Relationship between Colored Microstructure under Polarized Light and Shape Recovery Characteristics on the Thermomechanical Cycled CuAlNi Single Crystals

The paper studied the relationship between microstructure and shape recovery characteristics by using colored microstructure analysis under polarized light on the thermomechanical cycled CuAlNi single crystals. The two-way shape memory effect in quenched thin bar resulted from the preferential formation/extinction of martensite variant due to the internal quench stress, and the variant was formed at an angle of about 45 deg. with the tension direction ([001] of the βphase). Initial thermomechanical cycling under relatively low stress single variant stress-induced martensite was formed at an angle of 45 deg. with the tension and its morphology was a lath of parallel twins. More than one group of variants were formed after several training cycles and such variants also caused tilting of some thermally formed accommodated martensite. By overheating the trained sample containing stabilized multi-variants of stress-induced martensite, very coarse martensite structure with a strong asymmetry was produced, which caused the reverse two-way shape memory effect.

Study on microstructures and properties of preheated flash butt welded SW400 steel joints

Under the spirit of sustainable development, ‘lightweight’ has been gradually included into the vehicle design criterion by many manufacturers and used in automobile production. Following this trend, domestic wheel suppliers also begin to study the technology of lightweight wheel. One way to achieve this goal is improving strength grade of the steel and optimizing the structure design in the field of steel wheels. But there are a few problems in flash butt welding process in the application of high strength steel, leading to high rejection rates. SW400 steel is a special high strength wheel steel developed by Benxi Steel. Taking SW400 steel as the research material, this article studys the feasibility of improving the properties of rim flash butt welded joints by adding preheating process.

Finite Element Simulation of Thermal Field in Double Wire Welding

In this paper, the thermal field of double wire welding is simulated by using ANSYS software. Simulation results were shown that the total heat input (E) is the most significant parameters to change the value of t8/5;By the mean of rationally controlling the proportion of the front arc heat input (E1) in the total heat input (E) and appropriately selecting double wire spacing (L), It is effective means to get the double wire welding thermal cycle. By the way of simulation, it is possible to manage the thermal input in the double welding wires and to control the temperature field and cooling rate that are fundamental for the final joint quality, it is great importance guidance to optimize the double wire welding process parameters.

Comparative Study on Two-Stage Absorption Refrigeration Systems with Different Working Pairs

The objective of this paper is to present a simulation study on the two-stage absorption refrigeration systems of 2.5 kW capacity using LiBr-H2O,NH3-H2O and R124-DMAC as working pairs.Under the design condition that the generating,absorbing,evaporating and condensing temperatures are 75℃,45℃,5℃and 40℃,respectively,the high and low pressure side solution circulation ratios and the coefficient of performance(COP)for the systems are calculated.Then the influences of medium,generating,absorbing,evaporating and condensing temperatures on system performances are analyzed.The results show that under the design condition,the COP of the LiBr-H2Osystem can reach 0.49,superior to those of the NH3-H2O and R124-DMAC systems,which are 0.32 and 0.31,respectively.Furthermore,the medium temperature for higher COP lies in an interval of 64-67℃for the LiBr-H2O.NH3-H2O and R124-DMAC systems.High generating temperature and low absorbing temperature can decrease the high and low pressure side solution circulation ratios,and can also increase the COP.High evaporating temperature can decrease the low pressure side solution circulation ratio and increase the COP.Low condensing temperature can decrease the high pressure side solution circulation ratio and increase the COP.