Fe-Cu二元合金中的B2析出相及时效硬化

研究了不同成分的Fe-Cu合金在过饱和固溶体状态下其硬度随Cu含量的变化规律,分析了Cu元素在Fe中的固溶强化作用.研究了Fe-cu合金的时效硬化现象以及Cu的析出过程,结果表明Fe-Cu合金硬度值增加近一倍,通过透射电镜观察到随时效时间的增加,析出相的尺寸逐渐增大,形状由球状转变为棒状.电子衍射分析得知,时效处理硬度达到最大值时对应的析出相具有B2型晶体结构,与基体之间保持平行位向关系.     

合金元素Cu对Zr-Sn-Nb合金淬火及时效过程微观组织的影响

通过光学显微镜、扫描电镜和透射电镜对Zr-Sn-Nb系两种合金淬火时效样品进行观察分析,研究了合金元素Cu对锆合金淬火后微观组织的影响及在时效过程中对第二相析出规律影响。结果表明:淬火态样品中没有第二相析出,且Cu元素的添加可以细化晶粒及淬火板条组织,提高合金硬度;经过时效处理后,第二相首先在晶界位置析出;随着保温时间的延长,合金元素扩散充分。透射电镜结果显示,Cu元素促进第二相形核析出以及细化第二相尺寸。     

高性能Cu-Ni-Co-Si合金的二次时效行为及析出相特征

采用显微硬度计、电导仪、透射电镜(TEM)和能谱仪(EDS)等研究了二次时效Cu-1.6Ni-1.2Co-0.6Si合金的性能和显微结构;根据衍射花样标定和能谱结果,分析了合金的析出相特征。结果表明:合金冷轧过程中形成的高密度位错,促进了二次时效析出相的析出;这些二次析出相与一次时效析出相具有相同的结构和组成,都是正交结构的(Ni,Co)_2Si;但二次时效析出相分布更密集、尺寸更细小;二次时效后合金硬度的提高主要是由这些细小密集的δ-(Ni, Co)_2Si相的强化所贡献;析出相与铜基体之间的位向关系为:(001)_(Cu)//(001)_p,[110]_(Cu)//[010]_p。     

Cu含量对Al-Mg-Si-Cu合金微观组织和性能的影响

采用DSC热分析、硬度、电导率、拉伸和晶间腐蚀等测试及透射电镜组织观察,研究Cu含量对Al-Mg-Si-Cu合金微观组织和性能的影响。实验表明:180℃时效时,4种合金硬度上升至峰值后持续下降,且随着Cu含量增加,合金的时效硬度随之提高,硬化速率加快而软化速率降低;时效时电导率先下降至最低值后又持续上升,且Cu含量越高,电导率越低。随着Cu含量增加,T6和T4态合金的强度随之提高,晶间腐蚀抗力下降,但无Cu合金不发生晶间腐蚀;T6态合金析出相类型随Cu含量增加而变化,Cu含量较低时(0.6以下),析出β″相;而Cu含量为0.9时,析出相为β″相和Q′相共存;且随着Cu含量增加,析出相数量和体积分数增加而尺寸减小,T4态合金析出相为原子团簇。     

Al-Er-Cu合金架空导线的导电性能

通过导电率、硬度测试方法研究了Al-Er-Cu合金在等时时效与等温时效过程中的性能变化规律,利用透射电镜(TEM)、能谱分析(EDS)观察了合金析出相的析出及生长规律。结果表明:随着时效温度升高,整体上同一合金的导电率与硬度峰值出现时间均提前;300 ℃时效时,Al-Er-0.22Cu合金已经析出大量纳米级弥散相,析出强化了合金强度,提高了导电率,时效2 h时达到导电率峰值60.15%IACS,10 h达到硬度峰值43.1 HV0.05,Al-Er-0.22Cu合金在拥有高导电率的同时保持了较好的硬度。     

添加元素Cu对Al-Mg-Si合金析出相行为的影响

研究了添加元素Cu对6082Al-Mg-Si合金时效过程及微观组织变化的影响.结果表明,添加元素Cu后提高了Al-Mg-Si合金的峰值硬度,同时缩短了合金达到峰值硬度的时间.根据透射电镜及三维原子探针的观察可知,经过170℃时效2h后,添加元素Cu的Al-Mg-Si合金中所形成的β"析出相中有Cu原子的富集,而未添加元素Cu的合金仍以GP区为主.170℃时效8h后,在含0.6%Cu合金中形成了明显的板条形Q'析出相.     

稀土Er对Al-5.3Cu-0.8Mg-0.6Ag合金组织与性能的影响

采用硬度测试、拉伸性能测试、X射线衍射、金相观察、扫描电镜与透射电镜等方法,研究了添加0.2wt%Er对Al-5.3Cu-0.8Mg-0.6Ag合金的组织与性能影响.结果表明,微量稀土Er可显著降低铸态合金的晶粒尺寸,提高铸态合金的室温与高温力学性能;然而,Er降低了挤压态合金的时效硬化与拉伸性能,这是由于Er与合金中的Al、cu形成了Al8Cu4Er稀土化合物,减少了用于固溶时效的Cu元素,最终使强化析出相Ω相的体积分数减少.     

