Effect of Heat Treatment on the Corrosion Resistance of Cast Mg-7.3Al Alloy

2010 ◽  
Vol 146-147 ◽  
pp. 585-588
Author(s):  
Su Qiu Jia ◽  
Guo Jun Liu ◽  
Qi Shuang Chen
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Microstructural Characterization ◽  
Main Role ◽  
Β Phase

Mg-7.3Al magnesium alloys were investigated in the paper. The paper presents microstructural characterization of Mg-7.3Al alloy after casting and heat treatment. The casting temperature was 740°C and heat treatment was performed at 420 °C for 24 h with aging at 180 °C for 8h,16h,24h. The microstructure of the casting alloy consists of α-Mg phase matrix with a primary β phase (Mg17Al12) at grain boundaries. After solution treatment β phases were soluted in α-Mg phase matrix . Aging treatment caused β phases precipitation. The corrosion resistance of magnesium alloy was determined in 3.5 % NaCl by immersion tests and polarization curves. The results shows that the corrosion resistance of magnesium alloy after solution treat is the best than that of the others heat treatment in polarization curve tests and the samples with aging for 16h and 24h presents higher corrosion resistance than those with solution and aging for 8h in immersion tests. Solution treatment plays a main role for corrosion resistance of Mg-7.3Al magnesium alloy in short term corrosion, but more continuous β phases in Mg-7.3Al alloy after ageing act as a barrier and play a main role in long term corrosion.

Effect of Solution Treatment on Microstructure and Mechanical Hardness of Ti-6Al-7Nb

2020 ◽  
Vol 860 ◽  
pp. 218-222
Author(s):  
Della Maharani ◽  
Anawati Anawati ◽  
I. Nyoman Jujur ◽  
Damisih
Keyword(s):  
Centrifugal Casting ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Xrd Analysis ◽  
Optical Microscope ◽  
Alloying Element ◽  
Mechanical Hardness ◽  
Β Phase ◽  
Permanent Implant

The metastable β Ti-6Al-4V alloy has been used clinically as a permanent implant material owing to its suitable mechanical properties and biocompatibility. However, the alloying element V was accused of causing toxicity when released to human body fluid. In this work, Nb was used in the alloy to replace V. This study presents the characterization of microstructure and mechanical hardness of as-cast Ti-6Al-7Nb and after solution treatment. The Ti-6Al-7Nb alloy was fabricated by the centrifugal casting method. Solution treatment was carried out at 970°C for 1 hour, followed by oil quenching, and consecutively an aging treatment was applied at 500°C for 8 hours. The microstructure was studied by an optical microscope. The mechanical hardness was measured by microhardness Vickers. The results show that the mechanical hardness of the Ti-6Al-7Nb decreased from 396.2 to 377.2 HV as a result of the solution treatment. Reduction in the hardness was attributed to the phase transformation of α to the β phase during the solution treatment. The XRD analysis showed a reduction in the intensity of α phases at the (011), (012), and (020) planes in the alloy after the solution treatment. The results indicated that the microstructure and mechanical hardness of Ti-6Al7-Nb alloy were affected by the solution treatment.

scholarly journals Microstructure Evolution and Mechanical Properties of AZ80 Mg Alloy during Annular Channel Angular Extrusion Process and Heat Treatment

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4223 ◽  
Author(s):  
Xi Zhao ◽  
Shuchang Li ◽  
Fafa Yan ◽  
Zhimin Zhang ◽  
Yaojin Wu
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Microstructure Evolution ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Annular Channel ◽  
Mg Alloy ◽  
Strengthening Effect ◽  
Β Phase ◽  
Angular Extrusion

Microstructure evolution and mechanical properties of AZ80 Mg alloy during annular channel angular extrusion (350 °C) and heat treatment with varying parameters were investigated, respectively. The results showed that dynamic recrystallization of Mg grains was developed and the dendritic eutectic β-Mg17Al12 phases formed during the solidification were broken into small β-phase particles after hot extrusion. Moreover, a weak texture with two dominant peaks formed owing to the significant grain refinement and the enhanced activation of pyramidal <c + a> slip at relative high temperature. The tension tests showed that both the yield strength and ultimate tensile strength of the extruded alloy were dramatically improved owing to the joint strengthening effect of fine grain and β-phase particles as compared with the homogenized sample. The solution treatment achieved the good plasticity of the alloy resulting from the dissolution of β-phases and the development of more equiaxed grains, while the direct-aging process led to poor alloy elongation as a result of residual eutectic β-phases. After solution and aging treatment, simultaneous bonding strength and plasticity of the alloy were achieved, as a consequence of dissolution of coarse eutectic β-phases and heterogeneous precipitation of a large quantity of newly formed β-phases with both the morphologies of continuous and discontinuous precipitates.

