材料科学
合金
冶金
微观结构
共晶体系
沉淀硬化
压铸
原子探针
粒度
模具(集成电路)
硬化(计算)
复合材料
铸造
图层(电子)
纳米技术
作者
Mitsuhiro Okayasu,Naoki Sahara,Norihito Mayama
标识
DOI:10.1016/j.msea.2021.142120
摘要
The mechanical properties of a die-cast Al–Si–Cu alloy (DC ADC12) were improved using new processing techniques that induce grain refinement and precipitation hardening. Several gravity-cast ADC12 (GC ADC12) samples with different microstructural sizes were also evaluated to better understand the material properties of DC ADC12. The material properties of DC ADC12 indicate that the alloy has both advantages (fine grains) and disadvantages (defects). The mechanical properties of ADC12 can be improved by adding Na before the T5 process. The grain refinement of ADC12 was achieved by introducing Na using benign and inexpensive NaHCO3 rather than metallic Na. The Na elements including sodium oxide retained in the melt cause fine spherical eutectic structures to form in the spherical α-Al matrix by interrupting the Si phase growth. The phenomenon can be detected via a three-dimensional atom probe tomography analysis. Precipitation hardening of the die-cast Al alloy was achieved by subjecting it to T5 treatment and a large amount of Cu, replacing the T6 treatment, for 3 h at 175 °C, because the die casting process can be replaced with the solid solution process in T6 owing to its high cooling rate. Precipitation hardening occurred in the grain-refined DC ADC12-Na sample during the T5 process, which was verified via in situ observation of its microstructure using laser microscopy during the heating and cooling processes. Al2MgCu, CuAl2, and fine Si particles, which were different from the precipitates obtained using the T6 process, were produced in the spherical α-Al phase. The demonstrated techniques resulted in remarkable improvements in the ultimate tensile strength and fracture strain of DC ADC12.
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