Al-Mg-Si-Cu alloys with and without Zn addition were fabricated by conventional ingot metallurgy method. The microstructures and properties were investigated using optical microscopy （OM）, field emission scanning el...Al-Mg-Si-Cu alloys with and without Zn addition were fabricated by conventional ingot metallurgy method. The microstructures and properties were investigated using optical microscopy （OM）, field emission scanning electron microscopy （FE-SEM）, transmission electron microscopy （TEM）, tensile test, hardness test, and electrical conductivity measurement. It is found that the as-cast A1-Mg-Si-Cu-Zn alloy is composed of coarse dendritic grains, long needle-like ~/5-A1FeSi white intermetallics, and Chinese script-like a-A1FeSi compounds. During high temperature homogenization treatment, only harmful needle-like ^-A1FeSi phase undergoes fragmentation and spheroidizing at its tips, and the destruc- tive needle-like 5-phase does not show any morphological and size changes. Phase transitions from ^-A1FeSi to ^-A1FeSi and from 6-A1FeSi to [3-A1FeSi are also not found. Zn addition improves the aging hardening response during the former aging stage and postpones the peak-aged hardness to a long aging time. In T4 condition, Zn addition does not obviously increase the yield strength and decrease the elongation, but it markedly improves paint-bake hardening response during paint-bake cycle. The addition of 0.5wt% Zn can lead to an increment of 99 MPa in yield strength compared with the value of 69 MPa for the alloy without Zn after paint-bake cycle.展开更多
Microstructural evolution and phase transformation induced by different heat treatments of the hypereutectic aluminium-silicon alloy, Al-25Si-5Fe-3Cu （wt%, signed as 3C）, fabricated by traditional cast （TC） and sp...Microstructural evolution and phase transformation induced by different heat treatments of the hypereutectic aluminium-silicon alloy, Al-25Si-5Fe-3Cu （wt%, signed as 3C）, fabricated by traditional cast （TC） and spray forming （SF） processes, were investigated by differential scanning calorimetry （DSC） and scanning electron microscopy （SEM） combined with energy dispersive X-ray spectroscopy and X-ray diffraction techniques. The results show that A17Cu2Fe phase can be formed and transformed in TC- and SF-3C alloys between 802-813 K and 800-815 K, respectively. The transformation from β-Al5FeSi to δ-Al4FeSi2 phase via peritectic reaction can occur at around 858-870 K and 876-890 K in TC- and SF-3C alloys, respectively. The starting precipitation temperature of δ-Al4FeSi2 phase as the dominant Fe-bearing phase in the TC-3C alloy is 997 K and the exothermic peak about the peritectic transformation of δ-Al4FeSi2→β-Al5FeSi is not detected in the present DSC experiments. Also, the mechanisms of the microstructural evolution and phase transformation are discussed.展开更多
基金financially supported by the Beijing Natural Science Foundation (No. 2112030)
文摘Al-Mg-Si-Cu alloys with and without Zn addition were fabricated by conventional ingot metallurgy method. The microstructures and properties were investigated using optical microscopy （OM）, field emission scanning electron microscopy （FE-SEM）, transmission electron microscopy （TEM）, tensile test, hardness test, and electrical conductivity measurement. It is found that the as-cast A1-Mg-Si-Cu-Zn alloy is composed of coarse dendritic grains, long needle-like ~/5-A1FeSi white intermetallics, and Chinese script-like a-A1FeSi compounds. During high temperature homogenization treatment, only harmful needle-like ^-A1FeSi phase undergoes fragmentation and spheroidizing at its tips, and the destruc- tive needle-like 5-phase does not show any morphological and size changes. Phase transitions from ^-A1FeSi to ^-A1FeSi and from 6-A1FeSi to [3-A1FeSi are also not found. Zn addition improves the aging hardening response during the former aging stage and postpones the peak-aged hardness to a long aging time. In T4 condition, Zn addition does not obviously increase the yield strength and decrease the elongation, but it markedly improves paint-bake hardening response during paint-bake cycle. The addition of 0.5wt% Zn can lead to an increment of 99 MPa in yield strength compared with the value of 69 MPa for the alloy without Zn after paint-bake cycle.
基金supported by the Major State Basic Research & Development Program of China (No2006CB605204)
文摘Microstructural evolution and phase transformation induced by different heat treatments of the hypereutectic aluminium-silicon alloy, Al-25Si-5Fe-3Cu （wt%, signed as 3C）, fabricated by traditional cast （TC） and spray forming （SF） processes, were investigated by differential scanning calorimetry （DSC） and scanning electron microscopy （SEM） combined with energy dispersive X-ray spectroscopy and X-ray diffraction techniques. The results show that A17Cu2Fe phase can be formed and transformed in TC- and SF-3C alloys between 802-813 K and 800-815 K, respectively. The transformation from β-Al5FeSi to δ-Al4FeSi2 phase via peritectic reaction can occur at around 858-870 K and 876-890 K in TC- and SF-3C alloys, respectively. The starting precipitation temperature of δ-Al4FeSi2 phase as the dominant Fe-bearing phase in the TC-3C alloy is 997 K and the exothermic peak about the peritectic transformation of δ-Al4FeSi2→β-Al5FeSi is not detected in the present DSC experiments. Also, the mechanisms of the microstructural evolution and phase transformation are discussed.
