Papers by Author: Li Jun Zhu

Abstract: High strength tungsten alloys with different deformation of 20%, 40%, 50% and 60% were prepared by swaging, and the impact strength and impact fracture morphologies were tested and observed respectively by Charpy tester and SEM to study the influence of deformation degree on fracture behavior. The results show that with the deformation degree increasing from 20% to 40%, 50% and 60%, the toughness reduces from 99J to 51J, 43J and 29J. The fracture mode of impact changes from intergranular to cleavage fracture.

Abstract: The penetration characteristics of tungsten fiber reinforced metallic glass matrix composite with different tungsten fiber spacing were simulated by LS-DYNA programme. It is indicated that J-C constitutive model for describing deformation behaviour of tungsten fiber can accurately reflect the penetration process of the composite. The simulation results show that the composite has obvious self-sharpening behaviour, and its penetration performance is higher than tungsten alloy. The higher penetration performance depends on close-packing of tungsten fibers separated by metallic glass.

Abstract: Because of excellent mechanical, physical and chemical property Wf/Zr-based amorphous matrix composite attracts people’s interest and becomes the hot spot of science study and engineering application. In this paper, change regulation of hardness of target around crater by Wf/Zr-based amorphous matrix composite projectile and its mechanism are studied after firing test, and it is found that the section can be divided into 3 layers: the Martensite layer, the deformed fine grain layer and the normal matrix from the crater surface to the interior of the steel target and that the thickness of Martensite layer increases first and then decreases in the penetration direction when the velocity of projectile is 1200m/s.

Abstract: W_f/Zr-based amorphous matrix composite is supposed as a potential penetrator material of armor-piercing projectile because it has both advanced piercing performance and environmentally friendly property, and it becomes the hot spot of science study and engineering application. To get a deeper understand of the penetration mechanism and the influence of temperature rise on structure of target, target which is penetrated by penetrator made of W_f/Zr-based amorphous matrix composite is studied by SEM and micro-hardness tester. Oxidation of back of target is severe, and Martensite transformation happens around the crater. From the crater surface to the interior of the steel target, the section can be divided into 3 layers: the Martensite layer, the deformed fine grain layer and the normal matrix. Martensite transformation indicates the target steel around crater is heated and softened in penetration, so this phenomenon is beneficial to penetrate and get a deeper understand of the penetration mechanism. CLC: TJ04 Document code: A

Abstract: Contrast ballistic tests were carried out on 93W alloy and W fiber reinforced Zr-based bulk metallic glass composite. The influence of penetrator material on micro-hardness around target crater was studied using microstructure observation and micro-hardness test. The results show that adiabatic shear band appears in both targets after severe plastic deformation of impact. The effect of composite on micro-hardness of target is greater than that of W alloy, and the thickness with high micro-hardness around target crater formed by composite penetrator is 2.5 times than that by W alloy penetrator.

Abstract: The effect of yield strength and elastic modulus of matrix on shear stress in two phases of composite reinforced with W fiber under pulse loading was simulated by ANSYS software. The results show that the effect of mechanical properties of matrix on composite should be taken into consideration in designing composite. The matrix with high yield strength and low elastic modulus can reduce the shear stress in W fiber, and is beneficial to keeping the integrity of W fiber during penetration, thus resulting in the improvement of penetration capacity.

Abstract: The morphology and collection rate of Cu-30wt%Ag alloy nano particle prepared by induction plasma system with different power were studied. The results indicate that with the power of plasma increasing from 30 KW to 45 KW and then to 60 KW, the average size of Cu-30wt%Ag nano particle of 89 nm, 72 nm and 50 nm is obtained respectively, and the collection rate improves from 47.5% to 50.1% and 55.2%. Meanwhile, the plasma power has an obvious effect on the specific area of nano particle.

Abstract: Mechanical properties of Al-Mg porous materials which were made by self melting reactions at low temperatures are investigated in this work. The results showed that the yield strength of Al-20%Mg was up to 240 MPa, and this is the compressive characteristics of brittle porous materials. The excellent of mechanical properties of Al-Mg porous material was analyzed and the reason was ascribed to the homogenous distributed pore with cell wall strengthening.