Bao Hong Zhu’s research while affiliated with Wanhua Chemical Group Co.,Ltd. and other places

AlSn20Cu alloy is currently one of the most widely used bearing materials, and its microstructure is the most important indicator in application. In this paper, AlSn20Cu alloy ingots were prepared by two methods: ordinary casting and semi-continuous casting, and deformation and annealing process of the two ingots were studied. Scanning electron microscope (SEM) and Image Pro Plus software were used to observe and analyze the evolution of the microstructure, and the morphological information such as the average grain size and area fraction of the Sn phase was quantitatively characterized. The effects of casting method, deformation temperature, deformation amount and annealing temperature on the morphology of Sn phase were studied in this paper. Compared with ordinary casting, the cooling rate of semi-continuous casting is higher, so the Sn phase is smaller, the casting defects are less, and the deformability of the alloy is better. The AlSn20Cu alloy prepared by ordinary casting has better deformability at about 140 °C, while the AlSn20Cu alloy prepared by semi-continuous casting can be rolled and deformed at room temperature. When the deformation is greater than 40%, after annealing at 250 °C, the average grain size of the Sn phase in the AlSn20Cu alloy prepared by semi-continuous casting is around one hundred square microns and the area fraction is more than 10%, and the Sn phase morphology is better than ordinary casting alloy under any processing conditions.

The hot deformation behavior of spray-formed AlSn20Cu alloy during hot compression deformation was studied, and the constitutive equation of AlSn20Cu alloy was established. The samples of spray-formed AlSn20Cu alloy were compressed on Gleeble-3500 thermal simulation test machine. The error of the true stress caused by adiabatic heating effect in the experiment was corrected. The constitutive equation of spray-formed AlSn20Cu alloy could be represented by Zener-Hollomon parameter in a hyperbolic sine function. The results showed that the deformation temperatures and strain rates had a notable effect on the true stress of the alloy. At the identical deformation temperature, the true stress increased with the increase of strain rate. When the strain rate was constant, the stress decreased with the increase of deformation temperature. After hot compression deformation, the tin phase was elongated along the direction perpendicular to the compression axis with short strips and blocks. With the increase of deformation temperature and the decrease of strain rate, Sn phase distribution became more homogeneous.

The electron beam melting-printed Ti6Al4V shows a great potential application for orthopedic implants and aerospace in recent years. A systematic study on the microstructure of additive manufactured Ti6Al4V by electron beam melting both parallel to and perpendicular to the building directions (Z axis) is presented in the present investigation. The results showed that the microstructure of the alloy was α lamina with HCP structure and β bar with BCC structure. The original β phase grew as columnar crystal along the direction of construction, showing an equiaxial shape in the cross section, numerous small α lamellae block the original β phase, and presenting a cluster distribution on the original β grain boundary, and a basket-like distribution in the original β grain. This may be due to the rapid cooling of the small pool after melting, the repeated heating of the subsequent constructed layer on the formed layer, and the subsequent limited vacuum cooling, resulting in the formation of the micro morphology, which leads to the original β grain boundaries broken, and the formation of a distinctive basket or widmanstatten structure [1, 2]. In addition, XRD results indicated that there was α′ martensite, part of which has been decomposes into α phases and β phases, SEM and TEM experiments also proved this. Of note is that random distribution dislocation was observed in TEM. Using EBSD results, and it may be understand that the sample build direction was parallel to [0001] crystal orientation and build plane parallel to (1210) and (1100) crystal facets.

The 8009 aluminum alloys were fabricated by spray forming and extrusion process. The microstructure and properties of the alloy were investigated by means of metallographic, scanning electron microscope and tensile test. The results indicate that at room temperature, the tensile strength of the extruded alloys can reach 415MPa, the yield strength 345MPa, elongation 22.5%. The tensile strength and yield strength of the alloys decrease with the increasing temperature, the plastic of alloys shows a down-up medium temperature brittleness law.

