The effect of Ca on corrosion behavior of heat‐treated Mg–Al–Zn alloy

The effect of 0.5, 1.0, and 1.5 wt% Ca additions on the microstructure and corrosion resistance of the heat‐treated Mg–Al–Zn alloy was investigated. Addition of 0.5 wt% Ca did not form any new phase but suppressed the discontinuous precipitation of the β ‐Mg₁₇Al₁₂ phase by being dissolved in both the second phase and magnesium matrix. In the materials containing higher amounts of Ca, however, metallographic investigation shows that Ca added to Mg–Al–Zn can obviously decrease the size of β ‐Mg₁₇Al₁₂ and forms Al₄Ca intermetallic compounds in the shape of bone‐like morphology. The corrosion tests used include constant immersion technique, and potentiodynamic polarization experiments and salt spray test. Surface examination and analytical studies were carried out using optical and scanning electron microscopy, EDX, and XRD. The results of corrosion tests show that magnesium alloy Mg–Al–Zn with 1.0 wt% Ca addition has the best corrosion resistance behavior.     

热处理对轧制态Mg5Gd合金腐蚀行为的影响

通过浸泡试验、电化学测试、扫描电化学显微镜和腐蚀形貌分析等手段研究热处理工艺对轧制态Mg5Gd合金在3.5 wt.％NaCl饱和Mg(OH)2溶液中腐蚀行为的影响及机理,以期达到提高镁合金耐蚀性的目的.结果表明:固溶处理能显著降低Mg5Gd合金的腐蚀速率,并且使其腐蚀变均匀,腐蚀坑变浅,这主要归因于固溶处理可以熔解镁基...     

Influence of temperature and chloride ion concentration on the corrosion behaviour of Mg–4Al–3Ca–0.5RE alloy

The influence of temperature and chloride ion concentration on the corrosion behaviour of Mg?4Al?3Ca?0.5RE alloys were studied in this paper. Corrosion rates of the alloys were measured by weight loss test and electrochemical measurement. The results revealed that a shorter incubation period to the onset of corrosion, a more negative corrosion potential, and a higher corrosion rate was correlated with a higher temperature in 3% NaCl solution and a higher chloride ion concentration at 30°C. The corrosion behaviour of the alloys was affected by surface film and the corrosion mainly occurred at the breaks or defects in surface films.     

热处理制度对2056铝合金微观组织和抗应力腐蚀性能的影响

采用光学显微分析、扫描电镜及透射电镜观察、慢应变速率拉伸测试等研究2056铝合金在T6、T851及T351热处理状态下的微观组织和抗应力腐蚀性能.结果表明:2056合金在T6态下,晶内析出相主要为粗大的S'相和少量粗大的含锰相,抗拉强度为445.13 MPa,晶界析出相粗大且呈非连续分布,无沉淀析出带(PFz)为0.1～0.2μm,应力腐蚀敏感性最大;T851态下,晶内析出相主要为细小弥散的S'相,合金具有最高的抗拉强度,达到502.01MPa,晶界析出相呈离散状分布,PFZ较窄,约为0.02 μm,抗应力腐蚀性能优于T6态的;T351时效状态下,晶内观察到大量的位错和位错塞积以及少量GPB区,抗拉强度为469.73MPa,介于T6和T851之间,晶界无粗大平衡相析出,无明显PFZ,抗应力腐蚀性能最好.     

Ca对铸态Mg-4Zn合金组织及腐蚀性能的影响

为开发生物医用镁合金,利用高纯原材料,在氩气气氛保护下熔炼浇铸制备了Ca合金化的Mg-4Zn合金(Ca含量分别为0.4%和1.0%,质量分数)。通过OM、SEM以及XRD分析了合金的微观组织和相组成,采用析氢法、腐蚀质量损失法以及电化学法测试了合金在Hanks模拟体液中的腐蚀行为。结果表明,合金由初生Mg固溶体和共晶体组成;随Ca含量增加,合金的电荷传递电阻减小,自腐蚀电位下降,自腐蚀电流密度增加;析氢法和腐蚀质量损失法均表明合金的腐蚀速率随时间延长而减小。共晶体对合金的耐蚀性有影响;当Ca含量从0.4%增加到1.0%时,共晶体含量增加,促进了合金的电偶腐蚀,合金耐蚀性降低。Mg-4Zn-(0.4,1)Ca合金的腐蚀形式主要为晶间腐蚀和点蚀。     

