(1. 中南大學 材料科學與工程學院，長沙 410083；
2. 中南大學 航空航天學院，長沙410083；
3. 中南大學 粉末冶金國家重點實驗室，長沙 410083)
摘 要: 基于Thermo-Calc熱力學計算軟件及相應(yīng)的Ni基合金數(shù)據(jù)庫，模擬計算一種新型Ni-Co-Cr基粉末高溫合金可能的平衡析出相及其與溫度的關(guān)系；采用金相顯微鏡、掃描電子顯微鏡(SEM)并結(jié)合定量分析軟件，對合金在不同退火制度下的晶粒與γ′相的演化行為進行分析；同時，利用納米壓痕儀研究退火制度對合金力學性能的影響。結(jié)果表明：合金中γ′相的溶解溫度約為1154 ℃。當退火溫度低于1000 ℃時，γ′相均以近球形為主，其尺寸及含量隨退火溫度的升高和保溫時間的延長變化不大；γ′相對晶粒生長起到了有效的釘扎作用，合金的晶粒尺寸無明顯增長。當退火溫度高于1000 ℃時，γ′相的形貌逐漸向方形或花瓣狀轉(zhuǎn)變，且隨著保溫時間的延長有分裂的趨勢；退火溫度的升高使γ′相的尺寸及含量均有較大幅度的降低，合金的晶粒尺寸也有較明顯的增加。隨著退火溫度的升高和保溫時間的延長，合金的硬度逐漸降低，但彈性模量無明顯變化。綜合考慮退火后擠壓態(tài)合金的微觀組織和硬度，優(yōu)化的退火制度在1000 ℃、1~2 h條件下進行。
關(guān)鍵字: 鎳基粉末高溫合金；退火；晶粒；γ′相；納米壓痕
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. School of Aeronautics and Astronautics, Central South University, Changsha 410083, China;
3. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China）
Abstract:Based on the Thermo-Calc thermodynamic calculation software and the corresponding database of Ni-Co-Cr based alloy, the possible equilibrium phases in a new nickel-based powder superalloy and its relationship with temperature were simulated. The evolutions of γ grain and γ′ phase under various annealing conditions were analyzed by optical microscopy and scanning electron microscopy (SEM) combining with the quantitative analysis software. At the same time, the influence of annealing condition on the mechanical properties of the alloy was studied by nanoindentation. The results show that the dissolution temperature of γ′ phase for the alloy is about 1154 ℃. When the annealing temperature is lower than 1000 ℃, the γ'''' phase mainly exhibits spherical morphology. Increasing the annealing temperature and the holding time lead to limited variation in the size and volume fraction of γ'''' phase. The grains slowly grow due to the effective pinning of the undissolved γ′ phase. When the annealing temperature is higher than 1000 ℃, the morphology of γ′ phase gradually changes from spherical to cubical or petaloid shape. In the case of longer holding time, γ′ phase exhibits a tendency of splitting from a large precipitates to several small ones. The increase of annealing temperature results in significant decreasing in the size and volume fraction of γ′ phase so that the grain size of the alloy also increases rapidly. The nanoindentation test reveals that, as annealing temperature and holding time increase, the hardness of the alloy gradually decreases, while the elastic modulus does not change apparently. Comprehensively considering the microstructure and hardness of the as-annealed alloys, the annealing treatment of the as-extruded alloy is suggested to be at the temperature of 1000 ℃ and the holding time between 1 and 2 h.
Key words: nickel-based powder superalloy; annealing; grain; γ′ phase; nanoindentation
