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Kyu Cho - One of the best experts on this subject based on the ideXlab platform.
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Additive manufacturing of dense We43 Mg Alloy by laser powder bed fusion
Additive Manufacturing, 2020Co-Authors: Holden Hyer, Brandon Mcwilliams, Kyu Cho, Le Zhou, George Benson, Yongho SohnAbstract:Abstract We43 is a high-strength, corrosion-resistant Mg-Alloy containing rare earths such as Y and Nb, and has potential for many lightweight structural or bioresorbable prosthetic applications. In this study, additive manufacturing of dense We43 Alloy by laser powder bed fusion (LPBF) from gas atomized powders has been accomplished through studies involving single track scan of wrought We43, parametric variation of LPBF, microstructural analysis and mechanical testing, both in compression and tension. The Archimedes method and image analyses from optical micrographs were employed to document the LPBF of dense (>99 % relative density) We43 using optimum parameters of 200 W laser power, 1100 mm/sec scan speed, 0.13 mm hatch spacing, and 0.03 mm slice thickness. Moreover, the LPBF processing window for dense (>99 %) We43 Alloy was observed to exist for a range of power, 100 ∼ 250 W, using an energy density range of 32−37 J/mm3. The as-built microstructure consisted of fine ( β 1 -Mg3Nd precipitates and (Y,Zr)2O3 oxides. After the heat treatment, which consisted of solutionizing at 536 °C for 24 h and subsequent ageing at 205 °C for 48 h, the globular β 1 -Mg3Nd precipitates were observed to have dissolved and re-precipitate into thin sheets. The (Y,Zr)2O3 oxides were not found to dissolve or coalesce, but were agglomerated within α-Mg (hcp) matrix. Under compression, the as-built LPBF We43 had, on average, yield strength of 224 MPa, compressive strength of 417 MPa and strain at failure of 9.5 %. In tension, the as-built LPBF We43 had, on average, yield strength of 215 MPa, tensile strength of 251 MPa and strain at failure of 2.6 %. After the heat treatment, the LPBF We43 had yield strength of 219 MPa, tensile strength of 251 MPa and strain at failure of 4.3 %. These values are comparable to those of We43 design data specified by Magnesium Elektron.
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Effect of friction stir processing on microstructure and mechanical properties of laser-processed Mg4Y3Nd Alloy
Materials & Design, 2016Co-Authors: Nilesh Kumar, Rajiv S. Mishra, K J Doherty, Narendra B. Dahotre, R.e. Brennan, Kyu ChoAbstract:Abstract The development of advanced structural materials is dependent, among many factors, on the choice of manufacturing processes. Laser processing and friction stir processing (FSP) are two such advanced manufacturing processes. Individually, they have been studied quite extensively to understand their potential for developing high efficiency structures. However, there is no study describing the sequential integration of laser processing and FSP on microstructure and mechanical properties. The present study deals with FSP of the laser processed Mg 4Y 3Nd (We43) Alloy. The laser surface melting was carried out in air at 1800 W laser power, 30 mm/s laser speed, and 0.6 mm spot size on the surface using continuous wave Nd:YAG fiber laser followed by FSP of laser processed region at 500 rpm and 4 ipm. Scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy were carried out to understand microstructural evolution within the laser melted and friction stir processed regions. Mechanical properties were evaluated using uniaxial tensile testing at a strain-rate of 10 − 3 s − 1 . FSP led to significant improvement in strength and ductility of the laser processed material. An analysis of the strengthening mechanisms revealed that the dominant strengthening mechanism(s) in the We43 Alloy was dependent on the processing step.
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effect of initial microstructure on the microstructural evolution and joint efficiency of a We43 Alloy during friction stir welding
2013Co-Authors: S. Palanivel, Rajiv S. Mishra, B Davis, Rick Delorme, K J Doherty, Kyu ChoAbstract:The initial microstructure plays an important role in determining the spatial and temporal evolution of the microstructure during friction stir welding (FSW). The overall kinetics of microstructural evolution is location sensitive and the effect of the process strain, strain rate and thermal cycle creates complexities. In the present study, magnesium based We43 Alloy has been welded employing two different welding conditions. Joint efficiency has been subsequently evaluated. The results have been correlated with detailed micro structural information obtained from SEM and OIM-EBSD. The influence of microstructural evolution on strength has been analyzed. This framework provides an approach to maximize joint efficiency.
