Microstructure Evolution and Mechanical Properties of Mg-7Gd-3Y-1Nd-2Zn-0.5Zr Alloy during Two-Step Homogenization Heat Treatment

2019 ◽  
Vol 950 ◽  
pp. 15-23
Author(s):  
Ting Li ◽  
Zhi Wei Du ◽  
Wei Liu ◽  
Jia Wei Yuan ◽  
Kui Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Microstructure Evolution ◽  
Cast Alloy ◽  
Eutectic Structure ◽  
Second Step ◽  
Lpso Phase ◽  
Homogenization Heat Treatment ◽  
Long Period ◽  
The Matrix

This paper proposes a two-step homogenization heat treatment to dissolve the eutectic structure and long period stacking ordered phase (LPSO) formed during solidification into the α-Mg matrix. The microstructure evolution and mechanical properties of Mg–7Gd–3Y–1Nd–2Zn–0.5Zr alloy during the two-step homogenization heat treatment have been investigated systemically. The results reveal that as-cast alloy is composed mainly of α-Mg, (Mg,Zn)3RE, eutectic phase, stacking fault, block-like LPSO phase and square-shaped compounds rich in RE. The HRTEM results suggest that the block-like long period stacking ordered phase in as-cast alloy is 14H-type rather than 18R structure, and the stacking sequences of the 14H-LPSO phase are ABABACBCBCBCAB. After the first step homogenization of 520°C for 48 h, the eutectic structure has dissolved into the matrix, whereas the 14H-LPSO phase remains in the alloy. To further dissolve the LPSO phase into matrix, the second step homogenization of 540°C for 24h was adopted. After the second-step of homogenization, the residual 14H-LPSO phase has dissolved into the matrix totally. The as-homogenized alloy is composed mainly of α-Mg and square-shaped compounds rich in RE. The tensile tests at room temperature (RT) exhibit that the ultimate tensile strength (UTS), yield strength (YS) and elongation of as-cast alloy are 172 MPa, 128MPa and 2.8%, whereas the UTS, YS and elongation of as-homogenized alloy are 253 MPa, 185 MPa and 8.4, respectively.

Microstructure Characterization and Mechanical Properties of a Zn and Rare Earth Modified Mg Alloy

2015 ◽  
Vol 727-728 ◽  
pp. 111-114 ◽  
Author(s):  
Li Yuan Sheng ◽  
Fang Yang ◽  
Ting Fei Xi
Keyword(s):  
Mechanical Properties ◽  
Cast Alloy ◽  
Hot Extrusion ◽  
Eutectic Structure ◽  
Crystal Defects ◽  
Treatment Results ◽  
Nanoscale Particles ◽  
Residual Phase ◽  
Heat Treated ◽  
The Matrix

In the present paper, the Mg-Zn-Y-Nd alloy is fabricated by as casting and hot extrusion. Microstructure and mechanical properties of the as-cast, heat treated and hot extruded alloys are investigated. The results exhibit that Mg24Y5 phase with eutectic structure forms in the as-cast alloy, which has an orientation relationship with matrix of . The precipitating phase separates the matrix semi-continuously. The heat treatment results in most precipitates solid soluted into matrix, but there are still some nanoscale particles and residual phase along grain boundary. The hot extrusion refines the microstructure and leads to the formation of stacking faults in the matrix. Compared with the as-cast and heat treated alloy, the hot extruded alloy obtain great improvement in mechanical properties, which should be attributed to the grain refinement, solid solution and fomation of crystal defects

Synthesis, Microstructure, and Mechanical Properties of FeCo-VC Composites

2006 ◽  
Vol 980 ◽  
Author(s):  
Hongbin Bei ◽  
E. P. George
Keyword(s):  
Mechanical Properties ◽  
Cast Alloy ◽  
Tensile Tests ◽  
Eutectic Structure ◽  
Directionally Solidified ◽  
Quaternary Alloys ◽  
The Matrix ◽  
Solid Solution Matrix ◽  
Solution Matrix

AbstractFe-Co-V-C quaternary alloys were drop cast and directionally solidified to obtain an in situ composite. It is found that the fully eutectic structure occurs at a composition of Fe - 40.5Co -10.4V- 8.6C (at. %) in a drop-cast alloy. Directional solidification of this composition in a high-temperature optical floating zone furnace produces a well-aligned microstructure, consisting of sub-micron VC fibers (~19% by volume) embedded in a FeCo-5V solid solution matrix containing ~ 1% C. The temperature dependencies of mechanical properties of this composite were examined by tensile tests and the composite was found to have higher yield strength and lower ductility than the matrix.

