This article used Mn-Mo-Cr-B low-carbon bainitic steel as the experimental material. The continuous cooling transformation curve of the steel during continuous cooling was determined using a Gleeble-1500D thermal simulation test machine, and a corresponding phase transformation model for bainitic steel during continuous cooling was established. The influence of different cooling rates and final cooling temperatures on the microstructure and mechanical properties of the steel was investigated. Employing metallography, SEM, and EBSD techniques, the microstructure, crystallographic orientation, and grain boundary angle distribution of the low-carbon bainitic steel were explored, and their relationship with the steel's strength and toughness was studied. The research findings reveal that varying cooling rates and final cooling temperatures impact the phase transformation process and microstructure of the steel, consequently affecting its mechanical properties indirectly. With increasing cooling rate, the diffusion and fineness of martensite increase, and the quantity of lath bainite grows while the laths become finer. Elevated final cooling temperatures lead to larger martensitic-austenitic (MA) islands and reduced lath bainite quantity, causing the laths to become wider. Through analysis of the substructure of bainitic steel, it was determined that the bainite organization in the tested steel comprises primary austenite grains, lath packet, and lath block in succession. Lath packets are composed of lath blocks with different orientations, where lath size predominantly controls strength. Finer lath size corresponds to higher strength, and the influence of substructure on toughness is comparatively minor.
{"title":"Effect of Cooling Process on Microstructure and Properties of Low Carbon Bainite Steel","authors":"Zhifeng CAO, JiMan WANG, Shenggang ZHOU, Hu YAN","doi":"10.5755/j02.ms.34199","DOIUrl":"https://doi.org/10.5755/j02.ms.34199","url":null,"abstract":"This article used Mn-Mo-Cr-B low-carbon bainitic steel as the experimental material. The continuous cooling transformation curve of the steel during continuous cooling was determined using a Gleeble-1500D thermal simulation test machine, and a corresponding phase transformation model for bainitic steel during continuous cooling was established. The influence of different cooling rates and final cooling temperatures on the microstructure and mechanical properties of the steel was investigated. Employing metallography, SEM, and EBSD techniques, the microstructure, crystallographic orientation, and grain boundary angle distribution of the low-carbon bainitic steel were explored, and their relationship with the steel's strength and toughness was studied. The research findings reveal that varying cooling rates and final cooling temperatures impact the phase transformation process and microstructure of the steel, consequently affecting its mechanical properties indirectly. With increasing cooling rate, the diffusion and fineness of martensite increase, and the quantity of lath bainite grows while the laths become finer. Elevated final cooling temperatures lead to larger martensitic-austenitic (MA) islands and reduced lath bainite quantity, causing the laths to become wider. Through analysis of the substructure of bainitic steel, it was determined that the bainite organization in the tested steel comprises primary austenite grains, lath packet, and lath block in succession. Lath packets are composed of lath blocks with different orientations, where lath size predominantly controls strength. Finer lath size corresponds to higher strength, and the influence of substructure on toughness is comparatively minor.","PeriodicalId":18298,"journal":{"name":"Materials Science-medziagotyra","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135738805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chao-Yang ZHANG, Shenyu CHEN, Lin-gjun XIE, Echo YANG, Tong BU, Ivan CHEUNG, Ming-Der JEAN
This work involves the preparation of WC/Co/Ni blends using different mixing ratios to form Co/Ni/WC composite-based coatings by laser cladding. The effect of each component and their mixtures on the mechanical properties was evaluated using a mixture design approach. The morphologies and microstructures of the laser clads were characterized using a scanning electron microscope and X-ray diffraction techniques. Cracking behavior and fracture based on residual stresses are explored. In addition, the mathematical models between the three-component mixtures and the mechanical properties of the laser clad were established. The results showed that the welds containing 50 % WC-50 % Ni alloys were successfully deposited by laser cladding with favorable mechanical properties. These welds reduced the remarkable fracture crack activities and did not cause delamination in the laser clads. An increase in WC content significantly enhances wear resistance and microhardness, except for the crack susceptibilities in all mixtures. Additionally, when increased Co/Ni on WC, the reduction of adhesive wear is more significant than that of abrasive wear. Wear resistance is improved by the high content of WC particles in the laser-clad joints. Based on the mixture models, better mixed ratios for the blends that were developed using a multi-objective superimposed optimization technique make these blended materials promising candidates and can ensure the quality of laser clads. The findings from this study will greatly contribute to optimizing the blend ratio of the three-ingredient mixture based on mixture design to enhance structural evolution and mechanical properties, and also obtain better quality laser-clad coatings.
