Fe85Ga15多晶在模拟海水中的应力腐蚀行为研究

Stress corrosion behavior of Fe_(85)Ga_(15) polycrystalline in simulated seawater

研究了新型磁致伸缩材料Fe-Ga合金的应力腐蚀性能。采用恒载荷和慢应变速率拉伸(SSRT)试验,结合电化学测试技术,研究了铸态Fe85Ga15多晶在模拟海水中的应力腐蚀。结果表明,开路电位下,模拟海水中薄板光滑试样恒载荷拉伸能够发生低于材料抗拉强度的断裂,且断裂时间明显依赖于外加应力的大小,外加应力愈大,断裂时间愈短。这表明铸态Fe85Ga15合金在模拟海水中能够发生应力腐蚀开裂(SCC),且SCC归一化门槛应力为σscc/σb=0.34。慢应变速率拉伸显示,SCC敏感性在应变速率为5×10-7/s时最大,用强度损失表示为Iσ=(1-σc/σb)×100%=35%。阴极极化升高而阳极极化降低恒载荷SCC断裂时间。这些结果初步表明铸态Fe85Ga15合金在模拟海水中的应力腐蚀为阳极溶解型。

Iron-gallium（Fe-Ga） alloy is a new class of magnetostrictive materials with an excellent combination of large low-field magnetostriction,high mechanical strength,good ductility and low cost.This paper reports the first measurement of the stress corrosion cracking（SCC） behaviors of polycrystalline of Fe-15at%Ga in simulated seawater（3.5wt% NaCl） environment by using constant load test,slow strain rate tensile（SSRT） test and combined of electrichemical method.Further the stress corrosion mechanism was discussed by combining electrochemical and mechanical tests.The results showed that constant load tensile fracture can occur below the ultimate tensile stess when smooth sheet specimens immerging in the simulated seawater at open circuit potential.And the fracture time is significantly dependent on the applied stress.The greater the applied stress,the shorter the time to rupture.It indicates that the SCC can occur for the Fe85Ga15 alloy in simulated seawater.The normalized threshold stress for SCC is σscc/σb=0.34.There is a maximal susceptibility to SCC when the strain rate is 5×10-7/s,which is Iσ=（1-σc/σb）×100%=35%.The fracture time decreased when anodic potential was imposed to the sample under constant load,while it increased when cathodic potential was done.The results seem that the stress corrosion for Fe85Ga15 in simulated seawater is controlled by anodic dissolution.