http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : 청웨이리 (검색결과 1 건)
-
Microstructures and deformation behavior of Mg-Sn based alloys
청웨이리 Changwon National Univ. 2011 국내박사
It is generally regarded that the main obstacle that must be overcome in Mg extrusions is their low extrusion speed, which leads to high production costs. Normally, high-strength Mg alloys such as AZ80 and ZK60 alloys are extrudable only at speeds of 0.5~2.5 m/min, well below those attainable with Al alloys. This is mainly due to an increase in the susceptibility to hot shortness during extrusion with increases in alloying elements such as Al and Zn caused by the incipient melting of second-phase particles. From this respect, it is believed that Mg-Sn based alloys have strong potential for use in high-speed extrusion processes, as they usually have higher thermal stability than conventional AZ and ZK series Mg alloys. In addition, their susceptibility to hot shortness can be decreased by applying an indirect extrusion process, since it can alleviate frictional heat during extrusion better than a conventional direct extrusion process. The hot deformation behaviors of homogenized Mg-8Sn-1Al-1Zn (wt.%) and AZ31 alloys were investigated in the temperature range of 523~723 K and at the strain rate range of 0.1~10 s-1 with a view to evaluate the optimum processing parameters for extrusion through processing map. The activation energy Q and flow stress of Mg-8Sn-1Al-1Zn alloy are lower compared to that of AZ31 in the studied conditions. The processing-map results indicated that homogenized TAZ811 can be deformed at lower temperature and similar strain rate ranges. Indirect extrusion of the binary Mg-Sn alloys with 6-10% Sn has been performed at ram speeds of 1.3 and at a temperature of 523K. Tensile and compressive strengths increased and yield asymmetry reduced with Sn addition. These changes are attributed to grain refinement and fine Mg2Sn precipitates. However, Mg-10%Sn alloy showed relatively poor tensile ductility due to the presence of coarse particles. A novel high strength wrought Mg-8Sn-1Al-1Zn developed for high-speed extrusion was successfully extruded at speeds in a range of 2-10 m/min and temperature of 523 K. The effects of extrusion speed on the microstructures and tensile properties of the extruded alloys were investigated. Grain size, recrystallization fraction and texture were found to be greatly affected by the extrusion speed, resulting in tensile properties showing lower strength and ductility as the extrusion speed increased. The strength and ductility of the extruded alloys are also discussed in terms of the formation of double twins during the tensile test. The extruded Mg-8Sn and Mg-8Sn-1Al-1Zn alloys present superior tensile properties compared to the commercial AZ31 alloy extruded at same condition due to the fine-grain strengthening, particle strengthening and solid solution strengthening as well as texture strengthening. The contribution when the alloy was strengthened fully with four strengthening mechanism was calculated. Compression tests of the extruded Mg-8Sn-1Al-1Zn alloys were conducted in the temperature range of 298~523 K and strain rate range of 0.001~10 s−1 with a view to evaluate the optimum processing parameters for post deformation by processing map. The different efficiency domains and flow instability region corresponding to various microstructural characteristics have been identified as follows: 423K/0.001-0.01s-1 and 473~523K/0.001-3.3s-1. The compression behaviors of the extruded Mg-8Sn-1Al-1Zn alloy were also analyzed by sin hyperbolic constitutive equations. The activation energy and stress exponent are 130.3kJ/mol and 6.73, respectively. Microstructure analyses indicate that LTDRX, TDRX and CDRX is the main deformation mechanisms of extrude TAZ811 alloy at 298-523 K. The newly formed DRX grains are perpendicular with the compression direction, namely original extrusion direction.
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