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Friction Stir Welding and Processing VII - Effect of Initial Microstructure on the Microstructural Evolution and Joint Efficiency of a We43 Alloy During Friction Stir Welding
Friction Stir Welding and Processing VII, 2013Co-Authors: S. Palanivel, Rajiv S. Mishra, B Davis, Rick Delorme, K J Doherty, Kyu ChoAbstract:The initial microstructure plays an important role in determining the spatial and temporal evolution of the microstructure during friction stir welding (FSW). The overall kinetics of microstructural evolution is location sensitive and the effect of the process strain, strain rate and thermal cycle creates complexities. In the present study, magnesium based We43 Alloy has been welded employing two different welding conditions. Joint efficiency has been subsequently evaluated. The results have been correlated with detailed micro structural information obtained from SEM and OIM-EBSD. The influence of microstructural evolution on strength has been analyzed. This framework provides an approach to maximize joint efficiency.
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Friction Stir Welding and Processing VII - Magnesium Based Composite Via Friction Stir Processing
Friction Stir Welding and Processing VII, 2013Co-Authors: Shamiparna Das, Rajiv S. Mishra, B Davis, K J Doherty, Kyu Cho, Rick DelormeAbstract:Friction stir processing (FSP) was used to incorporate 6 vol.% of micron sized B4C (6µm) reinforcements in We43 Alloy to form a surface composite. Multiple passes were utilized in order to achieve homogenization. Better distribution of the reinforcements, grain size refinement and an increase in hardness was observed after every FSP pass. The composite was 4–6 mm thick and showed higher values of hardness and modulus than that of the base material. Post FSP aging was performed at 210 °C for 48 h. The tensile properties were evaluated at room temperature for samples in as-FSP and after FSP+aging. The yield strength remained unaffected by the reinforcement addition.
Tomas Ruml - One of the best experts on this subject based on the ideXlab platform.
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structure mechanical characteristics and in vitro degradation cytotoxicity genotoxicity and mutagenicity of novel biodegradable zn mg Alloys
Materials Science and Engineering: C, 2016Co-Authors: Jiří Kubásek, Dalibor Vojtěch, Eva Jablonská, I Pospisilova, Jan Lipov, Tomas RumlAbstract:Abstract Zn–(0–1.6)Mg (in wt.%) Alloys were prepared by hot extrusion at 300 °C. The structure, mechanical properties and in vitro biocompatibility of the Alloys were investigated. The hot-extruded magnesium-based We43 Alloy was used as a control. Mechanical properties were evaluated by hardness, compressive and tensile testing. The cytotoxicity, genotoxicity (comet assay) and mutagenicity (Ames test) of the Alloy extracts and ZnCl 2 solutions were evaluated with the use of murine fibroblasts L929 and human osteosarcoma cell line U-2 OS. The microstructure of the Zn Alloys consisted of recrystallized Zn grains of 12 μm in size and fine Mg 2 Zn 11 particles arranged parallel to the hot extrusion direction. Mechanical tests revealed that the hardness and strength increased with increasing Mg concentration. The Zn–0.8 Mg Alloys showed the best combination of tensile mechanical properties (tensile yield strength of 203 MPa, ultimate tensile strength of 301 MPa and elongation of 15%). At higher Mg concentrations the plasticity of Zn–Mg Alloys was deteriorated. Cytotoxicity tests with Alloy extracts and ZnCl 2 solutions proved the maximum safe Zn 2 + concentrations of 120 μM and 80 μM for the U-2 OS and L929 cell lines, respectively. Ames test with extracts of Alloys indicated that the extracts were not mutagenic. The comet assay demonstrated that 1-day extracts of Alloys were not genotoxic for U-2 OS and L929 cell lines after 1-day incubation.
