铸态TiAl-Nb合金的组织结构与蠕变性能

通过蠕变性能测试和组织形貌观察,研究了铸态TiAl-Nb合金在近890~910℃温度区间的蠕变行为。结果表明,铸态TiAl-Nb合金的组织结构主要由层片状γ/α_2两相组成,不同取向γ/α_2两相层片状组织之间存在不规则锯齿状形态的晶界,该锯齿状非层片晶界由单一γ相组成。在高温蠕变期间,合金具有较好的蠕变抗力和较长的蠕变寿命;合金在蠕变期间的变形机制是大量位错以位错列的形式剪切层片状γ/α_2两相,其中,大量位错在基体中滑移,发生反应可形成位错网,可促进位错的攀移,减缓应力集中,改善合金的蠕变抗力。与α_2-Τi_3Al相比,γ-TiAl相有较弱的强度。因此,蠕变期间合金中的裂纹易于在与应力轴呈45°角、且与层状结构相平行的晶界处萌生与扩展,直至蠕变断裂是合金在蠕变期间的断裂机制;其中,与层状结构相平行的断口呈光滑表面,而与层状结构呈一定角度的断裂表面存在撕裂棱,为较高强度的α_2-Ti_3Al相阻碍裂纹扩展所致。     

AgInCd合金压缩蠕变性能研究

用RDL-50型拉伸蠕变试验机进行改装后的实验装置研究了铸态AgInCd合金在温度300~400℃及应力范围12~24 MPa内的压缩蠕变行为,分析了稳态速率与温度和应力的关系,计算了应力指数(n)和蠕变激活能(Q_a),并结合蠕变后样品在透射电子显微镜下的微观形貌及位错组态,探讨了合金的压缩蠕变机制。结果表明:随温度和应力水平的升高,合金的稳态蠕变速率增加。相比较指数关系,蠕变速率与应力之间更符合幂函数关系。300、350和400℃条件下,合金的蠕变应力指数n分别为3.31、4.09和5.77;12、18和24 MPa条件下,合金的蠕变激活能Q_a分别为68.1、103.7和131.6 kJ/mol。微观形貌以层错为主,孪生为300℃的主要蠕变机制,位错攀移生成位错墙为400℃的主要蠕变机制。     

Mg-5Sn-xLa合金的铸态组织与结构分析

用重力铸造法制备了不同La含量的Mg-5Sn-xLa合金。用光学金相、XRD、SEM、EDS等研究手段,研究了添加量在0～6%范围时,La对Mg-5Sn铸造合金组织结构的影响。结果表明:当x≤2%时,La的加入不改变Mg-5Sn合金的相组成,合金仍由α-Mg和(α-Mg+Mg2Sn)共晶组成;当在2%相似文献   

添加Ca对Mg-4Sn合金组织演变和蠕变性能的影响（英文）

通过压入蠕变试验,研究Ca添加量(最高达4%,质量分数)对Mg-4Sn合金的显微组织和蠕变性能的影响。压入蠕变试验的操作温度为445⁴75K,归一化应力(σ/G,σ为应力;G为剪切模量)为0.0225⁰.035。利用光学显微镜和扫描电子显微镜对样品的显微组织进行研究。结果表明,Ca的加入量大于2%(质量分数)可抑制较不稳定Mg Sn2相的形成,从而使晶界处形成热稳定性较高的Ca-Mg-Sn相和Mg2Ca,提高Mg-4Sn合金的抗蠕变性能。根据压入蠕变试验所得的应力指数(6.04相似文献   

弥散强化相对PtIr5合金高温蠕变性能的影响

研究了Pt-5Ir和ZGSPt-5Ir高温材料在1423～1523K温度范围内的蠕变行为。结果表明:由于氧化锆颗粒的添加,弥散强化PtIr5材料的高温蠕变性能比Pt-5Ir的性能优异。弥散强化PtIr5的蠕变机制为晶格自扩散引起的高温攀移控制,断裂方式为沿晶脆性断裂;Pt-5Ir的蠕变机制为牛顿粘滞滑移控制,断裂方式为穿晶韧性断裂。     

ZnAl27合金基复合材料高温蠕变性能研究

利用HBE-750型高低温硬度仪和H-800型TEM研究了SiC     

铸态Mg-5Sn-(0～3)Sr合金的组织和性能

利用SEM、EDS和XRD等研究了Mg-5Sn-xSr(x=0、0.3、1.0、1.5、2.0、3.0)镁合金的铸态显微组织,测试和分析了合金的室温力学性能.同时研究了Mg-5Sn-xSr合金在载荷为35 MPa和温度为175℃下的蠕变性能.结果表明,Sr的加入使得Mg-5Sn合金中生成一种新的MgSnSr耐热相,其形貌呈棒状和针状,随着Sr含量的增加,MgSnSr相的数量逐渐增多而MgzSn相的数量却逐渐减少.少量的Sr能细化晶粒,同时由于MgSnSr相的弥散强化作用,使得Mg-5Sn合金的室温力学性能得到改善,其中Sr含量为0.3%时,合金具有最优室温力学性能,抗拉强度达到165 MPa,伸长率达到10.4%;并且Sr含量的增加能不断改善Mg-5Sn合金的耐热性能,当Sr含量达到3%时,合金的稳态蠕变速率降低近50%.     