触变成型镁合金铸件热处理显微组织的演变

通过金相显微镜、SEM及XRD等观察手段研究了触变成型AZ91D镁合金铸件固溶、时效处理时显微组织的演变。结果表明:触变成型AZ91D镁合金在415℃时固溶处理时β相溶解入α-Mg固溶体的速度比高压压铸的快。在固溶处理初期,铝元素从β相扩散至块状初生α-Mg相,导致块状初生α-Mg晶粒周围形成富铝晕圈。时效处理时,触变成型铸件在5h左右硬度达到峰值,高压压铸铸件在12h左右达到峰值。触变成型铸件时效析出方式存在片层状不连续析出和针状连续析出两种。     

固溶处理态Mg-Nd-Gd-Sr-Zn-Zr生物镁合金的组织与均匀腐蚀行为

对Mg-(4-x)Nd-xGd-0.3Sr-0.2Zn-0.4Zr(质量分数,%,x=0, 1和3)镁合金进行了固溶处理。采用扫描电镜、能谱分析仪和X射线衍射仪研究了合金的显微组织与物相。利用失重和析氢法测试了合金在模拟体液中的腐蚀速率,并观察了合金的腐蚀形貌。结果表明,含1%Gd的合金晶粒最细小,且第二相较为连续地分布在基体周围,腐蚀速率也最低;而含3%Gd的合金晶粒最粗大,腐蚀速率最快。3种合金的腐蚀形貌较为均匀,是理想的生物可降解材料。     

稀土Y对AZ80镁合金组织及耐蚀性能的影响

通过静态失重法、电化学测试法、扫描电子显微镜、X射线衍射等测试手段对添加不同含量稀土元素Y的AZ80镁合金的微观组织和腐蚀性能进行了研究。结果表明:稀土Y的加入使实验合金中β-Mg17Al12相的数量明显减少,并且由连续网状分布变为断续状、均匀分布。同时,Y与合金中Al结合形成块状或颗粒状的稀土相Al2Y。本实验条件下,添加0.5%Y合金的耐腐蚀性能最佳,腐蚀速率为0.2585 mg.cm-2.d-1,仅为原始合金腐蚀速率的48.07%,此外加入适量Y可提高合金的平衡电位和腐蚀电位,降低腐蚀电流密度,提高了合金的耐蚀性能。     

The effect of heat treatment on the corrosion behaviour of 319 aluminium alloy

The effect of various heat treatments on the corrosion behaviour of 319 T1 cast aluminium alloy was investigated. From this alloy, specimens were heat treated in T5, T6 and two steps solution heat treatment T6 conditions and afterwards were subjected to electrochemical corrosion in a 0.1 M NaCl solution (pH = 12). From the above treatments, T5 heat treatment did not improve the corrosion resistance of the as‐received alloy in contrast to T6 heat treatment which improved the corrosion resistance of the same alloy. However, two steps solutionizing T6 treatment showed the best corrosion resistance of the aluminium alloy.     

热处理对Mg_(96.32)Er_2Zn_(1.5)Zr_(0.18)合金组织的影响

采用感应加热制备了Mg96.32Er2Zn1.5Zr0.18合金,对合金进行热处理,利用光学显微镜、扫描电镜背散射电子技术、能谱分析仪以及X射线衍射仪研究了合金不同状态的显微组织。结果表明:铸态Mg96.32Er2Zn1.5Zr0.18合金呈现树枝晶结构,相组成主要为α-Mg相、X相和W相;经过热处理后,合金的树枝晶组织得到完全消除,X相逐渐溶入基体中,合金晶粒尺寸没有发生明显的改变;热处理工艺为530℃×8 h时,合金的X相完全溶入基体中,W相的形态发生变化,由网状转变成谷粒状,同时热处理过程中还析出部分细小的谷粒状W相。     

碱热处理对搅拌摩擦加工AZ31镁合金耐腐蚀性能的影响

对AZ31镁合金进行搅拌摩擦加工(Friction stir processing,FSP),并对母材(Basal material, BM)和FSP试样进行碱热处理(Alkali heat treatment,AHT),研究了AHT对搅拌摩擦加工后AZ31镁合金微观组织和耐腐蚀性能的影响。结果表明,FSP可以显著细化晶粒,平均晶粒尺寸由BM的12.8 μm细化至FSP后的3.1 μm,高角度晶界比例从BM的75.9%降低至FSP后的45.3%,晶界亚结构增多。AHT使材料表面形成致密的MgO和Al₂O₃混合涂层,有效地提高了AZ31镁合金的耐浸泡腐蚀性能。     

