Influence of Magnetic Heat Treatment and Compressive Stress on Jump Effect of Magnetostriction of Tb_(0.3)Dy_(0.7)Fe_(1.95) Alloy

The 〈 110 〉 -oriented TTb0.3Dy0.7Fe1.95 polycrystalline alloy was magnetically annealed, and its influence on jump effect of magnetostriction was investigated. In the vacuum superconductive high magnetic field equipment, 〈 110 〉 -oriented Tb0.3Dy0.7Fe1.95 polycrystalline alloy of the directional solidification was annealed at 623 and 723 K for 5 min under the magnetic field vertical to specimen axis. It is found that magnetic annealing can enhance the jump effect under compressive stress, and increase the saturated magnetostriction coefficient λs, the λs of the magnetic annealing specimens at 623 K under 8.1 MPa is attained to 1950 × 10^-6, Magnetic annealing increases the maximum of dynamic magnetostriction coefficient, d33^max, as well as the magnetic field for d33^max under 8.1 MPa.

EFFECT OF TEMPERING IN PULSE MAGNETIC FIELD ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HIGH SPEED STEEL

Using a self-made pulse magnetic field heat treatment equipment with low or medium intensi- ty,the tempering process of high speed steel W6Mo5Cr4V2 was investigated.It was found that the secondary hardening process and the transformation of retained austenite for the steel were accelerated by the pulse magnetic field,and the tempering period could be reduced to half of the original.It was shown by the analyses of X-ray and eletron microscopy that the precipitation of carbides becomes more homogeneous and dispersive,and the tetragonality of martensite increases obviousely,which causes the improvement of hardness and red-hardness for the steel.It was confirmed that the service life of tools as centre bits,screw taps and punches for nuts could be increased by 0.4 to 1.4 times by the tempering in magnetic field.

Enhanced magnetic properties of Ce_(17)Fe_(76.5)Co_1Zr_(0.5)B_6 alloys by magnetic field heat treatment

In the present work,Ce_(17)Fe_(76.5)Co_1Zr_(0.5)B_6 ribbons were prepared by a direct melt spinning method.The effects of chamber pressure and magnetic field annealing temperature on the magnetic properties and microstructures of the alloys were investigated.The grain size and content of Ce_(2)Fe_(14)B phase can be changed by adjusting the chamber pressure,and the optimal magnetic performance is obtained at0.04 MPa.The magnetic properties can be influenced under magnetic field heat treatment.When the annealing temperature is lower than the Curie temperature,the refinement and a uniform distribution of the grains is obtained.The irreversible magnetic susceptibility curve reveals that magnetic field heat treatment enhances the exchange coupling interaction between grains of the Ce_(2)Fe_(14)B phase.When the magnetic field annealing temperature is 438 K,the alloy displays the optimal magnetic properties.Compared with the as-spun sample,the values of intrinsic coercivity(H_(ci)),remanence(B_r) and maximum energy product((BH)max) increase by 3.4%,9.8% and 18.7%,respectively.This work provides an effective approach by which to enhance the magnetic properties of Ce-Fe-B alloys.

Microstructure improvement related coercivity enhancement for sintered NdFeB magnets after optimized additional heat treatment

The micro structure, especially the Nd-rich phase and the grain boundary, in sintered NdFeB magnets plays an important role in magnetic reversal and coercivity mechanism. To better understand the effects of the microstructure on the coercivity, we investigated the microstructure and properties improvements of a commercial sintered NdFeB magnet after optimized additional heat treatment. The coercivity is enhanced from 1399 to 1560 kA/m. This enhancement has been explained in terms of the evolution of the grain boundary structure, and the formation of continuous thin layers of Nd-rich phase is important for high coercivity. The micromagnetic simulation together with the numerical analysis based on the nucleation model suggest that the reversed magnetic domains nucleate mainly at the interface of multijunctions of Nd_2 Fe_（14）B grains with high stray fields during the demagnetization process. Both improved anisotropy fields at grain boundaries and reduced stray fields at multi-junction Nd-rich phases contribute to the coercivity enhancement. This work has importance in understanding the crucial micro structure parameters and enhancing the obtainable properties for sintered NdFeB magnets.

Research of the Interface Microstructure and Thermal Treatment of Cold-Rolled Cu-Al Composite Strip Under Magnetic Field

The thermal treatment process of cold-rolled Cu-Al composite strip under magnetic field conditions is systematically investigated by means of metallographic microscope and universal testing machine to observe the interface microstructure and test the mechanical properties.The heat treatment parameters' effects to the interface structure and mechanical properties of Al-Cu cold-rolled strip are discussed.The conclusions is showed as follows:(1)when the magnetic field intensity is greater than 0.1 T,the interface layer grow widely and stimulate the interfacial compounds' generation,the shear strength is reduced.(2)When the Cu-Al specimen's annealing temperature is at the condition of 300℃,the interfacial layer narrows when the magnetic field strength stay 0.1T than that without magnetic field,the magnetic filed restrains the interfacial compounds' generation,the shear strength reaches as high as 124Mpa;(3)The interfacial compounds are meanly brittleness intermetallic compounds such as CuAl,CuAl_2,Cu_9Al.