CAJ | 학술논문

采用真空冶炼和定向凝固工艺制备一种具有优异抗腐蚀性能的镍基高温合金，并利用光学显微镜、扫描电镜和透射电镜研究合金的微观组织，分析合金在不同温度下的拉伸性能。结果表明，除γ′颗粒和γ基体外，在合金晶界上析出了一些MC碳化物、M3B2硼化物和Ni5Hf相。合金拉伸性能对温度有很强的依赖性，并呈现明显的的反常屈服和中温脆性行为。在650°C以下，合金的屈服强度随着温度的升高而略微降低，但抗拉强度几乎没有变化。当温度在650°C和750°C之间时，合金的屈服、抗拉强度快速升高，但拉伸塑性显著降低，并在700°C时达到最低值。当温度进一步升高时，合金的屈服、抗拉强度逐渐降低，塑性升高。透射电镜观察发现，在低温条件下，位错切割γ′是主要的变形机制；在高温条件下，位错绕过γ′是主要的变形机制；由位错切割γ′转变至位错绕过γ′的温度约为800°C。合金的反常屈服和中温脆性行为主要归因于合金中高的γ′含量。此外，碳化物和共晶组织对合金的中温脆性行为也有影响。
채용진공야련화정향응고공예제비일충구유우이항부식성능적얼기고온합금，병이용광학현미경、소묘전경화투사전경연구합금적미관조직，분석합금재불동온도하적랍신성능。결과표명，제γ′과립화γ기체외，재합금정계상석출료일사MC탄화물、M3B2붕화물화Ni5Hf상。합금랍신성능대온도유흔강적의뢰성，병정현명현적적반상굴복화중온취성행위。재650°C이하，합금적굴복강도수착온도적승고이략미강저，단항랍강도궤호몰유변화。당온도재650°C화750°C지간시，합금적굴복、항랍강도쾌속승고，단랍신소성현저강저，병재700°C시체도최저치。당온도진일보승고시，합금적굴복、항랍강도축점강저，소성승고。투사전경관찰발현，재저온조건하，위착절할γ′시주요적변형궤제；재고온조건하，위착요과γ′시주요적변형궤제；유위착절할γ′전변지위착요과γ′적온도약위800°C。합금적반상굴복화중온취성행위주요귀인우합금중고적γ′함량。차외，탄화물화공정조직대합금적중온취성행위야유영향。
A nickel-based superalloy with good corrosion resistance was fabricated by directional solidification, and its microstructure and tensile properties at elevated temperatures were investigated. Microstructure observations reveal that the γ′precipitates are arrayed in theγmatrix regularly with some MC, Ni5Hf and M3B2 particles distributed along the grain boundary. The tensile tests exhibit that the tensile properties depend on temperature significantly and demonstrate obvious anomalous yield and intermediate-temperature brittleness (ITB) behavior. Below 650 °C, the yield strength decreases slightly but the ultimate tensile strength almost has no change. When the temperature is between 650 °C and 750 °C, the yield and ultimate tensile strengths rise rapidly, and after then they both decrease gradually with temperature increasing further. The elongation has its minimum value at about 700 °C. The TEM examination exhibits that sharing of theγ′by dislocation is almost the main deformation mechanism at low temperatures, but theγ′by-pass dominates the deformation at high temperatures. The transition temperature from shearing to by-pass should be around 800 °C. The anomalous yield and intermediate-temperature brittleness behaviors should be attributed to the high content ofγ′. In addition, the carbides and eutectic structure also contribute some to the ITB behaviors of the alloy.