固溶處裡對SP-700鈦合金微結構及機械性質之影響

Effect of solution treatment on microstructures and mechanical properties of SP-700 Ti alloy

陳俊豪(Chun-hao Chen)

指導教授 ： 李勝隆

國立中央大學/工學院/材料科學與工程研究所/碩士(2014年)

摘要

藉由微結構觀察、機械性質測試，探討不同固溶溫度對水淬SP-700鈦合金微結構及機械性質之影響；結果顯示SP-700鈦合金於高溫單相區（950℃與900℃）進行固溶熱處理後水淬，微結構為較軟的殘留β(βr)基地相與散佈其中的硬脆針狀α”麻田散鐵相所組成，其抗拉強度與延性均不佳。在較高溫雙相區（850℃與800℃）進行固溶處理後水淬，由於室溫仍介於其合金組成之Ms與Mf溫度之間，此時微結構為較軟的βr基地相、硬脆的初析α相(αp)和α”麻田散鐵相組成，由於拉伸試驗時發生『應力誘發麻田散鐵相變化』，合金具有明顯加工硬化特性。而在較低溫雙相區（750℃）進行固溶處理後水淬，此時合金組成之Ms溫度已低於室溫，其微結構為殘留β基地相與初析α相所組成，水淬與拉伸過程皆無麻田散鐵相產生，不具明顯加工硬化特性，但具有最優異之衝擊韌性，與最高的硬度。
綜合而論，SP-700鈦合金於雙相區進行固溶處理後水淬，始能符合鈦合金裝甲材料規範(MIL-DTL-46077)之板材機械性質最低要求，同時具有高強度增幅與高延性之優異成型特性。其中800℃固溶處理後水淬之合金因含適量硬質αp相，且拉伸過程發生明顯應力誘發麻田散鐵相變化，故呈現最高強度增幅與高延性特性。

關鍵字

SP-700 ； 固溶處理 ； 機械性質

並列摘要

Effect of different solution temperature on microstructure and mechanical properties of water quenched SP-700 titanium alloy were studied by analysing the microstructure and mechanical properties .
The results indicated that SP-700 titanium alloy quenched from single-phase region (950℃ and 900℃), the microstructure consists brittle needle shape α" martensite phase and softer retained β phase (βr) base phase, it shows poor tensile strength and ductility. When quenched from two-phase region (850℃ and 800℃), the room temperature is between Ms and Mf, the microstructure consists primary α phase (αp), α" martensite phase and retained β phase (βr) base phase, during tensile test, alloy shows obviously “stress-induced martensite phase transformation”, will have a significant hardening properties. As the solution temperature at 800℃, contents more hard αp phase, will have a higher yield strength, ultimately lead to high strength and high ductility, while the tensile test. Furthermore, quenched from lower temperature (750℃), the Ms temperature of β phase has been below room temperature, the microstructure are retained β phase (βr) and primary α phase (αp), there are no martensite transformation during water quenching and tensile test process, doesn’t have hardening properties, but with the optimum toughness.
In conclusion, SP-700 titanium alloy quenched from two-phase region, the mechanical properties are conform to the titanium armor plate material specification (MIL-DTL-46077), which contains high hardness and elongation, and the solution temperature at 800℃ has best hardness and elongation.

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