固溶冷却介质对优质GH738合金组织及力学性能的影响

研究了不同固溶冷却介质(油、空、棉)及之后的时效处理对优质GH738 (HQGH738)合金组织及力学性能的影响.分别利用光学金相显微镜(OM)和场发射扫描电镜(FESEM)对热处理各阶段合金的晶粒组织及γ'相分布情况进行观察,同时检测热处理各阶段拉伸强度.结果表明:冷却介质对HQGH738合金晶粒尺寸无影响,而主要影响一次及二次γ'相的回溶及析出行为,进而影响合金的性能.固溶阶段,随冷速的提高(油淬＞空冷＞棉冷),合金中二次γ'相减少,尺寸越小,固溶后合金抗拉强度降低.经过稳定化处理后,3种冷却方式下合金强度顺序不变,但差值减小.再经过双时效后,三者抗拉强度相当.冷速越快,一次γ'相粗化越慢,从而在双时效过程中析出更多的细小二次γ'相,最终合金的屈服强度随冷速的增加而增强.

Effects of cooling mediums for solution treatment on the microstructure and mechanical properties of high quality GH738 alloy

The effects of solution cooling mediums??oil quenching, OQ; air cooling, AC; cotton cooling, CC?? and subsequent aging treatment on the microstructure and mechanical properties of high quality GH738??HQGH738?? were studied.The grain structure and ?á? distribution were studied by optical microscope (OM) and field emission scanning electron microscope (FESEM), and mechanical properties was studied by tensile testing machine. The results show that cooling mediums have no influences on the grain size of HQGH738, but have great impact on the re-dissolution and precipitation of primary and secondary ?á?, which is important to the mechanical properties. During the solution heat treatment process, the size and amount of the secondary ?á? reduce and the ultimate tensile strength of HQGH738 decreases with increasing the cooling rate (OQ>AC>CC). After stabilization treatment, strength order of HQGH738 remains the same for the three cooling mediums, but strength difference decreases. After standard aging treatment, there are no obvious differences in ultimate tensile strength for the three groups. Meanwhile, the yield strength increases with increasing the cooling rate because primary ?á? coarsening becomes slow and secondary ?á? precipitation increases.