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The Al-5Ti-1B, Al-10Ti, Al-4B master alloys and TiB2 powder were applied to refine the pure aluminum, respectively. The effects of the TiAl3 phase, TiB2 particle, and AlB2 phase on the grain size of pure aluminum were compared. The grain refinement mechanism of the Al-5Ti-1B grain refiner was studied. The results showed that the TiAl3 phase was an effective heterogeneous nucleus of the α-Al grain. But the TiAl3 phase in the Al-5Ti-1B grain refiner was not the heterogeneous nucleus of the α-Al grain due to its re-melting in the Al melt. The separate TiB2 particle or AlB2 phase was not the heterogeneous nucleus of the α-Al grain. However, the TiB2 coated by the TiAl3 phase can be the effective heterogeneous nucleus of the α-Al grain. The grain refinement mechanism of the Al-5Ti-1B grain refiner can be summarized as follows: when the Al-5Ti-1B grain refiner is added into the Al melt, the TiAl3 phases are re-melted to release the Ti atoms, while the TiB2 particles are remaining in the Al melt. During the solidification of the Al melt, the Ti atoms are segregating on the surface of TiB2 particles to form the TiAl3 phases. The TiB2 particles coated by the TiAl3 phases then reacts with the Al melt to generate α-Al crystal nucleus.

The effects of La and Ce mixed rare earth on the microstructure and properties of Al-0.75Mg-0.6Si alloy were studied by optical microscopy, digital eddy current conductive instrument and tensile testing machine. Results showed that the addition of La and Ce mixed rare earth had a positive effect on the grain refinement of Al-0.75Mg-0.6Si alloy, which is beneficial to improve the electrical conductivity and strength. With increasing the additive amount of La and Ce mixed rare earth, the electrical conductivity, tensile strength and elongation of Al-0.75Mg-0.6Si alloy gradually increased. When the additive amount of La and Ce mixed rare earth increased to 0.5%, the electrical conductivity of Al-0.75Mg-0.6Si alloy was 55.7% IACS, the tensile strength and elongation of Al-0.75Mg-0.6Si alloy were 236 MPa and 16.7%, respectively. The electrical conductivity increased by 5.7%, tensile strength and elongation increased by 11.3% and 15.2% compared with that of Al-0.75Mg-0.6Si alloy without adding the La and Ce mixed rare earth.

In the present investigation the casting-forging integrated technology was adopted to manufacture Al-1.1Mg-0.6Si-0.4Cu alloy automobile brake calipers. The effect of forging pressure on the microstructure and mechanical properties of Al-1.1Mg-0.6Si-0.4Cu alloy calipers were studied. The results showed that the shrinkage porosities and cracks in the Al-1.1Mg-0.6Si-0.4Cu alloy calipers could be removed by the forging process. The ultimate tensile strength and elongation of Al-1.1Mg-0.6Si-0.4Cu alloy calipers increased with the increase of forging pressure. When the forging pressure was 120 MPa, the ultimate tensile strength and elongation of Al-1.1Mg-0.6Si-0.4Cu alloy calipers with T6 heat treatment were 365.3 MPa and 11.5%, which were improved by 22.8% and 38.2%, respectively compared with that of Al-1.1Mg-0.6Si-0.4Cu alloy calipers without forging. The tensile fracture images revealed that the fracture modes of Al-1.1Mg-0.6Si-0.4Cu alloy calipers were more ductile at higher forging pressure.

The microstructure of Al-5Ti-1B grain refiner was analyzed by XRD and SEM. The effect of the Al-5Ti-1B grain refiner on the microstructure and mechanical properties of 7075 aluminum alloy were studied. Results show that when the addition amount of Al-5Ti-1B grain refiner is 0.1%, the microstructure of 7075 aluminum alloy is refined from coarse dendrite to equiaxed grains with an average diameter of 55.1μm. The tensile strength and elongation of 7075 aluminum alloy are improved by 11.32% and 36.04% compared with that of 7075 aluminum alloy without adding Al-5Ti-1B grain refiner. With increasing the addition amount of Al-5Ti-1B grain refiner from 0.1% to 0.5%, both the tensile strength and elongation are improved. When the addition amount of Al-5Ti-1B grain refiner increases to 0.5%, the microstructure of 7075 aluminum alloy is refined to uniform equiaxed grains with an average diameter of 32.5μm. The tensile strength and elongation are improved by 18.11% and 48.76%, respectively.