Effect of Heat Treatments on the Bio-Corrosion Resistance of Magnesium Alloy Mg-8.0Al-1.0Zn-xGd

2011 ◽  
Vol 213 ◽  
pp. 497-501
Author(s):  
Lei Li ◽  
Rui He ◽  
Guo Jie Huang ◽  
Shui Sheng Xie
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Annealing Treatment ◽  
Microstructure Analysis ◽  
Β Phase ◽  
Α Phase ◽  
Treatment Procedures ◽  
Human Fluid

In order to improve the bio-corrosion resistance of magnesium alloy Mg-8.0Al-1.0Zn-xGd in the simulated human fluid, different heat treatment procedures were studied. Results showed that annealing treatment lowered the alloy’s corrosion resistance and hardness, while T6 treatment (solid solution+ aging) improved the alloy’s corrosion resistance and hardness. Microstructure analysis showed that the β phase dissolved into α phase after the annealing treatment. Hence, annealing treatment decreased the alloy’s corrosion resistance. However, lots of β-phases were precipitated in the T6 heat treatment, and they impeded the corrosion extending.

Hydrogen-Induced Microstructure Optimization of the Ti-6Al-4V Alloy

2020 ◽  
Vol 986 ◽  
pp. 24-32
Author(s):  
Mohammed Kasim Mohsun
Keyword(s):  
Heat Treatment ◽  
Electron Backscatter Diffraction ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Martensite Phase ◽  
Hydrogen Gas ◽  
Hydrogen Treatment ◽  
Alloying Element ◽  
X Ray ◽  
Β Phase

To obtain advanced materials through the development of traditional materials without the addition of another alloying element, advanced heat treatment can be used. One such innovative process is a thermo-hydrogen treatment (THT); it facilitates a purposeful adjustment of an improved microstructure using hydrogen as a temporary alloying element within heat treatment. In this paper, the five-step process of homogenization, hydrogenation, solution treatment, dehydrogenation, and aging was used in THT. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), backscattered electron (BSE), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD) were utilized to analyze the phases and phase transformations in Ti-6Al-4V. Three different homogeneous microstructures were established for the investigation using different homogenization parameters values. The hydrogenation was carried out for these microstructures via hydrogen gas charging leading to hydrogen concentrations for the formation of hydride (δ TiH2). After the solution treatment at a temperature above β transus temperature (Tβ), the metastable phases of a martensitic structure consisting of a mixture of α ́ (hcp) and α ́ ́ (orthorhombic) was found. Steps 4 and 5 of THT were a vacuum annealing (hydrogen degassing) followed by aging treatment. The aging treatment was applied to complete the martensite phase decomposition and the precipitation of two phases. By means of this THT cycle, very fine equiaxed microstructures could be established. These microstructures consist of the αs phase (secondary α) in the β phase matrix and the α2 phase (Ti3Al) in the αp phase. The precipitation of these phases increases the strength of the Ti-6Al-4V alloy and, consequently, enhances the mechanical properties. No evidence of the δ phase was found.