Heat-resistant Al-8.5Fe-1.3V-1.7Si aluminum alloys were prepared by spray forming technique. The phase transition of deposited alloys from room temperature to 500°C was measured by Differential Scanning Calorimeter. The organization and the second phases of the alloys were observed and studied by transmission electron microscopy. The research results show that No endothermic peak appears in the deposited alloys during heating process, there is no phase transition occur in the alloy during the heating process from room temperature to 500°C. The deposited alloys mainly include α-Al and α-Al12(Fe,V)3Si phase. Under the transmission electron microscopy, there are also a small amount of slug, fan-shaped, needle-like, block, strip second phases, these phases are Al12Fe3Si, Al8Fe2Si, θ-Al13Fe4, Al9FeSi3, Al6Fe.

In this paper, the Al-8.5Fe-1.3V-1.7Si alloys were fabricated by spray forming and extrusion process. The microstructure and mechanical properties of the alloy were investigated by means of metallographic, scanning electron microscope and tensile test. The results indicate that the tensile strength of the extrued alloys can reach 353MPa, the yield strength 300MPa, elongation 19.12%, at room temperature. At 250°C, the tensile strength of the extrued alloys can reach 221MPa, the yield strength 208MPa, elongation 13.33%.

This study examines the effects of the addition of Mn or Zr on the microstructure and mechanical properties of Al–Cu–Mg–Ag alloy using optical microscopy, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, transmission electron microscopy, tensile test, and tear test. The results showed that the alloy with Zr exhibited the highest strength and the lowest fracture toughness, which may be attributed to the segregation of the secondary phases containing the Zr element on the recrystallization grain boundaries. The alloy with Mn exhibited strength that is roughly equal to the Al–Cu–Mg–Ag alloy and the highest fracture toughness, which may be due to the formation of secondary phases containing Mn and Fe elements. Mn or Zr addition also has no remarkable influence on the characteristics of the precipitates. The Ω phase and a small quantity of θ′ phases dominated the microstructure of the three alloys after aging.

The microstructure of 5182 alloys, standard and modified by Zr, before/after homogenizing heat treatment were investigated by optical microscope (OM), scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS) and transmission electron microscope (TEM). The microstructures on optimum condition for homogenizing heat treatment and the effect of Zr were discussed. It is found that the intermetallic compounds formed on the grain boundaries are less in Zr modified 5182 than 5182 alloys for the as-cast structure. After the two alloys homogenized at 475 for 24h, the dendritic structure disappear and intermetallic compounds become discontinuous, Al2Mg3 phases are decomposed, and there are some precipitates of Al6(Mn,Fe) and Al6Mn in the grain interior. In addition, precipitates of Al3Zr distributed in the matrix of Zr modified 5182 alloys.

In the present work, quench sensitivity of an Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr alloy is investigated by temperature-time-property (TTP) curve and TEM analysis, comparing with traditional AA 7B04 and AA 7150. The results indicate that the nose temperature of TTP curve and the corresponding incubation period of the alloy, AA 7150 and AA 7B04 are about 290°C/4.5s, 320°C/2.6s and 335°C/0.1s, respectively, The nose temperature of the alloy is the lowest among three alloys and the critical time at the nose temperature is the longest for the alloy, which is obvious that the alloy has lower quench sensitivity. Further TEM analysis shows that, with the prolongation of keeping time at the nose temperature, quench-induced precipitation phenomenon becomes obvious.

In this present work, the microstructure and properties of an Al-7.5Zn-1.5Mg-1.4Cu-0.12Zr alloy forging in T7452 condition has been investigated by means of OM, TEM and EBSD analysis and varied properties test. The results indicate that there are obvious differences in grain morphology, precipitation characteristics and recrystallization degree along the thickness direction of the forging. The strength of the alloy forging is stable and varies less than 10% along the thickness direction. The alloy forging in the T7452 condition shows high strength, high toughness and good corrosion resistance, with the UTS, TYS, elongation and electrical conductivity values being 500 similar to 530 MPa, 460 similar to 500 MPa, 7.0 similar to 15.0% and 23.9 similar to 24.2 MS/m, respectively, and the fracture toughness in L-T, T-L and S-L direction being 33.5 similar to 39.5, 25.5 similar to 27.0, 23.0 similar to 24.5 MPa.m(1/2), respectively, and the EXCO rating being EA.