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  • Trans Tech Publications, Ltd.  (12)
  • Zhang, Yong An  (12)
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  • Trans Tech Publications, Ltd.  (12)
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  • 1
    Online Resource
    Online Resource
    Trans Tech Publications, Ltd. ; 2022
    In:  Materials Science Forum Vol. 1071 ( 2022-10-18), p. 11-19
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 1071 ( 2022-10-18), p. 11-19
    Abstract: The dissolution of second phase with relatively high melting point in as-cast Al-Zn-Mg-Cu alloys was closely related to Mg and Cu contents. In present work, second phases in three Al-Zn-Mg-Cu alloys with simultaneously enhanced Mg and Cu contents (named by LMC alloy, MMC alloy and HMC alloy as Mg and Cu contents progressively enhanced) were analyzed and the correlated dissolution during homogenization was investigated. The results showed that both Mg(Zn,Cu,Al) 2 phase and Cu-rich phase existed in as-cast alloys while HMC alloy possessed more eutectic phases. As homogenized by 470°C/24h, Mg(Zn,Cu,Al) 2 phase had dissolved completely, LMC alloy contained little Al 2 CuMg phase and the amount of it for the three alloys was arranged as LMC alloy 〈 MMC alloy 〈 HMC alloy. As furtherly homogenized by a second stage at 480°C for 12h, no endothermic peak for Al 2 CuMg phase was observed for LMC alloy and only Fe-rich phase existed. Meanwhile, Al 2 CuMg phase still remained in MMC and HMC alloy. As the homogenization time prolonging to 36h, Al 2 CuMg phase in MMC alloy dissolved completely while that still existed in HMC alloy. Adding a third stage at 490°C for HMC alloy, no Al 2 CuMg phase could be observed for 24h. This gave rise to a method by incrementally grading homogenization temperature combined with prolonging soaking time to fulfill the dissolution of second phase for Al-Zn-Mg-Cu alloys with enhanced Mg and Cu contents
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2022
    detail.hit.zdb_id: 2047372-2
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  • 2
    Online Resource
    Online Resource
    Trans Tech Publications, Ltd. ; 2018
    In:  Materials Science Forum Vol. 941 ( 2018-12), p. 1077-1082
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 941 ( 2018-12), p. 1077-1082
    Abstract: Intermediate annealing on anisotropy and mechanical properties of an Al-0.78Mg-0.90Si-0.65Zn-0.16Cu (wt. %) alloy was investigated by tensile test, optical microscope (OM) and electron back-scattered diffraction (EBSD). The results indicated that alloy sheet displayed various microstructure after without intermediate annealing, intermediate annealing treatment at 350°C for 2 h, 450°C for 2 h and 500°C for 5 min. Compared with the alloy without intermediate annealing, the alloy exhibited equiaxed grain with 35.0µm after annealing at 500°C for 5 min, grain orientation of the alloy was distributed randomly, and plastic strain ratio value of 45° direction was more than 0.6. The anisotropy of the sheet was significantly reduced. Annealing at 500°C for 5 min was suitable for the production process of automobile body sheets.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2018
    detail.hit.zdb_id: 2047372-2
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  • 3
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 1003 ( 2020-7), p. 3-10
    Abstract: The fatigue crack propagation of Al-Zn-Mg-Cu alloys could be influenced by the content of main alloying element. In the present work, two Al-Zn-Mg-Cu alloys with a same Zn/Mg ratio were treated by two stage over-aging aging treatment and typical T7651 states were extracted via mechanical properties. Fatigue crack propagation of the two alloys were tested and the related precipitation characteristics and fracture morphology were observed. The results showed that the alloy with higher Zn, Mg contents possessed a better fatigue crack propagation resistance compared with the alloy with lower Zn, Mg contents. The corresponding fracture morphology also showed the difference of fatigue striation, which provided an additional support. The precipitation observation demonstrated that the both alloys possessed GPII zone, η' phase and η phase while the alloy with higher Zn, Mg contents had a larger average precipitate size and a larger proportion of large size precipitates compared with the alloy with lower Zn, Mg contents. Cut and bypass mechanisms of dislocation-precipitate interactions were used to explain the difference of fatigue crack propagation between the two alloys.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2020
    detail.hit.zdb_id: 2047372-2
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  • 4
    Online Resource
    Online Resource
    Trans Tech Publications, Ltd. ; 2022
    In:  Key Engineering Materials Vol. 921 ( 2022-05-30), p. 75-83
    In: Key Engineering Materials, Trans Tech Publications, Ltd., Vol. 921 ( 2022-05-30), p. 75-83
