The present study investigated the effect of as-built and post heat-treated microstructures of IN738LC alloy fabricated via selective laser melting process on high temperature oxidation behavior.The as-built microstru...The present study investigated the effect of as-built and post heat-treated microstructures of IN738LC alloy fabricated via selective laser melting process on high temperature oxidation behavior.The as-built microstructure showed fine cell and columnar structure due to high cooling rate.Ti element segregation was observed in inter-cell/inter-columnar area.After post heat-treatment,the initially-observed cell structure disappeared,instead bimodal Ni_3(Al,Ti)particles formed.High temperature(1273 K and 1373 K)oxidation test results showed parabolic oxidation curves regardless of temperature and initial microstructure.The as-built IN738LC fabricated via the selective laser melting process displayed oxidation resistance similar to or slightly better than that of IN738LC fabricated via wrought or cast process.Heat-treated SLM IN738LC,although had similar oxidation weight-gain values to those of the SLM asbuilt material at 1273K,showed relatively better oxidation resistance at 1373 K.Bimodal Ni_3(Al,Ti)precipitate formed in the post heat treatment changed the local chemical composition,thereby led to changes in alumina former/chromia former location and fraction on the alloy surface.It was concluded that in heat-treated IN738LC increased alumina former fraction was found,and this resulted in excellent oxidation resistance and relatively low weight-gain.展开更多
The inverse gradient-grained CoCrFeMnNi high-entropy alloy with a desirable mechanical property that evades the strength-ductility trade-off is fabricated by the process of cold rolling and subsequent laser surface he...The inverse gradient-grained CoCrFeMnNi high-entropy alloy with a desirable mechanical property that evades the strength-ductility trade-off is fabricated by the process of cold rolling and subsequent laser surface heat-treatment.Due to the gradually decayed thermal effect along with the thickness,the grain size increases from the hard core to the soft surface in terms of the inverse gradient-grained sample,which is in good consistent with the microhardness profiles.The hetero-deformation induced strengthening and strain hardening caused by the inverse gradient-grained structure improve the strength-ductility combination,as well as the high-order hierarchal nanotwins due to the enhanced interaction with dislocations.For the laser surface heat-treatment technique,the strength and ductility are significantly increased by enlarging the microhardness difference and decreasing the thermal stress.Considering the high volume fraction of gradient-grained layer and a great deal of high-order hierarchal nanotwins in the central region,the laser surface heat-treatment technique is a promising way to produce the gradientstructured materials without thickness limitation.展开更多
Selective laser melting(SLM) is an attractive rapid prototyping technology for the fabrication of metallic components with complex structure and high performance. Aluminum alloy, one of the most pervasive structural m...Selective laser melting(SLM) is an attractive rapid prototyping technology for the fabrication of metallic components with complex structure and high performance. Aluminum alloy, one of the most pervasive structural materials, is well known for high specific strength and good corrosion resistance. But the poor laser formability of aluminum alloy restricts its application. There are problems such as limited processable materials, immature process conditions and metallurgical defects on SLM processing aluminum alloys. Some efforts have been made to solve the above problems. This paper discusses the current research status both related to the scientific understanding and technology applications. The paper begins with a brief introduction of basic concepts of aluminum alloys and technology characterization of laser selective melting. In addition, solidification theory of SLM process and formation mechanism of metallurgical defects are discussed. Then, the current research status of microstructure, properties and heat treatment of SLM processing aluminum alloys is systematically reviewed respectively. Lastly, a future outlook is given at the end of this review paper.展开更多
基金the Fundamental Research Program of the Korea Institute of Materials Science(Grant No.PNK5520)Korea Institute for Advancement of Technology(KIAT)grant funded by the Korea Government(MOTIE)(P0002007,The Competency Development Program for Industry Specialist)。
文摘The present study investigated the effect of as-built and post heat-treated microstructures of IN738LC alloy fabricated via selective laser melting process on high temperature oxidation behavior.The as-built microstructure showed fine cell and columnar structure due to high cooling rate.Ti element segregation was observed in inter-cell/inter-columnar area.After post heat-treatment,the initially-observed cell structure disappeared,instead bimodal Ni_3(Al,Ti)particles formed.High temperature(1273 K and 1373 K)oxidation test results showed parabolic oxidation curves regardless of temperature and initial microstructure.The as-built IN738LC fabricated via the selective laser melting process displayed oxidation resistance similar to or slightly better than that of IN738LC fabricated via wrought or cast process.Heat-treated SLM IN738LC,although had similar oxidation weight-gain values to those of the SLM asbuilt material at 1273K,showed relatively better oxidation resistance at 1373 K.Bimodal Ni_3(Al,Ti)precipitate formed in the post heat treatment changed the local chemical composition,thereby led to changes in alumina former/chromia former location and fraction on the alloy surface.It was concluded that in heat-treated IN738LC increased alumina former fraction was found,and this resulted in excellent oxidation resistance and relatively low weight-gain.
基金financially supported by the Zhejiang Provincial Natural Science Funds of China(No.LZ20E050003)the Wenzhou Science and Technology Projects(Nos.ZG2020038 and H2020004)。
文摘The inverse gradient-grained CoCrFeMnNi high-entropy alloy with a desirable mechanical property that evades the strength-ductility trade-off is fabricated by the process of cold rolling and subsequent laser surface heat-treatment.Due to the gradually decayed thermal effect along with the thickness,the grain size increases from the hard core to the soft surface in terms of the inverse gradient-grained sample,which is in good consistent with the microhardness profiles.The hetero-deformation induced strengthening and strain hardening caused by the inverse gradient-grained structure improve the strength-ductility combination,as well as the high-order hierarchal nanotwins due to the enhanced interaction with dislocations.For the laser surface heat-treatment technique,the strength and ductility are significantly increased by enlarging the microhardness difference and decreasing the thermal stress.Considering the high volume fraction of gradient-grained layer and a great deal of high-order hierarchal nanotwins in the central region,the laser surface heat-treatment technique is a promising way to produce the gradientstructured materials without thickness limitation.
基金sponsored by National Key Research and Development Program "Additive Manufacturing and Laser Manufacturing" (No. 2016YFB1100101)Natural and Science Foundation of China (Grant Nos. 51775208, 51505166)+4 种基金Hubei Science Fund for Distinguished Young Scholars (No. 0216110085)Wuhan Morning Light Plan of Youth Science and Technology (No. 0216110066)Graduates’ Innovation Fund, Huazhong University of Science and Technology (No. 5003110027)Fundamental Research Funds for the Central University (No. 2017JYCXJJ004)the Academic frontier youth team at Huazhong University of Science and Technology (HUST)
文摘Selective laser melting(SLM) is an attractive rapid prototyping technology for the fabrication of metallic components with complex structure and high performance. Aluminum alloy, one of the most pervasive structural materials, is well known for high specific strength and good corrosion resistance. But the poor laser formability of aluminum alloy restricts its application. There are problems such as limited processable materials, immature process conditions and metallurgical defects on SLM processing aluminum alloys. Some efforts have been made to solve the above problems. This paper discusses the current research status both related to the scientific understanding and technology applications. The paper begins with a brief introduction of basic concepts of aluminum alloys and technology characterization of laser selective melting. In addition, solidification theory of SLM process and formation mechanism of metallurgical defects are discussed. Then, the current research status of microstructure, properties and heat treatment of SLM processing aluminum alloys is systematically reviewed respectively. Lastly, a future outlook is given at the end of this review paper.
