Pub Date : 2017-04-30DOI: 10.7777/jkfs.2017.37.2.38
Dae-hwan Kim, Hyun-Ju Jung, Su-gun Lim
Given that the conventional extrusion of high-strength Al alloys such as 7075 aluminum alloys is difficult due to their very low extrudability as compared to that of 6061 aluminum alloys, thixo-extrusion can be used to obtain a high-strength material easily at a lower extrusion pressure as compared to conventional extrusion. In this study, hotand thixo-extruded 7075 aluminum alloys are prepared by a vertical forward extrusion process and their microstructures, hardness levels, and compressive properties are investigated. Hot-extruded alloy bars are assessed to obtain a microstructure elongated in the extrusion direction, whereas with thixoextruded alloy bars, it was possible to obtain a microstructure having fine and equiaxed grains by dynamic recrystallization. The resulting isotropy and improved formability at the hot deformation temperature of the thixo-extruded alloy were attributed to the fine and equiaxed grains formed by the thixo-extrusion process.
{"title":"A Study on the Compressive Properties of Thixo-Extruded 7075 Aluminum Alloy","authors":"Dae-hwan Kim, Hyun-Ju Jung, Su-gun Lim","doi":"10.7777/jkfs.2017.37.2.38","DOIUrl":"https://doi.org/10.7777/jkfs.2017.37.2.38","url":null,"abstract":"Given that the conventional extrusion of high-strength Al alloys such as 7075 aluminum alloys is difficult due to their very low extrudability as compared to that of 6061 aluminum alloys, thixo-extrusion can be used to obtain a high-strength material easily at a lower extrusion pressure as compared to conventional extrusion. In this study, hotand thixo-extruded 7075 aluminum alloys are prepared by a vertical forward extrusion process and their microstructures, hardness levels, and compressive properties are investigated. Hot-extruded alloy bars are assessed to obtain a microstructure elongated in the extrusion direction, whereas with thixoextruded alloy bars, it was possible to obtain a microstructure having fine and equiaxed grains by dynamic recrystallization. The resulting isotropy and improved formability at the hot deformation temperature of the thixo-extruded alloy were attributed to the fine and equiaxed grains formed by the thixo-extrusion process.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"68 1","pages":"38-44"},"PeriodicalIF":0.0,"publicationDate":"2017-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80329089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-28DOI: 10.7777/JKFS.2017.37.1.1
Hak-Chul Lee, P. Seo, C. Jin, Hyung-Yoon Seo, C. Kang
The purpose of this study is to increase the part recovery rate (to more than 70%) during the casting of a ductile cast iron turbo charger housing using a heater around the riser. Before creating a casting mold, various runner and riser systems were designed and analyzed with a casting simulation analysis tool. The design variables were the heater temperature, top insulation, riser location, riser diameter and the riser shape. During the feeding from the riser to the part, the reverse model was better than the forward model. When heating the riser (above 600 o C), solidification of the riser was delayed and the feeding effect was suitable compared to that without heating. At a higher heating temperature, less solidification shrinkage and porosity were noted inside the part. On the basis of a casting simulation, eight molds were fabricated and casting experiments were conducted. According to the experimental conditions, external and internal defects were analyzed and mechanical properties were tested. The ultimate tensile strength and elongation outcome were correspondingly more than 540MPa and 5% after a heat treatment. In addition, a maximum part recovery rate of 86% was achieved in this study.