    Abstract: Homogenization treatment is vital for eliminating eutectic structure and ensuring a preferable microstructure foundation for Aluminum Lithium (Al-Li) alloys. In this paper, solidification phases in an as-cast Al-Li alloy were revealed and their evolutions during multiple homogenization processes were analyzed by means of scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and differential scanning calorimetry (DSC) analysis. The results showed that the as-cast microstructure mainly contained needlelike Al 2 CuLi and Al 2 Cu phase, large size Cu-rich phases and netlike Ag-containing phases attached to them. As the alloy homogenized by 455°C/16h, except for needle-like phases inside grains, part of phases on grain boundaries had dissolved into the matrix and exhibited rounded shapes. As homogenized by 455°C/16h+495°C/16h, Ag-containing phase had completely dissolved into the matrix while the Cu-rich phases remained and showed two different morphologies depending on whether Mg element was contained. Prolonging the second homogenization time to 28h, no obvious change occurred for the Cu-rich phase. As homogenized by 455°C/16h+495°C/20h+512°C/20h, most Cu-rich phase had dissolved into the matrix while residual phase was mainly Fe-containing phase. This proposes an effective way to eliminate various solidification phases in Al-Li alloys and identify their contents.
    Type of Medium: Online Resource
    ISSN: 1662-9795
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2022
    detail.hit.zdb_id: 2073306-9
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  • 5
    Online Resource
    Online Resource
    Trans Tech Publications, Ltd. ; 2021
    In:  Materials Science Forum Vol. 1035 ( 2021-06-22), p. 3-9
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 1035 ( 2021-06-22), p. 3-9
    Abstract: Second phase dissolution of Al-Zn-Mg-Cu alloys during solution treatment was closely associated with the content of main alloying elements. In present work, the phase characteristics of several Al-Zn-Mg-Cu alloys with various main alloying contents were investigated, and the second phase dissolution of these alloys during solution treatment was analyzed. The results showed that the extrusion alloys possessed abundant second phases, mainly including Mg(Zn,Cu,Al) 2 phase and Fe-rich particles. The DSC analysis proved that the larger endothermic peak corresponded to the alloy with larger main alloying content, and the XRD spectrogram also backed up the advantage of Mg(Zn,Cu,Al) 2 phase. After solution treated at 450°C, the residual phases remained in the alloys and the quantity of them were positively correlated with the main alloying content. With the increase of solution temperature, the electrical conductivity of the alloys showed a decremental trend, while the alloys with relatively low main alloying contents exhibited an inversion at the solution temperature of 475°C. The SEM observation demonstrated that no Mg(Zn,Cu,Al) 2 phase was observed in the alloys with relatively low main alloying contents while seldom still remained in the alloy with high main alloying content after solution treated at 470°C. After solution treated at 475°C, Mg(Zn,Cu,Al) 2 phase completely dissolved into the matrix for the alloy with high main alloying content. The statistics of residual phase quantity also proved this.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2021
    detail.hit.zdb_id: 2047372-2
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  • 6
    Online Resource
    Online Resource
    Trans Tech Publications, Ltd. ; 2016
    In:  Materials Science Forum Vol. 879 ( 2016-11-15), p. 2336-2341
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 879 ( 2016-11-15), p. 2336-2341
    Abstract: The microstructure of as-extruded Al-9.8Zn-2.0Mg-1.8Cu aluminum alloy and its evolution during solution treatment were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), differential scanning calorimetry (DSC) analysis and electron back-scatter diffraction (EBSD). The results indicated that second phase of the as-extruded alloy mainly consisted of Mg (Zn, Cu, Al) 2 and Fe-rich phases. After solution treated at 475°C for 4h, Mg (Zn, Cu, Al) 2 phases were dissolved into the matrix, while Fe-rich phases still existed. Fe-rich phases cannot dissolve by prolonging solution time. The room temperature tensile strength gradually increased by prolonging solution time at 475 o C. The ultimate tensile strength of the alloy reached 700MPa after both single and two-step solution treatments.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2016
    detail.hit.zdb_id: 2047372-2
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  • 7
    Online Resource
    Online Resource
    Trans Tech Publications, Ltd. ; 2020
    In:  Materials Science Forum Vol. 993 ( 2020-5), p. 321-326
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 993 ( 2020-5), p. 321-326
