Superfine Grain Research Articles

The Study on the Low Yield Strength for Super Fine Grain and High Strength Bearing Nb if Steel

The cold rolling and simulative continuous annealing experiments after rolling were carried out in the laboratory on the base of super fine grain (SFG) steel sheet. The microstructure and the second-phase particles precipitated behavior were analyzed by the technology of OM, TEM and EDX. It is found that the fined Nb(C, N) can be formed by adding micro-alloy element Nb. It is noted that the yield strength is low as well as the tensile strength is high by the PFZ which is free of precipitate called precipitated free zone on the one side of the grain boundary. Contrast to the conventional IF steel, the super fine grain steel has super fine grains and gives excellent press-formability such as low yield strength, high r-value（the plastic strain ratio）. High strength cold-rolled steel sheets (HSS) with high formability have been developed in the last decade, in which the major strengthening method was solid-solution hardening with silicon, manganese and phosphorous [1-3]. When the IF steel is strengthened with the high amount of solid-solution elements, it becomes susceptible to the secondary work embrittlement because of the lack of grain boundary strength [4-6]. In this paper, High strength cold-rolled steel sheets (HSS) with high formability have been developed for the IF steel-bases. The grain refinement and precipitation hardening are achieved by means of the fine distribution of carbide under the appropriate combination of the relatively higher carbon content near 0.0070 mass% with niobium. As the result, this type of IF-HSS has been successfully developed to reach a higher r-value as compared with the conventional IF-HSS.

Dynamic Recrystallization Behavior of Biomedical CCM Alloys in Hot Compression Process

Dynamic recrystallization behavior of Co-29Cr-6Mo-0.16N alloy was analyzed in details. Compression tests were carried out in a computer aided Thermecmaster- Z hot forging simulator. The results showed that uniformly distributed superfine grain size could be obtained by continuous dynamic recrystallization (DRX) process; Texture-free microstructure with uniformly distributed equiaxed fine grains was obtained. The formation of profuse stacking faults and their subsequent intersections are considered to be the principle mechanisms of DRX.

Marker-assisted improvement of bacterial blight resistance in parental lines of Pusa RH10, a superfine grain aromatic rice hybrid

Pusa RH10, the widely cultivated superfine grain aromatic rice hybrid, and its parental lines Pusa6B and PRR78 are susceptible to bacterial blight (BB) disease caused by Xanthomonas oryzae pv. oryzae. Pusa1460, a Basmati rice variety, was utilized as the donor for introgressing BB resistance genes xa13 and Xa21 into Pusa6B and PRR78 using a marker-assisted backcross breeding program. The markers RG136 and pTA248 linked to BB resistance genes xa13 and Xa21, respectively, were used for foreground selection. Seventy-four STMS markers polymorphic between Pusa6B and Pusa1460, and 54 STMS markers polymorphic between PRR78 and Pusa1460, were utilized for background selection to recover the recurrent parent genome ranging from 85.14 to 97.30% and 87.04 to 92.81% in the 10 best BC2F5 families of Pusa6B and PRR78, respectively. RM6100, an STMS marker linked to fertility restorer gene (Rf), was used for marker-assisted selection of Rf gene in an improved version of PRR78. The extent of donor segments in the improved version of Pusa6B was estimated to be <0.97 and <2.15 Mb in the genomic regions flanking xa13 and Xa21, respectively, whereas in improved PRR78, it was estimated to be <2.07 and <3.45 Mb in the corresponding genomic regions. Improved lines of Pusa6B and PRR78 showed yield advantages of up to 8.24 and 5.23%, respectively. The performance of the BB-resistant version of Pusa RH10 produced by intercrossing the improved parental lines was on a par with or superior to the original Pusa RH10.

