CAJ | 학술논문

实验合金中Bi的加入量为0.5％～2％，合金在SF61％/CO2混合气体保护下熔炼，通入氩气精炼后在预热至250℃的金属型中浇铸成230 mm×40 mm×20 mm的板状试样，浇铸温度720℃.将铸态试样经过固溶处理(420℃，12 h)后，在200℃进行时效.实验结果表明，Bi的加入延长了合金的时效进程，有效地抑制了时效组织中非连续析出相的形成，促进了连续沉淀相的析出.电子束微区分析(EDAX)和透射电镜(TEM)研究表明，Bi的加入使AZ9l合金中形成了组成较复杂的连续析出相Mg17(Al，Bi)12，该析出相与基体之间具有复杂的半共格位向关系，提高了强化相的热稳定性，从而有助于合金高温力学性能的改善.
실험합금중Bi적가입량위0.5％～2％，합금재SF61％/CO2혼합기체보호하용련，통입아기정련후재예열지250℃적금속형중요주성230 mm×40 mm×20 mm적판상시양，요주온도720℃.장주태시양경과고용처리(420℃，12 h)후，재200℃진행시효.실험결과표명，Bi적가입연장료합금적시효진정，유효지억제료시효조직중비련속석출상적형성，촉진료련속침정상적석출.전자속미구분석(EDAX)화투사전경(TEM)연구표명，Bi적가입사AZ9l합금중형성료조성교복잡적련속석출상Mg17(Al，Bi)12，해석출상여기체지간구유복잡적반공격위향관계，제고료강화상적열은정성，종이유조우합금고온역학성능적개선.
The bismuth additive contents cover a range of 0.5％～2％. A mixture of CO2/1％ SF6 is used as a protective gas during melting process. The melt is homogenized with argon bubbling before pouring. The test sample plates (230 mm×40 mm×20 mm) are cast at the pouring temperature of 720℃ in a permanent mold preheating to about 250℃. All the specimens are heated at 420℃ for 12 h followed by quenching, then aged at 200℃ for different times. The results show that the bismuth addition to AZ91 retards the aging process, suppresses the discontinuous precipitation and accelerates the formation of continuous precipitates. EDAX and TEM study indicates that the continuous precipitate in the Bi-bearing magnesium alloys has a stoichiometric composition of Mg17 (Al, Bi)12, which has semicoherent orientation relationship with matrix and increases the thermal stability of the precipitates. Accordingly, the heat resistance of magnesium alloy at elevated temperature could be increased by addition of bismuth.