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RISS 인기검색어
- 검색키워드
- 저자 : H. Puga (검색결과 4 건)
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Light‑Alloy Melt Ultrasonication: Shorter T6 with Higher Precipitation Strengthening
H. Puga,V. H. Carneiro 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9
In this paper the influence of ultrasonic melt treatment on the T6 heat-treatment of light alloys is studied. An Al–Zn–Mg–Cualloy is processed to analyze the artificial ageing in cast samples with non-treated and ultrasonic treated melts. Peak-ageingin samples with acoustic activated melts occurs in shorter time spans (saving 75 min) and higher hardness (up to 22 Hv),relatively to samples with non-treated melts. These changes are attributed to the increase in number of vacancies by thestimulation to form monovacancies rather than divacancies and their homogenized distribution within the alloy matrix byultrasonic vibration. These effects allow the nucleation of a higher number of solute cluster and GPI zones that will grow intothe coarse GPII and fine η′ that characterizes the peak-ageing in these 7xxx series alloys. The reported technique presentedas promising route for the reduction of energy consumption in industrial scale heat-treatments.
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H. Puga,V. H. Carneiro,J. Barbosa,D. Soares 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.5
The present study evaluates the role of the microstructure in the static and dynamic mechanical behavior of as-cast Al7075 alloy promoted by ultrasonic treatment (US) during solidification. The characterization of samples revealed that US treatment promoted grain and intermetallics refinement, changed the shape of the intermetallic phases (equilibrium phases of soluble M and/or T (Al, Cu, Mg, Zn) and their insoluble Al-Cu- Fe compounds) and lead to their uniform distribution along the grain boundaries. Consequently, the mechanical properties and damping capacity above critical strain values were enhanced by comparison with values obtained for castings produced without US vibration. This results suggest that the grain and secondary phases refinement by US can be a promising solution to process materials to obtain high damping and high strength characteristics.
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T6 Heat Treatment Impact on the Random Frequency Vibration Stress of Al–Si–Mg Alloys
V. H. Carneiro,H. Puga 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
Recent studies show an interest on the static and dynamic mechanical properties in applications where both infl uence theoverall performance of mechanical systems. This study explores the impact of the T6 heat treatment in the elastic and dampingproperties of Al–Si–Mg alloys. Consequently, the role of such properties is characterized by the stresses that are developedin resonant structures. Experimental testing shows that, due to pinning length modifi cations, the heat treatments generate aprogressive increase in Young’s modulus and a reduction in loss factor. Recurring to fi nite element analysis, it is concludedthat such modifi cations in material properties generate a reduction in resonant stress after solution treatment. This stress tendsto increase as the artifi cial ageing progresses. A model, based on an exponential decay function, is proposed to describe thevariation of resonant stress as the elastic and damping properties are changed during the T6 treatment.
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Grain Refinement of Al-Mg-Sc Alloy by Ultrasonic Treatment
N. Q. Tuan,H. Puga,J. Barbosa,A. M. P. Pinto 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.1
In foundry practice, ultrasonic treatment has been used as an efficient technique to achieve grain refinementin aluminium and magnesium alloys. This article shows the strong effect of pouring temperature and ultrasonictreatment at various temperatures on the grain refinement of Al-1 wt% Mg-0.3 wt% Sc alloy. Without ultrasonictreatment, a fine grain structure was obtained at the pouring temperature of 700 °C. The average grain sizesharply decreases from 487 ± 20 to 103 ± 2 μm when the pouring temperature decreases from 800 to 700 °C. Ultrasonic vibration proved to be a potential grain refinement technique with a wide range of pouring temperature. A microstructure with very fine and homogeneous grains was obtained by applying ultrasonic treatmentto the melt at the temperature range between 700 and 740 °C, before pouring. Cavitation-enhanced heterogeneousnucleation is the mechanism proposed to explain grain refinement by ultrasound in this alloy. Moreover,ultrasonic treatment of the melt was found to lead to cast samples with hardness values similar to those obtainedin samples submitted to precipitation hardening, suggesting that ultrasonic treatment can avoid carrying out heattreatment of cast parts.
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