CAO La-mei, LIU Li-jun, CHEN Jing-yang, XUE Ming. Effect of Hot Isostatic Pressing Temperature on the Microstructure of a Third Generation Single Crystal Superalloy DD10[J]. Journal of Materials Engineering, 2013, 0(6): 1-4,24.
The effects of different hot isostatic pressing temperatures on the microstructures of the third generation single crystal superalloy DD10 were investigated by using optical microscope (OM), scanning electron microscope (SEM) and electron microprobe analyzer (EPMA). The results show that the hot isostatic pressing temperature 1290℃ was enough for the microporosity of DD10 to be eliminated completely at 150MPa; the volume fraction of eutectic was decreased markedly with the increase of the hot isostatic pressing temperature. The eutectic disappeared with hot isostatic pressing of 1310℃ or above, and there were internal incipient melting after hot isostatic pressing at 1340℃/150MPa. Meanwhile, the hot isostatic pressing process with different temperatures also resulted in more uniform morphology of γ' precipitates to the same extent. The dendritic segregation was homogenized gradually because of increasing of the hot isostatic pressing temperature.
HU Yong-qiang, GUO Xi-ping, GUO Hai-sheng. Effects of Heat Treatments on the Microstructure and Microhardness of Directionally Solidified Nb-Ti-Si Based Ultrahigh Temperature Alloy[J]. Journal of Materials Engineering, 2013, 0(6): 5-11.
Directionally solidified specimens of Nb-Ti-Si based ultrahigh temperature alloy with the withdrawing rates of 2.5μm/s and 50μm/s were homogenized at 1250, 1350℃ and 1400℃ for 50h, respectively. The constituent phases were Nbss, β(Nb,X)5Si3 and γ(Nb,X)5Si3. The needle-like precipitates of Cr2(Nb,Ti) appeared in the specimens directionally solidified at the withdrawing rate of 2.5μm/s after homogenizing treatments, and its amount increased with the homogenizing temperatures. After homogenizing treatments, the straight boundaries and sharp edges of the primary hexagonal silicides became smooth, the fine silicides in the center of the eutectic cells became spheroidzed, and some silicide blocks in the eutectic cells broke into small ones. The transformation from β(Nb,X)5Si3 to α(Nb,X)5Si3 did not occur during the homogenizing treatments. After homogenizing treatments, the microhardness of the alloy increased remarkably, and its value first increased and then decreased with the increasing of the homogenizing temperatures. The maximum value of microhardness of the constitute phases occurred in the specimens homogenized at 1350℃ for 50h.
MAO Da-heng, ZHAO Su-kun, LI Jian-ping, FU Zong-li, SHI Chen. Effect of Cold Rolling Reduction on Texture and Properties of Cast-rolled Aluminum Strip Under Electromagnetic and Ultrasonic Field[J]. Journal of Materials Engineering, 2013, 0(6): 12-17.
Cast-rolled aluminum strip stock had been successfully prepared under electromagnetic and ultrasonic field, and cold rolling experiment was conducted for the strip stock. The effect of cold rolling reduction on the microstructure, mechanical properties and texture of cast-rolled aluminum strip under composite energy field was investigated, and compared with general cast-rolled aluminum strip of the same pass. The results show that: With the increase of cold rolling reduction, the two kind of cast-rolled aluminum strip was gradually flattened and elongated,and eventually the apparent fibrous tissue was obtained. And the fibrous tissue of cast-rolled strip under composite energy field was more uniform. The tensile strength σb and elongation δ of each pass of cast-rolled strip under composite energy field were both higher than the general cast-rolled strip at the same pass, and the anisotropy index (IPA) was significantly lower than the general one. With the increase of cold rolling reduction, the density of Brass (B), S and Copper (C) texture of the two kind of cast-rolled aluminum strip was increased at different degrees, while the Goss (G) texture first increased and then decreased, the rotated-cube (RC) texture gradually decreased. The original texture of cast-rolled strip under composite energy field was diffused and the density of all kinds of texture with the same pass was lower than the general one. The drawing experimental results show that the draw ability of cast-rolled strip under composite energy field was obviously better than the general one, and the earing ratio was only 1.7%.
PEI He-zhong, HUANG Pan, SHI Qing-nan, LU Feng, ZHANG Jun, ZHANG Guo-liang. Influences of Additive and Current Density on the Microstructure of the Electroforming Ni-Co Alloy[J]. Journal of Materials Engineering, 2013, 0(6): 18-24.
