ZHENG Liang, GU Chen-qing, ZHENG Yun-rong. Microstructure of Ru-containing Cast Nickel Base Superalloy[J]. Journal of Materials Engineering, 2002, 0(5): 3-6.
The effect of 3%(mass fraction) Ru on cast Ni-base superalloy with low content of Cr and high content of W was investigated The as-cast microstructure of two kinds of alloys in which 3%(mass fraction)Ru was added or was not contained, the microstructure after 1260℃/4h, 1260℃/4h+1280℃/4h, 1260℃/4h+1300℃/4h solid solution heat treatment and after 1260℃/4h+1100℃/100h thermal exposure test have been comparatively studied The results indicate that the sorts of precipitation is not changed by the addition of Ru Ru influences the stability of γ′ phase and M6C carbide It can decrease the solid solution temperature of γ′ about 10℃ and the Ru-contained alloy tends to transform to the rafted structure at the temperature of 1100℃ Furthermore, Ru can restrict the formation of primary and secondary M6C, and it is beneficial to stabilizing the microstructure of superalloy.
LI Ying, SU Bin. Cyclic Deformation of Single Crystal Nickel Base Superalloy DD6 at 760℃[J]. Journal of Materials Engineering, 2002, 0(5): 7-10.
Fully reversed low cycle fatigue tests were conducted on [001] and [111] oriented single crystals of the nickel base superalloy DD6 at 760℃ The results show that the [111] and [001] specimens under high total strain amplitudes exhibit cyclic hardening depending on the imposed total strain amplitudes, and this cyclic hardening is related to the dislocation-particle interactions. There are two different factors that act on the tension-compression asymmetry of the DD6 under cyclic loading, the LCP-model mechanism and mechanical hardening mechanism. Which mechanism will dominate the asymmetry lay on the imposed total strain amplitudes.
YUAN Chao, GUO Jian-ting. Endurance Life of a Directionally Solidified Nickel-Base Superalloy DZ17G[J]. Journal of Materials Engineering, 2002, 0(5): 11-13.
The stress-rupture data at high temperature (650～980 ℃) and in a wide range of applied stress (105～950MPa) in a directionally solidified nickel-base superalloy DZ17G has been analysed. The results show that a semi-logarithmic law can describe the relationship between the endurance life and applied stress at a given temperature. It is suggested that the endurance life can be predicted in terms of Manson-Succop time-temperature parameter. The endurance life equation and the thermal-strength parameter equation of DZ17G superalloy are given in this paper. The endurance life predicted by parametric equation conforms to the experimental results.
DING Shuo, WEN Guang-wu, LEI Ting-quan, ZHOU Yu. Preparation of Nano-micro Particles Reinforced B4C Matrix Composite by In situ Reaction[J]. Journal of Materials Engineering, 2002, 0(5): 14-17,21.
A novel nano-micro particles reinforced B4C matrix composite, Al2O3-TiB2/B4C, has been designed and fabricated via in-situ synthetic reaction. Theoretical calculations and experimental results show that the anticipated in-situ reaction can be conducted at relatively low sintering temperature of 1950℃, while high density is obtained. In the composite, fine intergranular Al2O3 and TiB2 particles disperse homogeneously in the matrix, while the nano Al2O3 particles are uniformly located within the matrix grains. It indicates that the inter intragranular structure shapes in the composite. The Al2O3-TiB2/B4C composite is an excellent structural material owing to its outstanding mechanical properties The Vickers hardness of the composite is 28.8GPa. The fracture toughness of the composite reaches a high value of 8.27MPa·m1/2. Compared with pure B4C, the wear resisting property is doubled with the value of KIC3/4·HV1/2 of 26. Furthermore, the toughening mechanism of the nano-micro composite is discussed.
ZHU Zi-xin, XU Bin-shi, ZHANG Wei, DU Ze-yu. Microstructure and Properties of Iron Aluminide Coatings Prepared by High Velocity Arc Spraying[J]. Journal of Materials Engineering, 2002, 0(5): 18-21.
The microstructure and properties of iron aluminide intermetallic coatings in-situ synthesized by cored wire and high velocity arc spraying (HVAS) were investigated. Chemical compositions of the coating were also analyzed The results show that the compositions are Fe-13.87Al-17.27C-3.35W-2.59Ni-1.27Cr-18.14O (atom fraction,%). The microstructure is consisted of Fe3Al, FeAl and α-Fe regions mainly, together with WC, W2C hard phases and fine oxide (Al2O3) layers. Moreover, TEM images of the coating show that the solidified splats are polycrystalline and have a fine grain size, and also indicate partial amorphization in some areas. It can be concluded that a very high cooling rate is obtained during HVAS process. Moreover, the iron aluminide intermetallic coating has relatively higher adhesion strength and microhardness, as well as lower density and porosity.
ZHANG Yong-zhong, XI Ming-zhe, SHI Li-kai, CHENG Jing, Xu Jun. Research on Laser Direct Deposition of 316L Stainless Steel[J]. Journal of Materials Engineering, 2002, 0(5): 22-25.
