Version 1
: Received: 1 October 2024 / Approved: 1 October 2024 / Online: 2 October 2024 (09:46:40 CEST)
How to cite:
LU, J.; lordan, E.; Dou, K. The Evolution of Dilatant Shear Bands in High Pressure Die Casting for Al-Si Alloy. Preprints2024, 2024100105. https://doi.org/10.20944/preprints202410.0105.v1
LU, J.; lordan, E.; Dou, K. The Evolution of Dilatant Shear Bands in High Pressure Die Casting for Al-Si Alloy. Preprints 2024, 2024100105. https://doi.org/10.20944/preprints202410.0105.v1
LU, J.; lordan, E.; Dou, K. The Evolution of Dilatant Shear Bands in High Pressure Die Casting for Al-Si Alloy. Preprints2024, 2024100105. https://doi.org/10.20944/preprints202410.0105.v1
APA Style
LU, J., lordan, E., & Dou, K. (2024). The Evolution of Dilatant Shear Bands in High Pressure Die Casting for Al-Si Alloy. Preprints. https://doi.org/10.20944/preprints202410.0105.v1
Chicago/Turabian Style
LU, J., ewan lordan and Kun Dou. 2024 "The Evolution of Dilatant Shear Bands in High Pressure Die Casting for Al-Si Alloy" Preprints. https://doi.org/10.20944/preprints202410.0105.v1
Abstract
Bands of interdendritic porosity and positive macrosegregation are commonly observed in pressure die castings, with previous studies demonstrating their close relation to dilatant shear bands in granular materials. Despite recent technological developments, the micromechanism governing dilatancy in the high pressure die casting (HPDC) process for alloys between liquidus and solidus temperature region is still not fully understood. To investigate the influence of fluid flow and the size of externally solidified crystals (ESCs) on the evolution of dilatant shear bands in HPDC, various filling velocities were trialled to produce HPDC samples of Al8SiMnMg alloy. This study demonstrates that crystal fragmentation is accompanied by a decrease in dilatational concentration, thus producing an indistinct shear band. Once crystal fragmentation stagnates, the enhanced deformation rate associated with a further increase in filling velocity (from 2.2 ms-1 to 4.6 ms-1) localises dilatancy into a highly concentrated shear band. The optimal piston velocity is 3.6 ms-1, under which the average ESC size reaches the minimum and the average yield stress and overall product of strength and elongation reaches the maximum value of 144.6 MPa and 3.664 GPa%, respectively. By adopting the concept of force chain buckling in granular media, the evolution of dilatant shear bands in equiaxed solidifying alloys can be adequately explained based on further verification with DEM-type modelling in OpenFOAM. Three mechanisms for ESC enhanced dilation are presented, elucidating previous reports relating the presence of ESCs to the subsequent shear band characteristics. By applying the physics of granular materials to equiaxed solidifying alloys, unique opportunities are presented for process optimization and microstructural modelling in HPDC.
Keywords
Shear bands; Segregation; Defects; Aluminium alloys; High pressure die casting
Subject
Chemistry and Materials Science, Materials Science and Technology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