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structure mechanical characteristics and in vitro degradation cytotoxicity genotoxicity and mutagenicity of novel biodegradable zn mg Alloys
Materials Science and Engineering: C, 2016Co-Authors: Jiří Kubásek, Dalibor Vojtěch, Eva Jablonská, I Pospisilova, Jan Lipov, Tomas RumlAbstract:Zn-(0-1.6)Mg (in wt.%) Alloys were prepared by hot extrusion at 300 °C. The structure, mechanical properties and in vitro biocompatibility of the Alloys were investigated. The hot-extruded magnesium-based We43 Alloy was used as a control. Mechanical properties were evaluated by hardness, compressive and tensile testing. The cytotoxicity, genotoxicity (comet assay) and mutagenicity (Ames test) of the Alloy extracts and ZnCl2 solutions were evaluated with the use of murine fibroblasts L929 and human osteosarcoma cell line U-2 OS. The microstructure of the Zn Alloys consisted of recrystallized Zn grains of 12 μm in size and fine Mg2Zn11 particles arranged parallel to the hot extrusion direction. Mechanical tests revealed that the hardness and strength increased with increasing Mg concentration. The Zn-0.8 Mg Alloys showed the best combination of tensile mechanical properties (tensile yield strength of 203 MPa, ultimate tensile strength of 301 MPa and elongation of 15%). At higher Mg concentrations the plasticity of Zn-Mg Alloys was deteriorated. Cytotoxicity tests with Alloy extracts and ZnCl2 solutions proved the maximum safe Zn(2+) concentrations of 120 μM and 80 μM for the U-2 OS and L929 cell lines, respectively. Ames test with extracts of Alloys indicated that the extracts were not mutagenic. The comet assay demonstrated that 1-day extracts of Alloys were not genotoxic for U-2 OS and L929 cell lines after 1-day incubation.
Rajiv S. Mishra - One of the best experts on this subject based on the ideXlab platform.
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accelerated age hardening response by in situ ultrasonic aging of a We43 Alloy
Materials and Manufacturing Processes, 2018Co-Authors: S. Palanivel, Rajiv S. Mishra, Raymond E BrennanAbstract:ABSTRACTCustom built in-situ ultrasonic aging equipment was used to investigate the precipitation hardening response in a commercial We43 Alloy at 210°C. Three power levels (100, 300, 400 W) with time intervals of 15, 30, and 60 s between sonication were used to measure the change in hardness. Aging response was 24 times faster, decreasing the time to achieve peak hardness from 48 hrs during conventional aging to 2 hrs under the influence of ultrasonic waves. While higher power increased the peak hardness, shortening the interval time from 30 to 15 s did not have any influence. Transmission electron micrographs revealed well-developed β1 variants in as little as 15 minutes for ultrasonically aged samples, which was the reason for enhanced age hardening response.
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Effect of friction stir processing on microstructure and mechanical properties of laser-processed Mg4Y3Nd Alloy
Materials & Design, 2016Co-Authors: Nilesh Kumar, Rajiv S. Mishra, K J Doherty, Narendra B. Dahotre, R.e. Brennan, Kyu ChoAbstract:Abstract The development of advanced structural materials is dependent, among many factors, on the choice of manufacturing processes. Laser processing and friction stir processing (FSP) are two such advanced manufacturing processes. Individually, they have been studied quite extensively to understand their potential for developing high efficiency structures. However, there is no study describing the sequential integration of laser processing and FSP on microstructure and mechanical properties. The present study deals with FSP of the laser processed Mg 4Y 3Nd (We43) Alloy. The laser surface melting was carried out in air at 1800 W laser power, 30 mm/s laser speed, and 0.6 mm spot size on the surface using continuous wave Nd:YAG fiber laser followed by FSP of laser processed region at 500 rpm and 4 ipm. Scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy were carried out to understand microstructural evolution within the laser melted and friction stir processed regions. Mechanical properties were evaluated using uniaxial tensile testing at a strain-rate of 10 − 3 s − 1 . FSP led to significant improvement in strength and ductility of the laser processed material. An analysis of the strengthening mechanisms revealed that the dominant strengthening mechanism(s) in the We43 Alloy was dependent on the processing step.
