Effect of CeO2 Size on Microstructure, Synthesis Mechanism and Refining Performance of Al-Ti-C Alloy

The effects of CeO2 size on the microstructure and synthesis mechanism of Al-Ti-C alloy were investigated using a quenching experiment method. A scanning calorimetry experiment was used to investigate the synthesis mechanism of TiC, the aluminum melt in situ reaction was carried out to synthesize master alloys and its refining performance was estimated. The results show that the Al-Ti-C-Ce system is mainly composed of α-Al, Al3Ti, TiC and Ti2Al20Ce. The addition of CeO2 obviously speeds up the progress of the reaction, reduces the size of Al3Ti and TiC and lowers the formation temperature of second-phase particles. When the size of CeO2 is 2–4 μm, the promotion effect on the system is most obvious. The smaller the size of CeO2, the smaller the size of Al3Ti and TiC and the lower the formation temperature. Al-Ti-C-Ce master alloy has a significant refinement effect on commercial pure aluminum. When the CeO2 size is 2–4 μm, the grain size of commercial pure aluminum is refined to 227 μm by Al-Ti-C-Ce master alloy.

Refining performance and recession of Al–TiO2–C–La2O3 refiners

Al–TiO2–C–La2O3 refiners were synthesized by the in-situ exothermic dispersion method using TiO2, C, Al and La2O3 powders as raw materials. Scanning electron microscopy equipped with energy dispersive X-ray spectrometry and X-ray diffraction were used to investigate the microstructures of the Al–TiO2–C–La2O3 refiners. Commercial pure aluminum was refined by the Al–TiO2–C–La2O3 refiners, aimed at investigating refining performance and the resistance to recession. The results show that the Al–TiO2– C–La2O3 refiner with 0.2% La2O3 is composed of α-Al, blocky Al3Ti, dispersive Al2O3 and TiC, which has a better refining effect on commercial pure aluminum than the Al– TiO2–C refiner. The average grain size refined by the above refiner is about 80 μm and it performs better and has a longer refining effect. The grain structure refined by Al–TiO2– C–La2O3 becomes finer within 5 min and remains the same after 120 min, while refined by the Al–TiO2–C refiner the equivalent times are 10 min and 30 min respectively.

Improving the Fracture Toughness of Multi-Layered Commercial Pure Aluminum via Warm Accumulative Roll Bonding

In this study, the fracture toughness of the multi-layered commercial pure aluminum samples (AA1050) prepared by warm accumulative roll bonding (WARB) was investigated for the first time. Based on the ASTM E561 standard, the R-curve method was utilized to measure the plane stress fracture toughness. Compact tension (CT) samples were prepared from the sheets that were processed by different ARB cycles. Mechanical properties, microstructure, and fracture surfaces of the CT samples were studied by uniaxial tensile test, electron backscatter diffraction (EBSD), and scanning electron microscopy (SEM), respectively. By increasing the number of WARB cycles, fracture toughness increased; after five cycles, 78% enhancement was observed compared to the pre-processed state. A correlation was seen between the fracture toughness variations and ultimate tensile strength (UTS). WARB enhanced UTS up to 95%, while the grain size showed a reduction from 35 to 1.8 µm. Measured fracture toughness values were compared with the room temperature ARB outcomes, and the effective parameters were analyzed. Fractography results indicated that the presence of tiny cliffs and furrows and hollow under fatigue loading zones and shear ductile rupture in the Quasi-static tensile loading zone.

Investigation of Microstructure of Al-5Ti-0.62C System and Synthesis Mechanism of TiC

Al-Ti-C master alloys have been widely investigated by various researchers. However, their refining effectiveness is still severely compromised by the preparation process. In this work, the aluminum melt in-situ reaction was carried out to synthesize the Al-5Ti-0.62C, and its refining performance was estimated. The thermodynamics calculation and differential scanning calorimeter experiment were used to investigate the synthesis mechanism of TiC. Quenching experiment was conducted to explore phase and microstructure transformation of the Al-5Ti-0.62C system. The results show that the main phases of Al-5Ti-0.62C master alloys are α-Al, Al3Ti, and TiC and it has a positive effect on commercial pure aluminum refining. Commercial pure aluminum is completely refined into the fine equiaxed structure by adding 0.3% Al-5Ti-0.62C master alloy. TiC particles mainly distribute in the grain interior and grain boundaries. The excess Ti came from the dissolution of Al3Ti spreading around TiC and finally forming the Ti-rich zone to promote the nucleation of α-Al. The experiments certified that TiC was formed by the reaction between solid C and excess Ti atoms. The main reactions in the Al-5Ti-0.62C system were that solid Al is transferred into liquid Al, and then liquid Al reacted with solid Ti to form the Al3Ti. At last, the release of a lot of heat promotes the formation of TiC which formed by the Ti atoms and solid C.

The New Plastic Flow Machining Process for Producing Thin Sheets

A new severe plastic deformation (SPD) process called plastic flow machining (PFM) was recently proposed to produce thin sheets with gradient structures. In the present paper, the role of the die geometry is investigated by studying the effects of the produced sheet thickness (h) on the material properties of commercial pure Aluminum (Al1050) processed by PFM. The obtained experimental results show that an increase of h in the range of 0.65 to 1.5 mm improved the formation efficiency of the sheet. Microstructures of the produced sheets show gradient structures with an average grain size varying from 0.8 to 3.81 µm across the sheet thickness. Both experiments and finite element (FE) simulations document that the degree of the gradient in the microstructure became more significant when h was increased. Sheets produced by PFM exhibited a better strength-ductility balance than sheets obtained in other SPD processes. Tensile strength of 160–175 MPa and total ductility of 18–25% were obtained for the processed samples after PFM. A rise of h from 0.65 to 1.5 mm lowered the strength but enhanced the ductility of the produced sheet, which is due to the coarser microstructure at larger values of h.