Papers by Author: Jin Jun Tang

Abstract: This paper mainly studies the composition of strengthening phase, characteristic precipitation temperature and composition range of strengthening phase in Ti-Al-Mo-Zr-Si medical titanium alloy, and the influence of element changes on the content and microstructure of strengthening phase. Promote the formulation of thermodynamic process of titanium alloy powder metallurgy, as well as the formulation of alloy hot working and solid solution aging process. In this paper, Panda thermodynamic software is used to calculate the multicomponent alloy thermodynamics and multicomponent phase diagram of titanium alloy materials. The effects of Al, Mo, Zr, Si and other elements on the precipitation of strengthening phase and the phase transformation content of solidification structure were obtained. It is found that the content of Mo is more than 2 wt.% β phase transition precipitation angle. Meanwhile, in order to avoid the excess of precipitates such as Mo5Si3 and M3Si, the content of Mo should be less than 4.6 wt.%. The content of Zr can be maintained at about 1.5 wt.%. If the aging precipitation of the material is considered, it can be controlled to be less than 2 wt.%. The content of this paper is the basis and improvement of titanium powder metallurgy technology and rapid prototyping technology.

Abstract: In this paper, aiming at the heat resistance and thermal deformation process of titanium matrix composites 0 vol.%, 2.5.vol.%, 5.vol.%. Thermal simulation experiment of titanium matrix composites with different (TiB+TiC) strengthening phase content. The measurement accuracy of material displacement is 0.01 mm. The compression is 70%, and the strain rate is 0.1 mm/s and 0.01 mm/s respectively. Compression tests at different strain rates and temperatures were carried out. The experimental results show that when the (TiB+TiC) 5vol% titanium composite is deformed at 0.01mm/s low strain rate, the peak stresses corresponding to 25°C, 250°C,350 °C and 500°C are increased to 1096MPa, 835MPa, 646MPa and 416MPa respectively. Under the condition of high strain rate of 0.1mm/s, the peak stresses corresponding to 25 °C, 250 °C, 350 °C and 500 °C are increased to 1230 MPa, 896 MPa, 723 MPa and 471 MPa respectively. The deformation law of stress rheological curve is roughly the same, and the high temperature zone has good plastic deformation ability. The titanium matrix composite has high compression rheological mechanical properties and good high-temperature plastic deformation ability. It is the preferred material component for the preparation of titanium matrix composite and powder forging.

Abstract: In the quantitative characterization of linear defect structure of Piston Alloy, non-destructive testing and micro-morphology of defect, shape and outline of prefabricated linear defect are used in this paper. Based on ANSYS finite element software, an experimental simulation of line defect was carried out by using the finite element software of micromechanics. The defects of piston alloy components are assigned with material parameters, the model grid is divided, the boundary condition is defined and the finite element simulation is carried out under ANSYS/Mechanical environment. The calculation of the micro-stress field of the interface with various defects is obtained. Under the service condition of high-power density diesel engine, the local stress concentration caused by line defect is less than the strength limit of alloy material. Therefore, in this location eddy current testing non-destructive testing control line defect size is 0.12 mm×0.2 mm×5 mm. It is suitable for Eddy current nondestructive testing of piston components and can ensure the material safety and work reliability of Piston components under service condition.

Abstract: Taking M142 high power density piston alloy as the research object, using thermo Calc thermodynamic calculation. The solidification path of the alloy system is calculated in the composition range of Cu (3.5% - 6.0wt%), Mg (0.5% - 1.2wt%), Si (11% - 14wt%) and Ni (2.1% - 3.0wt%). The microstructure formation laws of Cu, Mg and Ni elements were obtained. And the relationship between residual structure and temperature and composition in different states and stages. Analysis of alloy element pairs δ Phase (Al3CuNi) γ Phase (Al7Cu4Ni) and other main strengthening phases are analyzed and evaluated comprehensively. Based on the calculation of the solidification path of the alloy, the microstructure of the alloy is optimized, especially the multi eutectic and peritectic structure platform. The microstructure content, composition and temperature precipitation space are comprehensively designed and calculated, so as to optimize the process parameters such as the best composition, temperature and pressure of the alloy.