高强高导低溶质Cu-Ag-Cr合金时效析出特性的研究

Cu-Ag-Cr合金经时效处理后，显微硬度和电导率都有很大的回升。经480℃时效2h后，硬度峰值为117HV，此时电导率达到94％IACS。利用透射电镜对合金时效过程中析出相的变化及其对显微硬度的影响进行了分析，在峰值状态下，析出相与基体保持共格关系。由于析出相尺寸较大，合金以Orowan机制提高强度，并利用位错理论计算出以Orowan机制强化合金的析出相的临界尺寸，与实验数据十分吻合。     

Al−Si−Mg−Er合金的热稳定性和析出相的显微组织

采用显微硬度计和透射电镜研究Er元素对热处理Al?Si?Mg合金显微硬度和析出行为的影响.作为对照,同时研究人工时效前引入自然时效对合金硬度和析出行为的影响.研究结果表明,过时效Al?Si?Mg?Er合金的热稳定性与析出相的平均尺寸密切相关.未引入自然时效时,Al?Si?Mg?Er合金中 β'相的平均尺寸小于Al?Si...     

Cu-Cr-Zr合金时效强化机理

研究了不同时效工艺对Cu-0．7Cr-0．13Zr合金硬度、强度和导电率性能的影响,利用透射电镜分析合金时效后的微观形态和析出相。结果表明：在500℃时效30min析出相为Cu5Zr,硬度和导电率可达116．7HV和47％IACS。500℃时效6h后,硬度和导电率为140HV和76％IACS,强度达到峰值430MPa,弥散共格的析出相Cr是强度提高的重要原因,强化效应与采用共格强化机理计算的结果非常接近。合金在500℃时效8h硬度和强度仍具有135．6HV和410MPa,导电率为77％IACS,析出相仍较细小但与基体失去共格关系。     

Transformation of austenite in Fe-Cu alloys. III: Copper precipitation during cooling and holding of steels alloyed with copper

Strengthening of Fe-Cu alloys during isothermal aging has been considered. The size of particles that provides a maximum strength has been found. A theory of particle growth under the conditions of continuous cooling has been developed. The cooling rate that provides the maximum contribution from age hardening has been calculated.     

Strengthening mechanism of Fe-Cu alloy during aging

To give a further research on strengthening mechanism of binary Fe-Cu alloys during the aging process, the compositions, size distributions and volume fractions of precipitates were investigated by carbon extraction replicas. Both the size and the volume fraction of precipitates increase with the aging time prolonged. The precipitate sizes are corresponding with Weibull distribution. The stability of the sample aged for 35 min is worse than that aged for 1800 min and 18000 min. The precipitate is Cu-rich phase in the early aging process, and Cu content increases with the prolonging aging time. Before aging peak, the precipitation of Cu-rich phase plays a dominant role in strengthening. The growth and the change in crystal structure of the precipitate particles are the main factors leading to the decrease in strengthening after the aging peak.     

热轧淬火Cu-Cr系合金的性能和组织演变

利用在线热轧淬火工艺和随后的形变热处理工艺制备Cu-Cr系列合金带材,并采用硬度、电导率测试与光学显微镜、透射电子显微镜观察的方法,研究合金在制备加工过程中的性能和组织演变。结果表明:在线热轧淬火和后续的形变热处理工艺可成功地制备高硬度、高导电和抗软化性能优异的Cu-Cr系合金带材。具有有序FCC结构、与基体呈立方立方位向关系的Cr相从过饱和固溶体中分解出来是时效过程中合金硬度和电导率提高的原因。Cu-Cr系合金的高硬度是细晶强化、应变强化和析出强化共同作用的结果,而高电导率是由于时效析出极大地降低了基体中溶质原子浓度。     

Microstructures and properties of Mg–7Gd alloy containing Y

Mg–7 mass%Gd–x mass%Y (x = 0, 1, 3 and 5) alloys were prepared by casting method, and the microstructures, age hardening behavior and mechanical properties have been investigated. The results show that the addition of Y to the binary Mg–7Gd alloy could reduce the grain size of the as-cast alloys, and enhance the age hardening response and improve mechanical properties during the investigated temperature range. The Mg–7Gd–5Y alloy exhibits maximum ultimate tensile strength and yield strength at peak hardness, and the values are 258 and 167 MPa at room temperature, and 212 and 140 MPa at 250 °C, respectively, which is about 1.8 times as high as the Mg–7Gd binary alloy. When x is more than 3, the amount of Mg₅(Gd,Y) phase is observed at the peak hardness of aged alloys. The significant improvement of the tensile strength at peak hardness is mainly attributed to the fine dispersion of the β-Mg₅(Gd,Y) precipitate.     

