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Liao H.,Shanghai JiaoTong University | Fu P.,Shanghai JiaoTong University | Fu P.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | Peng L.,Shanghai JiaoTong University | And 4 more authors.
Materials Science and Engineering A | Year: 2017

Mg-10Gd-3Y-0.4Zr (wt%) (GW103K) Mg-RE based alloy was manufactured in Laser melting deposition (LMD) process and its microstructure and mechanical properties were studied in as-fabricated and T6-treated conditions. As-fabricated LMDed GW103K alloy consists of equiaxed grains about 19 µm in size and Mg3Gd, GdH2 particles. Under conventional solution and aging treatment parameters, grains of LMDed alloy coarsen significantly, from 19 to 158 µm. Plenty of GdH2 particles can be observed after solution treatment. Yield strength (YS), ultimate tensile strength (UTS) and elongation of as-fabricated and T6-treated LMDed GW103K alloy at room temperature are 118–232 MPa-13.9% and 191–298 MPa-8.9%, respectively. Compared with sand cast alloy, as-fabricated LMDed GW103K alloy has comparable YS (−5 MPa), much higher UTS (+51 MPa) and elongation (+12.1%). Unfortunately, after T6 treatment under conventional heat treatment parameters, YS and UTS were about 40 MPa lower than those of sand cast alloy, with relatively higher elongation (+5.8%). Reduction of Gd, Y content during LMD process, grain growth and formation of GdH2 particles during heat treatment are believed to be the main reasons of the reduced YS and UTS. © 2017 Elsevier B.V.


Rong W.,Shanghai JiaoTong University | Zhang Y.,Shanghai JiaoTong University | Wu Y.,Shanghai JiaoTong University | Sun M.,University of Shanghai for Science and Technology | And 6 more authors.
Journal of Alloys and Compounds | Year: 2017

The effects of Zr and Mn additions to Mg-15Gd-1Zn alloy on the formation of long period stacking ordered (LPSO) structure under solution-treated (T4-treated) condition and the dynamic recrystallization (DRX) behavior alloy during extrusion have been investigated. The underneath mechanisms have also been proposed. The results indicate that Zr hinders the formation of LPSO structure by consuming Zn, while the Mn promotes it. On the other hand, Zr suppresses the grain growth by introducing Mg(Zn, Zr) precipitates during the DRX, while Mn effectively hinders the recrystallization process due to increasing LPSO structure. As the LPSO structure has dissolved in recrystallized grains, Mn addition affects little on suppressing grain growth in the grain growth step. Zr addition improves the mechanical properties of both the casting and extruded Mg-15Gd-1Zn alloys by refining grains and introducing Mg(Zn, Zr) precipitates. By contrast, the Mn addition is beneficial for the tensile properties of casting Mg-15Gd-1Zn alloy because of the LPSO structure with high ductility but harmful for the properties of the extruded alloys due to the coarse un-recrystallized grains. © 2016 Elsevier B.V.


Jiang L.,Shanghai JiaoTong University | Liu W.,Shanghai JiaoTong University | Liu W.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | Li Y.,Shanghai JiaoTong University | And 2 more authors.
Journal of Materials Research | Year: 2014

Different parts of a casting may receive different microstructures during cooling particularly for the large scale casting, which can affect the fatigue behavior. In the present study, in consideration of the safety and reliability, the microstructures, tensile properties, and high cycle fatigue behaviors of different regions in a low-pressure sand-cast Mg-10Gd-3Y-0.5Zr (GW103K) magnesium alloy component with large scale and complicated structure were investigated. The results showed that the tensile properties particularly ultimate tensile strength (UTS) and elongation (EL) varied with regions and the fatigue strength varied in a range from 100 to 115 MPa. In addition, crack initiation, crack propagation, and fracture behavior of the studied alloys after tensile test and high cycle fatigue test were also investigated systematically. © Materials Research Society 2014.


