Zhi Hao Zhao

Experimental Study on Horizontal Continuous Casting of 6061 Aluminium Alloy Bar Process

The aluminium alloy bar is mainly obtained by hot extrusion in the past. In order to increase the production efficiency and reduce the cost, a new mold is designed, and horizontal continuous casting is used to produce the aluminium alloy bar in this work. The results show that aluminium alloy bar can be cast by horizontal continuous casting. The asymmetry of the sump is overcome by optimizing the design of the mold. When the temperature of the melt was 730°C, casting speed is 650 mm/min, cooling water is 15 L/min, the quality of lubricating oil is 0.5 ml/min, and the ingot with good surface quality can be cast.

The Effect of Al-5Ti-1B and Combination Electromagnetic Field on Grain Evolution of Die Casting Commercial Aluminum

The effect of increasing the amount of added grain refiner and combination electromagnetic filed on grain size and morphology has been investigated by die casting of commercial aluminum. The results show the grain size and the grain morphology both are transited with the increasing of the addition of Al-5Ti-B. The grain size continuously decreased with increasing the addition of grain refiner. Without grain refiner additions, an obvious transition in grain size and morphology is observed with the application of low frequency electromagnetic field (LFES). The efficiency in grain refinement of LFES decreases with increasing the amount of grain refiner. However, even when the addition of grain refiner is 2 wt. % Al-5Ti-B, 63 % grain size reduction still is observed by the affect of LFES. This result shows that the LFES can enhance the efficiency in grain refinement of grain refiner.

Effect of Zn, Mg, Cu, Zr on Microstructure and Properties of Laser Welding Aluminium Alloy

A series of Al-6.3Zn-2.3Mg-2.3Cu-0.15Zr alloys with different reduce of Zn, Mg, Cu and Zr were prepared by ingot-metallurgy processing. The metallurgical structure and mechanical properties were investigated by optical microscope, scanning electron microscopy and other equipment. The results indicated that the ingot’s microstructures of the four alloys contain the phrases of η (MgZn2) and θ (Al2Cu), which mostly distribute at the grain boundaries in a shape of continuous network. After extrusion processing, the grain of laser welding aluminium alloy was elongated along the extrusion direction, therefore forming fibrous structures, and meanwhile the second phase particles with different degrees of fragmentation were arranged along the extrusion direction since the microstructure of extruded bars was inherited by the as-cast structure. Zr could significantly inhibit recrystallization of alloy; the recrystallization of the alloy with lower Zr was more obvious. As the content of Zr reduced, the tensile strength of alloy decreased, but the electrical conductivity and hardness increased. When the content of Cu was lower, the hardness were decreased.

The Structure Evolution of a 99.995 Percent High Purity Aluminum during Multi-Forging Process in Room Temperature

In this study, a purity of 99.995percent high purity aluminum was multi-directionally forged up to a maximum cumulative strain of 4.5 at room temperature. The macro and micro structure evolution in the multi-directionally forge process was investigated by structure observations and hardness measurements. The results show that the inhomogeneous deformation of multi-directional forging results in that the structure and hardness is quite different between the easy deformation zone and stagnant zone. Dynamic recrystallization occurs in easy deformation zone of high purity aluminum sample at room temperature as the cumulative true strain is 1.5 (3 forging passes), while the structure in the stagnant zone is still not recrystallizated even at a cumulative true strain of 4.5 (9 forging passes). The recrystallized grain size in the easy deformation zone is reduced with the number of forging passes, and the area of recrystallize grains increase with the number of forging passes.

Grain Refinement of Direct Chill Cast 7050 Aluminium Alloy with Low Frequency Electromagnetic Field

Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy 162mm ingots and study its effect on the as-cast microstructure. Effects of electromagnetic field parameters such as frequency and current intensity on microstructures were systemically investigated. The results showed that LFEC has a significant grain refining effect on 7050 alloy. The microstructures of LFEC ingot from the border to the center of the cross section are all equiaxed or nearly equiaxed grains which are much finer and more uniform than those of DC cast ingot. It was also found that electromagnetic field frequency and current intensity play important roles on the microstructure refinement. The discussion was mainly focused on the mechanism of grain refinement by LFEC process.