The influences of additives and current density on the stress and cobalt content of nickel-cobalt alloy electroforming layer were studied. The effects of additives and current density to the morphology and microstructure of nickel-cobalt alloy electroforming layer were investigated by SEM, EDS and X-ray diffraction. The results showed that compressive stress was generated in the electroforming layer when the additive TN2 added in the electroforming solution; the additive TN3 could make tensile stress. So electroforming layer might have a balance of zero stress by adding TN2 and TN3 together. When the current density was less than 6A/dm2, the stress of electroforming layer increased along with the current density; when the current density was greater than 6A/dm2, the stress of electroforming layer decreased along with the current density. The additives’ influence on the cobalt content of electroforming layer was not obvious. The current density’s influence on the cobalt content of electroforming layer was more obvious. Smoother and finer grain could be acquired when the TN2 or TN3 added in the electroforming solution. The additive TN2 had a large effect on the diffraction peak(200)and certain selectivity to the crystal face.The additive TN3 had a strong selectivity to the crystal face, easily adsorbed on the (200) surfaces to inhibit their growth, so the crystal growth direction was mainly [100]. With the current density increasing, the diffraction peak had the widening trend.
LIU Jing, XIE Guo-liang, ZHANG Ke. Mechanical Properties of High Boron Alloyed Stainless Steel Composite Plate[J]. Journal of Materials Engineering, 2013, 0(6): 25-28,34.
High boron alloyed stainless steel composite plate(HBASSCP) with boron content 2%-2.5% was fabricated by composite casting and hot forming process. The test of three-point bending shows that the tensile and compression deformation of middle layer of boron alloyed stainless steel have reached 5.6% and 6.0% respectively after solution treatment. The plasticity of boron alloyed stainless steel composite plate after solution treatment is close to 304BN7(B grade) of ASTM Standard. The boron alloyed stainless steel composite plate has better plasticity than single plain stainless steel when they are bended by this method. Typical morphology of dimples are observed in the matrix of both outer and middle layers. Cleavage fracture are observed between the borides and matrix in the middle layer, leading to the reduction of plasticity.
ZHA Ji-li, LONG Si-yuan, WU Xing-yu, ZHANG Jun-cheng, WANG Xiang-jie. Formation Mechanism of Hydrogen Pore in Die Cast AZ91D Magnesium Alloy Laser Re-melting Zone[J]. Journal of Materials Engineering, 2013, 0(6): 29-34.
In order to investigate the mechanism of pore formation in fusion welding zone of die cast Mg alloys, local re-melting of die cast magnesium alloy AZ91D of 6mm thickness and hot extruded AZ71 Mg alloy of 2.2mm utilizing CO2 laser have been conducted. Base metal microstructure and pore morphology have been observed by adopting SEM. The size of pores has been measured by particle size analysis software Nano measure 1.2. The results indicate that large pores have irregular shape and hackly inner wall of obvious traces scoured by metal, and these pores are developed by shrinkage blowhole of base metal; Small pores, resulted from hydrogen, have smooth inner wall and upside down broadening formation. The formation mechanism of hydrogen induced pores was analyzed, a model of hydrogen induced pores’ formation was established. Furthermore, the model was compared with the experimental photographs, which could be used to explain the formation of hydrogen induced pore.
JIANG Jin-xing, TANG Di, WU Hui-bin, ZHANG Jie, YANG Liu. Analysis of Propagation Behavior of Secondary Cracks in the E550 Offshore Platform Steel[J]. Journal of Materials Engineering, 2013, 0(6): 35-39.
An analysis of secondary cracks in the E550 offshore platform steel has been carried out using optical microscope (OM) and electron backscattering diffraction (EBSD). The crystallographic orientation in the vicinity of the secondary cracks was studied. The results showed that the misorientation between the neighboring grains in the steel had an important influence on the propagation behavior of the secondary crack: 40% of misorientations between neighboring grains were low-angle ones, and these misorientations had a slight influence on crystallographic propagation orientations of the secondary cracks so that the types of cracks propagation were mainly transcrystalline. However, high-angle misorientations made much difference, 40% of misorientations were ultra high-angle ranging from 50° to 62°, these misorientations led to cracks deviation or arrest.
SI Jia-yong, LI Sheng, ZHANG Ji. Effects of Large Deformation Near-isothermal Forging on Microstructures and Properties of TiAl Alloy[J]. Journal of Materials Engineering, 2013, 0(6): 40-44.