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Effect of microstructure on the uniaxial tensile deformation behavior of Mg–4Y–3RE Alloy
Materials Science and Engineering: A, 2014Co-Authors: Nilesh Kumar, Nilesh Dendge, Rajarshi Banerjee, Rajiv S. MishraAbstract:Abstract This paper reports microstructure–mechanical property correlations for a Mg–4Y–3RE (We43) Alloy. Friction stir (FS) processing was employed to modify the microstructure of hot-rolled (as-received) We43 Alloy. The grain size decreased from 10 to 300 µm in as-received condition to an average of 3.1±0.4 µm in FS processed condition. The Alloy in AR condition contained globular, acicular, and rectangular (cuboidal) shaped precipitates located at twin boundaries, grain boundaries, and intragranular regions, along with fine scale honeycomb network of intragranular β1 precipitates. A very good combination of strength and ductility was observed for the Alloy tested in FS processed condition. Detailed fractography was done to differentiate mode of fracture between as-received and FS processed conditions. Based on Schmid factor analysis, it was concluded that basal slip system controlled the yielding of the material in both the conditions. An empirical relationship was developed between work hardening rate and ductility. This can be applied to microstructural design of magnesium Alloys used for applications where high uniform ductility is needed.
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effect of initial microstructure on the microstructural evolution and joint efficiency of a We43 Alloy during friction stir welding
2013Co-Authors: S. Palanivel, Rajiv S. Mishra, B Davis, Rick Delorme, K J Doherty, Kyu ChoAbstract:The initial microstructure plays an important role in determining the spatial and temporal evolution of the microstructure during friction stir welding (FSW). The overall kinetics of microstructural evolution is location sensitive and the effect of the process strain, strain rate and thermal cycle creates complexities. In the present study, magnesium based We43 Alloy has been welded employing two different welding conditions. Joint efficiency has been subsequently evaluated. The results have been correlated with detailed micro structural information obtained from SEM and OIM-EBSD. The influence of microstructural evolution on strength has been analyzed. This framework provides an approach to maximize joint efficiency.
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Friction Stir Welding and Processing VII - Effect of Initial Microstructure on the Microstructural Evolution and Joint Efficiency of a We43 Alloy During Friction Stir Welding
Friction Stir Welding and Processing VII, 2013Co-Authors: S. Palanivel, Rajiv S. Mishra, B Davis, Rick Delorme, K J Doherty, Kyu ChoAbstract:The initial microstructure plays an important role in determining the spatial and temporal evolution of the microstructure during friction stir welding (FSW). The overall kinetics of microstructural evolution is location sensitive and the effect of the process strain, strain rate and thermal cycle creates complexities. In the present study, magnesium based We43 Alloy has been welded employing two different welding conditions. Joint efficiency has been subsequently evaluated. The results have been correlated with detailed micro structural information obtained from SEM and OIM-EBSD. The influence of microstructural evolution on strength has been analyzed. This framework provides an approach to maximize joint efficiency.
Jiří Kubásek - One of the best experts on this subject based on the ideXlab platform.
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Specific interface prepared by the SPS of chemically treated Mg-based powder
Materials Chemistry and Physics, 2021Co-Authors: Drahomir Dvorsky, Jiří Kubásek, Filip Průša, Eva Kristianová, Dalibor VojtěchAbstract:Abstract This work focuses on a new way of preparation of magnesium-based composite materials by powder metallurgy. This method consists of combination of chemical treatment of magnesium powder in hydrofluoric acid and subsequent compaction by spark plasma sintering. As a result a continuous network of magnesium fluoride coating is created inside material. However, magnesium Alloys behave differently in hydrofluoric acid. In the case of We43 Alloy a network consisting of magnesium fluoride and newly emerged yttrium fluoride is prepared. This specific interface of the prepared composite material resulted in a corrosion rate that was three times lower compared to that of the sample sintered without chemical treatment. The cause of improvement of corrosion properties is illustratively shown on the cuts of the samples after immersion. The corrosion front is slowed down on the fluoride interface. The presence of yttrium fluoride phases on the interface slightly reduced mechanical properties.