HPHT Synthesis of High-Quality Diamond Single Crystals with Micron Grain Size

High-quality diamond single crystals with micron grain size are synthesized with a new high-pressure and high-temperature (HPHT) synthesis technique in a cubic anvil high pressure apparatus. Morphology of the synthesized diamonds is observed by a scanning electron microscope (SEM). The samples are characterized using laser Raman spectra. The results show that the new synthesis technique improves the nucleation of diamond greatly, and diamond single crystals with perfect morphology and micron grain size are successfully synthesized, with the average grain size of about 6μm. This work provides a new synthesis technique to implement industrialization of high-quality diamond single crystals with super-fine grain size, and paves the way for future development.

The comparative study of thermal fatigue behavior of laser deep penetration spot cladding coating and brush plating Ni–W–Co coating

For improving the thermal fatigue behavior of hot work die steel in engineering application, the present work compare the influence of thermal fatigue resistance by the two different surface modified processes, the laser deep penetration spot cladding (LDPSC) and brush plating on the Cr12MoNi hot rolling tool steel. The thermal fatigue tests were fulfilled by heating and quenching in water at a cycle period of 2 min. Before and after thermal fatigue testing, the microhardness distribution profile and microstructure of LDPSC have been investigated. The results show that the LDPSC can be divided to three zones: cladding zone, alloying zone and heat affected zone. The major phases in cladding zone consist of Fe 3C, Cr 7C 3, Cr 23C 6 and martensite. The oxidation resistance and thermal stability of brush plating Ni–W–Co coating and reference materials has been determined. The results of thermal fatigue testing show that LDPSC and brush plating Ni–W–Co coating can improve thermal fatigue resistance as compared to the reference material. The brush plating Ni–W–Co coating is more effective than the former owing to its higher thermal stability, oxidation resistance, superfine grain, high-density dislocation in microstructure and combination of strength and ductility.

Utility of a fertility restorer gene linked marker for testing genetic purity of hybrid seeds in rice (Oryza sativa L.)

2 Topic: Genetics Key Author: A.K. Singh Correspondence Address: Division of Genetics Indian Agricultural Research Institute New Delhi 110 012 India E-mail: aks_gene@mailcity.com Authors: A. Garg, A.K. Singh, K.V. Prabhu, T. Mohapatra, N.K. Tyagi, N. Nandakumar, R. Singh and F.U. Zaman Utility of a fertility restorer gene linked marker for testing genetic purity of hybrid seeds in rice (Oryza sativa L.) Pages: 9-18 The utility of a fertility restorer (R f ) gene linked co-dominant STMS marker RM258 was examined for testing the genetic purity of hybrid seeds in rice. DNA isolated from 450 seedlings of a superfine grain aromatic rice hybrid Pusa RH10, was PCR amplified using RM258. Of these, 15 plants were found homozygous for either of the parental type (CMS line Pusa 6A and restorer line PRR 78) allele. The rest 435 plants were heterozygous at the RM258 locus indicating their true hybrid nature. The genetic purity of hybrid seed lot was thus found to be 96.67%. The results of molecular analysis were confirmed by the Grow Out Test (GOT). Further, the efficacy of RM258 was compared with markers, RM201, 206, 216, 228, 247 and 263, which were not linked to R f gene but were polymorphic between the corresponding A and R lines. Some of the plants identified as hybrid, using RM258 appeared as self of the parental lines at certain unlinked marker loci. Similarly, among the 15 plants homozygous for either of the parental type alleles at the RM 258 locus, the distribution of homozygous and heterozygous genotypes at unlinked marker loci was observed in varying frequency. These observations indicated that the assessment of genetic purity of hybrid seeds based on unlinked markers might not be fully reliable. The study suggests that a single R f gene linked co-dominant marker can provide a precise and quick alternative to GOT, for testing hybrid seed purity.

Thermal behavior of ammonium perchlorate and metal powders of different grades

The effects of aluminum (Al) and nickel (Ni) powders of various grain sizes on the thermal decomposition of ammonium perchlorate (AP) were investigated by TG and DSC in a dynamic nitrogen atmosphere. The TG results show that Al powders have no effect on the thermal decomposition of AP at conventional grain size, while the nanometer-sized Ni powders (n-Ni) have a great influence on the thermal decomposition of AP with conventional and superfine grain size. The results obtained by DSC and an in situ FTIR analysis of the solid residues confirmed the promoting effects of n-Ni. The effects of n-Ni have been ascribed to its enhancement on the gas phase reactions during the second step decomposition of conventional grain size AP.