Nodooshan H.R.J.,Shanghai JiaoTong University | Liu W.,Shanghai JiaoTong University | Liu W.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | Wu G.,Shanghai JiaoTong University | And 2 more authors.
Journal of Materials Research | Year: 2016

The effects of different Gd additions on wear behavior of the T6 heat treated Mg-xGd-3Y-0.5Zr alloys were investigated. The wear tests were carried out using a Ball-on-flat type wear apparatus against an AISI 52100 type bearing steel ball counterface in the load range of 3-15 N, sliding speed range of 0.03-0.18 m/s, temperature range of 25-200 °C and at a constant sliding distance of 400 m. The results showed that the wear rate of the tested alloys increased with increasing sliding load. By increasing the wear temperature to 200 °C, the wear rate of the Mg-6Gd-3Y-0.5Zr alloy decreased by about 24%. At higher wear speeds, wear resistance of the alloys increased due to the formation of stable oxide layers on the worn surfaces. The alloy containing 12 wt% Gd exhibited higher wear resistance compared with the alloys containing lower Gd contents under the same conditions. Copyright © 2016 Materials Research Society.


Jiang L.,Shanghai JiaoTong University | Liu W.,Shanghai JiaoTong University | Liu W.,Shanghai Light Alloy Net Forming National Engineering Research Center Co | Wu G.,Shanghai JiaoTong University | Ding W.,Shanghai JiaoTong University
Materials Science and Engineering A | Year: 2014

Microstructures, tensile properties and high cycle fatigue behavior of sand-cast Mg-Gd-Y-Zr alloys with different Gd and Zr contents have been investigated. With decreasing Gd content from 9 to 11 wt%, the amount of eutectic phase in sand-cast Mg- xGd-3Y-0.5Zr alloys and of the β' precipitates in peak-aged (T6) conditions decreased, and increasing Zr content from 0.3 to 0.5 wt% led to a decrease in the grain size. The variation of Gd content had a slight influence on the tensile properties, while Zr content had an obvious influence on the tensile properties particularly the elongation. Gd and Zr affected the fatigue behavior in different ways, i.e. the increase of Zr content improved the fatigue strength while the increase of Gd content extends the fatigue life under relatively high stress. © 2014 Elsevier B.V.


Mei J.,Shanghai JiaoTong University | Liu W.,Shanghai JiaoTong University | Liu W.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | Wu G.,Shanghai JiaoTong University | And 2 more authors.
Journal of Materials Research | Year: 2014

A continuous nonflux inclusion-removal method, rotating gas bubble stirring, is used to purify Mg-10Gd-3Y-0.5Zr melt. The effects of rotating gas bubble stirring process parameters (Ar flow rate, time, and rotating speed) on purifying effectiveness, mechanical properties, and fracture behavior of sand-cast Mg-10Gd-3Y-0.5Zr alloy are studied. The results show that too high or too low Ar flow rate is unfavorable for inclusion-removal. The results also indicate that the high rotary speed of spraying gas is helpful to improve the inclusion-removal and mechanical properties. But when the melt is subjected to overtime gas bubbling treatment, the mechanical properties became poor again. Nonflux purification does not change the microstructure of Mg-10Gd-3Y-0.5Zr alloy. However, rotating gas bubble stirring has a certain effect on the fracture pattern of the alloy. In addition, the melt purifying mechanism of the gas bubble stirring treatment for the sand-cast alloy was discussed systematically. © 2015 Materials Research Society.


