本文選題：鈦合金大型復(fù)雜整體構(gòu)件　切入點(diǎn)：局部加載等溫鍛造　出處：《西北工業(yè)大學(xué)》2015年博士論文　論文類型：學(xué)位論文

【摘要】：鈦合金大型整體構(gòu)件易于實(shí)現(xiàn)裝備的輕量化、高性能、高可靠性、功能高效化而在航空航天領(lǐng)域得到廣泛應(yīng)用。局部加載等溫鍛造技術(shù)為解決該類構(gòu)件的成形制造能力不足問題、成形成性一體化提供了新的途徑。然而，在鈦合金局部加載等溫鍛造過程中，模具長時間處于高溫?zé)岜┞叮洳牧衔⒂^組織和性能將發(fā)生變化；同時模具受力復(fù)雜且不均勻，易引發(fā)模具產(chǎn)生局部變形甚至開裂失效，這嚴(yán)重制約著成形過程的實(shí)現(xiàn)和成形質(zhì)量的保證。因此如何實(shí)現(xiàn)鈦合金大型整體構(gòu)件局部加載等溫鍛造模具的失效預(yù)測，提高模具使用可靠性和壽命成為迫切需要解決的關(guān)鍵問題。為此，本文采用理論分析、實(shí)驗(yàn)研究和有限元數(shù)值模擬相結(jié)合的方法，研究了鎳基合金模具材料高溫?zé)岜┞�、高溫變形及斷裂行為，進(jìn)而對鈦合金大型整體構(gòu)件局部加載等溫鍛造過程、模具的應(yīng)力分析及失效預(yù)測、模具結(jié)構(gòu)改進(jìn)的問題進(jìn)行了系統(tǒng)深入的研究。主要的研究內(nèi)容和結(jié)果如下： 采用熱暴露試驗(yàn)、室溫拉伸試驗(yàn)，研究揭示了熱暴露溫度、時間對用作鈦合金局部加載等溫鍛造模具材料的K403鎳基合金微觀組織演變和性能的影響規(guī)律。發(fā)現(xiàn)K403合金在800~950℃溫度下熱暴露50~200h后，仍為典型的樹枝晶組織，MC碳化物部分發(fā)生分解，強(qiáng)化相γ'相聚集長大，且隨著熱暴露溫度的提高和熱暴露時間的延長，γ'相粗化現(xiàn)象越顯著；在850℃和900℃下熱暴露后，有少量針狀有害的TCP相（σ相）析出，且析出量隨著熱暴露時間的延長而增多；高溫?zé)岜┞逗蠛辖鸬拿x屈服強(qiáng)度和抗拉強(qiáng)度均下降，其主要原因是γ'強(qiáng)化相的聚集粗化和TCP相的析出。 通過熱模擬壓縮和拉伸試驗(yàn)研究獲得了變形溫度、應(yīng)變速率以及應(yīng)力狀態(tài)對K403鎳基合金高溫變形行為和微觀組織的影響規(guī)律，探明了合金的高溫?cái)嗔褭C(jī)制，建立了K403鎳基合金高溫?cái)嗔涯Ｐ汀＝Y(jié)果表明：K403合金高溫拉伸變形時，隨著變形溫度的升高、應(yīng)變速率和應(yīng)力三軸度的減小，，合金的峰值應(yīng)力和斷裂應(yīng)力降低，而斷面收縮率和斷裂應(yīng)變則隨之而增大；溫度低于900℃時，K403合金拉伸斷口以準(zhǔn)解理斷裂為主，隨著變形溫度的升高，斷裂類型由準(zhǔn)解理斷裂向沿晶斷裂轉(zhuǎn)變。 研究提取了反映鈦合金大型整體構(gòu)件高筋薄腹板特點(diǎn)的兩類筋板特征結(jié)構(gòu)件，探明了特征結(jié)構(gòu)件和具有代表性的大型整體隔框件局部加載等溫鍛造成形的變形行為和模具應(yīng)力分布特征，確定了模具的危險區(qū)域，并揭示了模具幾何參數(shù)對模具應(yīng)力的影響規(guī)律。研究發(fā)現(xiàn)：大型整體隔框件局部加載等溫鍛造模具的危險區(qū)域?yàn)橄履Ｍ苟钔鈧?cè)筋條的型腔外側(cè)圓角區(qū)域，容易產(chǎn)生應(yīng)力集中；增大模具型腔凹圓角半徑和模鍛斜度，可一定程度上降低模具應(yīng)力；增大模具壁厚則可顯著降低模具應(yīng)力，但增大到一定程度后其效果減弱。 基于所建立的K403合金高溫?cái)嗔涯Ｐ停Y(jié)合有限元分析，實(shí)現(xiàn)了鈦合金大型整體隔框件局部加載等溫鍛造模具的失效預(yù)測，并采用增加模具壁厚和預(yù)應(yīng)力組合式下模兩種方法改進(jìn)模具結(jié)構(gòu)，降低了模具應(yīng)力和開裂失效的風(fēng)險，其中采用預(yù)應(yīng)力組合式下模更為有效。
[Abstract]:Titanium alloy large integral component is easy to realize equipment lightweight, high performance, high reliability, high efficiency and is widely used in the aerospace field. Local loading isothermal forging technology for solving the forming of this kind of member manufacturing capacity problems, the formation of integration provides a new way. However, in titanium alloy local loading isothermal forging process, die long time in high temperature heat exposure, and the performance of the material microstructure will be changed; at the same time the die stress is complex and uneven, easy to cause the mold to produce the local deformation or even cracking failure, which seriously restricts the forming process and forming quality assurance. So how to realize the failure prediction of titanium alloy large integral component isothermal local loading forging die, improve the mould life and reliability has become a key problem to be solved urgently. Therefore, this paper uses theory The analysis method of combining experimental research and finite element numerical simulation of thermal high temperature nickel base alloy die material exposure, high temperature deformation and fracture behavior of titanium alloy, and large integral component isothermal local loading forging process, and failure prediction analysis of mould, systematically studied the mould structure improvement the problem. The main research contents and results are as follows:
The heat exposure test, room temperature tensile test, the research reveals the thermal exposure temperature, effects of time on Microstructure of K403 nickel based alloy and titanium alloy used for the evolution performance of local loading isothermal forging die materials. K403 alloy under 800~950 DEG C after 50~200h heat exposure is still a typical dendritic structure, MC carbide partial decomposition, strengthen the Y "phase together with the set up, heat exposure with the increase of temperature and thermal exposure time prolonged, gamma 'phase coarsening phenomenon is more obvious; at 850 DEG C and 900 C after thermal exposure, there is a small amount of needle like harmful TCP phase (Xiang) precipitation, and precipitation with time. The increased exposure to heat; alloy after thermal exposure of the nominal yield strength and tensile strength decreased, the main reason is the gamma' Strengthening precipitates in the aggregation and coarsening and TCP phase.
Through thermal simulation compression and tensile test obtained the deformation temperature, strain rate and the effects of the stress state of K403 high temperature nickel base alloy deformation behavior and microstructure of the high temperature, the fracture mechanism of the alloy, a nickel based superalloy K403 fracture model. The results show that the K403 alloy with high temperature tensile deformation. The increase of deformation temperature, strain rate and the reduction of the stress axis three, alloy peak stress and fracture stress decreased, while the section shrinkage and fracture strain increases; the temperature lower than 900 DEG C, K403 alloy tensile fracture to quasi cleavage fracture, with the increase of deformation temperature, fracture type from the quasi cleavage fracture to intergranular fracture.
Study on the extraction of titanium alloy large integral component reflects the aerocraft characteristics of two kinds of characteristics of stiffened plate structure, proved the characteristics of structure and large representative frame pieces of local loading and deformation behavior of isothermal forging die stress distribution characteristics, identify areas of risk of the mould, and reveals the influence of geometric parameters of the die on die stress. The study found: dangerous area of large integral bulkhead pieces isothermal local loading forging die for lateral cavity die fillet region lug most lateral ribs, prone to stress concentration; increasing the mold cavity concave fillet radius and the draft, to a certain extent on the lower die stress; increasing the mold wall thickness can significantly reduce the die stress, but increased to weaken the effect of a certain extent.
K403 alloy high temperature fracture based on the model with finite element analysis, the overall frame of large titanium alloy parts failure prediction of isothermal local loading forging die, and by using the improved die structure increase the mold wall thickness and prestressed die two methods, reduce the risk of failure and cracking force should die, which the prestressed die is more effective.

【學(xué)位授予單位】：西北工業(yè)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TG146.23;TG319

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