Abrasive Technology of Single-Crystal Diamond by Diamond Abrasive Wheel

Single-crystal diamond tools can be used for cutting high precise parts with high efficiency, but it is very difficult to abrade it, which is one of study purposes in this paper. This project can be done on the high precise machine tools by using a diamond abrasive wheel with super fine grain size. In this paper, the abrading mechanism is represented, an efficient abrasive method is invented, the major factors which have an important effect on abrasive efficiency and accuracy are discussed, such as abrasive wheel grain size, bonding agent, hardness, speed, pressure and feeding speed etc and some results raising abrasive efficiency and accuracy are obtained. By using the single-crystal diamond tool abraded by author, the degree of roughness of the parts can come up to Ra0.05.

Study on Fullerene Wheel and Diamond Wheel with Super Fine Grain for Creating Super Smooth Surface(Superabrasive/new wheel grinding process)

Fullerene has some special structural, physical, and mechanical properties. The precise and efficient machining by this material to the required quality has not yet been well established. In this paper, a comparative study was conducted to investigate the special aspects in the polishing of silicon wafer using the fullerene wheel, and the diamond wheel of super fine grains. The stability of surface roughness, effects of material grains sizes on the grinding results, and microscopic analysis of grinding phenomena by both materials were also analyzed in detail. The sintering temperature of near 700℃ is suitable for manufacturing diamond wheel. The carbon beads fit to fabricate the small pores in the vitrified-bonded wheel in comparison with the polyethylene beads. The surface roughness of hardened steel is rather larger when ground by 0〜1/8μm than when ground by 0〜1/4μm of diamond grain. This is because the abrasive grains were covered with the bond. It was clarified that we can obtain the surface roughness of 5nm Ra when using fullerene in polishing of silicon wafer.

Improving Joint Properties of Friction Welded Joint of High Tensile Steel

This report describes the improvements in the joint properties of friction welded joint of 780MPa class high tensile steel. Welded joint made by a continuous drive friction welding machine, the conventional method, had not obtained 100% joint efficiency despite applying forge pressure. This was due to the softening of the welded interface zone for heat input during braking times. Therefore, we developed a continuous drive friction welding machine with an electromagnetic clutch to prevent heat input during braking time. We proposed the process as “The Low Heat Input Friction Welding Method (the LHI method).” In this case, the joint had the same tensile strength as the base metal at friction time when the friction torque reached the initial peak torque. That is, the welded joint obtained 100% joint efficiency by using only the friction stage up to the initial peak torque without the forge (upsetting) stage, despite the existence of a slightly softened region adjacent to the welded interface. Furthermore, the softened region was hardly generated when this joint was made by applying forge pressure at the initial peak torque. In conclusion, a welded joint of high tensile steel made by only the friction stage of the LHI method had excellent joint properties. The LHI method has a lot of advantages for joining such materials as super fine grain steel with which conventional fusion welding processes have difficulty.

Surface characterization of tungsten and tungsten carbide–cobalt probe materials for a fine‐pitch four‐point probe by variable excitation XPS using synchrotron radiation