铸态Mg-5Sn-(0~2)Cu合金的显微组织，力学性能和蠕变性能

利用XRD,SEM手段研究了铸态Mg-5Sn-(0~2.0)Cu合金的显微结构。结果表明Mg-5Sn合金由枝晶状的α-Mg和Mg2Sn相组成,Cu的加入使合金出现Mg2Cu相。随着Cu含量的增加,晶粒逐渐细化,Mg2Sn相和Mg2Cu相的量也逐渐增加,但是这两种相的尺寸亦随之增加。室温拉伸结果表明,Cu质量分数在0.5%~1.0%时对合金起促进作用,然而,过多的Cu会弱化合金的拉伸性能。Mg-5Sn-1.0Cu合金具有最优的力学性能,抗拉强度达到180 MPa,延伸率达到12%。合金在温度为175℃,载荷为35~75 MPa的压蠕变性能表明,Cu可以提高Mg-Sn合金的抗蠕变性能。     

Al-Cu-Mn-Ti系耐热铸造合金高温蠕变性能研究

为探究新型耐热铸造铝合金Al-Cu-Mn-Ti的高温蠕变性能并探明合金有效热强化相,采用扫描电镜、EDS能谱分析、JMat-Pro材料仿真软件及蠕变持久性能测试等分析手段,对合金试样的显微组织、断口形貌和蠕变应变抗力进行了分析。结果表明,Al-Cu-Mn-Ti合金在250℃服役时合金中有效耐热相以θ′相为主,θ相、T相为辅,300℃时合金有效耐热相以T相、θ相为主;合金在300℃、100 MPa服役条件下测试,持久时间不超过40 h,且断裂方式呈塑性和脆性断裂同时发生;合金在250℃的蠕变强度极限达到了120 MPa,在300℃的蠕变强度极限达到了80 MPa。     

铸态ZA27合金的压蠕变行为

采用自制的实验装置研究了铸态ZA27合金在常温及高温时的压蠕变行为。在温度为20～160℃和压应力为50～137．5MPa的范围内，随温度和应力的升高，合金的压蠕变量增大，稳态蠕变速率的对数分别与应力和温度的对数曲线有较好的线性关系，稳态蠕变速率符合半经验公式。在不同的温度下，应力指数n相近，平均值为3．87；不同的应力下，表观激活能Qa相差不大，平均值为83．73kJ／mol，材料结构常数A为0．002，稳态蠕变速率由锌的点阵扩散和位错的攀移所控制。     

Effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy

The effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy was investigated. The results indicate that adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can effectively refine the as-cast microstructure of the alloy, and the CaMgSn phase with high thermal stability is formed in the alloy. In addition, adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can also improve the creep properties of the alloy. After adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy, the second creep rate of the alloy at 150°C and 50 MPa for 100 h decreases from 4.67 × 10⁻⁸ to 1.43 × 10⁻⁸ s⁻¹. The strengthening mechanism is mainly attributed to the microstructural refinement and the formation of CaMgSn phase.     

Creep resistance of as-cast Mg-5Al-5Ca-2Sn alloy

In the present study, creep properties of as-cast Mg-5Al-5Ca-2Sn(AXT552) alloy were investigated by means of a GWT304 creep testing machine at temperatures of 175 °C and 200 °C in the stress range of 35-90 MPa. Results show that creep rates increase with applied stress at an identical temperature. Creep strain at 100 hours is 0.0518% and 0.083% at creep conditions of 175°C/75 MPa and 200°C/60 MPa, respectively, which is comparable to MRI230 D and much lower than most of AX series alloys. By the observation and analysis for samples before and after creep tests using a Shimadzu XRD-7000 type X-ray diffractometer(XRD) and a Hitachi S-3400 N type scanning electron microscope(SEM), it was found that Al_2Ca(C15) phase precipitated out of C36 phase or matrix. The cavity formation and connection at the interface of soft matrix and hard intermetallics caused the propagation of cracking along the eutectic phase during creep process and dislocation accommodated grain/phase boundary sliding is expected to be the dominant creep mechanism.     

Creep properties and controlled creep mechanism of as-cast Mg-5Zn-2.5Er alloy

The creep behaviors of as-cast Mg-5Zn-2.5Er alloy(mass fraction,%) ,under various applied stresses(50-70 MPa) and creep temperatures(150-200℃) for 100 h,were investigated.The stress exponent n is in the range of 1.5-5.8,and the activation energy Qc is in the range of 28.3-77.1 kJ/mol.With respect to the calculated n and Qc as well as the microstructures after creep,it is suggested that there is a transition region between grain boundary sliding(GBS) dominated creep to dislocation creep mechanism(from n3 to n3) ,arising in the steady-stage creep rate value of 2.89×10-9 s-1.     