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structure mechanical characteristics and in vitro degradation cytotoxicity genotoxicity and mutagenicity of novel biodegradable zn mg Alloys
Materials Science and Engineering: C, 2016Co-Authors: Jiří Kubásek, Dalibor Vojtěch, Eva Jablonská, I Pospisilova, Jan Lipov, Tomas RumlAbstract:Abstract Zn–(0–1.6)Mg (in wt.%) Alloys were prepared by hot extrusion at 300 °C. The structure, mechanical properties and in vitro biocompatibility of the Alloys were investigated. The hot-extruded magnesium-based We43 Alloy was used as a control. Mechanical properties were evaluated by hardness, compressive and tensile testing. The cytotoxicity, genotoxicity (comet assay) and mutagenicity (Ames test) of the Alloy extracts and ZnCl 2 solutions were evaluated with the use of murine fibroblasts L929 and human osteosarcoma cell line U-2 OS. The microstructure of the Zn Alloys consisted of recrystallized Zn grains of 12 μm in size and fine Mg 2 Zn 11 particles arranged parallel to the hot extrusion direction. Mechanical tests revealed that the hardness and strength increased with increasing Mg concentration. The Zn–0.8 Mg Alloys showed the best combination of tensile mechanical properties (tensile yield strength of 203 MPa, ultimate tensile strength of 301 MPa and elongation of 15%). At higher Mg concentrations the plasticity of Zn–Mg Alloys was deteriorated. Cytotoxicity tests with Alloy extracts and ZnCl 2 solutions proved the maximum safe Zn 2 + concentrations of 120 μM and 80 μM for the U-2 OS and L929 cell lines, respectively. Ames test with extracts of Alloys indicated that the extracts were not mutagenic. The comet assay demonstrated that 1-day extracts of Alloys were not genotoxic for U-2 OS and L929 cell lines after 1-day incubation.
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structure mechanical characteristics and in vitro degradation cytotoxicity genotoxicity and mutagenicity of novel biodegradable zn mg Alloys
Materials Science and Engineering: C, 2016Co-Authors: Jiří Kubásek, Dalibor Vojtěch, Eva Jablonská, I Pospisilova, Jan Lipov, Tomas RumlAbstract:Zn-(0-1.6)Mg (in wt.%) Alloys were prepared by hot extrusion at 300 °C. The structure, mechanical properties and in vitro biocompatibility of the Alloys were investigated. The hot-extruded magnesium-based We43 Alloy was used as a control. Mechanical properties were evaluated by hardness, compressive and tensile testing. The cytotoxicity, genotoxicity (comet assay) and mutagenicity (Ames test) of the Alloy extracts and ZnCl2 solutions were evaluated with the use of murine fibroblasts L929 and human osteosarcoma cell line U-2 OS. The microstructure of the Zn Alloys consisted of recrystallized Zn grains of 12 μm in size and fine Mg2Zn11 particles arranged parallel to the hot extrusion direction. Mechanical tests revealed that the hardness and strength increased with increasing Mg concentration. The Zn-0.8 Mg Alloys showed the best combination of tensile mechanical properties (tensile yield strength of 203 MPa, ultimate tensile strength of 301 MPa and elongation of 15%). At higher Mg concentrations the plasticity of Zn-Mg Alloys was deteriorated. Cytotoxicity tests with Alloy extracts and ZnCl2 solutions proved the maximum safe Zn(2+) concentrations of 120 μM and 80 μM for the U-2 OS and L929 cell lines, respectively. Ames test with extracts of Alloys indicated that the extracts were not mutagenic. The comet assay demonstrated that 1-day extracts of Alloys were not genotoxic for U-2 OS and L929 cell lines after 1-day incubation.
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Structural characteristics and elevated temperature mechanical properties of AJ62 Mg Alloy
Materials Characterization, 2013Co-Authors: Jiří Kubásek, Dalibor Vojtěch, M. MartínekAbstract:Abstract Structure and mechanical properties of the novel casting AJ62 (Mg–6Al–2Sr) Alloy developed for elevated temperature applications were studied. The AJ62 Alloy was compared to commercial casting AZ91 (Mg–9Al–1Zn) and We43 (Mg–4Y–3RE) Alloys. The structure was examined by scanning electron microscopy, x-ray diffraction and energy dispersive spectrometry. Mechanical properties were characterized by Viskers hardness measurements in the as-cast state and after a long-term heat treatment at 250 °C/150 hours. Compressive mechanical tests were also carried out both at room and elevated temperatures. Compressive creep tests were conducted at a temperature of 250 °C and compressive stresses of 60, 100 and 140 MPa. The structure of the AJ62 Alloy consisted of primary α-Mg dendrites and interdendritic nework of the Al 4 Sr and massive Al 3 Mg 13 Sr phases. By increasing the cooling rate during solidification from 10 and 120 K/s the average dendrite arm thickness decreased from 18 to 5 μm and the total volume fraction of the interdendritic phases from 20% to 30%. Both factors slightly increased hardness and compressive strength. The room temperature compressive strength and hardness of the Alloy solidified at 30 K/s were 298 MPa and 50 HV 5, i.e. similar to those of the as-cast We43 Alloy and lower than those of the AZ91 Alloy. At 250 °C the compressive strength of the AJ62 Alloy decreased by 50 MPa, whereas those of the AZ91 and We43 Alloys by 100 and 20 MPa, respectively. The creep rate of the AJ62 Alloy was higher than that of the We43 Alloy, but significantly lower in comparison with the AZ91 Alloy. Different thermal stabilities of the Alloys were discussed and related to structural changes during elevated temperature expositions.
