Abstract
The quench sensitivities of an AlSi10Mg alloy in permanent mold (PM) and high-pressure vacuum die (HPVD) castings were investigated with time–temperature–transformation and time–temperature–property diagrams using an interrupted quench technique. The quench-sensitive temperature range of the HPVD casting sample is 275–450 °C, and its nose temperature is 375 °C. The quench-sensitive range of the PM casting sample is 255–430 °C, and the nose temperature is 350 °C. The mechanical strength versus the cooling rate in both casting samples were predicted via a quench factor analysis and verified experimentally. The critical cooling rate of the HPVD casting sample is 20 °C/s whereas it is 17 °C/s for the PM casting sample. With a shorter critical time, higher nose temperature, and higher critical cooling rate, the HPVD casting sample exhibits a higher quench sensitivity than the PM casting sample. The differences in the quench sensitivities of the AlSi10Mg alloy due to the different casting processes is explained via the different precipitation behavior. At the nose temperature, coarse β-Mg2Si precipitates mainly precipitate along the grain boundaries in the HPVD casting sample, whereas rod-like β-Mg2Si precipitates distribute in the aluminum matrix in the PM casting.
Highlights
Al–Si foundry alloys possess excellent castability, high strength-to-weight ratio, and good corrosion resistance [1]
They reported that the high pressure die casting had much finer α-Al grain and Al–Si eutectic structures than the permanent mold (PM) casting
The changes in electrical conductivity (EC) are correlated with the phase transformation, because transforming solute atoms into precipitates will result in an increase in the sample EC
Summary
Al–Si foundry alloys possess excellent castability, high strength-to-weight ratio, and good corrosion resistance [1]. To obtain heat-treatable AlSi10Mg alloys with high mechanical properties, precipitation-hardening heat treatments (T6 and T7) are generally used [1]. They involve three main steps: solution treatment, quenching, and artificial aging. Okayasu et al [17] studied the mechanical properties of an Al–Si–Cu alloy produced via various casting processes. They reported that the high pressure die casting had much finer α-Al grain and Al–Si eutectic structures than the PM casting. In our previous work [18], the microstructure and mechanical properties of AlSi10Mg permanent mold and high-pressure vacuum die castings were investigated. The differences in the quench sensitivities were explained based on the different precipitation behaviors
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