{"title":"Multi-objective Optimization of Laser Welds with Mixed WC/Co/Ni Experiments Using Simplex-centroid Design","authors":"Chao-Yang ZHANG, Shenyu CHEN, Lin-gjun XIE, Echo YANG, Tong BU, Ivan CHEUNG, Ming-Der JEAN","doi":"10.5755/j02.ms.33626","DOIUrl":"https://doi.org/10.5755/j02.ms.33626","url":null,"abstract":"This work involves the preparation of WC/Co/Ni blends using different mixing ratios to form Co/Ni/WC composite-based coatings by laser cladding. The effect of each component and their mixtures on the mechanical properties was evaluated using a mixture design approach. The morphologies and microstructures of the laser clads were characterized using a scanning electron microscope and X-ray diffraction techniques. Cracking behavior and fracture based on residual stresses are explored. In addition, the mathematical models between the three-component mixtures and the mechanical properties of the laser clad were established. The results showed that the welds containing 50 % WC-50 % Ni alloys were successfully deposited by laser cladding with favorable mechanical properties. These welds reduced the remarkable fracture crack activities and did not cause delamination in the laser clads. An increase in WC content significantly enhances wear resistance and microhardness, except for the crack susceptibilities in all mixtures. Additionally, when increased Co/Ni on WC, the reduction of adhesive wear is more significant than that of abrasive wear. Wear resistance is improved by the high content of WC particles in the laser-clad joints. Based on the mixture models, better mixed ratios for the blends that were developed using a multi-objective superimposed optimization technique make these blended materials promising candidates and can ensure the quality of laser clads. The findings from this study will greatly contribute to optimizing the blend ratio of the three-ingredient mixture based on mixture design to enhance structural evolution and mechanical properties, and also obtain better quality laser-clad coatings.","PeriodicalId":18298,"journal":{"name":"Materials Science-medziagotyra","volume":"172 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135202995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This manuscript attempts to explore the macroscopic morphology microstructural aspects and mechanical properties of different laser welding speed and power on the 2.5 mm thick DSS welding joint. Through the evaluation of 12 groups samples with different welding parameters, we found that the optimal laser welding process parameters were a welding speed of 6mm/s, laser power of 1.6 kW and welding speed of 8 mm/s, laser power of 1.7 kW. When the heat input was 2.125 kJ/cm, the content of ferrite and austenite was relatively uniform, and the ratio was close to 1:1. We found that the hardness of the weld metal zone was slightly higher than that of the base metal, with an average value of 330 HV. When the heat input was 2.125 kJ/cm, the microhardness of welded joint was better than other parameters, reaching 400 HV in the welding metal zone. The tensile strength of the weld was enhanced with the increase of heat input, and the maximum was 900 MPa. Through SEM analysis, the fracture locations of tensile specimens were all in the weld zone, and the fracture morphology had a large number of dimples, belonging to the ductile fracture.