The effects of increasing deformation strain on the microstructure uniformity and mechanical property stability of Ti-46.5Al-2.5V-1.0Cr-0.3Ni alloy were quantitative studied by single near-isothermal forging. The observed microstructure and measured hardness and strength can revealing the basic relationship among deformation strain, macrostructure and microstructure. The results show that distribution of flow lines is more uniform and the area of uniform zone is enlarged with the engineering strain raised from 65%, 70%, 75%, 80% to 85%. In the forged pancake, the proportion of uniform zone expand to 68.0％ when the strain is 85%. And the deformation microstructure is composed by equiaxed γ,α2 and a few remnant laminas. The grain dimension is obviously refined and the vast majority is equiaxial microstructure. The hardness testing shows that hardness of uniform zone is tending to be uniformity and the average hardness is continuous to increase. The room temperature compression samples were machined from stagnant zone and uniform zone with heat treatment at 1250℃/15h/AC. The dispersity of room temperature compression results is reduced and it means that property stability is improved with the increased engineering strain.
LI Guo-lu, ZHANG Zhi-qiang, WANG Hai-dou, XU Bin-shi, PIAO Zhong-yu. Fatigue Damage Acoustic Emission Characteristic Parameters and Mechanism for Coating[J]. Journal of Materials Engineering, 2013, 0(6): 45-49,71.
Fe-based alloy coating was deposited on 1045 steel by a supersonic plasma spraying device. The variation regularities of acoustic emission characteristic parameters in the process of contact fatigue damage were researched using a ball-disk contact fatigue tester, and the contact fatigue damage mechanism of as-sprayed coating was analyzed. The results show that pitting is main failure mode of the coating under the experimental conditions of the 1.58GPa contact press and 2500r/min. Many pitting pits were observed on the wear track, and depth of the pitting pits was in the range from 20μm to 30μm. The pitting failure was closely associated with adhesive wear caused by rolling contact between rough salient on coating surface and bearing balls, and three-body abrasive wear among the coating, abrasives and rolling bearings within the contact region. Acoustic emission characteristic parameters, such as amplitude, root mean square (RMS), energy, count and average frequency are sensitive for rough salient removal on coating surface, elastic and plastic deformation, crack initiation, crack stable growth and unstable growth, and which are different during different fatigue damage stages.
KONG De-jun, LONG Dan, WU Yong-zhong, YE Cun-dong. Analysis of Impact Toughnesss and Fracture Morphologies of X80 Pipeline Steel Welded Joints with Submerged-arc Welding[J]. Journal of Materials Engineering, 2013, 0(6): 50-54.
The Charpy impact test at temperature range of -80-20℃ was conducted for X80 pipeline steel welded joints fabricated with submerged-arc welding. The impact absorption energy and brittle section rates were tested, and the fracture morphologies were observed with Scanning Electron Microscopy (SEM). The fracture modes and fracture morphologies of X80 pipeline steel joints were analyzed, and the ductile-brittle transition temperature of the joints and mechanical behaviors of the impact fractures were studied. The results show that the fracture at room temperature occurred in dimple fracture mode, and the ductile-brittle transition temperature of the joint was -28℃. The fracture characteristics were changed from toughness to brittleness fracture, and the joint fractured mainly in cleavage mode.
YAN Jun, CEN Qi-hong, JIANG Ye-hua, ZHOU Rong. As-cast Microstructure of High-boron Middle-carbon Alloy Tool Steel[J]. Journal of Materials Engineering, 2013, 0(6): 55-58.
A new wear-resistant material containing boron instead of those high-cost alloying elements was designed for the high contents of alloying elements in common alloy tool steel. The as-cast microstructure of high-boron middle-carbon alloy tool steel was researched by means of optical microscopy, X-ray diffraction, scanning electron microscopy and energy dispersive spectrometer. The results show that the as-cast microstructure of high-boron middle-carbon alloy tool steel consists of lath martensite, a small amount of retained austenite and eutectic borocarbides or boides of Fe2B, Fe3(B,C), Fe23(B,C)6, Cr7(B,C)3 and (W,Mo)2(B,C). The micro-hardness of the matrix is 540-620HV while that of the hard phase is 1180-1520HV, and the hardness of as-cast high-boron middle-carbon alloy tool steel is 55HRC.