Dalibor Vojtěch - One of the best experts on this subject based on the ideXlab platform.
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Specific interface prepared by the SPS of chemically treated Mg-based powder
Materials Chemistry and Physics, 2021Co-Authors: Drahomir Dvorsky, Jiří Kubásek, Filip Průša, Eva Kristianová, Dalibor VojtěchAbstract:Abstract This work focuses on a new way of preparation of magnesium-based composite materials by powder metallurgy. This method consists of combination of chemical treatment of magnesium powder in hydrofluoric acid and subsequent compaction by spark plasma sintering. As a result a continuous network of magnesium fluoride coating is created inside material. However, magnesium Alloys behave differently in hydrofluoric acid. In the case of We43 Alloy a network consisting of magnesium fluoride and newly emerged yttrium fluoride is prepared. This specific interface of the prepared composite material resulted in a corrosion rate that was three times lower compared to that of the sample sintered without chemical treatment. The cause of improvement of corrosion properties is illustratively shown on the cuts of the samples after immersion. The corrosion front is slowed down on the fluoride interface. The presence of yttrium fluoride phases on the interface slightly reduced mechanical properties.
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Preparation of We43 Using Powder Metallurgy Route
Manufacturing Technology, 2016Co-Authors: Drahomir Dvorsky, Jiri Kubasek, Dalibor Vojtěch, Filip Prusa, Katerina NovaAbstract:Magnesium Alloy We43 is well known for its low density and good mechanical properties. It has also fair corrosion resistance and relative usability up to 300 °C. All those properties are connected with the content of rare earth elements and determine this Alloy not only for automotive and aviation industry, but also for applications as biodegradable materials. In this work, We43 Alloy prepared by powder metallurgy methods is characterized. Final products are prepared by cold uniaxial pressing with subsequent extrusion or spark plasma sintering (SPS). Present paper deals with the characterization of processing methods used for the We43 Alloy preparation and also the characterization of prepared We43 products as themselves.
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structure mechanical characteristics and in vitro degradation cytotoxicity genotoxicity and mutagenicity of novel biodegradable zn mg Alloys
Materials Science and Engineering: C, 2016Co-Authors: Jiří Kubásek, Dalibor Vojtěch, Eva Jablonská, I Pospisilova, Jan Lipov, Tomas RumlAbstract:Abstract Zn–(0–1.6)Mg (in wt.%) Alloys were prepared by hot extrusion at 300 °C. The structure, mechanical properties and in vitro biocompatibility of the Alloys were investigated. The hot-extruded magnesium-based We43 Alloy was used as a control. Mechanical properties were evaluated by hardness, compressive and tensile testing. The cytotoxicity, genotoxicity (comet assay) and mutagenicity (Ames test) of the Alloy extracts and ZnCl 2 solutions were evaluated with the use of murine fibroblasts L929 and human osteosarcoma cell line U-2 OS. The microstructure of the Zn Alloys consisted of recrystallized Zn grains of 12 μm in size and fine Mg 2 Zn 11 particles arranged parallel to the hot extrusion direction. Mechanical tests revealed that the hardness and strength increased with increasing Mg concentration. The Zn–0.8 Mg Alloys showed the best combination of tensile mechanical properties (tensile yield strength of 203 MPa, ultimate tensile strength of 301 MPa and elongation of 15%). At higher Mg concentrations the plasticity of Zn–Mg Alloys was deteriorated. Cytotoxicity tests with Alloy extracts and ZnCl 2 solutions proved the maximum safe Zn 2 + concentrations of 120 μM and 80 μM for the U-2 OS and L929 cell lines, respectively. Ames test with extracts of Alloys indicated that the extracts were not mutagenic. The comet assay demonstrated that 1-day extracts of Alloys were not genotoxic for U-2 OS and L929 cell lines after 1-day incubation.
