scholarly journals Effects of Zn content on Hot Tearing Susceptibility of Mg–7Gd–5Y–0.5Zr Alloy

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 414
Author(s):  
Ziqi Wei ◽  
Shimeng Liu ◽  
Zheng Liu ◽  
Feng Wang ◽  
Pingli Mao ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Parent Phase ◽  
Hot Tearing ◽  
Shrinkage Stress ◽  
Second Phase ◽  
Residual Liquid ◽  
Long Period ◽  
Zn Content ◽  
Feeding Effect ◽  
Hot Tearing Susceptibility

Mg–7Gd–5Y–0.5Zr alloy has excellent mechanical properties but poor hot tearing resistance. The latter makes it difficult to cast billets, which limits the size of subsequently processed parts. Therefore, the hot tearing susceptibility of Mg–7Gd–5Y–xZn–0.5Zr (x = 0, 3, 5, 7 wt%) alloys was studied. It was found that Zn can significantly reduce hot tearing susceptibility of Mg–7Gd–5Y–0.5Zr alloy, which almost linearly decreased with Zn content. When Zn content was 3 wt%, 5 wt% and 7 wt%, hot tearing susceptibility will be reduced by 27%, 83% and 100%, respectively. It was further revealed that the solid solubility of Gd and Y in α-Mg decreased with the increase of Zn content, and the nucleation temperature decreased accordingly, which resulted in the increase of nucleation rate and the refinement of final grains. On the macro level, it showed that the dendrite coherency temperature decreased, the solidification shrinkage stress of α-Mg slowed down, and the residual liquid channel became shorter and hot tearing susceptibility decreased. It was also found that with the increase of Zn content, the content of Zn, Gd and Y enriched on the grain boundary increased, the content of residual liquid phase between dendrites increased after α-Mg crystallization, and the solidified precipitated second phase also changed from Mg5RE phase to long-period stacking ordered phase + W-phase (a little), long-period stacking ordered phase + W-phase (much) and finally to W-phase only. The feeding effect of sufficient intergranular residual liquid on the shrinkage of α-Mg dendrite and the bridging effect of the precipitated phase at the grain boundary (especially long-period stacking ordered phase which is coherent with the parent phase) also led to the decrease of hot tearing susceptibility.

Effects of Zn Content on Hot Tearing Susceptibility of Mg–Zn–Gd–Y–Zr Alloys

2022 ◽  
Author(s):  
Ziqi Wei ◽  
Shimeng Liu ◽  
Zheng Liu ◽  
Le Zhou ◽  
Yan Li ◽  
...  
Keyword(s):  
Hot Tearing ◽  
Zn Content ◽  
Hot Tearing Susceptibility ◽  
Zr Alloys

High-Resolution STEM Characterisation of Discontinuous Precipitate Products in Aluminum-Zinc

1985 ◽  
Vol 43 ◽  
pp. 356-357
Author(s):  
G. Solórzano
Keyword(s):  
Grain Boundary ◽  
Parent Phase ◽  
Practical Importance ◽  
Diffusion Path ◽  
Composition Gradient ◽  
Second Phase ◽  
Fast Diffusion ◽  
State Transformation ◽  
Diffusion Controlled ◽  
Boundary Reaction

Discontinuous precipitation is an interface diffusion-controlled transformation resulting from the decomposition of a supersaturated parent phase α° to yield generally a lamellar second phase 8 and a less-supersaturated matrix α'. The main transformation interface is therefore a grain boundary which acts as a fast diffusion path, enabling the required composition to change at temperatures too low for appreciable volume diffusion. The practical importance of this transformation, present in a large number of alloy systems, is related to the degradation of precipitation hardening microstructures, wherein an otherwise long lived microstructure is discontinuously coarsened by the sweeping grain boundaries.The Kinetic and thermodynamical aspects of the steady state transformation has been Know, in theory, for many years. The theory predicts that the grain boundary-reaction front is capable of supporting a composition difference across it and a composition gradient along it.

