Three Al?Zn?Mg?Cu alloys used for oil drill pipes (Alloy A: Al?6.9Zn?2.3Mg?1.7Cu?0.3Mn?0.17Cr; Alloy B: Al?8.0Zn?2.3Mg?2.6Cu?0.2Zr, Alloy C: Al?8.0Zn?2.3Mg?1.8Cu?0.18Zr) were studied by hardness tests, tensile tests a...Three Al?Zn?Mg?Cu alloys used for oil drill pipes (Alloy A: Al?6.9Zn?2.3Mg?1.7Cu?0.3Mn?0.17Cr; Alloy B: Al?8.0Zn?2.3Mg?2.6Cu?0.2Zr, Alloy C: Al?8.0Zn?2.3Mg?1.8Cu?0.18Zr) were studied by hardness tests, tensile tests and transmission electron microscopy (TEM). The results show that the ultimate tensile strength, yield strength and elongation for Alloys A, B and C are 736 MPa, 695.5 MPa and 7%; 711 MPa, 674 MPa and 12.5%; 740.5 MPa, 707.5 MPa and 13%, respectively after solid solution treatment ((450 °C, 2 h)+(470 °C, 1 h)) followed by aging at 120 °C for 12 h. The dominant strengthening phases in Alloy A are GPII zone andη′ phase, the main precipitate in Alloy B isη′ phase, and the main precipitates in Alloy C are GPI zone, GPII zone andη′ phase, which are the reason for better comprehensive properties of Alloy C. The increase of zinc content leads to the improvement of the strength. The increase of copper content improves the elongation but slightly decreases the strength. Large second-phase particles formed by the increase in the manganese content induce a decrease in the elongation of alloys.展开更多
The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg（-Cu） system. They are widely used in high-performance structural aerospace and transportation applications. Apart from composi...The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg（-Cu） system. They are widely used in high-performance structural aerospace and transportation applications. Apart from compositional, casting and thermo-mechanical processing effects, the balance of properties is also significantly influenced by the way in which the materials are heat-treated. This paper describes the effects of homogenisation, solution treatment, quenching and ageing treatments on the evolution of the microstructure and properties of some important medium to high-strength 7xxx alloys. With a focus on recent work at Monash University, where the whole processing route from homogenisation to final ageing has been studied for thick plate products, it is reported how microstructural features such as dispersoids, coarse constituent particles, fine-scale precipitates, grain structure and grain boundary characteristics can be controlled by heat treatment to achieve improved microstructure-property combinations. In particular, the paper presents methods for dissolving unwanted coarse constituent particles by controlled high- temperature treatments, quench sensitivity evaluations based on a systematic study of continuous cooling precipitation behaviour, and ageing investigations of one-, two- and three-step ageing treatments using experimental and modelling approaches, in each case, the effects on both the microstructure and the resulting properties are discussed.展开更多
The effects of major alloy element contents of Zn, Mg, Cu in Al-Zn-Mg-Cu alloys on the formation and evolution of intermetallic phases during casting, homogenization and solution treatment have been investigated throu...The effects of major alloy element contents of Zn, Mg, Cu in Al-Zn-Mg-Cu alloys on the formation and evolution of intermetallic phases during casting, homogenization and solution treatment have been investigated through using X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Experimental results showed that a relatively higher Zn content with lower Mg and Cu contents was beneficial to the formation of MgZn2 phase instead of the A12CuMg phase, which resulted in the unicity of the intermetallics in the A1 matrix, and that the MgZn2 phase was easier for diffusion and dissolution during homogenization and solution than the Al2CuMg phase. Additionally, the results of the first-principles calculations gave support for explaining the experimental phenomena. A larger absolute value of formation enthalpy and a smaller value of binding energy of the MgZn2 phase, as compared with the Al2CuMg phase, give it priority to precipitate during casting and make it easier to re-dissolve during homogenization and solution treatment. What＇s more, higher elastic constants with severe anisotropy of Young＇s modulus make undissolved blocks of AI^CuMg phase act as crack initiation, which degrade the perfor- mance of the materials.展开更多
