Such As Channel Hot Extrusion Deformation Of The Preparation Of Austenitic Stainless Steel Nano-scale Organizations

It has been showed that ECAP (Equal channal angular pressing) can observably decreased the grian size to sub-micronmeter even nanometer scale.In this paper ,a widely used 00Crl9Nil0 Austenite stainless steel has been pressed at different temperature(from 500℃ -1000℃ by one pass )and at 700℃ by 8 passes using own designed ECAP die .The average size from 150nm to 350nm grains were triumphantly gained by 8 passes.The microstructure evolution was observed and analyzed by means of microscope ,SEM ,TEM and X ray .The mechanisms of the grains how to fined and how to increase materials mechanical properties was also been studied.The ECAPed materials was processed by different heat treatment ,the heat stability was studied.The following summaries were obtained based on the experimental result:1.With the pressing temperature increased ,the main deforamtion ways changed from twins bands to slipping bands step by step;The result of the tensile test showed that the mechanical properties of the ECAPed materials was obviously improved.It was found that the ECAP process was not a uniform deforamtion, The deformation extent at the center of the materials was maximal;The high angular equiaxed grains of Austenite stainless steel were obtained by muti-passes pressed,and the statistical grain size obey the rule of normal school. The yield strength of the ECAPed materials was improved almost two times than the original one and the ultimate tensile strength was also improve nearly one time and the elongation percentage was about 30%,contraction percentage of area wasn't changed very much only decreased a little.2. It was founded that the grain refinement mechanisms can be concluded the three ways as the below:(1).The dislocation movement mechanisms: dislocation movement â†'slipâ†'slipping bandsâ†'dislocation wallsâ†'dislocation cellsâ†' subgrainâ†'high angular equiaxed grains.(2).The twins deformation mechanisms:The original twins were brokened into small pieces with ECAP processing and at the same time the deformation twins occurrenced.The original twins and deformation twins interact each other can directly formed high angular equiaxed grains at broken areas.(3).The dynamic recrystallization mechanisms:The dynamic recrystallization was occured at these areas(the original twins and deformation twins brokened areas,high density dislocation areas).It was founed that the dynamic recrystallization also can directly formed high angular equiaxed grains.The relationship among the three mechanisms were interactional,they together participated in the process of the grains refinement.But results of investigation showed that the twins deformation mechanism was the main mode when the deformation temperature was low and ECAPed passes were few.If the deformation temperature was higher 800°C or under multi-pass deformation,the main mode would be the dislocation and dynamic recrystallization mechanisms.3.It was founed that the ECAP process with fit heat treatment can reduce the Austenite stainless steel grain size from about 120fim to around 10/um,so the materals can be used at ultrafine grained steels and the grain size was not obviously increased with the annealling time prolonged,so it can be oncluded that the ECAPed materials have a good heat stability.