The quench sensitivity of 6351 alloy was determined by the time temperature-transformation（TTT） curves and time temperature-property（TTP） curves by an interrupted quench technique with measurement of as-aged hardn...The quench sensitivity of 6351 alloy was determined by the time temperature-transformation（TTT） curves and time temperature-property（TTP） curves by an interrupted quench technique with measurement of as-aged hardness and as-quenched electro-conductivity.The microstructure transformation during isothermal treatment was studied by the transmission electron microscopy（TEM） and Avrami equation.The results showed that the electro-conductivity of the 6351 alloy increased and the hardness decreased with prolonging the holding time at a certain isothermal temperature.The TEM observation indicated that the supersaturated solid solution decomposed and needles β″ precipitated at the initial stage of isothermal holding.With the prolongation of holding time at the nose temperature,rod β＇ and plate β phases formed.The isothermal transformation rate at 360℃ was the fastest,and became slow at 280℃ and reached the slowest at 440℃.The nose temperatures of the TTT and TTP curves were about 360℃ and the high quench sensitive temperature range was 230 430℃.The quench factor analysis indicated that the cooling rate should be more than 15℃/s in the quench sensitive areas in order to get optimal mechanical properties.展开更多
The microstructural evolution of a DC cast 7085 alloy during homogenization treatment was investigated by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry (EDS), differential scan...The microstructural evolution of a DC cast 7085 alloy during homogenization treatment was investigated by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry (EDS), differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The results showed that serious dendritic segregation existed in the as-cast 7085 alloy. Numerous eutectic microstructures and phases were observed at the grain boundary. During homogenization process, eutecticα(Al)+T(AlZnMgCu) microstructure gradually was dissolved into matrix. IntermetallicS(Al2CuMg) phase formed and grew along the eutectic microstructure and disappeared into the matrix completely when it was homogenized at 460 °C for 24 h. It could be found that the evolution of primary eutectic structure of 7085 alloy consisted of three processes, dissolution of eutecticα+T microstructure, phase transformation fromT phase toS phase and the dissolution ofS phase. The optimum homogenization parameter was at 470 °C for 24 h.展开更多
基金Project(2012M511552) supported by China Postdoctoral Science FoundationProject(2009A080205001) supported by the State Key Fundamental Research Program of China
文摘The quench sensitivity of 6351 alloy was determined by the time temperature-transformation（TTT） curves and time temperature-property（TTP） curves by an interrupted quench technique with measurement of as-aged hardness and as-quenched electro-conductivity.The microstructure transformation during isothermal treatment was studied by the transmission electron microscopy（TEM） and Avrami equation.The results showed that the electro-conductivity of the 6351 alloy increased and the hardness decreased with prolonging the holding time at a certain isothermal temperature.The TEM observation indicated that the supersaturated solid solution decomposed and needles β″ precipitated at the initial stage of isothermal holding.With the prolongation of holding time at the nose temperature,rod β＇ and plate β phases formed.The isothermal transformation rate at 360℃ was the fastest,and became slow at 280℃ and reached the slowest at 440℃.The nose temperatures of the TTT and TTP curves were about 360℃ and the high quench sensitive temperature range was 230 430℃.The quench factor analysis indicated that the cooling rate should be more than 15℃/s in the quench sensitive areas in order to get optimal mechanical properties.
基金Project(2012CB619503)supported by the National Basic Research Program of ChinaProject(2013AH100055)supported by the Special Foundation for Science and Technology Innovation of Foshan,China
文摘The microstructural evolution of a DC cast 7085 alloy during homogenization treatment was investigated by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry (EDS), differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The results showed that serious dendritic segregation existed in the as-cast 7085 alloy. Numerous eutectic microstructures and phases were observed at the grain boundary. During homogenization process, eutecticα(Al)+T(AlZnMgCu) microstructure gradually was dissolved into matrix. IntermetallicS(Al2CuMg) phase formed and grew along the eutectic microstructure and disappeared into the matrix completely when it was homogenized at 460 °C for 24 h. It could be found that the evolution of primary eutectic structure of 7085 alloy consisted of three processes, dissolution of eutecticα+T microstructure, phase transformation fromT phase toS phase and the dissolution ofS phase. The optimum homogenization parameter was at 470 °C for 24 h.