{"title":"Influence of Heat Input on Microstructure and Mechanical Properties of Laser Weld Metal in 2507 Duplex Stainless Steel by Different Welding Speed and Welding Power","authors":"Shuai ZHAO, Yaxuan BI","doi":"10.5755/j02.ms.34338","DOIUrl":"https://doi.org/10.5755/j02.ms.34338","url":null,"abstract":"This manuscript attempts to explore the macroscopic morphology microstructural aspects and mechanical properties of different laser welding speed and power on the 2.5 mm thick DSS welding joint. Through the evaluation of 12 groups samples with different welding parameters, we found that the optimal laser welding process parameters were a welding speed of 6mm/s, laser power of 1.6 kW and welding speed of 8 mm/s, laser power of 1.7 kW. When the heat input was 2.125 kJ/cm, the content of ferrite and austenite was relatively uniform, and the ratio was close to 1:1. We found that the hardness of the weld metal zone was slightly higher than that of the base metal, with an average value of 330 HV. When the heat input was 2.125 kJ/cm, the microhardness of welded joint was better than other parameters, reaching 400 HV in the welding metal zone. The tensile strength of the weld was enhanced with the increase of heat input, and the maximum was 900 MPa. Through SEM analysis, the fracture locations of tensile specimens were all in the weld zone, and the fracture morphology had a large number of dimples, belonging to the ductile fracture.","PeriodicalId":18298,"journal":{"name":"Materials Science-medziagotyra","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135397081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Fe-based alloy coating was prepared on the surface of 25Cr2Ni4MoV steel substrate by laser cladding. The microstructure, microhardness, shear strength, friction and wear properties of the laser cladding coating were systematically studied. The results show that a good metallurgical bond has been formed between Fe-based alloy coating and substrate. The laser cladding layer is a typical dendritic crystal, which is composed of light gray and dark gray phases. The shear strength displacement curve shows the typical characteristics of brittle fracture, with an average shear strength of 280.83 MPa. The average dry friction coefficient, wear track depth and average wear volume of laser cladding Fe-based alloy coatings are (0.45 ± 0.01), (26 ± 3) μm and 0.066615 m3, respectively. The average dry friction coefficient, wear track depth and average wear volume of 25Cr2Ni4MoV substrate are (0.60 ± 0.01), (39 ± 3) μm and 0.13085 m3, respectively. The laser cladded Fe-based alloy coating exhibits much better wear resistance than the steel substrate, and the shear strength of the coating displays its potential for the application in the service environment of shear stress.
{"title":"Microstructure and Mechanical Properties of Fe-Based Alloy Coatings Fabricated by Laser Cladding","authors":"Lu XIE, Yueming WANG","doi":"10.5755/j02.ms.33919","DOIUrl":"https://doi.org/10.5755/j02.ms.33919","url":null,"abstract":"The Fe-based alloy coating was prepared on the surface of 25Cr2Ni4MoV steel substrate by laser cladding. The microstructure, microhardness, shear strength, friction and wear properties of the laser cladding coating were systematically studied. The results show that a good metallurgical bond has been formed between Fe-based alloy coating and substrate. The laser cladding layer is a typical dendritic crystal, which is composed of light gray and dark gray phases. The shear strength displacement curve shows the typical characteristics of brittle fracture, with an average shear strength of 280.83 MPa. The average dry friction coefficient, wear track depth and average wear volume of laser cladding Fe-based alloy coatings are (0.45 ± 0.01), (26 ± 3) μm and 0.066615 m3, respectively. The average dry friction coefficient, wear track depth and average wear volume of 25Cr2Ni4MoV substrate are (0.60 ± 0.01), (39 ± 3) μm and 0.13085 m3, respectively. The laser cladded Fe-based alloy coating exhibits much better wear resistance than the steel substrate, and the shear strength of the coating displays its potential for the application in the service environment of shear stress.","PeriodicalId":18298,"journal":{"name":"Materials Science-medziagotyra","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135048100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
BiVO4 and its composites were prepared and compared with tetracycline hydrochloride, chlortetracycline hydrochloride and hygromycin hydrochloride to simulate the target degradation species for photocatalytic degradation experiments. All the prepared samples were found to have strong degradation effects on the three antibiotics, and the composite photocatalysts GB, PB and PGB showed faster photocatalytic reaction rates and higher photocatalytic activity than the pure BiVO4. In addition, the degradation of each sample to each antibiotic solution was in accordance with the primary reaction kinetic equation. The UV detection of PGB degradation of antibiotics was also carried out, and the results showed that the catalyst has a strong oxidation ability to degrade antibiotics to small molecules.
