Heat treatment of vacuum high pressure die cast magnesium alloy AZ91

Wang, Xiao Jing; Zhu, Su-Ming; Easton, Mark; Gibson, Mark; Savage, Gary

doi:10.1179/1743133613y.0000000091

Cited by 19 publications

(12 citation statements)

References 28 publications

(28 reference statements)

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“…1a shows the two-stage super vacuum assisted HPDC process applied for the fabrication of the present die-cast Al-Si-Mg-Mn-TiB2 composites. Different from the generally used one-stage vacuum by evacuation only from the die cavity, here the two-stage vacuum was applied by evacuation from both the shot sleeve and the die cavity simultaneously, and the super vacuum of ~20 mbar was obtained in limited evacuation time, which was far below the commonly achieved vacuum of ~50-100 mbar by the one-stage evacuation process [26][27][28][29]. The details of the two-stage evacuation process were introduced in our latest report [25].…”

Section: Materials Preparationmentioning

confidence: 96%

“…So TiB2 nanoparticles can be chosen to reinforce the die-cast aluminium alloys. Moreover, the super vacuum assisted HPDC process developed recently can achieve a high vacuum of ~20 mbar [25], which is far below the vacuum level of ~50-100 mbar obtained by the conventional vacuum assisted HPDC process [26][27][28][29], and it can largely decrease the gas porosities in HPDC castings and enable the further strengthening of the diecast aluminium alloys through heat treatment.…”

Section: Introductionmentioning

confidence: 92%

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High performance Al/TiB2 composites fabricated by nanoparticle reinforcement and cutting-edge super vacuum assisted die casting process

Dong

Youssef

Zhang

et al. 2019

Composites Part B: Engineering

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The enhancement of double strengthening by nanoparticles and nanoscale precipitates in diecast Al-Si-Mg-Mn-TiB2 composites has be achieved by introducing TiB2 nanoparticles into Al-*Si-*Mg alloy fabricated by super vacuum assisted high pressure die casting process. The composite with 3.5wt.% TiB2 nanoparticles could deliver the hardness of 1.5 GPa, the yield strength of 351 MPa and ultimate tensile strength of 410 MPa in association with an industrially applicable ductility of 5.2 %, after solution and peak ageing heat treatment. The TiB2 nanoparticles distributed at the grain boundaries rather than in the α-Al matrix of the composites in as-cast state. After solution and peak ageing, the TiB2 nanoparticles were enrolled into the α-Al matrix through the combining and coarsening of the α-Al phase during heat treatment, and nanoscale β′′ precipitates formed in the α-Al matrix. Both the TiB2 nanoparticles and the nanoscale β′′ precipitates had highly coherent interfaces with the α-Al matrix, i.e., Al(11-1)//TiB2(0001), Al[011]//TiB2[11-20], Al[320]//β''(a-axis), Al[1-30]//β''(caxis) and Al(020)//β''(b-axis), confirming strong interfacial strengthening. The double strengthening of the TiB2 nanoparticles and the nanoscale β′′ precipitates dispersing in the α-Al matrix resulted in the milestone high strength of the composites.

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Section: Materials Preparationmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 92%

High performance Al/TiB2 composites fabricated by nanoparticle reinforcement and cutting-edge super vacuum assisted die casting process

Dong

Youssef

Zhang

et al. 2019

Composites Part B: Engineering

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“…8, the rosettelike halo has relatively lower Al content in the grain. According to Wang et al, 16) the formation of these halos is caused by the insufficient diffusion of the Al element. We can confirm that this relatively large grain evolved from one of the rosettelike ESCs shown in Fig.…”

Section: Microstructural Evolution During the Early Stage Of Solutionmentioning

confidence: 99%

Microstructural Evolution of Vacuum Die-Cast AZ91D Magnesium Alloy during Solution Treatment

2019

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The microstructural evolution in different regions on the cross section of AZ91D vacuum die castings during solution treatment, especially during the early stage, was investigated. Optical microscope and scanning electron microscope were employed for the microstructure observation. The results exhibited that the supersaturated ¡-Mg solution located in the grain boundaries first dissolved. The ¢-Mg 17 Al 12 particles in the surface layer had a slower dissolution speed when compared to those in the central region, and the remaining ¢-Mg 17 Al 12 particles in the surface layer could effectively restrain the grain growth during the early stage. In the central region, due to the mergence of neighbouring dendrite arms of the same ESC, most remaining ¢-Mg 17 Al 12 particles were encapsulated in the relatively large near globular ¡-Mg grains evolved from the ESCs. The shrinkage porosities concentrated in the segregation band could effectively restrain the grain growth, causing the segregation band maintained a fine microstructure during the solution treatment.

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“…ZnZr 2 precipitations on grain boundaries limit the microstructure coarsening (Ref 37). The positive effects of rare metals are visible in the improvement of the specific strength at both room and elevated temperatures, as well as the creep resistance (Ref [36][37][38][39]. The chemistry of alloys is directly connected with melting temperatures, which were determined using DSC analysis ( Fig.…”

Section: Analysis Of Semi-solid Rangementioning

confidence: 99%

Microstructure Analysis and Rheological Behavior of Magnesium Alloys at Semi-solid Temperature Range

Ślęzak

Bobrowski

Rogal

2018

J. of Materi Eng and Perform

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Microstructure and rheological properties of AZ91 and Elektron 21 magnesium alloys in semi-solid state were studied. Differential scanning calorimetry revealed significant differences in melting range in analyzed materials. Isothermal annealing for 5, 30 and 80 min, in semi-solid range, corresponding to 50 and 70% of solid fraction, showed slower microstructure coarsening kinetics in Elektron 21 due to the presence of Zrand RE-enriched precipitations. Ostwald ripening and coalescence resulted in decrease in grains density with increasing annealing time and temperature. Hardness after annealing showed overall tendency to diminish with soaking time probably due to the growth of average grain size. Rheological analysis showed tendency to lower the value of dynamic viscosity coefficient as shear rate rise, which confirmed non-Newtonian flow behavior. The highest values of dynamic viscosity coefficient were obtained for alloy AZ91.

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Heat treatment of vacuum high pressure die cast magnesium alloy AZ91

Cited by 19 publications

References 28 publications

High performance Al/TiB2 composites fabricated by nanoparticle reinforcement and cutting-edge super vacuum assisted die casting process

High performance Al/TiB2 composites fabricated by nanoparticle reinforcement and cutting-edge super vacuum assisted die casting process

Microstructural Evolution of Vacuum Die-Cast AZ91D Magnesium Alloy during Solution Treatment

Microstructure Analysis and Rheological Behavior of Magnesium Alloys at Semi-solid Temperature Range

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