Abstract: To calculate the multi-angle penetration, this paper established a 3D finite element model of aluminum alloy plates and 7.62mm armor-piercing by using LS-DYNA software and the Johnson-Cook material model. The process of bullet penetrating 20mm thickness target with different angles of incidence was carried out. The impact of combinations on composite targets resistance projectile penetrating ability was analyzed. Simulation results show that,ballistic of composite targets can be between two aluminum target plate, clearly different combinations of composite targets for resistance to different angles of incidence between projectile penetrating relationship.

Abstract: To solve the thermal load problem of 1015 engine cylinder liner, based on the temperature field measured, the boundary condition of 1015 engine cylinder liner was determined, a comparatively perfect mathematic mode and a geometric model are built up, and the analysis of the three dimension temperature field of cylinder liner and the thermal deformation was performed using FEA method.

Abstract: Based on the understanding of material characteristics and interaction between projectile and target, a lightweight hybrid composite armor target consisting of alumina ceramics pellets and ultrahigh molecular weight polyethylene (UHMWPE) was designed and prepared. The target areal density of the armor panel was 7.5 g/cm². The standard size of the armor panel was 150mm×150mm×43mm. The Ballistic Performance of Alumina/UHMWPE composite armor against an impact of 12.7 mm armor piercing (AP) projectile was investigated at the nominal velocity of 818 m/s. The energy absorbing mechanism revealed that the armor was able to protect against the projectile, together with weight saving.

Abstract: Heat-resistant aluminum alloy because of its low density, low price, good heat resistance and corrosion resistance, has been widely used in aviation, aerospace, weapons and other industrial fields. In this paper, preparation of Al-Fe-V-Si heat-resistant aluminum alloy materials is used in the RS/PM process, and studied the influence law of effect of alloy composition on the microstructure and mechanical properties of heat-resistant aluminum alloy. The results show that, Fe, V, Si element content and Fe/V ratio has great effect on the microstructure and mechanical properties. When the Fe content is too low, the content of Al₁₂(Fe, V)₃Si phase is less. Mechanics to improve material properties cannot be maximum; if the content of Fe is excessive, the strength of the material do not increase, but decrease the plastic. The addition of V element can be stabilized in Al₁₂(Fe, V)₃Si Si phase; and the addition of Si can inhibit the second-phase dispersion phase coarsening and decomposition, increase the high temperature stability of materials; Fe/V ratio affects the coarsening rate of second-phase particles, thus affecting the thermal stability of materials.

Abstract: High strength aluminum alloy is mainly traditional alloy hypoeutectic composition, containing the solid solubility of alloy elements atomic fraction is greater than 2, and reached the alloy trengthening effect by the precipitation of intermetallic compounds in the process of aging. But in more than 150°C, the precipitated phases coarsening, the material performance dramatically, thus limiting its use scope. In the preparation process, the planar flow casting process will melt thrown by 35-80um thick slices with, because the cooling speed can reach 10⁵K/s the process of melt, so the microstructure is very fine, after extrusion. Grain size of about 1um, precipitates spherical and uniform distribution, the size of about 50nm, Al₁₂(Fe,V)₃Si phase coarsening rate is low, so the alloy has comprehensive mechanical performance and excellent high temperature stability.

Abstract: In this paper, the directional solidification microstructure of Bridgman system was simulated using phase-field method, and different calculated results were obtained with four pulling velocities. When the pulling velocity is 0.06 cm/s, the columnar crystals competitively grow in the initial stage, and have a necking phenomenon in the last stage. When the pulling velocity is 0.04 cm/s, the columnar crystals become thinner and competitively grow all the time, and the microsegregation is bigger. When the pulling velocity is 1.00 cm/s, planar interface comes back, and solute trapping takes place. The columnar crystals become much thinner, and microsegregation decreases. When the pulling velocity is 3.00 cm/s, the grain boundary of columnar crystals becomes unconspicuous, and the degree of microsegregation approaches 1.