Effect of Heat Treatment on Structure and Mechanical Properties of Al-30 Wt.% Si Alloys Refined and Modified with Sr+B+RE

2014 ◽  
Vol 556-562 ◽  
pp. 484-488
Author(s):  
Xiao Song Li ◽  
An Hui Cai ◽  
Ji Jie Zeng
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Orthogonal Experiment ◽  
Primary Silicon ◽  
Eutectic Structure ◽  
Holding Time ◽  
Solution Temperature ◽  
Fully Integrated ◽  
Alloy Hardness ◽  
The Matrix

On the basis of orthogonal experiment, the effect of heat treatment on structure and mechanical properties of Al-30 wt.% Si alloys refined and modified with Sr+B+RE has been investigated. The results show that the solution temperature and holding time on the alloy microstructure and hardness are affected. When the holding time is constant, as the solution temperature increased, primary silicon more fully integrated into the matrix, the matrix divided by the effect of more and more obvious, eutectic structure becomes coarse, roundness becomes high, the alloy hardness to improve. When the solution temperature is constant, with the holding time increased, primary silicon more fully integrated into the matrix, the matrix divided by the effect of more and more obvious, eutectic structure becomes coarse, roundness becomes high, the alloy hardness increase. When the temperature reaches 540°C, the holding time makes eutectic roundness variation, the hardness declines, the alloy hardness is hardest when solution temperature is 540°C and the holding time is 7h. Optimum heat treatment parameters: 540°C×7h.

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.

Effect of Long-Period Stacking Order Phase and α-Mg Phase on Strength and Ductility of Mg-Zn-Y Alloy

2012 ◽  
Vol 706-709 ◽  
pp. 1237-1242 ◽  
Author(s):  
Masafumi Noda ◽  
Yoshihito Kawamura
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
High Temperatures ◽  
Mg Alloys ◽  
Tensile Yield Strength ◽  
Block Type ◽  
Lpso Phase ◽  
Long Period ◽  
Stacking Order ◽  
Type Phase

Mg alloys are lightweight structural alloys that normally have a good castability and machinability as well as an excellent specific strength and rigidity. However, the mechanical properties of Mg alloys are inferior to those of Al alloys, and their range of industrial applications is limited. Recently, Mg–Zn–Y alloy has been found to show a high tensile yield strength with a good elongation. The alloy has a long-period stacking order (LPSO) phase as the secondary phase in an α-Mg phase. In general, the tensile yield strengths of LPSO-type Mg alloy are known to be markedly enhanced by the formation of kink bands in the LPSO phase and by microstructural refinement of the α-Mg phase during plastic deformation. The separate roles of the LPSO phase and the α-Mg phase in relation to the mechanical properties of high-strength LPSO-type Mg alloy were investigated at ambient and high temperatures. For high strengths at ambient and high temperatures, it was important that the α-Mg phase consisted of a fine-grain region and a nonrecrystallized region, and that the LPSO phase remained as a block-type phase. On the other hands, it was necessary to change the LPSO phase from a block-type phase into a plate-type phase by heat treatment before tensile testing to improve the ductility of the alloy while maintaining its tensile yield strength. Microstructural control of the LPSO phase and the α-Mg phase is necessary to obtained Mg–Zn–Y alloy with superior mechanical properties at ambient-to-high temperatures.