{"title":"Photodegradation of Antibiotic Drugs by BiVO4 Nanocomposites","authors":"Guang YANG, Yan LANG","doi":"10.5755/j02.ms.33595","DOIUrl":"https://doi.org/10.5755/j02.ms.33595","url":null,"abstract":"BiVO4 and its composites were prepared and compared with tetracycline hydrochloride, chlortetracycline hydrochloride and hygromycin hydrochloride to simulate the target degradation species for photocatalytic degradation experiments. All the prepared samples were found to have strong degradation effects on the three antibiotics, and the composite photocatalysts GB, PB and PGB showed faster photocatalytic reaction rates and higher photocatalytic activity than the pure BiVO4. In addition, the degradation of each sample to each antibiotic solution was in accordance with the primary reaction kinetic equation. The UV detection of PGB degradation of antibiotics was also carried out, and the results showed that the catalyst has a strong oxidation ability to degrade antibiotics to small molecules.","PeriodicalId":18298,"journal":{"name":"Materials Science-medziagotyra","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135045922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pengxi LI, Zhonghong LIU, Bing YANG, Zhiyong JIANG, Jingjing YANG
The S-doped g-C3N4 (SCN) was prepared by thermal condensation method using thiourea as a precursor, and then the phosphotungstic acid (PTA)/SCN composite photocatalytic material was prepared by reflux adsorption method. The photocatalytic degradation experiments of Rhodamine B showed that SCN20 had the highest photocatalytic degradation rate (74 %), which was 1.9 times and 3.5 times higher than that of PTA (39 %) and SCN (21 %), respectively. The photocatalytic degradation rate of SCN20 was increased by 5 times compared to that of SCN, indicating that the photocatalytic degradation performance of the composite material was significantly improved. The photocatalytic degradation mechanism study revealed that O2- was the main active species in the photocatalytic degradation of Rhodamine B, and the addition of PTA helped the effective separation of electrons-hole and improved the photocatalytic degradation rate. Our PTA/SCN is proposed as an environmental safety tool due to several advantages, such as low cost, convenient preparation, and efficient photocatalytic degradation of Rhodamine B.
{"title":"Synthesis of Phosphotungstic acid/S-doped g-C3N4 Photocatalyst and Its Photocatalytic Degradation of Organic Pollutants in Aqueous Solutions","authors":"Pengxi LI, Zhonghong LIU, Bing YANG, Zhiyong JIANG, Jingjing YANG","doi":"10.5755/j02.ms.31053","DOIUrl":"https://doi.org/10.5755/j02.ms.31053","url":null,"abstract":"The S-doped g-C3N4 (SCN) was prepared by thermal condensation method using thiourea as a precursor, and then the phosphotungstic acid (PTA)/SCN composite photocatalytic material was prepared by reflux adsorption method. The photocatalytic degradation experiments of Rhodamine B showed that SCN20 had the highest photocatalytic degradation rate (74 %), which was 1.9 times and 3.5 times higher than that of PTA (39 %) and SCN (21 %), respectively. The photocatalytic degradation rate of SCN20 was increased by 5 times compared to that of SCN, indicating that the photocatalytic degradation performance of the composite material was significantly improved. The photocatalytic degradation mechanism study revealed that O2- was the main active species in the photocatalytic degradation of Rhodamine B, and the addition of PTA helped the effective separation of electrons-hole and improved the photocatalytic degradation rate. Our PTA/SCN is proposed as an environmental safety tool due to several advantages, such as low cost, convenient preparation, and efficient photocatalytic degradation of Rhodamine B.","PeriodicalId":18298,"journal":{"name":"Materials Science-medziagotyra","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134974344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Transit providers have used social media (e.g., Twitter) as a powerful platform to shape public perception and provide essential information, especially during times of disruption and disaster. This work examines how transit agencies used Twitter during the COVID-19 pandemic to communicate with riders and how the content and general activity influence rider interaction and Twitter handle popularity. We analyzed 654,345 tweets generated by the top 40 transit agencies in the US, based on Vehicles Operated in Annual Maximum Service (VOM), from January 2020 to August 2021. We developed an analysis framework, using advanced machine learning and natural language processing models, to understand how agencies' tweeting patterns are associated with rider interaction outcomes during the pandemic. From the transit agency perspective, we find smaller agencies tend to generate a higher percentage of COVID-related tweets and some agencies are more repetitive than their peers. Six topics (i.e., face covering, essential service appreciation, free resources, social distancing, cleaning, and service updates) were identified in the COVID-related tweets. From the followers' interaction perspective, most agencies gained followers after the start of the pandemic (i.e., March 2020). The percentage of follower gains is positively correlated with the percentage of COVID-related tweets, tweets replying to followers, and tweets using outlinks. The average like counts per COVID-related tweet is positively correlated with the percentage of COVID-related tweets and negatively correlated with the percentage of tweets discussing social distancing and agency repetitiveness. This work can inform transportation planners and transit agencies on how to use Twitter to effectively communicate with riders to improve public perception of health and safety as it relates to transit ridership during delays and long-term disruptions such as those created by the COVID-19 public health crisis.