{"title":"Fabrication Technology of Turbo Charger Housing for Riser Minimizing by Fusion S/W Application and its Experimental Investigation","authors":"Hak-Chul Lee, P. Seo, C. Jin, Hyung-Yoon Seo, C. Kang","doi":"10.7777/JKFS.2017.37.1.1","DOIUrl":"https://doi.org/10.7777/JKFS.2017.37.1.1","url":null,"abstract":"The purpose of this study is to increase the part recovery rate (to more than 70%) during the casting of a ductile cast iron turbo charger housing using a heater around the riser. Before creating a casting mold, various runner and riser systems were designed and analyzed with a casting simulation analysis tool. The design variables were the heater temperature, top insulation, riser location, riser diameter and the riser shape. During the feeding from the riser to the part, the reverse model was better than the forward model. When heating the riser (above 600 o C), solidification of the riser was delayed and the feeding effect was suitable compared to that without heating. At a higher heating temperature, less solidification shrinkage and porosity were noted inside the part. On the basis of a casting simulation, eight molds were fabricated and casting experiments were conducted. According to the experimental conditions, external and internal defects were analyzed and mechanical properties were tested. The ultimate tensile strength and elongation outcome were correspondingly more than 540MPa and 5% after a heat treatment. In addition, a maximum part recovery rate of 86% was achieved in this study.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"54 1","pages":"1-13"},"PeriodicalIF":0.0,"publicationDate":"2017-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79240367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-28DOI: 10.7777/JKFS.2017.37.1.14
Dae-hwan Kim, Su-gun Lim
The microstructure, electrical conductivity and hardness variation of an AZ91-5wt%Sn Mg alloy sample during a solid-solution and aging heat treatment were instigated by optical microscopy, scanning electron microscopy, X-ray diffraction and by Rockwell hardness techniques in this study. The XRD result shows that the main phases in the as-casted alloy are α -Mg, Mg 17 Al 12 and Mg 2 Sn. From the SEM images of the AZ91-5wt%Sn Mg alloy after the solution treatment, the Mg 17 Al 12 phases in the alloy were found to have dissolved into the matrix with an increase in the holding time during the solution treatment, but Mg 2 Sn phases were clearly observable. The highest peak hardness of the AZ91-5wt%Sn Mg alloy is 82HRE at an aging temperature of 200 o C.
{"title":"Heat Treatment of AZ91-5wt.%Sn Magnesium Alloy","authors":"Dae-hwan Kim, Su-gun Lim","doi":"10.7777/JKFS.2017.37.1.14","DOIUrl":"https://doi.org/10.7777/JKFS.2017.37.1.14","url":null,"abstract":"The microstructure, electrical conductivity and hardness variation of an AZ91-5wt%Sn Mg alloy sample during a solid-solution and aging heat treatment were instigated by optical microscopy, scanning electron microscopy, X-ray diffraction and by Rockwell hardness techniques in this study. The XRD result shows that the main phases in the as-casted alloy are α -Mg, Mg 17 Al 12 and Mg 2 Sn. From the SEM images of the AZ91-5wt%Sn Mg alloy after the solution treatment, the Mg 17 Al 12 phases in the alloy were found to have dissolved into the matrix with an increase in the holding time during the solution treatment, but Mg 2 Sn phases were clearly observable. The highest peak hardness of the AZ91-5wt%Sn Mg alloy is 82HRE at an aging temperature of 200 o C.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"71 3 1","pages":"14-20"},"PeriodicalIF":0.0,"publicationDate":"2017-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74746228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-02-28DOI: 10.7777/jkfs.2017.37.1.21
Byung-Ki Yoo, Heung-Il Park, Cha-Hurn Bae, Sung-Gyoo Kim, Hae-Yong Jeong
The effects of W content and heat treatment on the microstructure and mechanical properties of Hastelloy C-276 alloy investment castings were discussed. As the W content was increased, dendritic microstructure was refined and network type precipitate formed during solidification was distributed on the dendritic grain boundaries. Cr, Fe and Mn were highly segregated in the Ni-based dendrite matrix, and Mo, W, C and Si were in the precipitates. Due to the heat treatment, fine granular and flake precipitates were newly formed in the matrix, and unresolved network type precipitates remained on the grain boundary. The network type precipitates and the granular and flake precipitates formed by heat treatment were confirmed to be µ phase intermetallic compounds with similar compositions. Due to the increase of the W content and the heat treatment, hardness and tensile strength were sig-nificantly increased. However, tensile strength after aging treatment was decreased with the W content. These results can be explained in that brittle fracturing by the unresolved network type precipitates dispersed in the grain boundary was predominant over ductile fracturing by the dimple ruptures originating from the fine granular precipitates in the matrix.
