Effects of Pouring Temperature on Microstructure and Mechanical Properties of the A356 Aluminum Alloy Diecastings

Abstract Diecastings of the A356 aluminum alloy were produced by rheo-diecasting (RDC) and High pressure die casting (HPDC), the microstructures of primary solidification, secondary solidification and eutectic Si of diecastings with different pouring temperature were explored and the mechanical properties of different parameters were tested. The result shows that the primary α-Al grains in RDC with self-inoculation method (SIM) are smaller and rounder than the dendrite structure in HPDC. During the RDC process, the amount of primary α-Al grains, average grain size and the lamellar spacing of the eutectic Si increase with the decrease of the melt treatment temperature. While the average grain size and the shape factor are gradually increasing with the increase of melt treatment temperature. As a result, RDC can significantly improve the mechanical properties of the A356 aluminum alloy compared with HPDC, the mechanical properties are optimal at 600°Cwith the tensile strength and elongation are 268.67MPa and 6.8%, respectively.

摘要 本研究采用流变压铸（rheo-diecasting, RDC）与高压压铸（High pressure die casting, HPDC）工艺制备了A356铝合金压铸件，系统探究了不同浇注温度下压铸件的初生凝固组织、二次凝固组织以及共晶硅（eutectic Si）微观组织，并测试了不同工艺参数下试样的力学性能。结果表明：采用自孕育法（self-inoculation method, SIM）的RDC试样中的初生α-Al晶粒相较HPDC工艺得到的枝晶组织更为细小圆整。在RDC工艺过程中，初生α-Al晶粒数量、平均晶粒尺寸以及共晶硅片层间距随熔体处理温度的降低而增大；而平均晶粒尺寸与形状因子（shape factor）则随熔体处理温度的升高逐渐增大。相较于HPDC工艺，RDC可显著提升A356铝合金的力学性能，当熔体处理温度为600℃时试样力学性能最优，其抗拉强度与断后伸长率分别可达268.67MPa与6.8%。