热处理对Mg-5wt%Sn合金组织与显微硬度的影响

研究了固溶处理(460-500 ℃保温1-96 h)加人工时效处理(210-290 ℃保温1-160 h)对Mg-5wt%Sn合金组织演变的影响及组织与显微硬度之间的关系.结果表明,经480℃过固溶处理后,合金中的Mg2Sn相基本溶解,随后的时效处理过程中Mg2Sn相以弥散形式析出.Mg-5wt%Sn合金具有明显的时效硬化特征:经480℃固溶处理后,时效温度采用210℃时,保温96h后显微硬度达到峰值为77.4 HV0.01;时效温度为250℃时,保温16h后显微硬度达到峰值为76.6 HV0.01;时效温度采用290℃时,保温4h后达到峰值为60.2 HV0.01.合适的时效处理制度能明显提高合金的显微硬度.     

Effects of calcium addition on as-cast microstructure and mechanical properties of Mg-5Zn-5Sn alloy

The effects of Ca addition on the as-cast microstructure and mechanical properties of the Mg-5Zn-5Sn (mass fraction,%) alloy were investigated.The results indicate that an addition of 0.5%-1.5% (mass fraction) Ca to the Mg-5Zn-5Sn alloy not only refines the as-cast microstructure of the alloy but also causes the formation of the primary and/or eutectic CaMgSn phases with high thermal stability;an increase in Ca amount from 0.5% to 1.5% (mass fraction) increases the amount and size of the CaMgSn phase.In addition,Ca addition to the Mg-5Zn-5Sn alloy improves not only the tensile properties at room temperature and 150 ℃ but also the creep properties.Among the Ca-containing Mg-5Zn-5Sn alloys,the one added 0.5% (mass fraction) Ca obtains the optimum ultimate tensile strength and elongation at room temperature and 150 ℃,however,the alloy added 1.5% (mass fraction) Ca exhibits the optimum yield strength and creep properties.     

Compressive creep behavior of Mg-Sn binary alloy

Mg-Sn based alloy is one of the potential alloys for application at elevated temperature.The compressive creep behavior of ageing-treated Mg-xSn(x=3%,5%) alloys was investigated at the temperatures of 423 and 473 K and the stresses from 25 MPa to 35 MPa.When the tin content varies,the ageing-treated Mg-xSn alloys show quite different creep resistance,which are mainly attributed to the size and distribution of Mg_2Sn phases in the ageing-treated Mg-xSn alloys.The calculated value of stress exponent, n=6.3...     

Effect of Sn on as-cast ageing behavior of Al-Si-Mg alloy

1　INTRODUCTIONTheAl Si basecastalloyshavebeenwidelyusedintheproductionofstructuralcomponentsinengi neeringbecauseofanexcellentcombinationofcasta bilityandmechanicalproperties ,aswellasgoodcor rosionresistanceandweldability .Sandand perma nentcastingswithsolutionandartificialageingheattreatmentweregenerallyneeded ,wherebymetastablephasesprecipitatedfromthesupersaturatedsolution ,whichhardenedthealloy .ThemainstrengtheningelementsincastAl SialloyswereMgandCuandtheagehardeningresponsewass…     

Mg-9Gd-4Y-0.5Zr合金高温蠕变行为

对Mg-9Gd-4Y-0.5Zr合金铸态的室温组织以及T6状态200、250、300℃/50 MPa条件下的蠕变行为和组织进行了研究。结果表明,铸态下合金组织主要由α-Mg固溶体和沿基体晶界分布的富含(Gd,Y)元素的片状共晶相构成。T6(固溶+时效)状态下,随着蠕变的进行,片状共晶相的数量有所增加。由合金的蠕变曲线可知,蠕变速率随温度的升高而增大。合金的蠕变机制主要是位错攀移和晶界滑移,蠕变断裂主要是通过三叉晶界处楔形裂纹形核+长大的方式实现的。     

Negative creep during compressive creep of as-cast ZA27 alloy

1　INTRODUCTIONAmongzinc aluminumcastalloy ,ZA2 7alloyex hibitsattractive physicalandmechanicalpropertiescombinedwithgoodfrictionandwearresistanceprop ertiesmakingitabearingalloyreplacingsomecopperalloys[1,2 ] .However ,somepropertiesofthisalloywhichmustbetakenintoaccountarecomparativelylowresistancetocreepdeformation ,poorstrengthanditsdimensionalinstabilityatmoderatelyelevatedtemperatures[35] .Thedimensionalchangesofas castZA2 7alloyonageingwerestudiedbysomework ers[1,3,6 ] ,butthesere…