材料期刊网

研究了含Hf (0~0.89%)的FGH4097粉末高温合金中拓扑密堆μ相的析出动力学、组织形态以及μ相对Hf含量为0.30%的合金盘坯力学性能的影响. 结果表明, Hf含量为0.30%和0.89%的合金, 经750~900 ℃长期时效后μ相已明显析出. 随着时效温度的升高、时效时间的延长以及Hf添加量的增加, μ相析出量增加且尺寸长大. μ相主要在晶内以长条片状形态析出. Hf含量为0.30%的FGH4097合金盘坯在550~650 ℃长期时效后未出现μ相, 高温拉伸性能和高温持久性能没有降低, 组织稳定性良好. 750 ℃长期时效后, 盘坯中析出了μ相, 析出的μ相对高温拉伸强度无明显影响, 有助于提高高温拉伸塑性, 降低了高温持久寿命, 高温持久塑性提高约30%. 详细讨论了μ相的析出行为、γ固溶体中合金元素的再分配以及合金断口特征. 解释了μ相对力学性能影响的脆-韧双重作用机理, 并提出控制和避免μ相大量析出造成性能劣化的措施和方法.

It is widely acknowledged that topologically close packed (TCP) phases are detrimental to comprehensive properties of superalloys, as TCP phases deplete strengthening elements from matrix and easily become crack initiations. In this work, the precipitation kinetics and morphology of topologically close packed μ phase in FGH4097 powder metallurgy (PM) superalloy with (0~0.89%)Hf and the effect of μ phase on the mechanical properties of FGH4097 PM superalloy billet with 0.30%Hf has been investigated. The results showed that μ phase precipitated obviously in the alloys with 0.30%Hf and 0.89%Hf after long-term ageing at 750~900 ℃, the amount and size of μ phase increased as the ageing temperature, ageing time and Hf content increasing. μ phase mainly precipitated in grains with strip and flake shapes. After long-term ageing at 550~650 ℃, no μ phase precipitated in FGH4097 PM superalloy billet with 0.30%Hf and the tensile properties and stress-rupture properties at high temperature were not decreased, which showed excellent microstructure stability. After long term ageing at 750 ℃, precipitated μ phase had little effect on tensile strength at high temperature, however, the tensile ductility increased and high temperature stress rupture life reduced, and the stress rupture ductility increased by about 20%. In this work, the precipitation behavior of μ phase, the redistribution of elements in γ solid solution and the FGH4097 PM superalloy fracture morphology characteristics have been discussed in detail. The mechanism of the brittle and ductile dual effect of μ phase on the mechanical properties has been explained. The methods of controlling and avoiding excessive μ phase precipitation which leaded to performance deterioration have been proposed.