AbstractIn the course of the development of a new fine‐pitch four‐point probe, surface oxide layers of the probe material were characterized by a non‐destructive depth profiling analysis with a variable excitation XPS using synchrotron radiation. The high surface sensitivity of this technique has allowed us to measure the ultra‐thin thickness of the oxide layer on the probe material without damage. The XPS of W 4f of the tungsten metal was measured in the excitation x‐ray energy range 100–1200 eV at the Photon Factory (BL‐13C), Tsukuba, Japan and analysed by the simulation of attenuation in the layer models using the values of inelastic mean free path (IMFP) and effective attenuation length (EAL) calculated by the National Institute of Standards and Technology (NIST) database programs 71 and 82, respectively. The values of practical EAL at 1 nm depth were smaller than the IMFP by 20–40% and resulted in a smaller thickness of the surface oxide layer than for that of IMFP by about 20%. The result showed that the thickness of the surface oxide layer of the tungsten metal was 1.0 nm ‘as received’ and 0.5 nm after polish. The XPS of W 4f of the superfine grain (grain size &lt; 0.5 µm) tungsten carbide–cobalt wires with 0.45 mm diameter, which is a probe size of conventional four‐point probes, were measured and the results indicated that the thickness of the surface oxide layer of the tungsten carbide–cobalt was 0.4 nm ‘as received’, and the thickness of the oxide layer was increased to 0.5 nm after polish. The XPS of W 4f of the tungsten carbide–cobalt wire with 0.05 mm diameter of an actual probe for a new fine‐pitch four‐point probe system was also measured and the results indicated that the thickness of the surface oxide layer was 0.6 nm. The XPS of W 4f also indicated the existence of an intermediate thin layer of WO2 between W and WO3. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Structural and magnetic characterization of super fine grain ceramics of YBa 2Cu 4O 8 synthesized by citrate pyrolysis method

YBa 2Cu 4O 8 (124) is synthesized at ambient pressure condition using citrate pyrolysis precursor method, and the weakly sintered 124 ceramics are studied by both SEM observation and ac magnetization measurement. Such ceramics can be regarded as a system of weak-coupled super fine grains, so that we may study experimentally the intergrain superconductive phase transition considering the effects of mesoscopic sintered structure. For this purpose, several specimens at different treatment time stage in the sintering process are examined. As the sintering is advanced, very small grains are fused into larger ones and the adjacent large grains tend to be fused at their interface. From magnetic measurements, the ceramics are equally confirmed to be weak-coupled grain systems which show the intergrain ordering at each T c2 determined consistently by sintering temperature. Utilizing the series of ceramics, we will be able to study the intergrain ordering further systematically.

Capability of nodular eutectic and austenite–bainite polyphase structure to resist impact abrasive wear

Wear behavior of austenite–bainite polyphase steel with nodular eutectics subject to impact abrasion has been investigated by means of transmission electron microscope (TEM), scanning electron microscope (SEM) and MDL wear tester. Results indicate that the nodular eutectic effectively prevents the penetration of the abrasive into the worn surface, and reduces the microcutting of the abrasive on the worn surface. The worn surface layer has a good match of strength and toughness because of strain-induced martensite, dislocation, twin crystal and deformed bainite structure, which can make the worn surface layer bear more plastic deformation and the impacting of the abrasive under low and medium impact working condition. However, there is amorphous structure and superfine grain in the worn surface, strain-induced martensite, dislocation, twin crystal and deformed bainite structure in the worn subsurface layer under high impact. As a result, the hardness from the subsurface layer to the worn surface of the steel increases gradually, which can effectively resist the impacting and the penetration of the abrasive. The austenite–bainite polyphase structure with nodular eutectics is a promising structure in resisting abrasive wear as compared with a bainite structure, bainite structure with nodular graphites and an austenite structure with nodular eutectics.