Effects of the second phase on hot tearing susceptibility of Mg-Zn-Y alloy

2018 ◽  
Vol 6 (1) ◽  
pp. 016529 ◽  
Author(s):  
Zijian Zhou ◽  
Zheng Liu ◽  
Yue Wang ◽  
Shimeng Liu ◽  
Wanru Tang
Keyword(s):  
Hot Tearing ◽  
Second Phase ◽  
Hot Tearing Susceptibility

scholarly journals Residual Stresses in the Hot Sprues of as-cast Mg-Zn Alloys Investigated by STRESS-SPEC Neutron Diffractometer

2013 ◽  
Vol 768-769 ◽  
pp. 428-432
Author(s):  
Wei Min Gan ◽  
Yuan Ding Huang ◽  
Zhi Wang ◽  
Norbert Hort ◽  
Michael Hofmann
Keyword(s):  
Residual Stress ◽  
Neutron Diffraction ◽  
Residual Stresses ◽  
Hot Tearing ◽  
Neutron Diffractometer ◽  
Zn Content ◽  
Residual Strains ◽  
Zn Alloys ◽  
Hot Tearing Susceptibility

Residual strains near the sprues of ingots with different contents of Zn (6 wt. % and 9 wt. %) were measured using neutron diffraction. The results showed that the increase of Zn content decreases the residual stress in the hot sprue region. These results are good in agreement with that obtained by the measurement of hot tearing susceptibility.

Hot Tearing Evaluation and Contraction Behaviors of Four AA7xxx Alloys

2015 ◽  
Vol 817 ◽  
pp. 21-26 ◽  
Author(s):  
Qing Ling Bai ◽  
Jun Cheng Liu ◽  
Yue Li ◽  
Hong Xiang Li ◽  
Qiang Du ◽  
...  
Keyword(s):  
Aluminum Alloys ◽  
Hot Tearing ◽  
Thermal Contraction ◽  
Solidification Range ◽  
Complex Interactions ◽  
Zn Content ◽  
Constrained Rod Casting ◽  
Hot Tearing Susceptibility

The hot tearing susceptibilities (HTS) of some AA7×××alloys, AA7050, AA7055, AA7085 and AA7022 were evaluated with constrained rod casting (CRC). Thermal contraction behaviors during solidification were measured as well in a T-shaped setup. The results showed that alloys with HTS from high to low were AA7055, AA7085, AA7050 and AA7022. Zn content in 7××× aluminum alloys seemed to play a major role with respect to the HTS index. Remarkable differences could be seen on thermal contraction behaviors within solidification range for each alloy. The rate and amount of thermal contraction for AA7055 was most prominent, followed by AA7085 and AA7050, while contraction curve of AA7022 was very flat together with least amount of thermal contraction. There was a well consistency between the amount of thermal contraction and HTS. Despite complex interactions of many variables in the formation of hot tear, thermal contraction behaviors within solidification range could give a quick evaluation of hot tearing susceptibility.

scholarly journals Fabrication and Microstructure of ZnO/HA Composite with In Situ Formation of Second-Phase ZnO

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 3948
Author(s):  
Shidan Yuan ◽  
Ye Ma ◽  
Xingyi Li ◽  
Zhen Ma ◽  
Hui Yang ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Boundary Migration ◽  
Energy Dispersive Spectrometer ◽  
Chemical Precipitation ◽  
Chemical Precipitation Method ◽  
Precipitation Method ◽  
Second Phase ◽  
Air Atmosphere ◽  
Powder Sintering ◽  
Zn Content