This paper reports on laser direct deposition of 316L stainless steel The microstructure and coating appearance for single cladding and multiple cladding under different laser power and scanning speed, the microstructure and properties of thin wall fabricated under different processing parameters are given in detail. Based on these, bulk material with simple shape and thin parts with complicate shape are formed successfully. The results indicate that the as-deposited parts are fully dense with rapid solidified microstructure. The mechanical properties are equivalent to that for casting and wrought annealed materials, and can meet the requirement for real usage.
LIU Tian-qi, ZHI Min-xue, ZHU Jie-yuan, LI Zhi, ZHAO Zhen-ye. Effect of Heat Treatment on Microstructure and Mechanical Properties of 0Cr13Ni8Mo2Al Steel[J]. Journal of Materials Engineering, 2002, 0(5): 26-29.
The effect of heat treatment on microstructure and mechanical properties of 0Cr13Ni8Mo2Al steel has been studied. The results show that: the lath martensite with high density dislocation and the formation of finely distributed β-NiAl phase coherent with the matrix are responsible for the high strength in this steel. The highest strength and the lowest impact toughness are gained on aging at temperatures about 530℃ and 510℃ respectively. The embrittlement of the steel on aging is not related to decomposition of austenite.
JIANG Zhong-liang, Wu Yan, CHEN Xiu-yun, BAI Fei-ming, LIU Xiu-ying, HUANG Tie-guang. Grain Refinement of δ/γ Duplex Stainless Steel by Heat Treatment[J]. Journal of Materials Engineering, 2002, 0(5): 30-33.
To eliminate the harmful effect of coarse δ ferrite, the method to refine the grain size of the Cr25Ni5Mo1.5 duplex stainless steel was investigated through heat treatment. The reactions employed in the heat treatment were σ reaction δ→γ+σ and anti-σ reaction γ+σ→δ. The results show through 750℃×38h σ treatment, the δ ferrite transforms to composite of fine γ and σ phases. Very fine δ ferrite can be obtained through rapid heating anti-σ treatment. After refining ferrite, the impact toughness of Cr25Ni5Mo1.5 increases greatly and the morphology of the fracture surface of the impact sample at 50 ℃ changes from large cleavage to fine dimples.
WANG Fei, ZHANG Lan-ting, SUN Jian, WU Jian-sheng, ZHAO Bin. The Effect of Heat Treatment on Microstructure of a Cast TiAl Alloy[J]. Journal of Materials Engineering, 2002, 0(5): 34-36.
The effect of heat treatments on microstructure of a cast Ti-47Al-2Nb-2Cr-0.2Si(atom fraction,%) alloy was investigated. The results show that the microstructure of the rapidly cooled cast alloy is single γ lamellae structure. The phase constitution and grain size of the cast alloy can be adjusted through various heat treatments. After a suitable heat treatment, the grain size reaches 40-50μm.
MA Qing-song, CHEN Zhao-hui, ZHENG Wen-wei, HU Hai-feng. Fabrication of Three dimensional Carbon Fiber Reinforced Si-O-C Composites via Polymer Pyrolysis Assisted by Hot pressing[J]. Journal of Materials Engineering, 2002, 0(5): 37-39.
Three dimensional braided carbon fiber(3D-B Cf) reinforced silicon oxycarbide(Si-O-C) composites were fabricated via precursor infiltration and pyrolysis using polysiloxane and divinylbenzene. The effect of processing on microstructure and properties was discussed. The results show that the density and mechanical properties of 3D-B Cf/Si-O-C can be increased markedly if the first pyrolysis cycle is assisted by hot-pressing. The flexural strength and the fracture toughness of the composite, which is hot-pressed at 1600℃ for 5min with a pressure of 10MPa in the first pyrolysis cycle and treated subsequently with six cycles of vacuum infiltration and pyrolysis under atmospheric pressure, are 502MPa and 23 7MPa m1/2, respectively. The high properties are mainly attributed to ideal interface structure and high density.
WUYUN Qi-qi-ge. Influence of Pre-polymerizing Process on Properties of 3233 Resin Matrix Composites[J]. Journal of Materials Engineering, 2002, 0(5): 40-41.
The batch stability of the pre-polymer for 3233 resin system was reported in this paper. The comparison between the properties of composites fabricated from large-scale produced pre polymer and small-scale synthesized one was also given.
ZHANG Wei-fang, LIU Gao-yuan, GAO Wei, TAO Chun-hu, ZHAO Ai-guo. Fatigue Life Retroestimation of Wing Structures on Different Load Spectra[J]. Journal of Materials Engineering, 2002, 0(5): 42-45.
The macro and micro-fracture characteristics of wing structures on two load spectra were observed. Crack spread life on different load spectra for wing structures on A and B airplane was retroestimated on account of stress distribution respectively. The results show that different macro and micro-fracture characteristics on fatigue spread zone are formed with the variety of stress distribution in a load spectrum. The fatigue life of engineering structure can be retroestimated by means of fracture quantity analysis. Also, the crack formation sequence can be obtained.
HUANG Fu-xiang, MA Ju-sheng. The Fracture Failure Analysis of 20CrMo Connecting Rod[J]. Journal of Materials Engineering, 2002, 0(5): 46-47,10.
The reason of fracture of 20CrMo motorcycle connecting rod has been analyzed by EPMA and optical metalloscope. The failure mechanism has been discussed. The results showe that the connecting rod is quenched to form coarse needle martensite microstructure at the surface layer, and resulted in the connecting rod brittle fracture with intergranular cracking.
