Effect Of Trace Clement Chromium On Microstructure And Mechanical Properties And Corrosion Resistance Of ZL101 Aluminum Alloy

With the continued advancement of environmental friendly,fuel efficient and exhaustion proof philosophy,ZL101 aluminum alloy has gained widespread awareness as a substantial lightweight material for industrial application.In recent years,the new requirements for the mechanical Properties and corrosion performance of ZL101 aluminum alloy parts have been raised by the rigorous operating conditions.It is generally,the comprehensive performance of ZL101 aluminum alloy can usually be improved by alloying and heat treatment.The application of Cr element in steel materials is comparatively widespread,and the hardness,wear resistance and corrosion durability of steel was improved by added appropriately amounts of Cr element.Nevertheless,the modification of Cr elements in aluminum alloys has been fewer studies.Based at this,this paper proposed to conduct of the effect of varied Cr element concentrations on ZL101aluminum alloy to provided experimental prototype and theoretical basis for the exploitation of new aluminum alloy.（1）The ZL101-XCr（X=0,0.1,0.2,0.3,0.5,0.8 Wt.%）aluminum alloy was prepared by a vacuum electromagnetic induction melting furnace.After the added microelement Cr in the alloy,the structures of ZL101 alloy were all refined and the subcooling degree has been increased.The increased in alloy supercooling causes narrowing of theα-Al dendrites and reduction of the eutectic region,while new Cr-rich compounds were formed in the eutectic region.With the increased Cr concentration,theα-Al averaged dimensions and subcooling showed the trend of decreased and subsequently increased,where the experimental alloy ZL101+3Cr showed the most refined effect and the finest room temperature mechanical properties for the alloy.（2）The heat treatment experimental findings suggested that after solid solution processing treated eutectic Si phase was obtained further to be refined and spheroidized,the eutectic area of the experimental alloy became narrowed,and the Al₁₃Cr₄Si₄andβ-Al₁₂（Cr,Fe）₃Si₂phases in the alloy were refined.After the aging treatment,the experimental alloy has precipitated the strengthened phase Mg₂Si in a coherent relationship with theα-Al,which had a positive effect on the enhanced mechanical properties of the alloy,and there exists a site-directed relationship between Mg₂Si and the substrate as[001]Mg₂Si//[001]Al.The optimized heat treatment regimen for the experimental alloy was535°C keep warm 6h solid solution and 160°C keep warm 26h aging,and were obtained the tensile strength and elongation of 310 MPa and 10.61%under this heat treatment Process.（3）Soak corrosion experiments（weight loss method）the results showed that:the experimental alloy to be corroded way mainly intergranular corrosion.The experimental alloy with added Cr elements all decreased the average corrosion rate,and the corrosion resistances of the experimental alloys all strengthened.With the increased Cr concentration,the average corrosion rate showed a tendency to increased first and then decreased.When the experimental alloy ZL101+3Cr,the average corrosion rate of the experimental alloy were the cheapest and the corrosion resistance was the highest.The corrosion resistance of the experimental alloy was increased after heat treatment.The sequences of the corrosion resistance of the experimental alloy in various states were as follows:T6>T5>cast state.（4）The electrochemical experimental resulted showed that:after the Cr element was added,the corrosion potential and impedance value of the experimental alloy were increased,and the average corrosion current density of the experimental alloy were reduced.ZL101+3Cr experimental alloy had the least corrosion current density of 1.31E-06 A cm^-2,which indicated that it had the best corrosion resistance.The results of the potential difference of the experimental alloy show that the highest potential difference exists between the newly formed Cr-rich phase and the matrix in the experimental alloy after the addition of the Cr element.The high-electric potential difference with the matrix between the Cr-rich phase and the matrix inhibits the galvanic coupling corrosion formed between the Fe-rich,eutectic Si phase and the matrix,resulting in improved corrosion resistance of the alloy.