Ti_3Al金属间化合物氢致解理断裂及其机理

Ｔｉ－２４Ａｌ－１１Ｎｂ合金在室温下恒载荷动态充氢以及交变载荷动态充氢时，氢通过促进裂纹在滑移面上的解理，促进了裂纹扩展。不连续的氢致解理裂纹优先在α_２相形核，α_２／β相界面是裂纹扩展的有效障碍。氢通过促进裂尖位错的发射、解理微裂纹在无位错区（ＤＦＺ）的形核以及解理裂纹的扩展，导致氢致解理断裂     

Ti3Al金属间化全物氢致解理断裂及其机理

Ｔｉ－２４Ａｌ－１１Ｎｂ合金在室温下恒载荷动态充氢以及交变载荷动态充氢时，氢通过促进裂纹在滑移面上的解一，促进了裂纹扩散，不连续的氢致解理裂纹优先在α２相形核，α２／β相界面是裂纹扩展的有效障碍，氢通过促进裂尖位错的发射、解理微裂无位错区（ＤＦＺ）的形核以及解理裂纹，导致氢致解理断裂。     

铝合金液体金属脆断过程的TEM原位观察

采用自制的恒位称加载台,在透射电镜（ＴＥＭ）中原位观察了７０７５铝合金吸附液体金属（Ｈｇ＋３％Ｇａ）后加载裂纹前方位错组态的变化以及脆性微裂纹的形核和扩展,结果表明：液体金属吸附后能促进位错的发射、增殖和运动;当吸附促进位错发射和运动达到临界状态时,脆性微裂纹就在原裂纹顶端或在无位错区中形核并解理扩展。     

氢促进纯镍位错发射的分子动力学模拟及实验证明

采用 ＥＡＭ多体势的分子动力学模拟表明，Ｎｉ中固溶的氢能使裂尖发射位错的临界应力强度因子ＫＩｅ（θ＝４５°）从 １．００ ＭＰａ·ｍ１／２降为 ０．９０ＭＰａｍ·１／２；使 ＫＩｅ（θ＝７０°）从 ０．８２ ＭＰａ＞·ｍ１／２降为 ０．７０ ＭＰａ·ｍ１／２，即氢能促进位错的发射 另外 氢能使（１１１）滑移面上的 Ｇｒｉｆｆｉｔｈ裂纹解理扩展的临界应力强度因子ＫＩＧ（θ＝０°）从 １．０３ ＭＰ·ａｍ１／２降为０．９３ ＭＰａ·ｍ１／２、即氢使(１１）面的表面能下降 γ１１１（Ｈ）＝０．８２θθγ１１１；从而促进位错的发射 透射电＃（ＴＥＭ）原位观察表明，在氢致裂纹形核之前氢就能促进位错的发射和运动。     

Ti3Al型金属间化合物中氢促进解理断裂的机理

对解理开裂,对氢致解理,氢能促进位错的增殖和运动,从而σ_0(H)<σ_0,k>1,即σ_F(H)<σ_F,K_(IH)相似文献   

Fe-3％Si单晶氢致解理断裂研究

用Fe-3％Si单晶试样对氢致解理断裂进行了研究。结果表明,Fe-3％Si单晶缺口试样在空气中拉伸时一般不发生解理,但在动态充氢条件下,即使室温慢加载也能产生解理断裂。对于Ⅰ+Ⅱ复合型试样,氢致裂纹并不沿断裂力学预示的开裂角扩展,而是沿解理面扩展,即氢促进了解理断裂。无论Ⅰ型还是复合型,氢致解理裂纹的da/dt—KⅠ曲线都由三个阶段组成,但Ⅰ型试样da/dt的平台值明显地比复合型的高。用各向异性断裂力学计算了作用在裂纹前各滑移系上的分切应立力,并配合断口观察确定了解理裂纹形核机理。研究了氢的促进作用。     

SrCeO_3基高温质子导体及Al液定氢探头SCIEI

以自制成分为ＳｒＣｅ_（０．９５）Ｙｂ_（０．０５）Ｏ_（３－α）的致密陶瓷管为固体电解质，以Ｃａ／ＣａＨ２混合物为参比物组装氢探头。探头插入Ａｌ液构成氢浓差电化学电池：Ｍｏ，Ｃａ／ＣａＨ_２｜Ｈ￣＋ｃｏｎｄｕｃｔｏｒ｜［Ｈ］ｍｏｌｔｅｎＡｌ’Ｍｏ对高氢含量Ａｌ液进行测定，电动势稳定时间长达１．８ｋｓ，准确反映了氢过饱和度．用六氯乙烷脱氢处理时电动势也有迅速正确的响应。使用后的固体电解质经Ｘ射线衍射未测出相变化。热重分析表明让ＳｒＣｅＯ３基陶瓷中Ｓｒ过量可减轻其中４价Ｃｅ离子被还原程度。     