222 有気孔ビトリファイドボンド超微粒ダイヤモンドホイールの試作と性能評価

222 有気孔ビトリファイドボンド超微粒ダイヤモンドホイールの試作と性能評価

ＹＡＧレーザを併用した超硬合金への微細深穴放電加工

This paper deals with fine deep boring of carbide alloys. Fine deep boring by EDM is superior for obtaining a qualitatively machined shape and high surface integrity compared to conventional processes. However, it is difficult to obtain a microhole smaller than 100μm in diameter with an aspect ratio larger than 5, because of remaining bubbles and debris in the small gap between the electrode and workpiece which cause unstable machining. A new fine boring method is proposed in which EDM and laser beam machining are combined. First, a penetrating prehole is machined with a YAG laser. In the next process, micro-EDM boring is carried out on the prehole. By removing the bubbles and debris through the prehole, it is possible to maintain stable EDM. With these two successive processes, a fine deep hole is obtained. The hole made by this method has a good roundness and a high aspect ratio that cannot be achieved using only the EDM process. We applied this method to a superfine grain carbide alloy which is widely used for precise metal molds and cutting tools. The main results of this study are as follows. (1) Using the combined process of EDM and LBM, ∅160μm holes were successfully machined through a 2-mm-thick superfine grain carbide. (2) It is possible to remove the bubbles and debris efficiently by suction flow through the prehole. (3) In the case of EDM boring with a prehole, electrode wear mainly occurs on the side of the electrode. (4) For a 1-mm-thick workpiece, it is possible to bore a microhole with a diameter of 100μm and an aspect ratio of 10.

Injection moulding and infiltration sintering of superfine grain tungsten-copper : B.Yang, R.M.German. (Pennsylvania State University, Pennsylvania, USA.) Int. J. Powder Metall., vol 33, no 4, 1997, 55–63

Injection moulding and infiltration sintering of superfine grain tungsten-copper : B.Yang, R.M.German. (Pennsylvania State University, Pennsylvania, USA.) Int. J. Powder Metall., vol 33, no 4, 1997, 55–63

High-Precision Surface Grinding of Ceramics with Superfine Grain Diamond Cup Wheels

High-precision surface grinding has been performed on the Si 3N 4 and AI 2O 3-TiC ceramics and Mn-Zn Ferrite using an ultra-precision surface grinder and very fine grain diamond cup wheels, where the maximum depth of cut was 2 μm and the maximum through feed rate being 100 mm/min. The surface roughness and percent brittle mode area were measured using an atomic force microscopy (AFM). These characteristics were discussed by a parameter “ S max” defined as S max = μa v f/ v s (μ: successive cutting edge spacing, a: depth of cut, v f: through feed rate, v s: wheel speed). With decreasing grain size from #1200 to #16000, the surface roughness Rmax decreases to 20 to 30 nm. Similarly, a remarkable reduction in percent brittle mode area is seen by changing grain size. The effect of dressing stone on the ground surface was also investigated using 3D wheel surface topography.

PNR162 (Renu), an Early Rice Variety with Superfine Grain and Multiple Resistances

PNR162 (Renu), an Early Rice Variety with Superfine Grain and Multiple Resistances

Analysis of Mirror Surface Generation of Hard and Brittle Materials by ELID (Electronic In-Process Dressing) Grinding with Superfine Grain Metallic Bond Wheels

Mirror surface grinding operations were conducted by using ultrafine grain metallic bond wheels with electrolytic in-process dressing(ELID). Workpieces of hard and brittle materials, such as monocrystalline silicon, glass, and ceramic, were ground. Wheel abrasive grains used mainly were diamond of several microns down to submicrons. Ground surface roughness versus grit size was shown. SEM and AFM were adapted to analyze ground mirror surface generation, and surface topographies due to grit size were compared. Subsurface damage was evaluated through X-ray, angle-polish and step-etching. High surface accuracy, good surface finish, and low subsurface damage were all successfully achieved. The advantage of a constant in-feed pressure in ultrafine grinding was shown, and Ra of several angstroms was achieved.

Thermal desorption of helium from homogeneously implanted graphite

Super-fine grain graphite (FGG) and pyrolytic carbon (PYC) of thicknesses around 200 μm were homogeneously implanted at room temperature with α-particles (0.5 MeV ≤ E α ≤ 22 MeV). Thermal helium desorption spectrometry in the temperature range from 400 to 1900 K can be described by diffusion kinetics with an activation energy of 1.1 eV in FGG and about 0.75 eV in PYC. Desorption during temperature ramping at a constant rate of 0.83 K/s also shows significant differences of the two graphite species. It is found that in FGG and especially in PYC a considerable fraction of the implanted helium is retained even beyond 1000 K. This is in contrast to results reported after low energy implantations to high doses for various graphite species.