To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are be...To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are being studied. The interface reactions between Al_(66)Fe_9Ti_(25)matrix and SiC reinforcement were investigated. It is determined that SiC is chemically incompatible with the Al_(66)Fe_9Ti_(25)matrix, Al_2O_3 barrier coating on SiC by sol-gel process was developed to minimize the interfacial reactions. On the other hand, a new type of Al_3Ti-based alloy having a L1_2 matrix with second phase precipitation has been developed. The quaternary alloys based on Al_(66)Fe_9Ti_(25)and modified with Nb additions, consist of a L1_2 matrix and D0_(22) second phase in the annealed state ,but the second phase can be dissolved by solution treatment and precipitated during high temperature aging.展开更多
In the present work,AZ91 alloy was successfully processed by equal channel angular pressing(ECAP)for up to 16 passes and rolling(R)for multiple passes with a total reduction of 75%in addition to a combination method w...In the present work,AZ91 alloy was successfully processed by equal channel angular pressing(ECAP)for up to 16 passes and rolling(R)for multiple passes with a total reduction of 75%in addition to a combination method with ECAP plus rolling(ECAP+R).The effects of various processes(ECAP,R and ECAP+R)on microstructure evolution were analyzed and the influence of ECAP process on the rolling performance was examined.The result shows that ECAP contributed to a homogenous grain structure and formed a texture with higher Schmidt factors that was easy for rolling.A plate with smoother surface and reduced edge cracks was observed in the ECAP+R process than in the single R process.Although the microstructure of the alloy was similar after ECAP+R and R process,the sample of ECAP+R was more refined and had stronger second phase precipitation than the sample of R,which resulted in better rolling characteristics,along with the external surfaces.展开更多
The phase diagram of superaustenitic stainless steel 654SMO was calculated by thermodynamic software and the precipitated phases in the specimens aged at 800-1100°C for 1hwere studied by methods of physicochemica...The phase diagram of superaustenitic stainless steel 654SMO was calculated by thermodynamic software and the precipitated phases in the specimens aged at 800-1100°C for 1hwere studied by methods of physicochemical phase analysis,scanning electron microscopy and transmission electron microscopy.The results showed that the size of precipitated particles increased with increasing the temperature.The amount of second phases reached the maximum value at 900°C,but decreased above 900°C.There were about eight kinds of precipitated phases in 654SMO includingσphase,Cr_2N,μphase,χphase,Laves phase,M_（23）C_6,M_6C and M_3C,in which theσphase and Cr_2N were the dominant precipitated phases.展开更多
文摘To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are being studied. The interface reactions between Al_(66)Fe_9Ti_(25)matrix and SiC reinforcement were investigated. It is determined that SiC is chemically incompatible with the Al_(66)Fe_9Ti_(25)matrix, Al_2O_3 barrier coating on SiC by sol-gel process was developed to minimize the interfacial reactions. On the other hand, a new type of Al_3Ti-based alloy having a L1_2 matrix with second phase precipitation has been developed. The quaternary alloys based on Al_(66)Fe_9Ti_(25)and modified with Nb additions, consist of a L1_2 matrix and D0_(22) second phase in the annealed state ,but the second phase can be dissolved by solution treatment and precipitated during high temperature aging.
基金This study was supported by the National Natural Science Foundation of China(51774109 and 51501039)the Key Research and Development Project of Jiangsu Province(BE2017148)+2 种基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province of China(KYLX16_0701)the Fundamental Research Funds for the Central Universities(HHU2016B45314&2018B48414)Q.X.is grateful for the support from the China Scholarship Council and the W.M.Keck Center for Advanced Microscopy and Micr1oanalysis at University of Delaware.
文摘In the present work,AZ91 alloy was successfully processed by equal channel angular pressing(ECAP)for up to 16 passes and rolling(R)for multiple passes with a total reduction of 75%in addition to a combination method with ECAP plus rolling(ECAP+R).The effects of various processes(ECAP,R and ECAP+R)on microstructure evolution were analyzed and the influence of ECAP process on the rolling performance was examined.The result shows that ECAP contributed to a homogenous grain structure and formed a texture with higher Schmidt factors that was easy for rolling.A plate with smoother surface and reduced edge cracks was observed in the ECAP+R process than in the single R process.Although the microstructure of the alloy was similar after ECAP+R and R process,the sample of ECAP+R was more refined and had stronger second phase precipitation than the sample of R,which resulted in better rolling characteristics,along with the external surfaces.
文摘The phase diagram of superaustenitic stainless steel 654SMO was calculated by thermodynamic software and the precipitated phases in the specimens aged at 800-1100°C for 1hwere studied by methods of physicochemical phase analysis,scanning electron microscopy and transmission electron microscopy.The results showed that the size of precipitated particles increased with increasing the temperature.The amount of second phases reached the maximum value at 900°C,but decreased above 900°C.There were about eight kinds of precipitated phases in 654SMO includingσphase,Cr_2N,μphase,χphase,Laves phase,M_（23）C_6,M_6C and M_3C,in which theσphase and Cr_2N were the dominant precipitated phases.