Nanometer hydroxyapatite (n-HA) powders were synthesized by the chemical precipitation method, and a novel ZnO/HA composite, which consisted of second-phase particles with different sizes and distributions, was successfully fabricated. ZnO/HA composites were prepared by using powder sintering with different Zn contents and a prefabrication pressure of 150 MPa. Microstructure and local chemical composition were analyzed by a scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS), respectively. The phase composition and distribution of the composite were determined with electron back-scattered diffraction (EBSD) and an X-ray diffractometer (XRD), respectively. The experimental results of the XRD showed that the chemical precipitation method was a simple and efficient method to obtain high-purity n-HA powders. When the sintering temperature was lower than 1250 °C, the thermal stability of HA was not affected by the Zn in the sintering process. Due to sintering in an air atmosphere, the oxidation reaction of Zn took place in three stages, and ZnO as the second phase had two different sizes and distributions in the composites. The compressive strength of ZnO/HA composites, of which the highest was up to 332 MPa when the Zn content was 20%, was significantly improved compared with pure HA. The improvement in mechanical properties was mainly due to the distribution of fine ZnO particles among HA grains, which hindered the HA grain boundary migration and refinement of HA grains. As grain refinement increased the area of the grain boundary inside the material, both the grain boundary and second phase hindered crack development in different ways.

scholarly journals Effect of long-period stacking ordered phase on hot tearing susceptibility of Mg–1Zn–xY alloys

2020 ◽  
Vol 8 (4) ◽  
pp. 1176-1185
Author(s):  
Ye Zhou ◽  
Pingli Mao ◽  
Le Zhou ◽  
Zhi Wang ◽  
Feng Wang ◽  
...  
Keyword(s):  
Hot Tearing ◽  
Long Period ◽  
Hot Tearing Susceptibility

Morphology of Σ3{/70.53°} grain boundaries in a C15 intermetallic compound

1994 ◽  
Vol 52 ◽  
pp. 684-685
Author(s):  
Fuming Chu ◽  
D. P. Pope ◽  
D. S. Zhou ◽  
T. E. Mitchell
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Crystallographic Analysis ◽  
Laves Phase ◽  
Second Phase ◽  
Bright Field Image ◽  
Boundary Edge ◽  
Arc Melting ◽  
Fcc Lattice ◽  
Diffraction Patterns

A C15 Laves phase, HfV2+Nb, shows promising mechanical properties and here we describe the structure of its grain boundaries. The C15 Laves phase has a fcc lattice with a=7.4Å. An alloy of composition Hf14V64Nb22 (including a C15 matrix and a second phase of V-rich bcc solution) was made by arc-melting. The alloy was homogenized at 1200°C for 120h. Preliminary study concentrated on Σ3{<110>/70.53°} grain boundaries in the C15 phase using Philips 400T and CM 30 microscopes.The most-commonly observed morphology of Σ3{<110>/70.53°} grain boundaries in the C15 phase is a faceted boundary. A bright field image (BFI) of the faceted boundary and the corresponding diffraction patterns with the grain boundary edge-on are shown in Fig. 1(a). From the diffraction patterns using a <110> zone axis for both grains, it is obvious that this is a Σ3{<110>/70.53°} grain boundary. Crystallographic analysis shows that the Σ3{<110>/70.53°} grain boundaries selectively facet with the following relationships between the two grains: {111}1//{111}2, {112}1//{112}2, {111}1//{115}2, and {001}1//{221}2.

scholarly journals A Study on the Damping Capacities of Mg–Zn–Y-Based Alloys with Lamellar Long Period Stacking Ordered Phases by Preparation Process

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 79
Author(s):  
Ruopeng Lu ◽  
Kai Jiao ◽  
Yuhong Zhao ◽  
Kun Li ◽  
Keyu Yao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Damping Capacity ◽  
Second Phase ◽  
Preparation Process ◽  
Obvious Effect ◽  
Lpso Phase ◽  
Long Period ◽  
Lamellar Phases ◽  
Ordered Phases

Mg alloys with fine mechanical properties and high damping capacities are essential in engineering applications. In this work, Mg–Zn–Y based alloys with lamellar long period stacking ordered (LPSO) phases were obtained by different processes. The results show that a more lamellar second phase can be obtained in the samples with more solid solution atoms. The density of the lamellar LPSO phase has an obvious effect on the damping of the magnesium alloy. The compact LPSO phase is not conducive to dislocation damping, but sparse lamellar phases can improve the damping capacity without significantly reducing the mechanical properties. The Mg95.3Zn2Y2.7 alloy with lamellar LPSO phases and ~100 μm grain size exhibited a fine damping property of 0.110 at ε = 10–3.

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