Effect of heat treatment on microstructure and properties of hot-extruded nickel-aluminum bronze

The effect of heat treatment on the microstructure and properties of a hot-extruded nickel-aluminum bronze was investigated. Experimental materials were heat treated through different processes, including quenching, normalizing, aging and annealing, and their microstructure, corrosion resistance and mechanical properties were characterized. It is found that quenching causes all β phase transformed into β phase, however, normalizing causes β phase transformed into β α and κ phases. When the quenched sample is aged, fine phase is precipitated from the as-quenched microstructure of β＇ phase. Annealing causes the transformation of β into a and κ phases. The results of mechanical property tests show that quenching, normalizing and aging improve the tensile strength and hardness of the experimental material, with a corresponding fall in elongation. Annealing raises the elongation but reduces the tensile strength and hardness. Furthermore, corrosion resistance of nickel-aluminum bronze ranks from worse to better in the following order： aged, quenched, normalized, hot-extruded and annealed. However, with the exposure time of corrosion test increasing, the difference of average corrosion rate between those nickel-aluminum bronzes tums small.     

热处理对Ti-Al-Nb基合金组织和性能的影响

用光学显微镜和透射电子显微镜研究了Ti-Al-Nb基三种合金在空冷和水淬后的微观组织及其力学性能.结果表明:Al含量为11%-14%的Ti-Al-Nb基三种合金经不同热处理后,在晶界上和晶内均有α2相析出;在1 100～1 150 ℃水淬后可观察到单相再结晶组织;小于1 050 ℃水冷和空冷后未发生再结晶转变;经1 050 ℃×1 h/AC + 820 ℃×5 h/AC双重退火处理后,晶界和晶内除有α2相析出外,晶内有弥散分布的O相析出,并形成网篮组织,其抗拉强度、屈服强度和耐热性能均得到提高,塑性反而降低.     

显微组织对Zr-Sn-Nb-Fe锆合金耐腐蚀性能的影响

将Zr-Sn-Nb-Fe锆合金样品分别进行不同热处理,在350℃、16.8MPa、0.01mol.L-1LiOH高压水溶液中腐蚀,并用高分辨透射电镜(HR-TEM)研究它们的显微组织和析出相粒子。结果表明,冷轧前在800℃保温的两种样品的耐腐蚀性能好于680℃保温的两种样品,冷轧后500℃保温样品的耐腐蚀性能好于560℃保温样品。HR-TEM分析表明800℃/500℃处理样品耐腐蚀性能最好的原因是析出相粒子中Nb含量较高,从而降低了Nb元素在基体αZr中的固溶含量。     

Effect of heat treatment on the Nb distribution and corrosion resistance of Zr-Sn-Nb-Fe zirconium alloy

After being treated in different ways,Zr-Sn-Nb-Fe alloy specimens are exposed in 0.01mol/L LiOH aqueous solution at 350℃ under 16.8 MPa.The examination of microstructures and second phase particles (SPPs) of these specimens was carded out by high-resolution transmission electron microscopy (HR-TEM).The specimens treated at 800℃ before the final cold roiling have a better corrosion resistance than those treated at 680℃,and the specimens treated at 500℃,after the final cold rolling,have a better corrosion resistance than those treated at 560℃.TEM examination shows that the SPPs existing in the 800℃/500℃ specimen,which has the best corrosion resistance,contains a lot of Nb dement,which results in the reduction of the niobium content in the a-Zr solid solution.     

热处理对钼铜奥氏体不锈钢组织和耐腐蚀磨损性能的影响

研究了热处理工艺(不同固溶温度和固溶时间)对钼铜奥氏体不锈钢析出物含量和形态的影响,以及在不同固溶温度下材料的耐腐蚀磨损性能.试验结果表明,钼铜奥氏体不锈钢析出物随固溶温度的升高和固溶时间的延长而增多,其形态也由针棒网状长成块状;在纯磨损环境下,1100 ℃×8 h空冷下的奥氏体不锈钢析出物数量最多,耐磨损性能最好;而在有酸的腐蚀磨损环境介质中,950 ℃×8 h空冷的热处理工艺下的材料耐腐蚀磨损性能最佳.