy powders were consolidated by spark plasma sintering process at 1123 K under 30 MPa conditions. The effect of space holder content on the pore size and distribution of the Ti-13wt% Nb-13wt% Zr (TNZ) alloys was observed by optical microscopy and scanning electron microscopy. These microstructure observations revealed that the volume fraction of the pores increased with increasing space holder content. The pore size of the TNZ alloy changed from the 100 mu m scale to the 10 mu m scale with increasing milling time and space holder content in the TNZ powders. The porous TNZ alloys exhibited good biocompatibility.

In most cases, graphite is using as a construction material for bipolar plates in PEM fuel cells. Graphite has a stabilized chemical reaction and excellent electrical conductivity. However, it also has weaknesses in that it is costly and prone to gas leaks because of its structural properties. Graphite has a porous structure, so graphite plates are thick for preventing these gas leaks. Even though, gas retention is still an issue, and bipolar plate thickness may conversely need to be increased further. Finally, graphite is difficult and expensive to manufacture via machining because of how brittle it is. Metal is a very attractive material for the industrial fields. Some engineers expect to overcome the weaknesses of graphite as a construction material for bipolar plates through the implementation of metallic substitutes. Metal is inexpensive and easy to manufacture while boasting a high-density structure and good electrical conductivity. However, metal has one weakness: its tendency toward corrosion. This study focused on commercial stainless steel’s corrosion behavior in a standard PEMFC operating environment during a 100-hour time frame. We investigated for changes in the microstructure using OM, SEM, and XRD, for corrosion properties using ICP, and for electrical properties using Potentiodynamic polarization.

The ultra fine grained TiC-10 vol.% binders (Nicrobraz 30, 150 and LC) hard materials were fabricated successfully by a high-frequency induction heated sintering (HFIHS) using high-energy mechanical ball milled TiC powder. The average grain size of high energy mechanical ball milled TiC powder was approximately 50 nm. TiC-Nicrobraz (30, 150, LC) hard materials with a relative density of up 99% were obtained by HFIHS. The hardness and fracture toughness of the sintered TiC-10 vol% Nicrobraz 30 hard materials produced by HFIHS were 2018.7 kg/mm(2) and 8.2 MPa . m(1/2), respectively.

In this work Ti–35Nb–xSn/15hydroxyapatite (HA, x=2.5, 5, 10wt.%) bulk biocomposites were fabricated by high energy mechanical milling (HEMM) and pulse current activated sintering (PCAS). The microstructure and characteristics of Ti–35Nb–xSn/15HA milled powders and bulk composites sintered from powders milled for 12h were studied. The results indicate that α-Ti transforms into β-Ti completely in 12h milled Ti–35Nb–2.5Sn/15HA powders due to the solid solution of Nb into Ti lattice. The ultrafine grains are obtained in the bulk Ti–35Nb–2.5Sn/15HA composites. All bulk Ti–35Nb–xSn/15HA composites have high compression strength and low elastic modulus (21–23GPa). The corrosion current density of bulk Ti–35Nb–2.5Sn/15HA composites is about 0.18μA/cm2 in Hank’s solution. Cell culture results reveal that MC-3T3 osteoblast cells have good growing and spreading ability on the surface of bulk Ti–35Nb–xSn/15HA composites. Cell viability for bulk Ti–35Nb–2.5Sn/15HA composite is 0.4 times higher than that for CP Ti. The results demonstrate that bulk Ti–35Nb–xSn/15HA composites are promising biomaterials.

Metallic biomaterials such as titanium and its alloys have been widely used as permanent implant materials due to their excellent corrosion resistance, fatigue property, and strength. Calcium pyrophosphate (CPP) is an attractive bioceramic for human tissue implantation due to its good biocompatibility and similar composition to human bone. High energy mechanical milling and spark plasma sintering (SPS) can be used to fabricate a sound composite of the Ti-Nb-Zr-CPP. In a biomaterial such as the Ti-6Al-4V ELI alloy, the coating property between the bioceramic and Ti-based alloy is very important. By addition of CPP to the Ti-Nb-Zr alloy, the Ti-Nb-Zr alloy can improve the wetability between the Ti alloy and bioceramic as a coating material. Also the porous surface of the biomaterials can improve the symphyseal ability with osteoblast. In this study, a porous surface can be made by using several different leaching solutions such as aqueous diluted H3PO4. Ti-Nb-Zr-CPP composite was fabricated by spark plasma sintering (SPS) at 1000 ℃ under 70 MPa using high energy mechanical milled powder. A porous surface was successfully fabricated by using a 40 vol%H3PO4+ 60 vol.%H2O leaching solution at room temperature for 24 h.