ZHAO Jia-qi, WU Guo-qing, CHENG Xiang-jun, NAN Hai. Effects of the Contamination of α Layer on the Impact Properties of ZTC4 Titanium Casting Samples[J]. Journal of Materials Engineering, 2013, 0(6): 59-62.
The surface contamination layers of ZTC4 titanium castings were characterized and the effects of α layer existence on impact properties of ZTC4 titanium castings were investigated. The results show that the microstructure of α layer is coarse lamellar, which is generated due to the interface reaction between titanium liquid and mold materials. The α layer has great influence on the impact properties of ZTC4 titanium castings. By comparison with that of the casting sample without α layer, as the side with α layer in castings sample is impacted, the decrease of impact strength of the casting sample is about 9%, while the opposite side in castings sample is impacted, the decrease of impact strength of the casting sample is about 80%. That is, α layer does harm to impact properties of ZTC4 casting sample seriously.
PAN Ying-hui, XU Xiao-jing. Friction/Wear Properties of Magnetron Sputtered High-hard SiC Films on Ti6Al4V Alloy[J]. Journal of Materials Engineering, 2013, 0(6): 63-66.
High-hard SiC film was developed on Ti6Al4V alloy using magnetron sputtering technique at room temperature, and its microstructure, nanoindentation and friction/wear properties were investigated. The results show that the SiC films were amorphous and exhibited the nano-hardness of 26.8GPa and the elastic modulus of 229.4GPa. As sliding against Si3N4 ball (2mm in radius) using ball-on-disc type wear tester under Kokubo SBF at room temperature, the SiC films exhibited the special wear rate in the magnitude order of 10-5 mm3 m-1 N-1 and the friction coefficient of about 0.173 and 0.280 at the load of 50g and 200g. The higher friction coefficient is primarily due to itself breakage of the SiC films.
XING Zhi-guo, ZHOU Xin-yuan, LYU Zhen-lin, ZHOU Yong-xin. Effect of SiC Content on the Erosion and Wear Resistance of Epoxy/SiC Composite[J]. Journal of Materials Engineering, 2013, 0(6): 67-71.
In order to improve the erosion and wear resistance of large flow parts in factories and mines, the epoxy/SiC composite coating was prepared using SiC particle and epoxy resin. The composite coating with excellent erosion and wear resistance can be solidified quickly and coated conveniently. The article studied the effect of SiC particle content on the erosion and wear resistance of epoxy/SiC composite. The erosion and wear test was carried out on a self-made erosion and wear tester. The erosion and wear morphologies of the composite were observed using SEM. The results showed that different SiC particle content in the composite could change the erosion and wear resistance. When the mass fraction of SiC was 66.66%, the interaction of "shadow effect" and "bonding effect" between the SiC particles and resin achieved the best. Meanwhile, the erosion and wear resistance of the composite was the best. When the content of SiC was optimal, the erosion and wear resistance of the composite was better than that of the white cast iron under the same erosion angle.
YANG Zhi-ping, SONG Yan-chun, HAN Yue, PAN Fei, LIU Peng-fei, ZHAO Yin-hong. Synthesis and Luminescence Properties of a Novel Red Sr5(BO3)3Cl:Eu3+ Phosphor[J]. Journal of Materials Engineering, 2013, 0(6): 72-76.
A novel red phosphor Sr5(BO3)3Cl:Eu3+ was prepared by high temperature solid state reaction method. Its luminescence properties and structure were studied. X-ray power diffraction show that the fabricated samples are pure phase crystals. The emission spectra of the Sr5(BO3)3Cl:Eu3+ phosphors consist of some sharp emission peaks of Eu3+ ions, which centered at 587, 596, 613nm and 626nm, corresponding to the 5D0→7F1, 7F2 typical transitions of Eu3+ respectively. Monitoring emission at 626nm, the strongest excitation spectra appears at 392nm, which indicate that this phosphor can be excited effectively by InGaN. The decay time of 5D0 level in Eu3+ is 2.28ms. The effect of Eu3+ concentration on the emission spectrum intensity of Sr5(BO3)3Cl:Eu3+ was investigated. The results show that the emission spectrum intensity increase with raising Eu3+ concentration until reach the maximum value at 16 %(mole fraction), then it decrease. The critical distance of Eu3+ was calculated as 1.46nm. The CIE coordinates of Sr5(BO3)3Cl:Eu3+ were measured, which were very close to the NTSC standard.