An Al-5Zr-1.1B grain refiner was prepared by in-situ synthesis from Al melt and K2ZrF4+KBF4 mixed powder. The microstructure of Al-5Zr-1.1B grain refiner was analyzed by XRD, SEM and EDS. The effect of Al-5Zr-1.1B grain refiner on the microstructure and mechanical properties of AZ91D magnesium alloy were studied. Results show that a large number of fine ZrB2 particles were observed in the Al-5Zr-1.1B grain refiner and the ZrB2 particles could act as the heterogeneous nuclei of α-Mg grains. With the increase of the addition amount of Al-5Zr-1.1B grain refiner, the α-Mg grains of AZ91D magnesium alloy were refined from coarse dendrites to equiaxed grains. When the addition amount of Al-5Zr-1.1B grain refiner increased to 0.6%, the α-Mg grains of AZ91D magnesium alloy were refined to fine equiaxed grains with an average diameter of 45 μm, and the tensile strength and elongation of AZ91D magnesium alloy were improved to 195.3 MPa and 3.94%, respectively. The α-Mg grains average diameter of AZ91D magnesium alloy decreased by 73.5% and the tensile strength and elongation improved by 25.9% and 27.9% compared with that of AZ91D magnesium alloy without adding the Al-5Zr-1.1B grain refiner. It is concluded that the Al-5Zr-1.1B is an effective grain refiner to refine the α-Mg grains of AZ91D magnesium alloy.

The effect of applied forging pressure on microstructure and mechanical properties of 6061 aluminum alloy was examined. The results showed that the ultimate tensile strength, elongation and hardness of the alloy after heat-treated treatment increase with the applied forging pressure, and the corresponding highest values, 365MPa, 11.52% and 146.53HV, were obtained at the applied forging pressure of 120MPa. Compared to casting condition without forging pressure, the ultimate tensile strength, elongation and hardness can be increased by 22.8%, 98.2% and 48.7%, respectively. The defects such as the shrinkage pores and cracks were absent in the microstructure due to the applied forging pressure. The SEM observation indicated that the fracture mode of 6061 aluminum alloy is more ductile at higher applied forging pressure.

The effect of the sintering temperature, quartz and sodium phosphate content on the core strength,shrinking percentage and solubility of alumina matrix ceramic cores was investigated．The results show that：the more the quartz is, the higher of the bending, tensile strength at room temperature of core are;It has the extreme point when quartz is 10wt%, then decreases slightly.The shrinkage rate and the room temperature strength of core increases with the rising of sintering temperature,but decreases with the increasing of content of sodium phosphate. Furthermore, the effect of the sintering temperature,quartz powder and sodium phosphate content on solubility of core was discussed.

Continuous semisolid extruding extending forming process was adopted to produce LY11 alloy flat bar. The forming process, metal flow behavior in die cavity and microstructure and mechanical property of flat bar were investigated. It is shown that the LY11 alloy flat bar with transverse section of 10×50 mm and with good surface and fine equiaxed grains can be obtained by the continuous semisolid extruding extending forming process with melt pouring temperature of 770～780°C. The metal streamlines show that the semisolid slurry fills the die cavity in radiation manner and moves forward layer by layer and the velocity of slurry flow in the central area of die cavity is the maximum, and then decreases gradually from the center to side of die cavity. The tensile strength and elongation of flat bar with T6 heat treatment are 420.5 MPa and 14.2%, respectively.

A two-step reheating process was proposed and applied to perform reheating experiments on the semi-solid 2024 alloy billet. In this process, the semi-solid billet was firstly heated over liquidus temperature and then isothermally held at solid-liquid zone temperature. Microstructure evolution of the semi-solid billet during two-step reheating was studied by optical microscope and compared with that during isothermal reheating. The results show that the remelting rate of the semi-solid billet during two-step reheating is faster than that during isothermal reheating. Under the same reheating time, the grains of the semi-solid billet reheated by two-step reheating process are finer and rounder than those by isothermal reheating process. The present experimental results indicate that accelerating the formation of liquid phase during the two-step reheating process can restrain the coalescence of grains to a certain extent, and thus refine the grain size and promote the grain spheroidization.