The Influence of Rare Earth, Strontium and Calcium on the Thermal Diffusivity of Mg-Al Alloys

2011 ◽  
Vol 312-315 ◽  
pp. 824-829 ◽  
Author(s):  
Tomasz Rzychoń ◽  
Andrzej Kiełbus
Keyword(s):  
Thermal Conductivity ◽  
Solid Solution ◽  
Rare Earth ◽  
Thermal Diffusivity ◽  
Magnesium Alloy ◽  
Aluminum Content ◽  
Volume Fraction ◽  
Al Alloys ◽  
Mg17al12 Phase ◽  
Increasing Temperature

The microstructure and thermal diffusivity of as-cast AM60, AE63, AJ63 and AXJ620 alloys were investigated over the temperature range 20–300°C. The microstructure of as-cast AM60 magnesium alloy consists of dendrites of α-Mg solid solution and divorced eutectic containing “islands” of α-Mg and Mg17Al12 phase. In regions adjacent with divorced eutectic, the supersaturation aluminum solute in the α-Mg matrix is observed. The addition of rare earth, calcium and strontium caused the decrease of the volume fraction of Mg17Al12 compound and aluminum content in α-Mg solid solution. Moreover, the intermetallic compounds such as: Al11RE3, Al4Sr, Al3Mg13Sr, Al2Ca are observed in the interdendritic regions. The thermal diffusivity of AM60 magnesium alloy increases with increasing temperature up to 150°C, above this temperature the increase is less marked. The change in the slope of the temperature variation of the thermal diffusivity is caused by a precipitation of Mg17Al12 phase in the supersaturation of α-Mg areas neighboring the divorced eutectic α-Mg+Mg17Al12. The addition of rare earth, calcium and strontium caused the increase of the thermal diffusivity and thermal conductivity due to the decreasing of aluminum content in α-Mg matrix.

Research on the Thermal Conductivity and Thermal Diffusivity of Magnesium Alloy

2014 ◽  
Vol 716-717 ◽  
pp. 84-87
Author(s):  
Rui Hua Guo ◽  
Jie Yu Zhang ◽  
Lin Min Wang ◽  
Yi Fan ◽  
Ying Jian Guo
Keyword(s):  
Thermal Conductivity ◽  
Rare Earth ◽  
Thermal Diffusivity ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Hot Spot ◽  
High Strength ◽  
Moderate Amount ◽  
Heat Diffusivity ◽  
Lightweight Engineering

Magnesium, as a kind of lightweight engineering material whose reserves is considerable abundant in the earth, is green environment-friendly materials for the 21st century. Magnesium alloys with its proportion of smaller than the advantages of high strength, good thermal conductivity and easy machining, is becoming a hot spot of attention and research. In this paper, the effects of magnesium alloys thermal conductivity and heat diffusivity were analyzed by consulting documents. Researches showed that all effects of the electron or phonon movement had affected thermal conductivity and thermal diffusivity of alloys. Furthermore, the thermal conductivity and thermal diffusivity of rare earth magnesium alloy were summarized by literature data, Researches showed that Add moderate amount of rare earth elements can improve the thermal conductivity and heat diffusivity of magnesium alloys.

Effect of Solid Solution Time on the Microstructure and Mechanical Properties of AZ81-4Gd Magnesium Alloy

2009 ◽  
Vol 610-613 ◽  
pp. 783-790 ◽  
Author(s):  
Quan Ying Guo ◽  
Ping Li Mao ◽  
Zheng Liu ◽  
Jing Sun ◽  
Chang Yi Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Magnesium Alloy ◽  
Volume Fraction ◽  
Solution Treatment ◽  
Holding Time ◽  
Solution Time ◽  
Mg17al12 Phase ◽  
The Matrix ◽  
Recrystallized Grain Size