SrCeO_3基高温质子导体及Al液定氢探头

以自制成分为ＳｒＣｅ_（０．９５）Ｙｂ_（０．０５）Ｏ_（３－α）的致密陶瓷管为固体电解质，以Ｃａ／ＣａＨ２混合物为参比物组装氢探头。探头插入Ａｌ液构成氢浓差电化学电池：Ｍｏ，Ｃａ／ＣａＨ_２｜Ｈ￣＋ｃｏｎｄｕｃｔｏｒ｜［Ｈ］ｍｏｌｔｅｎＡｌ’Ｍｏ对高氢含量Ａｌ液进行测定，电动势稳定时间长达１．８ｋｓ，准确反映了氢过饱和度．用六氯乙烷脱氢处理时电动势也有迅速正确的响应。使用后的固体电解质经Ｘ射线衍射未测出相变化。热重分析表明让ＳｒＣｅＯ３基陶瓷中Ｓｒ过量可减轻其中４价Ｃｅ离子被还原程度。     

重轨钢中氢促进位错发射、运动以及氢致裂纹形核

用自制的恒位移试样在TEM中原位研究了充氢前后位错组态的变化以及氢致微裂纹形核和位错运动及无位错区（DFZ）的关系．结果表明,氢能促进位错发射、增殖和运动．当氢促进的位错发射和运动达到临界条件时,氢致裂纹就在DFZ中或原缺口顶端形核．这个过程和空气中原位拉伸相类似,但氢的存在使得在较低的外应力下氢致裂纹就能形核．     

重轧钢中氢促进位错发射,运动以及氢致裂纹形核

用自制的恒位移试样在ＴＥＭ中原位研究了充氢前后位错组态的变化以及氢致微裂纹形核和位错运动及无位错区（ＤＦＺ）的关系。结果表明,氢能促进位错发射、增殖和运动。当氢促进的痊错发射和运动达到临界条件时,氢致裂纹就在ＤＦＺ中或原缺口顶端形核。这个过程和空气中原位拉伸相类似,但氢的存在使得在较低的外应力下氢致裂纹就能形核。     

MECHANISM OF HYDROGEN FACILICATED CLEAVAGE IN TITANUM ALUMINIDE

Both hydrogen induced cracking and overload crack initiated at same characteristic distance,r~*,within the plastic zone along the slip line when the plastic zone developed to a critical ex-tent.For the overload crack.K_(IC)=αr~*~(1/2)[σ_F~((n+1)/2n)/σ_(ys)~((1-n)/2n)],σ_F=σ_0+g[2μbσ_(th)/π~2L(1-v)]~(1/2)For the hydrogen induced cracking:K_(IH)=αr~*~(1/2)[σ_F(H)~((n+1)/2n)/σ_(ys)(H)~((1-n)/2n)],σ_F(H)={σ_0(H)+g[2μbσ_(th)(H)/π~2L(1-v)]~(1/2)}/kHydrogen pomoting the dislocation multiplication and motion would result in σ_0(H)<σ_0,k>1,Therefore,hydrogen promoting the cleavage fracture in titanum aluminide can be dueto that hydrogen facilitates the local plastic deformation,which results in σ_F(H)<σ_F and thenK_(IH)相似文献   

Stress corrosion crack propagation in a TiO alloy in aqueous and methanolic solutions

Stress corrosion crack propagation in a TiO alloy in aqueous NaCl and MeOH/HCl solutions has been examined in dynamic straining experiments. Crack velocity is determined by the value of the applied strain-rate. In aqueous solutions repassivation and crack arrest occur if the strain-rate falls below a certain value, designated s,. Embrittlement tests under either open circuit conditions or with applied anodic currents in Me0H/HCl solution result in 3-zone fractures: intergranular, caused by dissolution, transgranular cleavage, caused by absorbed hydrogen, and ductile fracture. The intermediate cleavage zone disappears if specimens are aged before fracture or if the intergranular dissolution rate is raised until it becomes comparable to the rate of hydrogen diffusion. Interrupted dynamic straining tests with periodic removal of solution indicated that an embrittling process occurs in stressed specimens after removal of the solution. Additions to the solutions that promote hydrogen entry into the metal increased the crack velocity while the addition of species that inhibit hydrogen entry lowered the crack velocity. Increasing the corrosion rate was shown to result either in a reduced crack velocity or an increased crack velocity, depending upon the presence in the solution of a species inhibiting hydrogen entry. It is concluded that intergranular cracking in McOH/HCl solutions occurs as a result of anodic dissolution while the transgranular cleavage observed in both aqueous and methanolic solutions is a form of slow strain-rate hydrogen embrittlement.     