Ti-6Al-4V ELI (Extra low interstitial) alloy have been widely used as alternative bone due to its excellent biocompatibility, although it still has problems such as high elastic modulus and toxic element. Therefore, biomaterial with low elastic modulus and nontoxic has to be developed. In this study, the raw materials which are nontoxic elements such as Nb and Zr were mixed for 24h and milled for 1 to 6h using high energy ball milling machine. Ti-35wt%Nb-7wt%Zr-10wt%-X(5,10,20)wt%CPP (calcium pyrophosphate) composites were fabricated by spark plasma sintering (SPS) at 1000°C under 70MPa using mixed and milled powders. The effects of CPP contents and milling time on biocompatibility and mechanical property have been investigated. By X-ray diffraction (XRD), chemical reaction during the sintering was occurred and revealed new phases, Ti2O, CaO, CaTiO3, and TixPy. The results of in vitro (MTT) and in vivo (Implanted), the sintered Ti-35%Nb-7%Zr-10%CPP composite has better biocompatibility than Ti-6Al-4V ELI alloy.

A high-energy mechanical milling (HEMM) process was introduced to improve sinter-ability, and rapid sintering of spark plasma sintering (SPS) under pressure was used to make ultra fine grain (UFG) of Ti-Nb-Mo-CPP composites, which have bio-attractive elements, for increasing mechanical properties. Ti-Nb-Mo-CPP composites were successfully fabricated by SPS at 1000 degrees C within 5 minutes under 70 MPa using HEMMed powders. The Vickers hardness of the composites increased with increased milling time and addition of CPP contents. Biocompatibility and corrosion resistance of the Ti-Nb-Mo alloys were improved by addition of CPP, and the Ti-35%Nb-10%Mo-10%CPP alloy had better biocompatibility and corrosion resistance than the Ti-6Al-4V ELI alloy.

Nowadays, many economists and scientist worry about sharply increased to fuel consumption. New energy sources have to be investigation now. This was a base on the low-emission gas, high-energy efficiency, permanence and possible with co-generation. Especially, transportation system has been restricted to system’s total weight. Light weight of a transportation system offers to increase performance. By using light weight in a transportation system, it gives another benefit that reduced oil consumption, improved fuel efficiency and increased Market-value. Fuel cell is one of the new energy systems for next generation. Normally, fuel cell consists of bipolar plate, MEA (Membrane Electrode Assembly) and GDL (Gas Diffusion Layer). Conventional bipolar plate material was used to graphite. Graphite has been very weak at external shock. Machining process is not easy, and the main problem is that the graphite material supplied by oxidizing and reducing agent composition of the gas leak comes. Thus, the manufacturing cost is increased by this reason. This study will be tried to bipolar plate material replacement from graphite materials to metallic material. In this experiment, STS316 base on austenite stainless steel was used. This experiment was observing an effect of surface conditions with corrosion behavior with Non-coated and CrN coated STS316 on a similar PEMFC operating condition. By the results of experimental, CrN coated condition has better corrosion resistance than that of Non-coated condition due to passivation layer on CrN coated surface.

Development of nanosized hard materials is desirable to improve the mechanical properties, and high energy mechanical milling (HEMM) method is widely used to fabricate nanosized powders. However, grain growth occurs during conventional sintering for long periods, which degrades the mechanical properties. In this work, high frequency induction heated sintering (HFIHS) was used to fabricate highly dense nanosized WC-10 vol.-% Nicrobraz 30, 150 and LC composites for short sintering time without grain growth. Therefore, control of grain growth during sintering is one of the keys to the commercial success of nanostructured cemented carbide composites. After sintering, the relative densities of WC-10 vol.-% Nicrobraz 30, 150 and LC composites were 99.9, 98.7 and 98.0% respectively. The grain sizes were confirmed by full width at half maximum from the result of X-ray diffraction. The highly dense nanosized WC-10 vol.-% Nicrobraz 30, 150 and LC composites were fabricated successfully using HEMM and HFIHS equipment.