Papers by Keyword: Refinement Mechanism

Abstract: Al-Ti-B master alloy is the most widely used grain refiner in the aluminum fabrication industry, while it’s refinement mechanism is not clearly understand yet. The TiB₂ in Al-Ti-B master alloy is one of important phase to grain refining, which intimately related to the generation of initial nucleus, the “fading” phenomenon of refining effect declines with the increase of holding or standing time in grain refining process. Besides, TiB₂ is analyzed in several studies about the “poisoning” phenomenon, a large extent weaken of refining effect when Zr, Cr, Mn etc. exists. In this article, the impact of TiB₂ to the refining effect of Al-Ti-B master alloy is discussed aiming at the roles and phenomenon mentions above.

Abstract: Grain size refinement by using equal channel angular Extrusion (ECAE) is an effective way to improve workability and strength of the magnesium alloys. Round workpieces of ECAE processes for AZ31 magnesium alloy are investigated by using numerical simulations and experimental studies in this paper. The processing of ECAE is simulated in order to study the influence of the processing on the deformation behavior of the workpiece and extruding load. The variation trends of the effective strain distributions in the workpiece are changed little for different cross-section. Punch load for extrusion is the major factor to be considered while designing a sound ECAE die. The deformation mechanism of ECAE for grain refinement is obtained. In addition, the experimental finally workpieces shapes and extruding load results are also consistent with FE analysis results.

Abstract: AlTiC master alloys have been prepared by Contact Reaction Method（CRM）.X-ray diffraction，SEM and EDS were used to analyse the AlTiC master alloys. It showed that morphology and distribution of TiC and Al3Ti particle have correspondingly changed with the transformation of temperature. As a result, the change in morphology and distribution of TiC and Al3Ti particle has considerably affected the gain refining performance of AlTiC master alloys. The result showed that it had excellent grain refining performance for commercially pure aluminum in 800°C.

Abstract: The ultra-fine grained (UFG) materials have been widely investigated due to their mechanical properties such as super high strength and super high plasticity. The finite element simulation schemes are planned for the deformation mechanism of ECAP pressing. It will greatly affect the extrusion process when processing parameter changed such as die geometrical parameters and friction condition. It is considerable to determinate the range of die channel angle and die corner angle during ECAP process, and a moderate die corner angle is usually chosen. The friction condition of the ECAP should be lubricated as good as possible in the pressing on the basis of optimal die geometrical conditions. The ECAP process is a non-uniform shear deformation process in the cross-section of the workpiece for first-pass pressing. There have low angle grain boundaries along the cross-section of the grain microstructures. For the multi-pass pressing, although the pressing pass numbers are same, the processing routes were of important significance on the grain sizes and grain distribution and grain boundaries (GBs) orientations of workpieces. The formation mechanism of nanostructure was given for the ECAP through studying the deformation behavior and dislocation’s evolution. The dislocation is one of the main defects in the processed materials, but the form of the dislocations and its density are difference for different processing route. The processed workpiece with high surface quality, refined grain microstructure and optimization grain boundaries were obtained with optimal processing parameters and routes.

Abstract: AlTiC master alloys have been prepared by Contact Reaction Method（CRM）.X-ray diffraction，SEM and EDS were used to analyses the AlTiC master alloys. It showed that morphology and distribution of TiC and Al3Ti particle have correspondingly changed with the change of the size of powder. As a result, the change in morphology and distribution of TiC and Al3Ti particle has considerably affected the gain refining performance of AlTiC master alloys. The result showed that: when the grain size of Ti is much smaller, the effect of refinement is much better.