魏氏组织对20#碳钢H2S应力腐蚀开裂性能的影响

文章对H2S-CO2-H2O腐蚀环境下发生H2S应力腐蚀的20#碳钢弯管(无缝钢管)进行了成分、组织、拉伸、硬度和应力腐蚀开裂等性能的试验研究,并与同材质、同时投产、腐蚀环境基本相似而未发生应力腐蚀开裂的在役弯管及未使用的新弯管作了对比。结果表明:魏氏组织是引起20#钢发生应力腐蚀开裂的主要原因;正火能消除魏氏组织,降低钢的应力腐蚀开裂敏感性。

在役X52输气管线钢塑性和韧性研究

陕北某气田输气干线由进口X52纵焊管段经现场焊接而成。输送的介质中，H2S含量为500～1000mg／L，CO2含量为5％左右，同时还有少量凝析水，该环境下潜伏着氢损伤危险。为此，测试了该输气干线X52钢的延伸率和J积分值，研究了经过NACE溶液中的浸泡、焊缝质量和残余应力等对延伸率和J积分值的影响。结果表明，输送含H2S的X52输气管线随着服役时间的延长，其延伸率和J积分值会有所下降，并且焊缝及其附近延伸率降低的幅度大于母材。

Relationships between microhardness, microstructure, and grain orientation in laser-welded joints with different welding speeds for Ti6Al4V titanium alloy

The microhardness curve trend and its relationships with microstructure and misorientation were analyzed to enhance the comprehension of the microstructure and mechanical property of micro-areas in Ti6 Al4 V laser-welded joints with different welding speeds. The microhardness measured on the fusion line(H_m) is the highest from the weld center to the base metal. H_m increases with increasing weld width in a welded joint and increasing degree of the non-uniformity in all studied welded joints. The microhardness decreases from the weld metal to the base metal with decreasing amount of martensite α’ and increasing amount of original α phase. When the microstructure is mainly composed of martensite α’, the microhardness changes with the cooling rate, grain size of the martensite, and peak values of the fraction of misorientation angle of the martensite in a wide weld metal zone or weld center at different welding speeds, whereas the difference is small in a narrow weld metal zone.

Wetting of molten Sn-3.5Ag-0.5Cu on Ni-P(-SiC) coatings deposited on high volume faction SiC/Al composite

The wetting of molten Sn-3.5Ag-0.5Cu alloy on the Ni-P(-SiC)coated SiCp/Al substrates was investigated by electroless Ni plating process,and the microstructures of the coating and the interfacial behavior of wetting systems were analyzed.The SiC particles are evenly distributed in the coating and enveloped with Ni.No reaction layer is observed at the coating/SiCp/Al composite interfaces.The contact angle increases from^19°with the Ni-P coating to 29°,43°and 113°with the corresponding Ni-P-3SiC,Ni-P-6SiC and Ni-P-9SiC coatings,respectively.An interaction layer containing Cu,Ni,Sn and P forms at the Sn-Ag-Cu/Ni-P-(0,3,6)SiC coated SiCp/Al interfaces,and the Cu-Ni-Sn and Ni-Sn-P phases are detected in the interaction layer.Moreover,the molten Sn-Ag-Cu can penetrate into the Ni-P(-SiC)coatings through the Ni-P/SiC interface and dissolve them to contact the SiCp/Al substrate.

Effect of yttrium and calcium additions on electrochemical behaviors and discharge performance of AZ80 anodes for Mg-air battery

The effects of yttrium(Y)and yttrium+calcium(Y+Ca)additions on the electrochemical properties and discharge performance of the as-extruded Mg−8Al−0.5Zn−0.2Mn(AZ80)anodes for Mg−air batteries were investigated.The results show that the addition of 0.2 wt.%Y increased the corrosion resistance and discharge activity of AZ80 anode.This was attributed to the fine and sphericalβ-Mg_17)Al_(12) phases dispersing evenly in AZ80+0.2Y alloy,which suppressed the localized corrosion and severe“chunk effect”,and facilitated the rapid activation ofα-Mg.Combinative addition of 0.2 wt.%Y and 0.15 wt.%Ca generated grain refinement and a reduction of theβ-Mg_17)Al_(12) phase,resulting in a further enhancement in discharge voltage.However,the incorporation of Ca in Mg_17)Al_(12) and Al_(2)Y compounds compromised the corrosion resistance and anodic efficiency of AZ80+0.2Y+0.15Ca anode.Consequently,AZ80+0.2Y anode exhibited excellent overall discharge performance,with the peak discharge capacity and anodic efficiency of 1525 mA·h·g^(−1) and 67%at 80 mA/cm^(2),13%and 14%higher than those of AZ80 anode,respectively.

Optimization of extrusion process parameters of Incoloy028 alloy based on hot compression test and simulation

True stress?true strain curves of Incoloy028alloy at high temperature and strain rate were investigated by hot compression test.These curves show that the maximum flow stress decreases with the increase in temperature and the decrease in strain rate.FEM simulation was employed to investigate the influence of temperature,extrusion speed and friction coefficient on the extrusion load,stress,strain and strain rate in the extrusion process.The increase of extrusion temperature results in decrease of load and deformation resistance,but has little influence on strain and strain rate.When extrusion speed changes between200and350mm/s,no obvious change about extrusion load can be found.Sharp peak value up to42500kN emerges in the extrusion load curve and the extrusion process becomes unstable seriously when extrusion speed rises up to400mm/s.Both stress and strain rate increase with the raise of extrusion speed.When friction coefficient is between0.02and0.03,deformation resistance is about160MPa and the strain rate can be limited below70s?1.Successful production of Incoloy028tube verifies the optimized parameters by FEM simulation analysis,and mechanical tests results of the products meet the required properties.

Precipitation response and hardening behaviors of Fe-modified Ti5553 alloy

Ti5553-xFe (x=0.4, 1.2, 2.0, wt.%) alloys have been designed and fabricated through BE (blended element) sintering to investigate the effect of Fe-addition on athermal ω-phase transformation, α-phase evolution and age hardening behavior. The results show that the formation of athermal ω-phase is fully suppressed in water-quenched specimens when Fe-addition is up to 2 wt.%. The relevant timescales of α formation during initial stages of aging indicate that incubation time increases with Fe-addition. Further aging results in continuous nucleation and growth of α-phase but finer intragranular α lamellae exhibit in Ti5553-2Fe alloy. In addition, the width and extent of grain boundary α-film increase slightly with incremental Fe-addition, especially in furnace cooling condition. Result of Vickers hardness manifests that Fe-addition leads to a strong hardening effect in both solution and aging treatment. The solid solution strengthening is quantitatively estimated by ab initio calculation based on the Labusch?Nabarro model. The evolution of α-precipitate is rationalized by Gibbs free energy. The prominent hardening effect of Ti5553?2Fe alloy is attributed to both large lattice misfit of β-matrix and fine α-precipitate distribution.