Zhang Y.,Shanghai JiaoTong University | Wu Y.,Shanghai JiaoTong University | Peng L.,Shanghai JiaoTong University | Peng L.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | And 4 more authors.
Journal of Alloys and Compounds | Year: 2014

An ultra-high strength casting Mg-15.6Gd-1.8Ag-0.4Zr alloy has been developed by conventional ingot metallurgy and heat treatment. The alloy exhibits outstanding ultimate tensile strength of 423 MPa and tensile yield strength of 328 MPa in the peak-aged condition. The main factors contributing to the ultra-high strength are the high number density of the prismatic β′ plates and basal γ″ plates and their relative perpendicular distribution. Besides, a newly intermetallic compound is found in the as-cast microstructure other than Mg5(Gd, Ag) compound. Although, the retained intermetallic compound at the grain boundaries in the alloy solution-treated at 480 °C for 18 h and at 500 °C for 8 h has a similar composition to Mg5(Gd, Ag) compound, its crystal structure is demonstrated to be different to the two types of intermetallic compounds in the as-cast condition. Lastly, the effects of intermetallic compounds and precipitation phases on the fracture behavior of the alloy have been investigated, namely dominant inter-granular fracture in the as-cast and peak-aged conditions and mainly trans-granular fracture in the solution-treated condition.© 2014 Elsevier B.V. All rights reserved.


Jafari Nodooshan H.R.,Shanghai JiaoTong University | Wu G.,Shanghai JiaoTong University | Liu W.,Shanghai JiaoTong University | Liu W.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | And 3 more authors.
Materials Science and Engineering A | Year: 2016

In this study, the compositional dependence of the age hardening response and high temperature tensile properties of the Mg- xGd-3Y-0.5 Zr (x=3, 6, 10, and 12. wt%) alloys are investigated. The amount of cuboid-shaped phases and β' precipitates increased significantly with increasing the Gd content. The Mg-10Gd-3Y-0.5 Zr alloy exhibited the maximum ultimate tensile strength at room temperature, while at higher temperatures the Mg-12Gd-3Y-0.5 Zr alloy exhibited the maximum yield strength and ultimate tensile strength. The yield strength and ultimate tensile strength of the Mg-12Gd-3Y-0.5 Zr alloy increased with the test temperature and showed its maximum at 150°C, and then decreased as the temperature increased further. The Mg-12Gd-3Y-0.5 Zr alloy maintained a high ultimate tensile strength of more than 300 MPa up to 250°C. The superior high temperature tensile strength of the tested alloy is mainly associated with solution strengthening and precipitation hardening of the cuboid-shaped phases and β' precipitates in Mg matrix. Especially, β' precipitates can hinder the dislocation movement at high temperature. © 2015 Elsevier B.V.


Mei J.,Shanghai JiaoTong University | Liu W.-C.,Shanghai JiaoTong University | Liu W.-C.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | Wu G.-H.,Shanghai JiaoTong University | And 6 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2015

The effect of complex melt-refining treatment (melt flux incorporating with rotating gas bubble stirring) on microstructure and mechanical behavior of the sand-cast Mg-10Gd-3Y-0.5Zr alloy was investigated. In addition, the melt purifying mechanism of the complex melt-refining treatment for the sand-cast alloy was discussed systematically. The results show that the new melt-refining method can significantly improve melt quality and mechanical behavior of the tested alloy, i.e., compared to the reference unpurified alloy, the volume fraction of inclusions decreased from 0.47% to 0.28%, the ultimate tensile strength and elongation for T6-treated alloy increased from 245 MPa and 0.7% to 312 MPa and 4.5%, respectively. Especially, combining 1% flux with rotating gas bubble stirring can get even better purifying effectiveness than conventional sole 2% flux purification; the use of melt flux decreased by 50% and significantly reduced environmental pollution. © 2015 The Nonferrous Metals Society of China.


Wang Y.-X.,Shanghai JiaoTong University | Wang Y.-X.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | Ding H.-X.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | Fu P.-H.,Shanghai JiaoTong University | And 2 more authors.
Zhuzao/Foundry | Year: 2014

Spectral analysis materials of Mg-Nd-Zn-Zr alloy were prepared by semi-continuous casting and extrusion technology. The standard certification and deviation of the spectral analysis materials were obtained primarily through cooperation certification of five laboratories. The uniformity was investigated and the working curves of Nd, Zn and Zr elements were constructed, which established development basis of spectral reference materials of Mg-Nd-Zn-Zr alloy.

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