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structure mechanical characteristics and in vitro degradation cytotoxicity genotoxicity and mutagenicity of novel biodegradable zn mg Alloys
Materials Science and Engineering: C, 2016Co-Authors: Jiří Kubásek, Dalibor Vojtěch, Eva Jablonská, I Pospisilova, Jan Lipov, Tomas RumlAbstract:Zn-(0-1.6)Mg (in wt.%) Alloys were prepared by hot extrusion at 300 °C. The structure, mechanical properties and in vitro biocompatibility of the Alloys were investigated. The hot-extruded magnesium-based We43 Alloy was used as a control. Mechanical properties were evaluated by hardness, compressive and tensile testing. The cytotoxicity, genotoxicity (comet assay) and mutagenicity (Ames test) of the Alloy extracts and ZnCl2 solutions were evaluated with the use of murine fibroblasts L929 and human osteosarcoma cell line U-2 OS. The microstructure of the Zn Alloys consisted of recrystallized Zn grains of 12 μm in size and fine Mg2Zn11 particles arranged parallel to the hot extrusion direction. Mechanical tests revealed that the hardness and strength increased with increasing Mg concentration. The Zn-0.8 Mg Alloys showed the best combination of tensile mechanical properties (tensile yield strength of 203 MPa, ultimate tensile strength of 301 MPa and elongation of 15%). At higher Mg concentrations the plasticity of Zn-Mg Alloys was deteriorated. Cytotoxicity tests with Alloy extracts and ZnCl2 solutions proved the maximum safe Zn(2+) concentrations of 120 μM and 80 μM for the U-2 OS and L929 cell lines, respectively. Ames test with extracts of Alloys indicated that the extracts were not mutagenic. The comet assay demonstrated that 1-day extracts of Alloys were not genotoxic for U-2 OS and L929 cell lines after 1-day incubation.
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Structural characteristics and elevated temperature mechanical properties of AJ62 Mg Alloy
Materials Characterization, 2013Co-Authors: Jiří Kubásek, Dalibor Vojtěch, M. MartínekAbstract:Abstract Structure and mechanical properties of the novel casting AJ62 (Mg–6Al–2Sr) Alloy developed for elevated temperature applications were studied. The AJ62 Alloy was compared to commercial casting AZ91 (Mg–9Al–1Zn) and We43 (Mg–4Y–3RE) Alloys. The structure was examined by scanning electron microscopy, x-ray diffraction and energy dispersive spectrometry. Mechanical properties were characterized by Viskers hardness measurements in the as-cast state and after a long-term heat treatment at 250 °C/150 hours. Compressive mechanical tests were also carried out both at room and elevated temperatures. Compressive creep tests were conducted at a temperature of 250 °C and compressive stresses of 60, 100 and 140 MPa. The structure of the AJ62 Alloy consisted of primary α-Mg dendrites and interdendritic nework of the Al 4 Sr and massive Al 3 Mg 13 Sr phases. By increasing the cooling rate during solidification from 10 and 120 K/s the average dendrite arm thickness decreased from 18 to 5 μm and the total volume fraction of the interdendritic phases from 20% to 30%. Both factors slightly increased hardness and compressive strength. The room temperature compressive strength and hardness of the Alloy solidified at 30 K/s were 298 MPa and 50 HV 5, i.e. similar to those of the as-cast We43 Alloy and lower than those of the AZ91 Alloy. At 250 °C the compressive strength of the AJ62 Alloy decreased by 50 MPa, whereas those of the AZ91 and We43 Alloys by 100 and 20 MPa, respectively. The creep rate of the AJ62 Alloy was higher than that of the We43 Alloy, but significantly lower in comparison with the AZ91 Alloy. Different thermal stabilities of the Alloys were discussed and related to structural changes during elevated temperature expositions.
