经形变热处理铜基形状记忆合金的晶粒生长、形状记忆和腐蚀行为

摘要

Metallurgical and mechanical properties along with shape memory and corrosion behavior of Cu−11.8% Al−3.7% Ni−1%Mn and Cu−11%Al−5.6%Mn shape memory alloys (SMAs) were comparatively studied. The influence of grain refinement on the properties was studied by optical microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), potentiodynamic polarizations and bend and tensile tests. Static recrystallization and kinetic grain growth show a rapid recrystallization in the first 15 s of annealing at 800 °C followed by grain growths. The minimum grain sizes obtained after 15 s are 90 and 260μm for Cu−Al−Ni−Mn and Cu−Al−Mn, respectively. Tensile tests show typical three-stage curves for both alloys, and it is seen that alloys exhibit high fracture stress and strain after grain refinement. Microstructural observations show zig-zag morphology of β1′ martensite in the Cu−Al−Ni−Mn and coexistence of β1′ and γ1′ in the Cu−Al−Mn, which were confirmed by differential scanning calorimetry results. The shape memory ratios (η) of the alloys before thermomechanical treatment, and after thermomechanical annealing at 800 °C for different time up to 15 min followed by water quenching, were evaluated. In addition, corrosion behavior of alloys after grain refinement was analyzed by means of potentiodynamic polarization measurements. The results showed that the anodic reactions were dominated by dissolution of copper, and Cu−Al−Ni−Mn alloy exhibits a better corrosion resistance than Cu−Al−Mn alloy.%比较研究了Cu−11.8%Al−3.7%Ni−1%Mn 和 Cu−11%Al−5.6%Mn形状记忆合金(SMAS)的形状记忆、腐蚀性能。采用光学显微镜(OM)、扫描电子显微镜(SEM)、差示扫描量热法(DSC)、动电位极化、弯曲和拉伸试验，研究了晶粒细化对这些性能的影响。在800°C退火时，在首先的15 s内静态再结晶和动态晶粒长达显示出一个快速的再结晶过程，随后才是晶粒生长。退火15 s后得到的Cu−Al−Ni−Mn 和 Cu−Al−Mn合金的最小晶粒尺寸分别为90μm和260μm。拉伸试验表明2种合金呈现典型的三阶段曲线，由此可以看出，晶粒细化后合金具有高的断裂应力和应变。显微组织表明，Cu−Al−Ni−Mn合金中存在锯齿状的β1′马氏体形态，通过差示扫描量热法也证实了β1′和γ1′共存于Cu−Al−Mn合金中。评估了形变热处理前、后及800°C退火15 min,随后进行水淬的合金的形状记忆性能。另外，采用动电位极化法分析了晶粒细化后合金的腐蚀行为。结果表明，铜溶解过程中主要为阳极反应，Cu−Al−Ni−Mn合金比Cu−Al−Mn合金具有更好的耐腐蚀性。