Crystallization behavior, Al-Ce intermetallic formation, and microstructure refinement of near-eutectic Al–Si alloys by rare-earth element additions

2020 ◽  
Vol 111 (11) ◽  
pp. 938-952
Author(s):  
Bo Chi ◽  
Zhiming Shi ◽  
Cunquan Wang ◽  
Liming Wang ◽  
Hao Lian ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Crystallization Behavior ◽  
Earth Element ◽  
Microstructural Refinement ◽  
Preferential Growth ◽  
Intermetallic Formation ◽  
The Matrix

Abstract Near-eutectic Al-Si alloys have low strength and high brittleness because of the presence of many eutectic b-Si flakes, needle-like Al-Fe-Si intermetallics, and coarse α-Al grains. This study disclosed the effects of cerium-rich RE (rare earth) element modification on orientation characters of crystals, formation of Al-Ce compounds, and microstructural refinement to improve the microstructure and mechanical properties of the alloys. The RE addition depressed preferential growth along the close-packed and/or sub-closepacked planes and promoted growth along the non-closepacked planes, in which La and other elements were dissolved into needle-like Al11Ce3 phase. When the temperature decreased, Al11Ce3 was preferentially crystallized from the melts and then devitrified by attaching to the surface of β-Al5FeSi needles. Moreover, many small Al11Ce3 particles were precipitated in the matrix and on the Si surface by a T6 heat treatment. Eutectic β-Si phases were constructed into discontinuous networks, short rods, and even particles by RE additions, which were further transformed into fine nodules following the T6 treatment. α-Al grains and primary β-Al5FeSi needles were simultaneously refined. The addition of 1.0 wt.% REs and subsequent T6 treatment yielded the highest tensile strength, elongation, and hardness of the alloy.

Effect of Heat-Treatment Time on Microstructure and Mechanical Properties of Mg-5Gd-2Y-2Zn-0.5Zr Alloy

2012 ◽  
Vol 482-484 ◽  
pp. 1384-1389 ◽  
Author(s):  
Ling Gang Meng ◽  
Can Feng Fang ◽  
Peng Peng ◽  
Nai Pu Li ◽  
Qiong Zhu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Treatment Time ◽  
Time Range ◽  
Lpso Phase ◽  
High Temperature Heat Treatment ◽  
Lpso Structure ◽  
The Matrix ◽  
New Type ◽  
The Stability

Microstructure evolution of Mg-5Gd-2Y-2Zn-0.5Zr alloy during high temperature heat-treatment at 500°C in the time range 10-70h was investigated. The results show that after adding the element Y, the as-cast Mg-5Gd-2Y-2Zn-0.5Zr alloy forms the Mg12Zn(Y,Gd) phase with 18R-LPSO structure at the grain boundary. During heat-treatment at 500°C, the stability of 18R-LPSO structure is weakened by Gd atoms, parts of LPSO phases dissolve gradually into the matrix with time prolonged and a new type Mg(Y,Gd)Zn phase come into being. LPSO phase in the grain boundary can ensure the ultimate tensile strength and elongation of the alloy, and effect of dissevering on the LPSO phase by Mg(Gd,Y)Zn phase results the decrease of UTS and elongation.

Microstructure Evolution and Mechanical Properties of Mg-Gd-Y-Zn-Zr Alloy during Compression

2021 ◽  
Vol 1035 ◽  
pp. 278-285
Author(s):  
Lei Chen Jia ◽  
Jian Min Yu ◽  
Guo Qin Wu ◽  
Wen Long Xu ◽  
Yong Gang Tian ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Plastic Strain ◽  
Microstructure Evolution ◽  
Large Angle ◽  
Compression Behavior ◽  
Kink Bands ◽  
Long Period ◽  
Different Temperatures ◽  
Compression Temperature ◽  
Zr Alloy

The compression behavior and mechanical properties of the Mg-13Gd-4Y-2Zn-0.5Zr (wt.%) alloy filled with intragranular long-period stacking ordered (LPSO) phases at different temperatures were investigated. The results showed that the higher the compression temperature, the smaller the plastic strain that the grains withstand. The grains changed from equiaxed to flat strips when compressed at 350°C, and the morphology of the grains did not change at 450°C. Due to the existence of DRX grains, compression at 450 °C didn’t cause large-angle kink, but the kink angle at 350°C was very large. DRX grains only appeared at the grain boundaries and around the intergranular LPSO phase at the beginning of compression, and only appear at the kink bands (KBs) after the lamellar LPSO phases begin to kink. DRX grains gradually increased with the KBs increasing.

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