The effect of solid solution treatment at temperature of 415oC and different holding time prior aging at 168oC for 16 hours on the mechanical properties and microstructure of AZ81-4Gd magnesium alloy were analyzed by X-ray and SEM. The results demonstrated that with increasing the solid solution time the primary β-Mg17Al12 phase dissolve in the matrix eventually. While the holding time increases to 20 hrs, the primary β-Mg17Al12 phase was completely vanished, but Al2Gd phase kept unchanged with increasing the holding time. In the mean while, the volume fraction of the β-Mg17Al12 phase precipitated during aging increased at first with increasing the holding time then decreased. Moreover, subgrains and twins began to form within the α grain matrix when the solid solution time increased to 12hrs, and the subgains parallele with each other or in the shape of oval. Increasing the solid solution time to 20 hrs the microstructure change dramatically and consist of very fine recrystallized α grains. Futher increasing the holding time the recrystallized grain size increased accordingly. The mechanical properties testing results showed that when the solid solution time increased to 24 hrs the ultimate tensile strength of AZ81-4Gd magnesium alloy was 270 MPa and the elongation was 11.6% respectively.

Influence of Mesocarp Fibre Inclusion on Thermal Properties of Foamed Concrete

2021 ◽  
Vol 87 (1) ◽  
pp. 1-11
Author(s):  
Siti Shahirah Suhaili ◽  
Md Azree Othuman Mydin ◽  
Hanizam Awang
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Volume Fraction ◽  
Thermal Constant ◽  
Volume Fractions ◽  
Foamed Concrete

The addition of mesocarp fibre as a bio-composite material in foamed concrete can be well used in building components to provide energy efficiency in the buildings if the fibre could also offer excellent thermal properties to the foamed concrete. It has practical significance as making it a suitable material for building that can reduce heat gain through the envelope into the building thus improved the internal thermal comfort. Hence, the aim of the present study is to investigate the influence of different volume fractions of mesocarp fibre on thermal properties of foamed concrete. The mesocarp fibre was prepared with 10, 20, 30, 40, 50 and 60% by volume fraction and then incorporated into the 600, 1200 and 1800 kg/m3 density of foamed concrete with constant cement-sand ratio of 1:1.5 and water-cement ratio of 0.45. Hot disk thermal constant analyser was used to attain the thermal conductivity, thermal diffusivity and specific heat capacity of foamed concrete of various volume fractions and densities. From the experimental results, it had shown that addition of mesocarp fibre of 10-40% by volume fraction resulting in low thermal conductivity and specific heat capacity and high the thermal diffusivity of foamed concrete with 600 and 1800 kg/m3 density compared to the control mix while the optimum amount of mesocarp fibre only limit up to 30% by volume fraction for 1200 kg/m3 density compared to control mix. The results demonstrated a very high correlation between thermal conductivity, thermal diffusivity and specific heat capacity which R2 value more than 90%.

Mixing Y89 Influence on Mechanical Properties of Casting Mg17Al12

2015 ◽  
Vol 667 ◽  
pp. 303-307
Author(s):  
Hang Song Yang ◽  
Shao Ju Hao ◽  
Jun Jie Liang
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Rare Earth ◽  
Powder Metallurgy ◽  
Magnesium Alloy ◽  
Light Quality ◽  
Mechanical Performance ◽  
Powder Metallurgy Method ◽  
Compression Performance ◽  
Refinement Effect

For its light quality, good thermal conductivity, and excellent electricity shielding performance, Magnesium alloy has been used in industry, agricultural and so on, for rare earth elements can improve the mechanical performance of magnesium alloy, the study of powder metallurgy is influence by rare earth magnesium is few at present. so, in this paper, by mixing powder metallurgy method the Y89 element was added in Mg17Al12 magnesium alloy, the influence of Y89 on microstructure, hardness and compression performance of Mg17Al12 magnesium alloy was studied, The experimental results show that when amount of Y89’s addition, the mechanical performance is more then and when is 1.22%, its mechanical performance is best, hardness is 66.7 HV, compressive strength is 113.6 MPa,increased respectively by 19.7% and 29.3% compared the Mg17Al12 magnesium alloy substrate, and the grain refinement effect of Mg17Al12 magnesium alloy is the best at this time.

