| Shape memory alloy is a new functional material. It is used widely in aeronautic and spaceflight industry, petroleum and chemical industry, mechanical industry, apparatus and instrument, and automobile industry. Iron-matrix shape memory alloy have important study value and application perspeetive due to its high strength and plasticity, easy-machinability and cheap cost. The pipeline joint is one of its applications,. The pipeline joint high trustworthy and easy to install, especially in the case of complex emergency. In this thesis, the structure and the properties of FeMnSiCrNi shape memory alloys are investigated, the manufacturing technique of the alloy is also investigated. The effect of the alloying elements (Mn, Cr, Ni and Si) on the stacking fault energy of the alloy is considered. The results show that the Mn, Cr and Ni increase the SFE of iron-matrix shape memory alloys, while the effect of Si on SFE of the alloy is opposite. Increasing respectively 1% content of Mn, Cr, Ni and Si, the effective ratio of the SFE of the alloy is Cr:Ni:Mn:Si=-1.1:1.64:0.21:-4.45. In order to get the iron-base shape memory alloys with good shape memory effect, the alloys should have lower stacking fault energy. The contents of chromium, nickel and manganese should be properly reduced and the contents of silicon should be appropriately increased. The present study results can be applied to the composition design of the iron-base shape memory alloys. The composition design of FeMnSiCrNi shape memory alloys is investigated. The composition of the alloys is expressed as: NiEQ = -25/32 × Cr EQ + 27 ± 0.5 (Cr E Q <19) NiEQ = 0.96 × Cr EQ -4.28 ± 0.5 (Cr E Q >19) Where %Nieq is Ni equivalent and Creq is Cr equivalent. Fe14Mn6Si9Cr5Ni alloy possess the best shape memory effect (SME) among all iron-based shape memory alloys. The SME of the alloy decreases with increasing the prestrain, the SME of the alloys greatly increases after training, especially, first training. The SME of the alloys in vertical to the rolling direction is higher than that in parallel to the rolling direction. The SME decreases with increasing the thickness of the sample. The SME of the alloy by bending is higher than that by tensioning, especially, the SME of the alloy is evidently improved after training. The absolute recovery strain of the alloy is 6.3% when prestrain is 9%. The alloy has good SME when annealing at 400℃.But further increasing the annealed temperature has no effect on the SME of the alloys. The amount of the stress-induced martensite in the structure of FeMnSiCrNi shape memory alloy increases with increasing the prestrain. The amount of the stress-induced martensite which is intensively crossed, widened, and penetrates the crystalline grains, increases at the same time. Twin crystalline presents too. During the annealed process, the stress-induced ε martensite can not completely transform. The ε (hcp) →γ (fcc) transformation firstly occurs on the body of the fine and single direction ε martensite, by which mainly realizes the SME of the shape memory alloy. The twin crystalline and stress-induced ε martensite, which is intensively crossed, widened and penetrates the crystalline grains, are difficult to transform in FeMnSiCrNi shape memory alloy during the annealed process, in hence, which doesn't contribute to the SME of the shape memory alloy. Training can cause to increase the transformation amount of the stress-induced martensite in the annealed process, and consequently improves the SME of the shape memory alloy. DSC measurements demonstrate that the ε (hcp) →γ (fcc) transformation, which doesn't finish at the temperature of 1000K, occuys in three temperature ranges. In fact, only the ε (hcp) →γ (fcc) transformation at the lower temperature contributes to the SME of the shape memory alloy. with increasing the prestrain, the beginning transformation temperature. (As) decreases, which shows that the SME of the shape memory alloy can be created at the lower temperature with increasing the prestrain and decreasing the beginning temperature from stress-induced ε martensite to autenite. The results of creep and the stress relaxation experiments at ambient temperature for the alloy show that the creep rate decreases to zero (τ >2600 h) with τ increases. The largest amount of creep is 0.2%, which is 3% of the largest εa of the alloy. The rate of stress relaxation gradually becomes small as τ increases. When τ =900 h, the stress almost remains constant. The largest creep rate is a little larger than the largest rate ofthe stress relaxation. However, the rate of stress relaxation decreases to zero in only half the time of creep rate. The good creep and stress relaxation charateristies of the alloy show a good prospect for the application of couplings. The pipeline joint is reamed by special reaming mold. The recovery strain in the direction of the radius is favorable to jointing pipe, and homogeneous deformation assures sealing the pipe without deforming in the direction of axis. The technological process of reaming the pipe joint is as the following: firstly prestrain and ream the pipe joint; and then anneal, (which is regarded as the training process); then prestrain and ream the pipe joint again; . then get rid of the uneven part of pipe joint; . then install the pipe joint on the pipes. Finally heat them to anneal. The relative strain recovery ratio (fsme)couid be about 60%,and absdute strain recovery ratio(εa) is above 3%. The sealing test shows that pipe joint don't leak under the pressure of 5PMa within the 10 minutes. The force to withdraw a connected pipe is 1.24t. The parameters above can meet usual requirements for the pipe joining in general industrial application. Now the 100 meters long oil pipeline with the pipe joints has been normally used for over one year.
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