{"title":"Transit communication via Twitter during the COVID-19 pandemic.","authors":"Wenwen Zhang, Camille Barchers, Janille Smith-Colin","doi":"10.1177/23998083221135609","DOIUrl":"10.1177/23998083221135609","url":null,"abstract":"<p><p>Transit providers have used social media (e.g., Twitter) as a powerful platform to shape public perception and provide essential information, especially during times of disruption and disaster. This work examines how transit agencies used Twitter during the COVID-19 pandemic to communicate with riders and how the content and general activity influence rider interaction and Twitter handle popularity. We analyzed 654,345 tweets generated by the top 40 transit agencies in the US, based on Vehicles Operated in Annual Maximum Service (VOM), from January 2020 to August 2021. We developed an analysis framework, using advanced machine learning and natural language processing models, to understand how agencies' tweeting patterns are associated with rider interaction outcomes during the pandemic. From the transit agency perspective, we find smaller agencies tend to generate a higher percentage of COVID-related tweets and some agencies are more repetitive than their peers. Six topics (i.e., face covering, essential service appreciation, free resources, social distancing, cleaning, and service updates) were identified in the COVID-related tweets. From the followers' interaction perspective, most agencies gained followers after the start of the pandemic (i.e., March 2020). The percentage of follower gains is positively correlated with the percentage of COVID-related tweets, tweets replying to followers, and tweets using outlinks. The average like counts per COVID-related tweet is positively correlated with the percentage of COVID-related tweets and negatively correlated with the percentage of tweets discussing social distancing and agency repetitiveness. This work can inform transportation planners and transit agencies on how to use Twitter to effectively communicate with riders to improve public perception of health and safety as it relates to transit ridership during delays and long-term disruptions such as those created by the COVID-19 public health crisis.</p>","PeriodicalId":18298,"journal":{"name":"Materials Science-medziagotyra","volume":"44 1","pages":"1244-1261"},"PeriodicalIF":3.5,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9659705/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74064747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-01Epub Date: 2021-04-12DOI: 10.1016/j.nrl.2021.04.004
G Gómez de Terreros Caro, S Gil Díaz, M Pérez Alé, M L Martínez Gimeno
{"title":"[Bell's palsy following COVID-19 vaccination: A case report].","authors":"G Gómez de Terreros Caro, S Gil Díaz, M Pérez Alé, M L Martínez Gimeno","doi":"10.1016/j.nrl.2021.04.004","DOIUrl":"10.1016/j.nrl.2021.04.004","url":null,"abstract":"","PeriodicalId":18298,"journal":{"name":"Materials Science-medziagotyra","volume":"29 1","pages":"567-568"},"PeriodicalIF":3.9,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8041139/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72932568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, the Co-based metallic glass coatings deposited on soft metal substrates by pneumatic squeezing method were investigated. Also, the effects of TiC additions (%0-10) on the mechanical properties of the coatings were discussed in terms of hardness measurements. Microstructural observations have shown that the coatings with a thickness range of about 20-30 µm can be produced as non-porous layers in either entirely amorphous (0-6% TiC) or composite (8-10% TiC) structures. The glassy and TiC-reinforced glass composite coatings exhibit good adhesion characteristics and form a harder layer with the average hardness values between 1000 and 1600 Hv respectively. The hardness measurements evaluated together with XRD and EDX analyses showed that (Ti,Ta)C crystals precipitated in the amorphous matrix are responsible for further increase of the coatings hardness value up to 1600 Hv. The results also provide clues for mass manufacturing route in one step synthesis of the metallic glass and their composite coatings.
