Relationship of Ca, B, and AlP in Al–12.6Si alloy

P modification has been widely used in Al-Si piston industry, but trace of Ca element has great influence on the P modification efficiency. In this work, it is found that primary Si can be heterogeneously nucleated by AlP in near eutectic Al-12.6Si alloy, but Ca element may destroy the P modification efficiency, whereas the addition of B can recover the P modification efficiency in near eutectic Al-12.6Si alloy with high Ca containing. The microstructure transformation was related to the reaction of Ca, B, and AlP. According to the thermodynamic calculation, Ca may react with AlP and form Ca3P2 compound in Al-Si alloy, whereas, when B was added into the melt, AlP could be reformed. The reaction of Ca, B, and AlP can be shown as follows: 2AlP +3Ca→Ca3P2+2Al; Ca3P2+18B+2Al→3CaB6+2AlP. In addition, with B added into the Al-12.6Si alloy with Ca and P addition, the mechanical properties were improved compared with single Ca and/or P addition.     

In situ scanning electron microscopy observation of deformation and fracture behavior of Ti-3Zr-2Sn-3Mo-25Nb alloy

The plastic deformation and fracture processes of Ti-3Zr-2Sn-3Mo-25Nb alloy for surgical implants were directly observed by in situ scanning electron microscopy(SEM).The effect of phase transformations on deformation-induced martensitic transformation accompanying the cyclic tensile fracture processes was investigated.The results reveal that the metastable alpha martensites(α")promotes deformation-induced martensitic transformation to ductile fracture,whereas the omega(ω)and alpha(α)phases drastically prevent slip dislocation and deformation-induced martensitic transformation to brittle fracture.     

Microstructure and mechanical properties of new metastable β type titanium alloy

A new metastable β type titanium alloy called TB-13 with the combination of excellent strength and ductility was developed successfully.In order to develop a perspective on this new alloy,the influence of several commonly used heat treatments on the microstructure and properties was studied.In solution-treated and quenched samples,a low-temperature aging at 480°C results in the precipitation of finerαphase.The precipitation of coarserαphase plate at higher aging temperature(560°C)leads to the increase of tensile ductility but reduction of strength.During low-temperature aging at 300°C,quite homogeneous distribution of fine isothermalωphase particles was found.The isothermalωphase provides nucleation sites forαphase during two-step aging process and makesαphase extremely fine and disperse uniformly in β matrix.Thus,TB-13 alloy is strengthened and its mechanical properties are improved.     

Effects of minor Sr addition on as-cast microstructure and mechanical properties of a Mg-3Sn-2Ca(wt.%) magnesium alloy

Minor Sr was introduced to the Mg-3Sn-2Ca(wt.%) alloy in this paper, and the effects of minor Sr addition on the as-cast microstructure and mechanical properties of the Mg-3Sn-2Ca(wt.%) alloy were investigated by using of optical and electron microscopies, differential scanning calorimetry(DSC) analysis, and tensile and creep tests. The results indicate that, after adding 0.034wt.%, 0.065wt.% or 0.10wt.% Sr to the Mg-3Sn-2Ca alloy, the morphology of the primary CaMgSn phase changes from the initial coarse needle-like net to relatively fi ne short block and/or particle-like shapes. At the same time, the additions of 0.034wt.% or 0.065wt.% Sr suppress the formation of the primary CaMgSn phase, and the addition of 0.10wt.% Sr not only suppresses the formation of the primary and eutectic CaMgSn phases but also promotes the formation of Mg2Ca phase. Furthermore, the addition of minor Sr to the Mg-3Sn-2Ca alloy can improve the tensile properties of the alloy both at room temperature and 150 ℃. The creep property of the Mg-3Sn-2Ca alloy at 150 ℃ is also improved by the additions of 0.034wt.% and 0.065wt.% Sr; however, the addition of 0.10wt.% Sr is not benefi cial to the creep properties of the Mg-3Sn-2Ca alloy.     

AZ31B镁合金冷轧及退火后的组织与性能

研究了AZ31B镁合金的冷轧工艺与冷轧后的组织变化,以及退火过程中退火温度、保温时间以及冷轧变形量对再结晶组织的影响,获得了静态再结晶图.当冷轧变形量大于15%,退火温度不超过400 ℃,可以获得细小的再结晶晶粒.最佳的冷轧及退火工艺为:冷轧变形量15%～25%,退火温度200～350 ℃,时间为30～60 min.冷轧退火AZ31B镁合金板材具有较好的力学性能,应变速率对镁合金冷轧退火板材的伸长率影响较大,而应变速率对强度基本上没有影响.     

冷轧退火对FeMnCoCrAl高熵合金组织和力学性能的影响

使用真空电弧炉熔炼出(Fe₅₀Mn₃₀Co₁₀Cr₁₀)₉₄Al₆合金,利用冷轧及在不同温度对合金进行退火,以期望得到由多尺度再结晶晶粒构成的层状结构;并对不同退火温度的样品进行拉伸性能测试。利用扫描电镜和EBSD对合金组织形貌进行表征,采用X射线衍射方法研究其相组成。结果表明:合金在铸态和冷轧后相组成未发生变化,700 ℃退火得到较好的多尺度再结晶晶粒的层状结构,其屈服强度为487 MPa,抗拉强度为708 MPa,断后伸长率为39%,表现出良好的综合力学性能。     

