A Study On The Hot Compressive Deformation Behaviors And Texture Analysises Of Mg₂B₂O₅w/AZ31Composite

In this paper, the stress-strain behaviors of Mg₂B₂O₅w/AZ31composite materials（whisker content of5vol%） prepared by the vacuum-gas pressure equipment werecompressed in the Gleeble3500thermal simulation instrument under the deformationtemperature250℃,300℃,350℃,400℃and the strain rate0.001s^-1,0.01s^-1,0.1s^-1,1s^-1respectively with a strain of40%were studied. The composite materials processingcharts were calculated based on the irreversible thermodynamics principle and theDynamic Material Modeling. The chart is tested to be efficient. The best compositeplastic deformation parameters were determined accurately based on the processing maptheory and observation of microstructure. The texture of the cross-sections of thecompressed samples, which perpendicular to the compression axis, was tested by D2700.The diffraction crystal face diffraction data was calculated and three-dimensionalorientation distribution function （ODF） of the texture got. Then, the main texture polefigure （PF） was calculated based on ODF. The change pattern of the deformationparameters was analyzed.Through the study of the rheological behavior of high temperature compression ofMg₂B₂O₅w/AZ31composite materials, the effect of deformation by strain rate andtemperature is significant in a given amount of deformation within the magnesiummatrix composites hot compressive deformation behavior of strain rate. Work hardening,dynamic recovery and dynamic recrystallization appeared. In certain strain rates, thepeak stress of the composites decreases with increasing deformation temperatures whilein certain temperature the strain rate on the peak stress of the composite increases withincreasing strain rates. Material at temperature250⁴00℃, within strain rates0.001¹s^-1deformation, the steady-state flowing stress accords with the hyperbolic sine model, and n of the material parameters are0.00981and5.16716, the averagedeformation activation energy Q is145.1867（KJ/mol）.Combined with the drawing power dissipation efficiency diagram and flowingstress instability diagram, the optimal thermal processing parameters for the compositedeformation of30%was determined. Optimal thermal processing parameters are thedeformation temperature of360⁴00℃and strain rate of0.001⁰.01s^-1, thedissipation efficiency η value in about45%. In this area, composite materials canachieve to maximum plastic deformation. When the strain rate is greater than0.01s^-1,the composite materials are in the rheological instability region in the entire temperaturerange.The validity of the processing maps of the composite materials was manifested bythe observation of microstructures in different conditions of deformation parameters andtesting of Rockwell hardness. The small grains and uniform microstructure wereobtained in the optimal thermal processing regions. Many clear cracks appeared in therheological instability region. Through the test of the Rockwell hardness of thecompression samples, the results shows that in certain strain rate, as the temperaturerises, the Rockwell hardness gradually become smaller. When the deformationtemperature is certain, as the strain rate increased, the Rockwell hardness also graduallybecome smaller. This is the same with the calculated.The texture of the material was tested by X-ray diffraction and the texture have beenanalyzed and calculated by software labotex3.0. It shows that texture compressiondeformation affects material strength, and deformation temperature also affects thestrength of the texture, the anisotropy of the deformation temperature increases, themagnesium based composites reinforced. In the deformation process,{0002}<1120>basic surface texture is always the main organization of the material structure withstrength increased from10.3to12.7. When the deformation temperature rises, materialnon-basal plane slip system starts.{1012}<100> pyramid surface texture strengthincreases, the intensity increased from2.5to3.5.