Aluminum-Matrix Aluminum Nitride Particle Composite as a Low-Thermal-Expansion Thermal Conductor

1993 ◽  
Vol 323 ◽  
Author(s):  
Shy-Wen Lai ◽  
D. D. L. Chung
Keyword(s):  
Thermal Conductivity ◽  
Tensile Strength ◽  
Thermal Expansion ◽  
Volume Fraction ◽  
Liquid Aluminum ◽  
Aluminum Matrix ◽  
Aluminum Matrix Composites ◽  
Matrix Composites ◽  
Low Thermal Expansion ◽  
Increasing Temperature

AbstractAluminum-matrix composites containing AIN or SiC particles were fabricated by vacuum infiltration of liquid aluminum into a porous particulate preform under an argon pressure of up to 41 MPa. Al/AIN was superior to Al/SiC in thermal conductivity. At 59 vol.% AIN, Al/AlN had a thermal conductivity of 157 W/m. °C and a thermal expansion coefficient of 9.8 × 10−-6°C−1 (35–100 °C). Al/AlN had similar tensile strength and higher ductility compared to Al/SiC of a similar reinforcement volume fraction at room temperature, but exhibited higher tensile strength and higher ductility at 300–400°C. The ductility of Al/AlN increased with increasing temperature from 22 to 400°C, while that of Al/SiC did not change with temperature. The superior high temperature resistance of Al/AlN is attributed to the lack of a reaction between Al and AIN, in contrast to the reaction between Al and SiC in AI/SiC.

scholarly journals Thermophysical properties of BiFeO3/REE multiferroics in a wide temperature range

2020 ◽  
Vol 10 (01n02) ◽  
pp. 2060019
Author(s):  
Sidek Khasbulatov ◽  
Suleiman Kallaev ◽  
Haji Gadjiev ◽  
Zairbek Omarov ◽  
Abumuslim Bakmaev ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Rare Earth ◽  
High Temperature ◽  
Thermal Diffusivity ◽  
Rare Earth Elements ◽  
Wide Temperature Range ◽  
Thermophysical Properties ◽  
Multiferroic Bifeo ◽  
Comprehensive Study

The paper presents the results of a comprehensive study of the thermophysical properties (thermal conductivity, thermal diffusivity, heat capacity) of high-temperature multiferroic BiFeO3 modified with rare-earth elements (REEs) (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu). The regularities of the formation of the mentioned characteristics were established. The assumptions about the nature of the observed phenomena were suggested.

Effect of timeliness on the thermal properties of paraffin-based Al2O3 nanofluids

2019 ◽  
Vol 33 (05) ◽  
pp. 1950051
Author(s):  
Yangyang Wu ◽  
Baichao Wang ◽  
Dong Li ◽  
Changyu Liu
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Volume Concentration ◽  
Volume Fraction ◽  
Thermal Conversion ◽  
Volumetric Heat Capacity ◽  
Energy Storage Material ◽  
Over Time

Paraffin is an excellent photo-thermal conversion phase change energy storage material, and extensively used in the thermal storage field at the medium-low temperature. However, the low thermal conductivity of paraffin restricts its application in practice. Adding nanoparticles into paraffin is one of the effective methods to improve its thermal conductivity. Nevertheless, the thermal diffusivity, specific heat and volumetric heat capacity of paraffin as well as timeliness were affected after the addition of nanoparticles. In this paper, the influences of volume fraction of Al2O3 nanoparticle and timeliness on these thermal parameters of paraffin were investigated. The results show that the thermal conductivity of paraffin-based Al2O3 nanofluids increases first and then decreases with time, and the maximum thermal conductivity is 0.34 W/[Formula: see text] for volume fraction 1% on third day. The higher volume concentration, the lower specific heat and volumetric heat capacity, all present downtrend over time, until stable in the range of 0.3 MJ/[Formula: see text] and 0.4 MJ/[Formula: see text]. The average enhancement rate of specific heat and volumetric heat capacity are concentrates on −6% to 9%, −10% to 0%, respectively. While increasing the volume concentration, the thermal diffusivity has no obvious regularity, and presents undulatory property over time.