LI Ping, CHENG Xiang-mei, LI An-na, TANG Zi-qiao. Ultrasonic Nondestructive Characterization of Average Grain Size in 304 Stainless Steel Solution Treatment Products[J]. Journal of Materials Engineering, 2013, 0(6): 77-81,86.
Specimens of 304 stainless steel exposed to solution treatment at 1080℃ for 1, 2h have been evaluated employing ultrasonic testing in order to discuss the feasibility and ultrasonic nondestructive characterization parameters for average grain size in 304 stainless steel solution treatment product. The results showed that the ultrasonic velocities decreased gradually and the attenuation coefficient increased apparently after solid solution treatment. The velocities continued decreasing slowly and the attenuation coefficient increased further with increasing solution treatment time at the same temperature. The spectral analysis exhibited an obvious decrease of the peak frequency and a gradual increase of the peak amplitude after solution treatments. The above studies are mainly attributed to the effects of the solution treatment to the grain size and the effects of the grain size to the propagation of ultrasonic wave through materials. Based on the least square method, the linear relationships between transverse wave velocity vt,longitudinal wave velocity vl and the average grain size were obtained vt=-0.49254d+3188.40138,vl=-0.07632d+5772.88964; meanwhile, the relevance of the attenuation coefficient to the average grain size was also described in the studied specimens as followed as α=1.2605×10-15d6.5012+0.0995.
YAN Hong-hao, WANG Sheng-jie, LI Xiao-jie, WU Lin-song. Influence of Oxygen Concentration on TiO2 Nanoparticles Prepared by Gaseous Detonation[J]. Journal of Materials Engineering, 2013, 0(6): 82-86.
TiO2 nanoparticles prepared by gaseous detonation which use hydrogen-oxygen gas mixture as the explosion source and the titanium tetrachloride as the precursor is a new method.The crystal composition, grain size and phase structure were studied by the methods of XRD and TEM, and analyzed the oxygen content on the influence of the product. The result shows that the rutile and anatase mixed crystal were obtained under certain conditions. The relative content of anatase grows as the oxygen content increases, but the mixed powder becomes intermediate product and rutile when the oxygen concent high enough. The grain are mostly spherical (or spherical),the grain dimension becomes bigger (about 80-100nm), the grain dispersivity is better and the grain becomes more uniform.
WANG Yong, ZHOU Hong, QIAO Li-ying, SONG Chang-jiang. Effect of Ca Content on Microstructure and Corrosion Performance in SBF of ZM61 Alloy[J]. Journal of Materials Engineering, 2013, 0(6): 87-91,98.
ZM61-xCa alloys with different contents of Ca were fabricated by using a vacuum induction furnace. As-cast microstructure and crystal structure of the alloys were investigated by using optical metalloscope (OM), scanning electron microscope (SEM) and X-ray diffractometer (XRD). The corrosion behavior of different alloys in simulated body fluid (SBF) was studied via hydrogen evolution and electrochemical test at 37℃. It is shown that the grain size decreases with the addition of Ca. And Ca exists in the precipitation phase primarily. With the increase of Ca content up to 0.5%(mass fraction,the same below), a continuous network of Ca2Mg6Zn3 is formed along the grain boundary. The corrosion resistance of the alloys is first improved and then decreased with the increase of Ca content. The alloy with 0.5% Ca shows the best corrosion resistance.
SHE Huan, SHU Da, CHU Wei, WANG Jun, SUN Bao-de. Effects of Fe and Si Impurities on the Microstructure and Properties of 7××× High Strength Aircraft Aluminum Alloys[J]. Journal of Materials Engineering, 2013, 0(6): 92-98.
Effects of Fe and Si impurities on the microstructure and mechanical properties of 7××× series aircraft aluminum alloys are overviewed. The Fe and Si impurities mainly form coarse and insoluble intermetallic particles in the microstructure. Among a variety of iron rich intermetallics, Al7Cu2Fe phase is typically found in the alloys with higher Cu content while the Mg2Si phase is the main silicon rich intermetallics. The increase of the Fe and Si contents has little effect on the strength, but markedly reduces the plasticity, fracture toughness and stress corrosion resistance of 7××× aluminum alloys in that the contents of coarse Fe-rich and Si-rich insoluble impurity phases increases.Reducing the contents of Fe and Si impurities is significant to develop the high comprehensive properties of aircraft aluminum alloys.
