http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
J. S. Oh(오재성),J. S. Bae(배정석),K. A. Lee(이기안) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
This study investigated the effects of strain rate and orientation on the tensile deformation behavior of Ni-based bulk powder porous material. Powder porous materials were produced through PVD (physical vapor deposition), electroplating, and debinding & sintering processes and manufactured in bulk form [500 x 300 x 60(t) mm] through an additional process. The average pore size of the manufactured powder porous materials was of two types: one was around 1,200μm, and the other was 3,000μm. The result of microstructure observation showed that both porous materials were composed of γ–Ni, γ"-Ni3Al. To investigate the effect of strain rate and direction on the mechanical characteristics, test specimens were processed in two directions -- RD (rolling direction) and TD (transverse direction); and tensile tests were conducted with initial strain rates of 10-2/s, 10-3/s, and 10-4/s, respectively. They were machined into tensile test specimens with gauge length of 2mm, width of 15 mm, and thickness (t) of 10mm, and tests were conducted at room temperature using Instron 8801 instrument. The tensile test result showed that the RD tensile strength of the 1,200μm porous material ranged from 6.0 MPa (10-4/s) to 7.2 MPa (10-2/s), and TD tensile strength, from 4.2 MPa (10-4/s) to 4.8 MPa (10-2/s). the tensile strength of the 3,000μm porous material ranged from 3.0 MPa (10-4/s) to 3.3 MPa (10-2/s) for RD and from 1.5 MPa (10-4/s) to 2.1 MPa (10-2/s) for TD. Regardless of direction, the tensile strength of the bulk porous materials showed minor increase as the strain rate increased, and the tensile strength in RD was observed to be higher than the one in TD. Even though the porous material`s strength is generally explained through its correlation with relative density, authors tried to identify its correlation with porous materials by suggesting and using a new concept called area fraction. The observation of tensile fracture surface showed that the strut of porous materials was arranged/elongated in the direction of tension; rupture then occurred at the nodes where struts were interconnected. Such tensile deformation behavior was shown to be a unique phenomenon generated by the porous material`s porosity and pore structures and was different from the deformation behavior of general bulk materials. Based on these results, the micro-deformation mechanism of bulk-type powder porous materials was also discussed.
오재성(J. S. Oh),공영민(Y. M. Kong),김병기(B. K. Kim),이기안(K. A. Lee) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
This study investigated the high temperature compressive deformation (25℃~800℃) behavior of Ni-22.4%Fe-22%Cr-6%Al porous metal that is manufactured via powder process. Two different porous metals - 580㎛ (cell size) and 800㎛ - were used. The relative densities were 8.51% for the 580㎛ and 6.19% for the 800㎛ material. Those materials were to consist of γ-Ni, γ’-Ni₃Al and β-NiAl phases. The compression results, regardless of temperature, revealed typical three stages of deformation behavior (elastic, plateau, and densification region). At all temperatures, 580㎛(a higher density) showed higher strengths than those of 800㎛. However, the difference of strength continuously decreased with increasing temperature. Fractography revealed that the fine cracks easily propagated along interphase boundary in the strut regardless of deformation temperature and porosity condition. Based on these results, the mechanism of high temperature deformation of porous metal was also discussed.