The Thermal Diffusivity of Mg-Al-Sr and Mg-Al-Ca-Sr Sand Casting Magnesium Alloys

2012 ◽  
Vol 326-328 ◽  
pp. 249-254
Author(s):  
Andrzej Kiełbus ◽  
Tomasz Rzychoń ◽  
Grzegorz Moskal
Keyword(s):  
Thermal Diffusivity ◽  
Chemical Composition ◽  
Magnesium Alloys ◽  
Volume Fraction ◽  
Intermetallic Phases ◽  
Sand Casting ◽  
Al Alloy ◽  
Temperature Dependent ◽  
Total Volume Fraction ◽  
Increasing Temperature

In the present study, the thermal diffusivity of four sand casting magnesium alloys: Mg-9Al-1Zn, Mg-6Al-2Sr, Mg-9Al-1.5Ca-0.3Sr and Mg-9Al-2.2Ca-0.8Sr were studied. Sand casting was performed at 730-780°C temperatures. Thermal diffusivity was measured by a LFA 427 Netzsch apparatus. The thermal diffusivity of the investigated alloys was chemical composition and temperature dependent and increased with increasing temperature. The thermal diffusivity of Mg-Al-Ca-Sr alloys was higher than that of Mg-Al alloy, because the total volume fraction of intermetallic phases in alloys containing calcium and strontium is larger than that in Mg-Al alloy. The formation of intermetallic phases caused the consumption of the solute element in the α-Mg matrix, and improved the thermal diffusivity of the Mg-Al-Ca-Sr magnesium alloy.

Damping Properties of AZ91D Magnesium Alloy with Y Addition

2012 ◽  
Vol 476-478 ◽  
pp. 3-10
Author(s):  
Hang Chen ◽  
Xuan Pu Dong ◽  
Xiao Qing Xiong ◽  
Rong Ma ◽  
Shu Qun Chen ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Magnesium Alloy ◽  
Fine Particles ◽  
Mechanical Analysis ◽  
Damping Capacity ◽  
Dislocation Model ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Mg17al12 Phase ◽  
Increasing Temperature

The influence of Y on the microstructure and damping capacity of AZ91D based alloys was investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and dynamic mechanical analysis. The results show that, with increasing Y content, the grain size of α-Mg matrix decreases tremendously and the distribution of β-Mg17Al12 phase is transformed from discontinuous network to fine particles. Meanwhile, a needle-shaped Al4MgY phase mainly distributing at the grain boundaries is identified. The damping capacity of the studied alloys shows sustained enhancement with increasing temperature. As to the strain dependent damping capacity, with the increase of Y content, the damping value of AZ91D alloy decreases gradually before Y content reaches to 0.5wt.%, and fluctuates when Y addition is between 0.5wt.%~0.9wt.%. G-L dislocation model was employed to explain the effects of parameters on damping capacity of magnesium alloy.

Measurement of Effective Thermal Conductivity of CNT-Nanofluids by Transient Short-Wire Method

2009 ◽  
Author(s):  
Masamichi Kohno ◽  
Koichi Kimura ◽  
Shogo Moroe ◽  
Yasuyuki Takata ◽  
Peter L. Woodfield ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Hot Wire ◽  
Wire Method ◽  
Different Shapes ◽  
Transient Short Hot Wire ◽  
Al2o3 Particles ◽  
Particle Shapes

Thermal conductivity and thermal diffusivity of CNT-nanofluids and Al2O3-nanofulids were measured by the transient short-hot-wire method. The uncertainty of their measurements is estimated to be within 1% for the thermal conductivity and 5% for the thermal diffusivity. Three different shapes of Al2O3 particles were prepared for Al2O3–water nanofluids. For the thermal conductivity of Al2O3-water nanofluids, there are differences in the enhancement of thermal conductivity for differences in particle shapes. Hardly any enhancement of thermal conductivity was observed for SWCNT-water nanofluids because the volume fraction of SWCNT was extremely low. However, we consider by increasing the volume fraction of SWCNTs, it will be possible to enhance the thermal conductivity.

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