Study On The Thermal Effect Of Cobalt/nickel-based Hastelloy

Solid-state refrigeration is a new type of refrigeration technology using the caloric effects(such as magnetocaloric,elastocaloric,electrocaloric and barocaloric)of solid phase change materials to achieve the purpose of cooling,its superiorities of eco-friendliness,energy-saving and high-efficiency make it a promising alternative to conventional vapor compression.Among all alternative non-vapor-compression technologies for refrigeration,elastocaloric refrigeration has caught more attentions for its lower driving force,wider temperature window and lower device cost.The elastocaloric effect of shape memory alloys is based on the absorption and release of latent heat during the uniaxial stress-induced martensitic transformation.In this text,we designed a new CoNiGa system and optimized the NiMnInCo existing system of elastocaloric effect based on the previous research results of Heusler alloys and their applications in the refrigeration areas.The Co-Ni-Ga-X(X = Fe,Mn)alloys and Ni45Co5Mn37-xCrxIn13(x = 0,1,2,3,5)series alloys were prepared by arc melting,induction melting,optical floating zone method and so on.XRD,SEM,Superconducting quantum interference device,Differential scanning calorimeter,universal testing machine,thermocouple and Infrared thermal imager were used to investigate the phase transformation as well as elastocaloric effect of these alloys.The main contents are as follows:Because of the intergranular fracture during the loading process,the Co50Ni20Ga30 polystalline did not exhibit significant elastocaloric effect.A giant elastocaloric effect was found in Co50Ni20Ga30 single crystal:At room temperature,a stress of less than 150 MPa could induce a full martensitic transformation of this single crystal.On the removal of the stress,a temperature change of 6? could be obtained.The critical stress increases linearly with temperature,a stress of 300 MPa could induce the complete phase transformation in the range of 10-70?,and the temperature change of more than 5? can be maintained while unloading the stress in this range.The sample showed good cyclic stability,no fatigue was observed during the 100 times of cyclic loading test.The doping of Fe and Mn showed no improvement on the elastocaloric effect of Co50Ni20Ga30 original component alloy.In the Ni45Co5Mn37-xCrxIn-3(x = 0,1,2,3,5)series polycrystalline alloys,the second phase is found to increase with the amount of Cr and the compressive strength of these alloys are greatly improved by the second phase from 150 MPa of x = 0 to 1.4 GPa of x = 5,but the second phase also reduces the elastocaloric effect at the same time,the alloys with x = 3,5 no longer have the elastocaloric effect.Among all of these series alloys,the alloy with x = 1 has the most excellent overall properties,a temperature change of more than 5? could be obtained at the moment of quick removal of 300 MPa stress in the range of 60-80?.The critical stress was lowered down during the 50 times of cyclic loading test and the temperature change fluctuated in a small range.