Effect of Heat Treatment on Microstructure and Corrosion Behavior of Az91d Magnesium Alloy

2013 ◽  
Vol 685 ◽  
pp. 102-106 ◽  
Author(s):  
Lih.T Chye ◽  
M.Z.M. Zamzuri ◽  
S. Norbahiyah ◽  
Khairul Azwan Ismail ◽  
M.N.B. Derman ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Treatment Process ◽  
Corrosion Behaviour ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Accelerated Corrosion ◽  
Β Phase ◽  
Cathode Area ◽  
Immersion Testing ◽  
Cast Condition

An AZ91D ingot in the as-cast condition was homogenized by heat treatment process. Then, the microstructures produced and corrosion behaviour after heat treatment was studied in detail. As-cast AZ91D was recrystallize by solution treatment at 415°C and then aged at 175°C for various period of time. The corrosion resistance of all the different microstructures was studied in NaCl solution through weight loss measurement in immersion testing. The β phase was found to have a significant influence on the corrosion behaviour. In solution treatment, β phase dissolution decreased the cathode area leading to accelerated corrosion rate. After aging treatment, fine β phase precipitates between grain and microstructure recrystallize causing an increase in the corrosion resistances.

Effects of Hot Extrusion and Heat Treatment on Mechanical Properties and Microstructures of AZ91 Magnesium Alloy

2012 ◽  
Vol 562-564 ◽  
pp. 242-245 ◽  
Author(s):  
Ming Tan ◽  
Zhao Ming Liu ◽  
Gao Feng Quan
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Strength ◽  
Magnesium Alloy ◽  
Solution Treatment ◽  
Annealing Treatment ◽  
Aging Treatment ◽  
Az91 Alloy ◽  
Az91 Magnesium Alloy ◽  
Az91 Magnesium

The effects of heat treatment on the microstructure, tensile property and fracture behavior of as-extruded AZ91 magnesium alloy were studied by OM and SEM. The results show that the grain of as-cast AZ91 alloy is refined by extruding and dynamic recrystallization, and the mechanical properties increase obviously. The ductility is significantly enhanced after solution treatment of the as-extruded AZ91 alloy, tensile strength is almost the same before and hardness is significantly reduced after solution treatment and artificial aging treatment. The tensile strength reduced and the ductility is significantly enhanced of as-extruded AZ91 magnesium alloy after annealing processes. The fracture surface of as-extruded AZ91 magnesium alloy has the mixture of ductile and brittle characteristic. But after T6 or annealing treatment, its dimple number increases evidently.

Optimization of Heat Treatment Process on Vacuum Die-Casting AT72 Magnesium Alloy

2013 ◽  
Vol 747-748 ◽  
pp. 307-312
Author(s):  
Da Quan Li ◽  
Yong Liu ◽  
Jun Xu ◽  
Shuang Shao ◽  
Chun Shui Xu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Magnesium Alloy ◽  
Grain Boundary ◽  
Treatment Process ◽  
Die Casting ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Heat Treatment Process ◽  
Vacuum Die Casting ◽  
The Matrix

The effect of heat treatment on vacuum die-casting (VDC) AT72 magnesium alloy was studied. The optimal process of heat treatment was obtained. The result shows that the alloy was composed of α-Mg, Mg17Al12and Mg2Sn. After solution treatment at 686K for 24h, Mg17Al12completely dissolved in α-Mg matrix. With the aging treatment following solution treatment, Mg17Al12kept precipitating in the matrix and along grain boundary. Moreover, Mg2Sn distributed along the grain boundary did not disappear after solution treatment at 686K. This indicates that Mg2Sn phase exhibits very high thermal stability. The heat treatment process was optimized with solution at 686K for 24h plus ageing at 473K for 18h, in the condition of which AT72 magnesium alloy exhibits a maximum hardness with value of 90.8Hv. The successful application of heat treatment for AT72 magnesium alloy could be attributed to the elimination of the air bubble in the casing through VDC. However, the porosity in the cast couldnt be efficiently eliminated by VDC, which result in the growth of shrinkage pore.

scholarly journals Characterization of Microstructure and Mechanical Properties of CuCr Alloy Produced by Stir Casting

2019 ◽  
Vol 12 (4) ◽  
pp. 82-91
Author(s):  
Asaad Kadhim Eqal ◽  
Sami Abualnoun Ajeel ◽  
Rabiha S. Yaseen
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Chromium Content ◽  
Pure Copper ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Stir Casting ◽  
Casting Method ◽  
Alloy Castings