应变路线对Ti-6242合金组织与力学性能的影响

对两道次轧制的Ti-6242锻坯板材样品进行双级退火处理,研究了3种轧制应变路线对合金板材力学性能的影响。结果表明,不同应变路线的Ti-6242合金具有相近的晶粒尺寸和维氏硬度,采用单向轧制板材样品的力学性能高于两步交叉轧制和交叉换向轧制样品,抗拉强度和断后伸长率分别可以达到1264 MPa和21%;换向轧制会弱化Ti-6242合金板材的晶粒择优取向,而单向轧制则会强化其()显微织构强度。      

Microstructures and mechanical properties of biocompatible Ti-42 wt.%Nb P/M alloy

Ti-42 wt. %Nb powder was prepared by high-energy mechanical milling (HEMM). The particle size distribution (PSD) of the as-milled powder has been investigated using a particle size distribution analyzer. The morphology and microstructure of the as-milled powder have been investigated by scanning electron microscopy (SEM), X-ray diffractometry (XRD), transmission electron microscopy (TEM), and differential thermal analysis (DTA). Also, the corrosion property and biocompatibility of sintered specimens comprising mixed and milled powders have been investigated. The milled powders were sintered using pulse current activated sintering (PCAS). PCAS was employed in order to provide more refined grain size and full density to Ti-42 %Nb alloy on the basis of short sintering time with pressure. The density of the sintered Ti-42 %Nb specimen fabricated using the milled powder increased with increased milling time due to high free surface area and defect density. The density of the sintered Ti-42 %Nb specimen fabricated using as-mixed powder increased with increased sintering temperature up to 950 °C. The microstructure of the sintered Ti-42 %Nb specimen fabricated using 4h-milled powder was composed of Nb-rich and Nb-poor phases that are more refined and homogeneously distributed. The mechanical properties and biocompatibility of the sintered Ti-42 %Nb specimen fabricated using milled powder were superior to those of a commercial, Ti-6wt.%Al-4wt.%V alloy.     

Microstructure of a Ti–50wt% Ta alloy produced via laser powder bed fusion

Ti-Ta alloys have been widely studied for biomedical applications due to their high biocompatibility and corrosion resistance.In this work,nearly fully dense and in situ alloyed Ti-50 wt% Ta samples were fabricated by the laser powder bed fusion(LPBF) of mechanically mixed powders.With increased exposure time,and thereby increased laser energy density,insoluble Ta particles were almost dissolved,and a Ti-50 wt% Ta alloy was formed.Cellular and dendritic structures were formed due to constitutional undercooling,which was caused by the high cooling rate of LPBF process.Both retained βphases and α " phases were observed in the LPBFed Ti-50 wt% Ta alloy.The α" phase was found at the boundary of the cellular structures,where the tantalum content was not high enough to suppress the bcc lattice transition completely but could suppress the β phase→α' phase transition.     

铌对冷轧带钢退火再结晶组织和屈服强度的影响

利用Gleeble3500热模拟试验机模拟了3种不同铌含量冷轧带钢在不同温度条件下的退火过程。通过对比分析显微组织和屈服强度,研究铌含量对冷轧带钢再结晶行为的影响。结果表明：随着退火温度的升高,不同铌含量冷轧带钢均发生回复、再结晶和长大,在不同温度下回复和再结晶行为主导因素不同;随着铌含量的增加,冷轧带钢退火再结晶温度提高80~120 ℃。     

冷镦紧固件用Ti-3Al-5Mo-4.5V钛合金的微观组织及性能

通过透射电镜、扫描电镜和光学显微镜等手段,研究丝材制备过程中BT16钛合金的组织结构演变。结果表明:BT16合金退火态丝材具有良好的力学性能,断面收缩率Ψ为62%~65%,冷镦变形量达到80%;退火后的合金组织由初生等轴α相、少量短条状α相及晶间β相组成的;固溶时效后合金组织由不规则的等轴状初生α相和析出针状α′相的β相组成,其中淬火时效合金中的针状α′相更细小。     

退火和平整工艺对冷轧HSLA钢组织性能的影响

 本文以Nb微合金化冷轧HSLA钢为研究对象,探讨了退火和平整工艺对钢板组织性能的影响,结果表明:退火温度从700℃升至840℃,钢板的强度逐渐降低,伸长率逐渐升高,纤维状组织逐渐减少,铁素体再结晶更加充分;预拉伸量对带钢抗拉强度和断后伸长率无明显影响,随着预拉伸量提高至2. 0%,屈服强度略有升高,屈服点伸长率Ae逐渐减小,但预拉伸量达到2. 0%时,屈服平台仍无法消除;平整压下率对带钢抗拉强度和断后伸长率无明显影响,当压下率达到1. 0%时,屈服平台可完全消除,屈服平台消除后,随着压下率提高,规定塑性延伸强度R_{p0. 2}缓慢升高。      

轧制及退火后Al_(0.3)CoCrFeNi高熵合金的组织和力学性能

利用X射线衍射仪、扫描电镜、电子背散射衍射、透射电镜以及拉伸实验,研究了FCC结构Al_(0.3)CoCrFeNi高熵合金经90%压下量轧制及退火后的组织和力学性能。结果表明:经轧制及退火(600~1000℃)后,合金发生再结晶,富集Al、Ni原子的有序BCC相优先形成于再结晶FCC相的晶界处,且其体积分数随着退火温度上升先增大后减小。轧制显著强化该合金,随后600℃退火可实现不牺牲均匀塑性而进一步强化该合金的目的,升高退火温度则引起该合金强度下降,塑性增大。经800℃退火后合金表现出较为理想的强度-塑性匹配,其均匀伸长率为34.1%,且抗拉强度可高达935MPa,约是铸态合金(303MPa)的3倍,这主要归结于再结晶组织细化及有序BCC相的析出强化。