SP-700鈦合金之 微結構及機械性質研究; Study on microstructure and mechanical properties of SP-700 Ti-alloy

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题名:	SP-700鈦合金之微結構及機械性質研究;Study on microstructure and mechanical properties of SP-700 Ti-alloy
作者:	潘昆嵩;Pan,Kuen-sung
贡献者:	機械工程學系
关键词:	SP-700;應力誘發;冷加工;SP-700;Stress induced martensite;Coldworking
日期:	2013-08-14
上传时间:	2013-10-08 15:28:29 (UTC+8)
出版者:	國立中央大學
摘要:	本研究係針對SP-700 鈦合金經固溶處理、淬火冷卻後施以不同冷加工量，再進行時效處理，藉由顯微結構與機械性質的分析，探討不同微結構下之拉伸變形特性。　　結果顯示SP-700鈦合金經固溶處理水淬後，合金微結構為塊狀初析α相(αp)、β殘留相（βr）及散佈於βr之針狀麻田散鐵相（α”）；若水淬合金施以冷加工，初析α相(αp）、與麻田散鐵相（α”）並未因加工而與水淬合金有所差異，但殘留β相（βr）將藉由應力誘發麻田散鐵相變化而數量減少，轉變為較硬脆之針狀麻田散鐵相（α”），針狀麻田散鐵相（α”）析出量隨著冷加工量上升而增加，且變得更為密集和細緻。　　水淬合金經時效處理後，針狀麻田散鐵相（α”）與殘留β相（βr）均將相變化為α+β平衡相，此時微結構為原先已存在的初析α相（αp），及針狀麻田散鐵相（α”）轉變為球狀α平衡相中散佈著細小β平衡相顆粒，與殘留β相（βr）轉變為β平衡相中散佈著細小的α平衡相顆粒。水淬合金經冷加工後再施以時效處理，隨著冷加工量上升α”麻田散鐵析出量增加且更為細緻，時效過後α平衡相數量也就更多且更為細小，且冷加工導致殘留β相（βr）晶粒高變形，時效後形成細致的β平衡相。　　水淬合金進行拉伸試驗時，由於βr為較軟韌相，合金發生「應力誘發麻田散鐵」相變化，合金因而呈現明顯加工硬化，造成淬火合金於拉伸過程中顯現高延性與高強度。水淬合金經冷加工後，因冷加工時已發生應力誘發麻田散鐵相變化的緣故，故於拉伸試驗時，隨著冷加工量的增加，二次硬化現象便越不明顯。　　水淬合金經時效處理後，其微結構因較硬脆的α平衡相增多，且無「應力誘發麻田散鐵」相變化，故時效後合金之降服強度大幅提升，且拉伸過程無顯著二次硬化現象，以致延性不高。水淬合金經冷加工-時效處理後，其微結構相較未加工之合金為細緻，所以其降伏強度會稍高於未加工之合金，但同樣地延性也不高。關鍵字：SP-700、應力誘發、冷加工　　The study analyzes the characteristics of tensile deformation under the different microstructures for SP-700 titanium alloy undergoing solution treatment and water quenching, followed by applying different amount of coldworking and aging treatment through the analysis of microstructure and mechanical properties. 　　 The results show that the microstructure of SP-700 titanium alloy contains block primary α-phase (αp), residual β-phase (βr) and lamellar-martensite phase (α”) distributed in βr after solution treatment and water quenching. The application of coldworking for water quenching alloy does not show difference on primary α-phase (αp) and lamellar-martensite phase (α”) due to work and quenching alloy. However, residual β-phase (βr) will reduce the quantity due to changes in the stress induced for lamellar-martensite phase, which then turns into hardened and brittle lamellar-martensite phase (α”). Lamellar-martensite phase (α”) increases following the rise in the amount of coldworking to become more intense and delicate. 　　The lamellar-martensite phase (α”) and residual β-phase (βr) will both undergo phase change into α+β equilibrium phase for water quenching alloy after receiving aging treatment, whereas the microstructure becomes the previously exiting primary α-phase (αp) while the lamellar-martensite phase (α”) transits into spherical α equilibrium phase distributed with tiny particles of β equilibrium phase and the residual β-phase (βr) transits into β equilibrium phase distributed with tiny particles of α equilibrium phase. After applying coldworking and aging treatment to the quenching alloy, the amount of α” lamellar-martensite phase increases following the rise in coldworking while becoming more delicate. After the aging treatment, the amount of α equilibrium phase becomes more and finer, while the cooling work causes the crystalline grains of residual β phase (βr) to increase and deform, forming more delicate β equilibrium phase after aging treatment. 　　When the water quenching alloy undergoes tensile testing, the alloy will undergo phase change with “stress induced for lamellar-martensite” due to the soft-tenacity phase contained in βr, which causes alloy to present significant hardening and the quenching alloy to exhibit high ductility and strength. After undergoing coldworking, quenching alloy will have less significant secondary hardening phenomenon during tensile testing with increasing coldworking, due to the change of stress induced for lamellar-martensite already occurred during coldworking. 　　Water quenching alloy will have substantial increase of yield strength after aging treatment since its microstructure increase in more hardened and brittle α equilibrium phase and without the phase change in “stress inducted for lamellar-martensite.”The ductility appears low due to the lack of significant secondary hardening phenomenon during the tensile process. The microstructure of water quench alloy undergone coldworking and aging treatment will have slightly highly yield strengthen than alloy without work while ductility remains low in the similar manner. Keywords: SP-700, Stress induced martensite, Coldworking
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