    Abstract: The second phase dissolution of Al-9.2Zn-2.0Mg-1.9Cu alloy conducted by various temperatures of 2h was researched with the help of optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), electrical conductivity and differential scanning calorimetry (DSC) analysis. The results gave rise to the second phase existence of Mg(Zn,Cu,Al) 2 and Fe-containing phases in the as-extruded alloy. When the alloy solution treated with a temperature varied from 450°C to 470°C, a small quantity of Mg(Zn,Cu,Al) 2 phase still existed in the alloy while its content exhibited a decrement trend with the solution temperature rose. For the alloy solution treated at a temperature of 475°C, Mg(Zn,Cu,Al) 2 phase dissolved into the matrix completely while Fe-containing phase still remained. The electrical conductivity of quenched alloy decrease with the solution temperature increase and reached a minimum value at 470°C, and then rose slightly for the solution temperature of 475°C.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2020
    detail.hit.zdb_id: 2047372-2
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  • 8
    Online Resource
    Online Resource
    Trans Tech Publications, Ltd. ; 2018
    In:  Materials Science Forum Vol. 941 ( 2018-12), p. 753-758
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 941 ( 2018-12), p. 753-758
    Abstract: In order to analyze aging behavior of an Al-8.0Zn-1.8Mg-2.0Cu alloy, the microstructure of the alloy subjected to T6 and T76 states are investigated by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). Based on the precipitate observations, precipitate size distributions and average precipitate size are extracted from bright-field TEM images projected along 〈110〉 Al orientation with the aid of an imaging analysis. The results indicate that the main precipitates are GPI zone, GPII zone and η' phase in the T6 alloy while η' phase and η phase in the T76 alloy. The bright-field TEM observations reveal that the matrix precipitates for the T6 alloy have small size and dispersive distribution while that for the T76 alloy has big size and sparse distribution. Both have discontinuously distributed grain boundary precipitates. Quantitative structural information including precipitate size distribution and average precipitate size has been calculated by an image analysis based on the bright-field TEM images projected along 〈110〉 Al orientation. The results show that the T6 alloy has a narrower precipitate size range than the T76 alloy and thus the T6 alloy possesses a smaller average precipitate size than the T76 alloy.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2018
    detail.hit.zdb_id: 2047372-2
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  • 9
    Online Resource
    Online Resource
    Trans Tech Publications, Ltd. ; 2016
    In:  Materials Science Forum Vol. 877 ( 2016-11), p. 606-610
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 877 ( 2016-11), p. 606-610
    Abstract: The microstructure solution treated by various temperatures of 2h in as-extruded Al-9.3Zn-2.0Mg-1.8Cu alloy was investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis. The mechanical properties treated at 465 o C for various times were tested by room temperature tensile mechanical properties test. The results indicated that second phase of the as-extruded alloy mainly consists of Mg (Zn,Cu,Al) 2 and Fe-rich phases. Mg (Zn,Cu,Al) 2 phase completely dissolved into the matrix solution treated at 465 o C or higher for 2h while residual phase was mainly Fe-rich phase. The mechanical properties treated at 465 o C for various time were tested and optimized solution treatment parameter was chosen as 465°C/1.5h.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2016
    detail.hit.zdb_id: 2047372-2
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  • 10
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 941 ( 2018-12), p. 949-954
    Abstract: Aging treatments of an Al-9.0Zn-2.0Mg-2.0Cu alloy, which belongs to high strength aluminum alloy widely used in aerospace industry, are investigated by various techniques, including hardness, electrical conductivity, mechanical properties, transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The result shows that hardness and conductivity for one-step aging treatment increase with aging time prolongs while those for two-step aging treatment exhibit increment and decrement, respectively. Besides, the ultimate tensile strength (UTS) and yield strength (YS) for one-step and two-step aging treatments show slow increase and obvious decrease, respectively. Based on these, typical T6 and T76 aging regimes are extracted for microstructure observation. The matrix precipitates for the T6 alloy have small size and dispersive distribution while that for the T76 alloy has big size and sparse distribution. The grain boundary precipitates for both exhibit discontinuous distribution and the T76 alloy has larger size and broader precipitate free zones. The selected area diffraction patterns and HREM observations reveal that main precipitates for the T6 alloy are GPI zone, GPII zone and η' phase while for the T76 alloy are η' phase and η phase.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2018
    detail.hit.zdb_id: 2047372-2
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