The relatively low mechanical properties of pure copper at low and high temperature made it very limited applications. The mechanical properties of the copper can be improved by adding a small amount of elements such as Cr. This work consists of four CuCr alloy castings (0.3, 0.8, 1.2 and 1.5%) by using the stir casting method in an argon atmosphere. Then, the heat treatment was done for these alloys which included solution treatment and aging. Heat treatment was treated at 980 ° C for 1 hour, then water-quenching, followed by an aging treatment at 480 ° C for 2.4 and 6 hours. The Optical Microscopy and the Scanning Electron Microscopy (SEM) with  (EDS) were used to study the microscopic structure of the produced alloys. The results showed that the mechanical properties of copper increased with increasing chromium content. The microstructure of the castings consist of  the dendiritic structure, columinar and segregation. It has been also indicated that after heat treatment and aging, the microstructure changed to fine grains and the clusters disappeared. XRD showed a α-Cu phase and a small amount of CrO2 in microstructures. The highest value of hardness and the ultimate tensile were 101 Hv and 239.12 MPa, respectively. They were achieved at 1.5wt% addition of Cr at 480oC and 4hrs aging

Investigation of heat treatment and subsequently surface modification by nano-TiO2 on Mg–Zn–Ca–Mn bio-magnesium alloy

2019 ◽  
Vol 9 (8) ◽  
pp. 931-939 ◽  
Author(s):  
Yandong Yu ◽  
Zehua Yan ◽  
Shiming Bi ◽  
Zhenduo Ma ◽  
Jiahao Qian
Keyword(s):  
Heat Treatment ◽  
Tensile Strength ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Cleavage Fracture ◽  
Corrosion Potential ◽  
Ceramic Membrane ◽  
Cast Alloy ◽  
Solution Treatment ◽  
Ceramic Film

The microstructure and mechanical properties of Mg–2Zn–0.5Ca–1.0Mn alloy under different treatments were investigated. Nano-TiO2 with biological activity was added to the self-optimized silicate electrolyte in order to enhance the corrosion resistance and the activity of micro-arc oxidation (MAO) coatings formed in the aged bio-magnesium alloy silicate electrolyte. Results show that the tensile strength and micro-hardness of solution treatment alloy were 194 MPa and 40.55 HV, respectively, which were increased by 11% and 30% comparing with as-cast alloy. Subsequently, the experimental alloy was aged at 175 °C from 0.5 h to 36 h, the tensile strength of the alloy reached 229 MPa when the alloy was aged to 16 h, which was 55 MPa higher than the as-cast alloy. Besides, the fracture mechanism transformed from the cleavage fracture to quasi-cleavage fracture after heat treatment. Different content of modified nano-TiO2 (1, 3 and 5 g/L) is added into based silicate electrolyte has been utilized to modify the bio-magnesium coatings for precoated metals. The sealing processes on MAO coatings surface effectively improve the corrosion resistance property of the bio-magnesium alloy. As the concentration of nano-TiO2 increases from 0 g/L to 5 g/L, the corrosion potential of MAO ceramic film increases gradually. When the concentration of nano-TiO2 is 5 g/L, the corrosion potential of the formed ceramic film is the highest, reaching – 1.3601 V, this shows that the ceramic membrane has good corrosion resistance.

Characterization of β and Mg41Nd5 Equilibrium Phases in Elektron 21 Magnesium Alloy after Long-Term Annealing

2010 ◽  
Vol 163 ◽  
pp. 106-109 ◽  
Author(s):  
Andrzej Kiełbus ◽  
Tomasz Rzychoń ◽  
Lidia Lityńska-Dobrzyńska ◽  
Grzegorz Dercz
Keyword(s):  
Solid Solution ◽  
Magnesium Alloy ◽  
Grain Boundaries ◽  
Β Phase ◽  
Equilibrium Phases ◽  
Cast Condition

The paper presents results of TEM and XRD investigations of Elektron 21 magnesium alloy in as cast condition and after long-term annealing at 250 and 350°C. In as cast condition Elektron 21 consists of primary α-Mg solid solution with α-Mg-Mg3RE eutectic and regular precipitates of MgRE3. Precipitation at 250 °C causes formation of the equilibrium β phase. Annealing at 350°C caused precipitation of globular Mg41Nd5 phases on solid solution grain boundaries. Also precipitates of MgRE3 phase have been observed.

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