The Effect of Casting Speed on Sump Shape and Ingot Surface of HDC Casting 7075 Aluminum Alloy Ingot

7075 aluminum alloy ingot with the diameter of 100 mm has been produced by horizontal direct chill casting in different casting speed. The effect of casting speed on the sump profile and the ingot surface quality was studied by sump profile observation. It was found that increasing the casting speed results in the deepening of the liquid pool, the adding of segregation knots and the reducing of cold shouts in the ingot surface. It is also found that the depth of the liquid pool is directly proportional to the casting speed and the squared radius of the ingot.

Low-Frequency Electromagnetic Field Influencing Horizontal Direct Chill Casting of Aluminum Alloy Rods

The horizontal direct chill (HDC) casting process is a well-established production route for an aluminum alloy ingot; however, the ingot may suffer from inhomogeneous microstructures and serious macrosegregation due to the unbalanced cooling condition and gravitational effect. In order to control the defect, a low frequency electromagnetic field has been applied in the HDC casting process and its influences on microstructures and macrosegregation have been studied. The results show that the low frequency electromagnetic field can improve macrostructures, reduce inhomogeneous microstructures and macrosegregation in HDC product; and two main parameters of the electromagnetic field—density and frequency influence the microstructures and solution distribution along the diameter of the ingot significantly. In the range of ampere-turns and frequency employed in the experiments, the optimum ampere-turns and frequency have been found to be 10000At, 30Hz.

Effect of Forging Temperature on Deformability and Structure Evolution of High Purity Aluminium during Multi-Directional Forging Process

The effects of final forging temperatures on deformability and structure evolution of high purity aluminum during multi-directional forging process were investigated. The results showed that increasing the initial forging temperature is beneficial for controlling the sample shape in the initial forging passes. Recrystallization during the initial forging passes improves the deformability of the sample in the following low-temperature forging processes. An X-shape fine grain zone is formed in the sample due to the inhomogeneous deformation of multi-directional forging process. When the forging pass is 6, the final forging temperature has an important influence on the grain size in the fine grain zone. The grain size decreases from 302 μm to 60 μm with the final forging temperature decreasing from 310 °C to 65 °C. The X-shape fine grain zone caused by the inhomogeneous deformation cannot be eliminated by increasing the final forging temperature (even higher than the recrystallization temperature of high purity aluminium).

Study on the Ageing Process of the 6xxx Series Aluminum Alloy Wires for Overhead Conductors

The 6xxx series aluminium alloy wires (with the diameters of 2.84 mm) produced by the continuous drawing and rotary-wheel continuous casting, were directly aged in different conditions. The results show that, when ageing temperature is at 150°C, the tensile strength of the wire firstly decreased from 283 MPa to 265 MPa as the ageing time extended from 0 to 4 hours, and then increased from 265 MPa to 270 MPa as the ageing time extended from 4 to 12 hours, and finally decreased from 270 MPa 263 MPa as the ageing time extended from 12 to 24 hours. The electrical resistively of the wires continued decreases with the ageing time extend from 0 to 24 hours. When the ageing temperature is at 160, 170, 180 and 190 °C, both the tensile strength and the electrical resistively of the wire continuously decreased with the ageing time extended from 0 to 24 hours. When the ageing time was identical, the wires with higher ageing temperature possessed lower tensile strength and electrical resistively.

Effect of Homogenizing Treatment on Microstructure and Property of Al-Zn-Mg-Cu-Zr Aluminum Alloy

A series of Al-6.3Zn-2.3Mg-2.3Cu-0.15Zr alloys with different reduce of Zn, Mg, Cu and Zr were prepared by ingot-metallurgy processing. Effects of homogenization on the microstructure and properties of Al-Zn-Mg-Cu-Zr aluminium alloy were respectively studied by means of metallographic microscopy, electrical conductivity test, differential thermal analysis and X-ray diffraction phase analysis. The results indicated that the overheating temperature of these alloys is between 473°C and 477°C, and there was little difference to the overheating temperature of 7050 alloy. During homogenization process, using three kinds of developed heat treatment of homogenization of 7050 alloy, with the rising of homogenization temperature and the complication of the homogenization heat treatment, the electrical conductivity decreased and hardness gradually increased. The three-step homogenization has a better effect than single homogenization, as it can completely eliminate the endothermic peak of non-equilibrium phases. Many MgZn2 phases are present in the ingot with three-step homogenization and slow cooling.