基金Project supported by the Open Foundation of CNPC Key Laboratory for Petroleum Tubular Goods Engineering,China
文摘Three Al?Zn?Mg?Cu alloys used for oil drill pipes (Alloy A: Al?6.9Zn?2.3Mg?1.7Cu?0.3Mn?0.17Cr; Alloy B: Al?8.0Zn?2.3Mg?2.6Cu?0.2Zr, Alloy C: Al?8.0Zn?2.3Mg?1.8Cu?0.18Zr) were studied by hardness tests, tensile tests and transmission electron microscopy (TEM). The results show that the ultimate tensile strength, yield strength and elongation for Alloys A, B and C are 736 MPa, 695.5 MPa and 7%; 711 MPa, 674 MPa and 12.5%; 740.5 MPa, 707.5 MPa and 13%, respectively after solid solution treatment ((450 °C, 2 h)+(470 °C, 1 h)) followed by aging at 120 °C for 12 h. The dominant strengthening phases in Alloy A are GPII zone andη′ phase, the main precipitate in Alloy B isη′ phase, and the main precipitates in Alloy C are GPI zone, GPII zone andη′ phase, which are the reason for better comprehensive properties of Alloy C. The increase of zinc content leads to the improvement of the strength. The increase of copper content improves the elongation but slightly decreases the strength. Large second-phase particles formed by the increase in the manganese content induce a decrease in the elongation of alloys.
基金The Aluminium Corporation of China Ltd.(Chalco)for supporting aspects of this work financiallyproviding AA7150 materials as part of the Australia-China International Centre for Light Alloy Research(ICLAR)+1 种基金Monash University for developing the retrogression and reageing Matlab model (as part of the PhD project of Dr Adrian GROSVENOR)The ARC Centre of Excellence for Design in Light Metals and its Directors (first Prof Barry MUDDLE and then Prof Xin-hua WU) for supporting
文摘The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg（-Cu） system. They are widely used in high-performance structural aerospace and transportation applications. Apart from compositional, casting and thermo-mechanical processing effects, the balance of properties is also significantly influenced by the way in which the materials are heat-treated. This paper describes the effects of homogenisation, solution treatment, quenching and ageing treatments on the evolution of the microstructure and properties of some important medium to high-strength 7xxx alloys. With a focus on recent work at Monash University, where the whole processing route from homogenisation to final ageing has been studied for thick plate products, it is reported how microstructural features such as dispersoids, coarse constituent particles, fine-scale precipitates, grain structure and grain boundary characteristics can be controlled by heat treatment to achieve improved microstructure-property combinations. In particular, the paper presents methods for dissolving unwanted coarse constituent particles by controlled high- temperature treatments, quench sensitivity evaluations based on a systematic study of continuous cooling precipitation behaviour, and ageing investigations of one-, two- and three-step ageing treatments using experimental and modelling approaches, in each case, the effects on both the microstructure and the resulting properties are discussed.
基金financially supported by the National Natural Science Foundation of China (Grant No. 51171156)
文摘The effects of major alloy element contents of Zn, Mg, Cu in Al-Zn-Mg-Cu alloys on the formation and evolution of intermetallic phases during casting, homogenization and solution treatment have been investigated through using X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Experimental results showed that a relatively higher Zn content with lower Mg and Cu contents was beneficial to the formation of MgZn2 phase instead of the A12CuMg phase, which resulted in the unicity of the intermetallics in the A1 matrix, and that the MgZn2 phase was easier for diffusion and dissolution during homogenization and solution than the Al2CuMg phase. Additionally, the results of the first-principles calculations gave support for explaining the experimental phenomena. A larger absolute value of formation enthalpy and a smaller value of binding energy of the MgZn2 phase, as compared with the Al2CuMg phase, give it priority to precipitate during casting and make it easier to re-dissolve during homogenization and solution treatment. What＇s more, higher elastic constants with severe anisotropy of Young＇s modulus make undissolved blocks of AI^CuMg phase act as crack initiation, which degrade the perfor- mance of the materials.