{"title":"Synthesis and Characterization of TiC-reinforced Metallic Glass Composite Coatings","authors":"Z. Ö. Yazici","doi":"10.5755/J02.MS.23362","DOIUrl":"https://doi.org/10.5755/J02.MS.23362","url":null,"abstract":"In this paper, the Co-based metallic glass coatings deposited on soft metal substrates by pneumatic squeezing method were investigated. Also, the effects of TiC additions (%0-10) on the mechanical properties of the coatings were discussed in terms of hardness measurements. Microstructural observations have shown that the coatings with a thickness range of about 20-30 µm can be produced as non-porous layers in either entirely amorphous (0-6% TiC) or composite (8-10% TiC) structures. The glassy and TiC-reinforced glass composite coatings exhibit good adhesion characteristics and form a harder layer with the average hardness values between 1000 and 1600 Hv respectively. The hardness measurements evaluated together with XRD and EDX analyses showed that (Ti,Ta)C crystals precipitated in the amorphous matrix are responsible for further increase of the coatings hardness value up to 1600 Hv. The results also provide clues for mass manufacturing route in one step synthesis of the metallic glass and their composite coatings.","PeriodicalId":18298,"journal":{"name":"Materials Science-medziagotyra","volume":"209 1","pages":"32-36"},"PeriodicalIF":1.0,"publicationDate":"2021-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87159207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Prior to micro-arc oxidation (MAO) treatment, a layer of high temperature oxide (HTO) prefab film was fabricated on the surface of 6061 aluminum alloy specimens. The formation mechanisms of the cracks and pores in the MAO coatings were investigated by means of Mg element as the tracer. The results showed that there were several different formation mechanisms for the pores and cracks formed in the MAO coatings as follows. Some of pores were attributed to the residual micro-discharge channels, and the others were attributed to the residual uncovered concave regions locating among the surrounding convex regions. The difference in oxide phase composition caused by the compositional fluctuations in the coating weakened the bond strength at the phase interface and resulted in forming cracks between every two convex regions. Some of cracks were resulted from the solidification and shrinkage of molten coating materials, and the others were resulted from the poor connection between every two convex regions. The surface morphology and the content of each element of the MAO coating were determined using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS).
{"title":"New Formation Mechanisms of Pores and Cracks in Micro-arc Oxidation Coatings on 6061 Aluminum Alloy with High Temperature Oxide Prefab Film","authors":"Guo-rui Wu, Dong‐dong Wang, Xin-tong Liu, Ming-Jung Wang, Dong Chen, Ye-kang Wu, Dejiu Shen","doi":"10.5755/J02.MS.24210","DOIUrl":"https://doi.org/10.5755/J02.MS.24210","url":null,"abstract":"Prior to micro-arc oxidation (MAO) treatment, a layer of high temperature oxide (HTO) prefab film was fabricated on the surface of 6061 aluminum alloy specimens. The formation mechanisms of the cracks and pores in the MAO coatings were investigated by means of Mg element as the tracer. The results showed that there were several different formation mechanisms for the pores and cracks formed in the MAO coatings as follows. Some of pores were attributed to the residual micro-discharge channels, and the others were attributed to the residual uncovered concave regions locating among the surrounding convex regions. The difference in oxide phase composition caused by the compositional fluctuations in the coating weakened the bond strength at the phase interface and resulted in forming cracks between every two convex regions. Some of cracks were resulted from the solidification and shrinkage of molten coating materials, and the others were resulted from the poor connection between every two convex regions. The surface morphology and the content of each element of the MAO coating were determined using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS).","PeriodicalId":18298,"journal":{"name":"Materials Science-medziagotyra","volume":"17 1","pages":"37-41"},"PeriodicalIF":1.0,"publicationDate":"2021-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74009225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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