(1. 中南大學(xué) 粉末冶金研究院，長沙 410083；
2. 中南大學(xué) 粉末冶金國家重點(diǎn)實(shí)驗(yàn)室，長沙 410083；
3. 哈爾濱工業(yè)大學(xué) 金屬精密熱加工國家級(jí)重點(diǎn)實(shí)驗(yàn)室，哈爾濱 150001；
4. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 利用Gleeble熱模擬試驗(yàn)機(jī)對(duì)FGH96合金進(jìn)行了等溫壓縮試驗(yàn)，獲得了變形溫度為1020~1110 ℃、應(yīng)變速率為0.001~1 s-1范圍內(nèi)合金的流變應(yīng)力數(shù)據(jù)，結(jié)合本構(gòu)方程回歸分析方法，計(jì)算不同變形條件下的Zener-Hollomon(Z)參數(shù)值；選取典型的Z參數(shù)條件，系統(tǒng)分析Z參數(shù)對(duì)FGH96合金熱機(jī)械處理(熱壓縮變形和熱處理)過程中微觀組織和性能的影響，并在此基礎(chǔ)上提出優(yōu)化的鍛造工藝參數(shù)。結(jié)果表明：隨著Z參數(shù)的減小，熱變形態(tài)合金的動(dòng)態(tài)再結(jié)晶程度逐漸提高、動(dòng)態(tài)再結(jié)晶晶粒尺寸有所增大，變形組織由混合組織向完全動(dòng)態(tài)再結(jié)晶組織轉(zhuǎn)變；不同Z參數(shù)下的形變儲(chǔ)能以及γ′相的演化對(duì)熱處理態(tài)合金的晶粒組織狀態(tài)有重要影響。熱變形態(tài)合金中二次γ′相在不同Z參數(shù)下均不同程度地溶解；隨著Z參數(shù)的減小，二次γ′相經(jīng)歷了明顯粗化到大量溶解的過程。在高Z參數(shù)和中等Z參數(shù)條件下，熱處理態(tài)FGH96合金試樣橫截面的不同位置發(fā)生了明顯的異常晶粒長大，合金的異常晶粒長大行為主要與變形條件(Z參數(shù)和應(yīng)變量)、變形組織儲(chǔ)能大小及分布以及γ′相的溶解行為有關(guān)。熱變形態(tài)合金的維氏硬度值隨Z參數(shù)的減小整體上呈現(xiàn)出明顯的降低趨勢(shì)，而熱處理態(tài)合金的維氏硬度值保持在478~500 HV之間。綜合考慮熱機(jī)械處理過程中FGH96合金的組織和性能，選擇Z參數(shù)為1.98×1015，即變形條件(1080 ℃，0.01 s-1)作為優(yōu)化的鍛造工藝參數(shù)。
關(guān)鍵字: FGH96合金；熱機(jī)械處理；Z參數(shù)；動(dòng)態(tài)再結(jié)晶；γ′相
（1. School of Aeronautics and Astronautics, Central South University, Changsha 410083, China;
2. State Key Laboratory For Powder Metallurgy, Central South University, Changsha 410083, China;
3. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin150001, China;
4. School of Materials and Engineering, Central South University, Changsha 410083, China）
Abstract:Isothermal compression experiments of FGH96 alloy were carried out on a Gleeble thermal simulator. Flow stress data at the temperatures from 1020 ℃ to 1110 ℃ with strain rates from 0.001 s-1 to 1 s-1 were obtained. The values of Zener-Hollomon (Z) parameters under different deformation conditions were calculated by combining the regression analysis of constitutive equation. Typical Z parameter conditions were selected to systematically investigate the effects of Z parameter on the microstructure and properties of FGH96 alloy during thermo-mechanical treatment (hot compression deformation and heat treatment). The optimized parameters of hot forging process for the alloy were proposed on the basis of experimental data. The results show that with the decrease of Z parameter, both the degree of dynamic recrystallization (DRX) and the size of DRX grains for the hot-deformed alloys gradually increase, and the deformed microstructure transforms from a mixed state to a fully DRX state. The deformation energy storage and the evolution of γ′ phase under different Z parameters have important effects on the grain structure of the heat-treated alloys. The secondary γ′ phases in the hot-deformed alloys dissolve to different degrees at various Z parameters, and they undergo a process from obvious coarsening to massive dissolution with decreasing Z parameter. Under the conditions of high and medium Z parameters, obvious abnormal grain growth occurs at different positions of the cross sections of the heat-treated FGH96 alloy samples. The abnormal grain growth behavior of the alloy is mainly related to the deformation conditions (Z parameter and strain), the value and distribution of energy storage in the deformed microstructure and the dissolution behavior of γ′ phase. An apparently decreasing tendency of Vickers hardness is shown in the hot-deformed alloys with decreasing Z parameter, while the hardness values of the heat-treated alloys are kept in the range from 478 HV to 500 HV. Comprehensively considering the microstructure and properties of the FGH96 alloys during thermo-mechanical treatment, the optimized forging process parameter is selected to be at the Z parameter of about 1.98×1015, i.e. under the deformation condition of 1080 ℃ and 0.01 s-1.
Key words: FGH96 alloy; thermo-mechanical treatment; Z parameter; dynamic recrystallization; γ′ phase