{"title":"Effect of Tungsten Contents and Heat Treatment on the Microstructures and Mechanical Properties of Hastelloy C-276 Alloy Investment Castings","authors":"Byung-Ki Yoo, Heung-Il Park, Cha-Hurn Bae, Sung-Gyoo Kim, Hae-Yong Jeong","doi":"10.7777/jkfs.2017.37.1.21","DOIUrl":"https://doi.org/10.7777/jkfs.2017.37.1.21","url":null,"abstract":"The effects of W content and heat treatment on the microstructure and mechanical properties of Hastelloy C-276 alloy investment castings were discussed. As the W content was increased, dendritic microstructure was refined and network type precipitate formed during solidification was distributed on the dendritic grain boundaries. Cr, Fe and Mn were highly segregated in the Ni-based dendrite matrix, and Mo, W, C and Si were in the precipitates. Due to the heat treatment, fine granular and flake precipitates were newly formed in the matrix, and unresolved network type precipitates remained on the grain boundary. The network type precipitates and the granular and flake precipitates formed by heat treatment were confirmed to be µ phase intermetallic compounds with similar compositions. Due to the increase of the W content and the heat treatment, hardness and tensile strength were sig-nificantly increased. However, tensile strength after aging treatment was decreased with the W content. These results can be explained in that brittle fracturing by the unresolved network type precipitates dispersed in the grain boundary was predominant over ductile fracturing by the dimple ruptures originating from the fine granular precipitates in the matrix.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"15 1","pages":"21-29"},"PeriodicalIF":0.0,"publicationDate":"2017-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90264945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.7777/JKFS.2017.37.4.101
S. Yim, B. Kang, D. Cho, I. Park
{"title":"The Effect of Pd addition on Mechanical Properties at High Temperature of Mg-4Al-2Sn Alloy","authors":"S. Yim, B. Kang, D. Cho, I. Park","doi":"10.7777/JKFS.2017.37.4.101","DOIUrl":"https://doi.org/10.7777/JKFS.2017.37.4.101","url":null,"abstract":"","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"63 1","pages":"101-107"},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76384484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.7777/jkfs.2017.37.4.108
Parkkyeongseob, Kim Hee-soo
{"title":"Change of Secondary Dendrite Arm Spacing of Hypoeutectic Al-Si Alloys according to Si Content and Cooling Rate","authors":"Parkkyeongseob, Kim Hee-soo","doi":"10.7777/jkfs.2017.37.4.108","DOIUrl":"https://doi.org/10.7777/jkfs.2017.37.4.108","url":null,"abstract":"","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"61 1","pages":"108-114"},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83782793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-12-09DOI: 10.7777/JKFS.2016.36.6.181
Jeong-Min Kim, Tae-Hyung Ha
{"title":"Microstructure and Properties of High Strength High Ductility Al-Mg-Zn Casting Alloy","authors":"Jeong-Min Kim, Tae-Hyung Ha","doi":"10.7777/JKFS.2016.36.6.181","DOIUrl":"https://doi.org/10.7777/JKFS.2016.36.6.181","url":null,"abstract":"","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"46 1","pages":"181-186"},"PeriodicalIF":0.0,"publicationDate":"2016-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82356825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-12-09DOI: 10.7777/jkfs.2016.36.6.208
H. Hwang, C. Nam, Y. Choi, Jun-Ho Hong
Casting defects, which are closely related to entrapped air bubbles and metallic oxides, occur very frequently in the casting process. Many researchers have shown that these defects can be reduced by adopting an appropriate gating system design. But, it is dif-ficult for field engineers to identify a specific gating system that is more appropriate for their products. In this study, we tried to draw a comparison of gating system designs with and without ceramic foam filters. A ceramic foam filter was added to the horizontal runner just after the sprue to prevent air bubble generation and to reduce turbulence without change of the gating system design. To verify the effects of initial pouring velocity, the experiment was conducted with four different amounts of water volume in the reservoir. Results of the water modeling experiment applying the filter showed remarkably changed flow characteristics. Although the study confirmed that use of the filter may change the flow characteristics, it needs to be noted that only filter use alone cannot solve all the problems caused by a poorly designed gating system.