Effect of alloying elements on fracture behavior of Fe-18Ni-2Ti-(8Co) alloys

Effect of alloying elements on fracture behavior of Fe-18Ni-2Ti-(8Co) alloys has been investigated in the light of grain boundary segregation of alloying elements. During isothermal aging at 540°C, hardness level in the cobalt-bearing alloy was higher than that in the cobalt-free alloy, which is attributed to the solid solution hardening of cobalt, and the bigger hardness difference after overaging was due to the relatively fine precipitates in the cobalt-bearing alloy. The grain boundary segregation behavior of the elements was similar in two alloys, regardless of the cobalt addition. In two alloys, the fracture behavior before and after the maximum tensile strength is mainly governed by two factors: titanium at the grain boundaries and over-aging. Up to the aging time corresponding to the maximum tensile strength, the intergranular fracture strength was roughly inversely proportional to the titanium level at the grain boundaries, and after the time the tensile strength decreased with restoring ductility. Nickel or cobalt was not effective on the grain boundary strengthening of the iron-based alloys.     

非晶态镍磷合金的组织结构与性能

研究了化学沉积非晶态镍磷合金的组织结构与性能。结果表明,随着沉积层中磷含量的增加,合金的非晶化趋势提高,非晶态镍磷合金层的硬度和耐磨性能下降,且明显低于晶态镍磷合金;经过大于６１３Ｋ的时效处理,非晶态镍磷合金晶化且有Ｎｉ３Ｐ生成,沉积层的硬度和耐磨性得以提高并超过晶态合金;非晶态镍磷合金经过时效处理晶化后且组织结构发生变化,耐腐蚀性能下降,硬化性能则提高。     

Effects of different tempers on precipitation hardening of 6000 series aluminium alloys

By means of Vickers hardness,mechanical property and formability tests,the effects of different tempers on precipitation hardening of 6000 series aluminium alloys for automotive body sheets were investigated.The results indicate that the short-time pre-aging at 170℃makes for subsequent artificial aging precipitation hardening.With the increase of pre-aging time,the artificial aging hardenability increases.The aging hardening rate reaches the maximum when pre-aging time is up to 10 min,and then it decreases.The short-time pre-aging at 170℃benefits sheets to obtain lower strength under delivery condition and consequently to improve stamping formability of automotive body sheets.The effects of different tempers on precipitation hardening are much more obvious than those of the alloying elements.It is a good treatment schedule to perform pre-aging for 5 min at 170℃right after solution treatment.     

Au-Ti足金的强化机理研究

采用拉伸试验、硬度测试和光学显微分析等手段研究了Au-Ti足金的强化机理。结果表明，Au-Ti足金的强化方式主要是细晶强化、加工硬化和时效强化，且其力学性能优于标准的Au917饰品用金合金Au917Ag55Cu28，Au917Ag32Cu51。并且，Au-Ti足金的冷加工性能优于千足金，这是由于其固溶态硬度、强度高，延性好。     

A mathematical model to predict the strength of aluminum alloys subjected to precipitation hardening

A number of alloys, notably most of the aluminum alloys, can be heat treated by aging. This aging due to time-dependent precipitation hardening increases the strength and hardness as well as modifying other mechanical properties. Precipitation hardening has been a popular strengthening mechanism for many decades; therefore, extensive information is available in literature about the precipitation-hardening response of various series of aluminum alloys. The age-har dening response of these alloys is usually represented in graphical form as plotted between property changes and aging time for different temperatures. In designing a suitable precipitation-hardening strategy, one can refer to these graphs. However, for automatic control of aging furnaces, as well as for decision making regarding optimal selection of aging conditions (time/temperature combination), it is desirable to express these relationships in a formal mathematical structure. A mathematical model is developed in this article for widely used heat treatable aluminum alloys used in the extrusion industry. This model is a condensed representation of all σ=f(T, t) curves in different series of aluminum alloys, and the parameters of this model characterize the various compositions of the alloys in the series.     

时效处理对Mg-6Al-1Nd-xGd合金组织及高温力学性能的影响

采用光学显微镜(OM)、扫描电镜(SEM)、EDS能谱分析等手段研究了Mg-6Al1Nd-xGd(0,0.5,1,1.5)合金的时效硬化行为及时效处理(T6)对合金高温拉伸性能的影响,结果表明:Gd元素的加入使Mg-6Al-1Nd合金的时效过程延长,随Gd含量的增多,合金在200℃时效时的硬度峰值从28 h延迟到36 h附近,且Gd含量为1%时合金峰值硬度最大,达到HV51.1。T6处理后,合金的强度及塑性都有所提升,Mg-6Al-1Nd-1Gd合金在200℃的抗拉强度为146 MPa,伸长率为22.3%,较铸态分别提高27.5%和29.7%,合金表现出良好的综合高温拉伸性能。