Papers by Author: Zhi Min Yin

Abstract: The fatigue characteristic of 2124 aluminum alloy in T851 condition was investigated by means of scanning electron microscopy (SEM) and transmission electron microscope (TEM). And the result shows that, the fatigue life is closely related to the thickness of plates, this is because that different thickness of plates results in the variation of grain size, grain boundaries and substructures of alloy, which thus influence the fatigue behavior of 2124-T851 alloy. The number of grain boundaries along the propagation direction of cracks and the amount of substructures after heat treatment increase with the decline of thicknesses of 2124 alloy plates, while the grain size is reverse. However, no obvious size and dispersion changes for the precipitates. Comparatively, the fatigue resistance performance of 30mm thickness plate is better than the 40mm and 55mm thickness plates, which is due to the more profitable grain size, grain boundary and substructure.

Abstract: Heterogeneity of composition and microstructure in cast large sized 3104 aluminium alloy slab were studied using AES-ICP, OM, SEM, etc. The results show that the cooling rate on the cross section of 3104 slab is different, macro-segregation is found in the different section in the slab .The content of Ti decreases gradually from the surface to about 1/4 thickness of the slab, then increases rapidly to the center of slab; other elements content increases gradually from the surface to the about 1/4 thickness and then decreases rapidly to the center; the grain size on the surface area is fine, and the grain size at the center is coarse , segregation of Mg is found within the grains; great amount compound is found to be of presence on the grain boundary, with chemical compositions of Al 87（FeMn）13 and Al83（FeMn）12Si5; The compound size at the surface area is comparatively smaller, and coarser at the centre of slab.

Abstract: The online-quenching process of 6005 aluminum alloy was simulated by using Abaqus software, the stress field of alloy profile in different quenching temperatures and quenching processing were obtained. The results indicate that during quenching the temperature of the profile is decreasing and the internal stress gradually increasing. At the same time the stresses of different parts of the profile are different, the maximum stress is at the corner, the second in the center and the rest lower. Under the premise of keeping the performance of the alloy, the internal stress after step quenching is significantly lower than that after one-time quenching.

Abstract: Effect of content of Fe,Si and Fe/Si on Structure and Properties of 3014 can-body were studied by using tensile test, stamping test, SEM, XRD, etc. The results show that:(1) The sum of Cube and Goss texture in 3104 aluminum-alloy canbody is about 40%. The influence of brass texture{011}, S texture{123}, copper texture Cu{112}, cube texture{001} and Goss texture{011} is balanced, resulting in ears in 8 directions and low earing rate. Fe/Si of 1.8 possesses less content of Brass compared to Fe/Si of 3.2 ，and less earing rate; (2)The phase size of compound particles of Al(Fe,Mn,Si) in the second phase of 3104 aluminum-alloy canbody shouldn’t exceed 22μm, Lumpy compound particles will compromise the life of moulds.

Abstract: The residual stresses on the top surface and side face of the diamond layer of PDC with 25.4mm in diameter and 3.2mm in thickness were measured using Micro-Raman Spectroscopy, thus the stresses and their radial and vertical distributions were obtained. To evaluate the magnitude of the thermal residual microstress in the diamond layer of PDC, the tungsten carbide substrate of PDC was cut by electric discharge machining (EDM), and several Raman measurements were performed on the top surface of the diamond layer. The results show that 1) the stresses in the central part of the diamond surface are compressive, the biggest stress is about 600 MPa, the magnitude of the stress decreases from the center to the edge of PDC, and at about 2mm near the edge of PDC, the stress becomes tensile; 2) the stresses on the side face of the diamond layer are tensile, the maximum is about 580 MPa near the interface. These tensile stresses are thought to be one of the main factors to cause delamination of PDC used for cutting tools; 3) the measured value of the microstress in the diamond layer is 62.5MPa.

Abstract: The influence of aging treatment on microstructure, mechanical and electrical properties of 7A52 alloy was investigated by mechanical property test, electrical conductivity measurement, XRD and TEM analysis. The results showed that the alloy was a typical aging hardening alloy. During aging supersaturated solution decomposed, G.P. zones and η'(MgZn2) precipitated. The precipitates of the alloy aging at 100°C were mainly G.P. zones with the size of about 5nm. During aging at 120°C, η’ precipitates nucleated from the G.P. zones. With increasing aging temperature and time, the size and amount of η' increased. As aged at 120°C for 24h the tensile strength, yield strength, elongation and electrical conductivity of the alloy were 496 MPa, 445 MPa, 9.5% and 26 %IACS, respectively. The G.P. zones and η' dispersion strengthening are the major strengthening mechanisms for the studied alloy at the single-stage peak aging.

Abstract: The effect of Sc and Zr on the fatigue property of Al-6.2Mg-0.4Mn alloy was investigated by control experiment; the fatigue lives of Al-6.2Mg-0.4Mn alloy with and without Sc and Zr at different loading stress amplitudes were measured. The relationships between their fatigue properties and microstructures were studied by means of optical microscope, scanning electronic microscope and transmission electron microscope. The addition of Sc and Zr improved the fatigue lives and fatigue strength of Al-6.2Mg-0.4Mn alloy. It is difficult for crack to initiate and propagate in the Al-6.2Mg-0.4Mn-Sc-Zr alloy. The fine and pancake-like grains of this alloy lead to the increase of fatigue life and fatigue strength. The high densities of dislocation and grain boundary in the Al-6.2Mg-0.4Mn-Sc-Zr alloy can prevent microcrack from propagating effectively. Additionally the dispersion precipitation of Al3Sc and Al3(Sc1-xZrx) particles enhance the toughness of Al-6.2Mg-0.4Mn-Sc-Zr alloy.