Applied Mechanics and Materials Vols. 275-277

Abstract: TiN coatings were deposited by Magnetron Sputter Ion Plating (MSIP) on the surface of high-speed steel W18Cr4V.The microstructure,coating thickness, micro-hardness and wear resistance of surface modification sample were investigated by the D/MAX-ⅢB X-ray diffraction tester, the coating thickness tester, the HV-1000 micro-sclerometer,the LKDM－2000 friction and wear tester,the S-3000N scaning electron microscopy.The influence of sputtering time,N2 partial pressures and sputtering current on the microstructure,coating thickness, micro-hardness and wear resistance of TiN coatings were also analysed.The best synthesis performance sputtering coatings of technologic scheme was established.

Abstract: QP steel has great application potential for automotive industry for its ultrahigh strength and good plasticity. In this paper, the forming limit diagram (FLD) of QP steel was experimentally studied using spherical punch test. The forming limit curves (FLC) of QP steel in room temperature under two pressing velocities (20mm/s, 2mm/s) were obtained. It has been found that the deformation velocity affects the FLC obviously; the FLC declines with the increase of pressing velocity. Compared with other AHSS under the same strength grade, QP steel keeps high strength without a significant loss of plasticity.

Abstract: The low silicon sintered ores are prepared, where SiO2 content is 4.4%, 4.6%, 4.8%, 5.0% and 5.2%, respectively. Their metallurgical properties are also measured. The results state that the low temperature reduction degradation of low silicon sinter is improved with the SiO2 content increase. With the SiO2 content increasing in low silicon sinter, the reducing index sharply decline, and reduction gradually deteriorate. In the meantime, softening initial temperature gradually reduced, softening interval gradually widened, so exceeded SiO2 content does harm to softening property.

Abstract: An investigation on behavior of the early stage of aging and its influence on theperformance of C17200 alloys is conducted in this paper. It is indicated that spinodal decomposition occured when the specimen is aged at 320 °C ,leading to the formation of G.P zones. A phase transformation from metastable precipitates to stable phase occurred with the increasing aging time, the sequence of which is believed as G..P→γ′′→γ′→γ. Spinodal decomposition and ordering of the matrix are found together in C17200 alloy.

Abstract: The effect of different tungsten addition on microstructure and mechanical property of TiAl-based alloy was investigated. The results indicate that the size and amount of β (B2) phase and equiaxed γ phase gradually increase with increasing content of tungsten. The grain size and lamellar spacing obey a parabolic law. The tungsten addition can increase the room temperature strength, high temperature strength but have a little effect on the ductility. The creep rupture life has inverse correlation relationship with the content of tungsten.

Abstract: Based on the production practice of boron microalloyed medium-carbon steel, oscillating curve, cooling water flow in mould, secondary cooling system and arc alignment precision, rolling gap precision on transversal corner crack in slab was analyzed, and the corresponding control measures were put forward. Such as: Stabilizing the [S] and making w(S） less than 0.015%; Increasing Mn/S, and making the Mn/S was not less than 37.6 in A36-LB; Strictly controlling the w(Ca)/w(Als) was more than 0.09. Decreasing stroke 1mm and improving frequency to reduce negative sliding time 32%; Stabilizing cooling water around 4000/380 L/min, less cooling, reduce the total water cold water and 50% Side water; Testing rolling gap termly, strengthening maintenance and Replacing bad roller column to make sure precision in the reasonable scope, the measures above suppressed the corner crack in slab effectively, and it’s degradation ratio and quality disputes were below that of Q235B in the mouth production level.

Abstract: The Mg-Gd alloy, Mg-Y alloy equilibrium phase diagram has been characterized using the multiple phase equilibrium calculation software (Pandat) and the magnesium alloy thermodynamic database. The Mg-Gd and Mg-Y diffusion couples were made by the rivet method. According to the local balance principle, these diffusion couples were processed using an equalization treatment at 450 °C, followed by EDS analysis with a scanning electron microscope. The results show that a concentration gradient resulting from atomic diffusion is apparent in the Mg-Y and Mg-Gd diffusion layer, showing that the diffusion layers belong to different phases. There are 5 two-phase regions and 2 single phase regions in the Mg-Gd diffusion layer and 4 two-phase regions and 2 single phase regions in the Mg-Y diffusion layer. These results are consistent with the data from the phase equilibrium calculation. This research can provide experimental support for the Mg-Gd-Y three element alloy phase diagram calculation.

Abstract: In the present research, a series of AZ80 magnesium alloy billets were compressed with 60% height reduction on hot process simulator at temperatures of 473,523,573,623,673,723K under strain rates of 0.001, 0.01, 0.1,1 and 10s-1. The value of the Cockcroft-Latham equation, i.e. critical damage value, was calculated from the finite element calculations for the compression tests. The results show that the critical damage value is not a constant but varies in a range from 0.1397 to 0.4653. Meanwhile, the processing maps based on the Dynamic Material Modeling (DMM) were constructed. From the processing maps, the optimal deformation processing parameters are the deformation temperatures ranging from 573 to 623K and strain rates ranging from 0.001 to 0.01s-1 in view of improving the mechanical properties of AZ80 alloy component.

Abstract: The bonded MoS2 films are widely used as solid lubricants in aerospace mechanisms due to their excellent tribological properties. Traditionally, the MoS2 was directly bonded on the Al substrate that was only treated by the technique named of sandblast. For improving the tribological properties of MoS2 films, micro arc oxidation (MAO) instead of sandblast was introduced as a new technique for treating of Al substrate. In this article, the tribological properties of MoS2 films which were bonded on different surface of Al substrate as mentioned above were discussed, respectively. It was concluded from the test results that the MoS2 films bonded on substrate treated by MAO have better tribological properties than those samples treated by sandblast. The endurance life against abrasion of the former is as high as twenty times of the latter by the stand test method of ball on disk using the UMT Multi-Specimen Test System. This test results could be illustrated by the following reasons. The first is the porous microstructures of MAO ceramic coatings on the Al substrate. The coatings have numerous pits to be good at increasing the binding force with the MoS2 films, and the pits can also provide a MoS2 lubricants reservoir during processes of friction. Both of them improved the MoS2 film’s ability of wear-protective. The second is that hardness of the coating is higher than the Al, and this ensures well wearing resistance, especially in practical application to big load-supporting moving parts, such as bearing, gear, etc…

Abstract: WC-Co cemented carbide specimens were prepared via vacuum sintering. The influences of composition and sintering temperature on phase composition, microstructure and mechanical properties of WC-Co cemented carbide were investigated. The results show that dense specimens were obtained in the sintering temperature range of 1280~1400°C and the relative density reached over 95%. Only WC and Co3W3C (-phase) were detected by XRD without any else phases, even though Co. With the ascended sintering temperature, hardness increased and the transverse rupture strength (TRS) ascended to peak value and then descended. WC-Co cemented carbide with excellent mechanical properties (HRA>90, TRS~700MPa and KIC>10MPa•m1/2) were obtained.