稳定奥氏体不锈钢的氢脆

用光学显微镜,扫描电镜和X射线衍射仪研究了稳定的奥氏体不锈钢的氢脆现象。结果表明:1.阴极充氢能引起试样表面γ→ε转变,并有新的f_(cc)相的出现。2.充氢可使试样表面形成裂纹。3.拉伸试样表面充氢层的断口是穿晶解理断口。断口中的二次裂纹是沿着滑移线的。 上述结果证明:α′马氏体转变对于奥氏体钢的氢脆并不是必要的条件。稳定的奥氏体不锈钢中也会发生氢脆现象。     

Micromechanism of Cleavage Fracture of Weld MetalsEI北大核心CSCD

Cleavage fracture is the most dangerous form of fracture. Cleavage fracture usually happens well before general yielding at low nominal fracture stress and strain. Cleavage fracture is often spurred by low temperature and determines the toughness in the lower shelf temperature region. This paper describes a new framework for the micromechanism of cleavage fracture of high strength low alloy (HSLA) steel weld metals. Cleavage fracture not only determines the impact toughness in the lower shelf but also plays a decisive role on the impact toughness in the transition temperature region. The toughness is determined by the extending length of a preceding fibrous crack which is terminated by cleavage fracture. Three non-stop successive stages, i.e. crack nucleation, propagation of a second phase particle-sized crack across the particle/grain boundary, propagation of a grain-sized crack across the grain/grain boundary are explained. The "critical event" of cleavage fracture is emphasized which offers the greatest difficulty during crack formation and controls the cleavage process. The critical event indicates the weakest microstructural component and its critical size which specifies the local cleavage fracture stress sigma(f) for cleavage fracture. In toughness-study it is paramount important to reveal the critical events for various test specimens. Three criteria for crack nucleation, for preventing crack nucleus from blunting and for crack propagation are testified. An active region specified by these criteria is suggested where the combined stress and strain are sufficient to trigger the cleavage fracture. It can be used in statistical analyses. A case study, using the new framework of micromechanism for analyzing toughness of 8% Ni steel welding metals is presented to analyze the experimental results.     

制氢装置水分离器入口法兰及三通失效分析

应用光学显微镜,扫描电镜、光电子谱,显微硬度仪,铁素体测量仪等对开裂失效试样进行分析,结果表明,三通和法兰开裂效是由于氢致开裂所致;同时也具有明显的氯化应力腐蚀破裂敏感性。     

HYDROGEN INDUCED INTERGRANULAR CLEAVAGE IN Fe-3%Si ALLOY

<正> 沿晶断裂是氢致开裂的一个重要方式.有人在氢致沿晶断口上观察到大量塑性变形,因而认为氢促进沿晶断裂是氢促进局部塑性变形的结果.但也有人认为是由于氢降低了晶界原子问的结合力造成的。用高压电镜进行动态观察的结果表明,Fe 和 Ni 中氢致沿晶界断裂实际上是由于晶界附近高度塑性变形引起的沿晶界附近的滑移面开裂.我们的工作表明,氢能够促进位错的增殖和运动.对于 Fe-3%Si 单晶体,氢能够促进由于位错运动和反应引起的沿{001}面解理。     

阳极溶解及氢进入对裂纹尖端局部材料力学行为的作用

在腐蚀疲劳过程中裂纹尖端阳极溶解及氢产生并进入材料内部两个过程同时存在.材料的阳极溶解过程增大裂尖塑性区尺寸,氢产生并进入材料内部减小裂尖塑性区尺寸.提出如果阳极溶解增大裂尖塑性区尺寸起主导作用,则总体上表现为裂尖塑性区尺寸增大,如果氢进入减小塑性区尺寸起主导作用,则总体上表现为裂尖塑性区尺寸减小.对上述设想给予实验验证.     

环境诱导氢致断裂的非比例过载效应

研究连续充氢条件下短时非比例过载对４２ＣｒＭｏ钢／０．５ｍｏｌ／Ｌ Ｈ２ＳＯ４体系氢致断裂寿命的影响。结果表明；短时非比例过载对于ＨＩＦ的影响较之比例过载更为严重     

环境诱导氢致断裂的过载效应

在连续充氢条件下，就４２ＣｒＭｏ／０．５ｍｏｌ／ＬＨ２ＳＯ４体系短时过载对氢致断裂寿命的影响进行了研究。实验结果表明：（１）在材料服股的早期加入短时过载将使氢致断裂寿命延长，（２）在材料服股的后期加入短时过载则会缩短氢致断裂寿命。文中过载引起残余压应力、位错屏蔽效应和过载损伤等方面进行了分析与讨论。     

充氢Ni_3Al｛110｝型解理断裂原位TEM观察SCIEI

利用ＴＥＭ原位观察技术研究了充氢Ｎｉ_３Ａｌ｛１１０｝型解理断裂裂纹萌生、扩展过程。发现｛１１０｝型解理裂纹的萌生是由于｛１１１｝型主裂纹前端位错塞积产生的局部应力集中造成的，且氢的存在降低了｛１１０｝面的解理能。