{"title":"A Study on the Effects of the Filter on Flow Pattern of the Traditional Gating System by the Water Modeling Experiment","authors":"H. Hwang, C. Nam, Y. Choi, Jun-Ho Hong","doi":"10.7777/jkfs.2016.36.6.208","DOIUrl":"https://doi.org/10.7777/jkfs.2016.36.6.208","url":null,"abstract":"Casting defects, which are closely related to entrapped air bubbles and metallic oxides, occur very frequently in the casting process. Many researchers have shown that these defects can be reduced by adopting an appropriate gating system design. But, it is dif-ficult for field engineers to identify a specific gating system that is more appropriate for their products. In this study, we tried to draw a comparison of gating system designs with and without ceramic foam filters. A ceramic foam filter was added to the horizontal runner just after the sprue to prevent air bubble generation and to reduce turbulence without change of the gating system design. To verify the effects of initial pouring velocity, the experiment was conducted with four different amounts of water volume in the reservoir. Results of the water modeling experiment applying the filter showed remarkably changed flow characteristics. Although the study confirmed that use of the filter may change the flow characteristics, it needs to be noted that only filter use alone cannot solve all the problems caused by a poorly designed gating system.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"4 1","pages":"208-214"},"PeriodicalIF":0.0,"publicationDate":"2016-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87799556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-12-09DOI: 10.7777/JKFS.2016.36.6.215
Dae-hwan Kim, In-Taek Im, Q. Jin, Su-gun Lim
In a recent study, the microstructures and mechanical properties of AM80-xSn magnesium alloys with semi solid casting and hot extrusion process were investigated. With increasing Sn content, the amount of β (Mg2Sn) phase increased, while the α -Mg den-dritic size decreased. The hardness was increased by the Mg2Sn as the Sn content increased. With increasing Sn content, permanent mold cast and semi solid cast AM80 Mg alloy showed less reduction of hardness and also of extruded AM80 Mg alloy after annealing. In the case of the mechanical properties, the extruded semi solid casting AM80 Mg alloy showed higher tensile strength and yield strength with increasing Sn content compared to the extruded permanent mold cast AM80 Mg alloy at room temperature.
{"title":"Microstructures and Mechanical Properties of AM80-xSn Magnesium Alloys with Semi-Solid casting and Hot Extrusion Process","authors":"Dae-hwan Kim, In-Taek Im, Q. Jin, Su-gun Lim","doi":"10.7777/JKFS.2016.36.6.215","DOIUrl":"https://doi.org/10.7777/JKFS.2016.36.6.215","url":null,"abstract":"In a recent study, the microstructures and mechanical properties of AM80-xSn magnesium alloys with semi solid casting and hot extrusion process were investigated. With increasing Sn content, the amount of β (Mg2Sn) phase increased, while the α -Mg den-dritic size decreased. The hardness was increased by the Mg2Sn as the Sn content increased. With increasing Sn content, permanent mold cast and semi solid cast AM80 Mg alloy showed less reduction of hardness and also of extruded AM80 Mg alloy after annealing. In the case of the mechanical properties, the extruded semi solid casting AM80 Mg alloy showed higher tensile strength and yield strength with increasing Sn content compared to the extruded permanent mold cast AM80 Mg alloy at room temperature.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"36 1","pages":"215-221"},"PeriodicalIF":0.0,"publicationDate":"2016-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80035560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-12-09DOI: 10.7777/JKFS.2016.36.6.195
Jae-Chan Jo, Kwang-Sam Kim, In-Taek Im, Dae-hwan Kim, Sung-Yong Shim, Su-gun Lim
The effects of Mg addition on heat treatment and mechanical properties of A356 alloy were investigated. With increased amounts of Mg addition to A356 alloy, the grain size decreased and eutectic Si was refined. And, this process can improve the mechanical properties. Solid solution heat treatment causes the spheroidizing of eutectic Si. In this study, although eutectic Si was refined with Mg addition, solid solution time increased from 2 hours to 6 hours with Mg addition, and aging time also increased, from 4 hours to 8 hours. After heat treatment, Mg2Si remained in a formation of Chinese script. And, Chinese script Mg2Si formed with Mg addition caused a reduction of the elongation of the alloys according to the stress concentration.
{"title":"Effects of Mg Addition on Heat Treatment and Mechanical Properties of A356 Alloy","authors":"Jae-Chan Jo, Kwang-Sam Kim, In-Taek Im, Dae-hwan Kim, Sung-Yong Shim, Su-gun Lim","doi":"10.7777/JKFS.2016.36.6.195","DOIUrl":"https://doi.org/10.7777/JKFS.2016.36.6.195","url":null,"abstract":"The effects of Mg addition on heat treatment and mechanical properties of A356 alloy were investigated. With increased amounts of Mg addition to A356 alloy, the grain size decreased and eutectic Si was refined. And, this process can improve the mechanical properties. Solid solution heat treatment causes the spheroidizing of eutectic Si. In this study, although eutectic Si was refined with Mg addition, solid solution time increased from 2 hours to 6 hours with Mg addition, and aging time also increased, from 4 hours to 8 hours. After heat treatment, Mg2Si remained in a formation of Chinese script. And, Chinese script Mg2Si formed with Mg addition caused a reduction of the elongation of the alloys according to the stress concentration.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"13 1","pages":"195-201"},"PeriodicalIF":0.0,"publicationDate":"2016-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82676395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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