【摘 要】
：
An experimental study together with numerical simulation was conducted to investigate the formation mecha-nisms and control methods for stray grains at melt-back of seed in this paper.The numerical simulation results showed that the convex solid/liquid (S
【机 构】
：
State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi’an,710072
论文部分内容阅读
An experimental study together with numerical simulation was conducted to investigate the formation mecha-nisms and control methods for stray grains at melt-back of seed in this paper.The numerical simulation results showed that the convex solid/liquid (S/L) interface changed very slowly into a concave interface during the initial solidification stage and the undercooling was slightly affected by the S/L curvature change.The formation of stray grains below melt-back interface at seed perimeter could be suppressed with the decrease of clearance between the seed and mold.However when the clearance was further decreased to 0,an orientation deviation layer formed originated from the deformation of un-melted seed caused by different expend coefficient between the seed and mold.The nucleation of stray grains above the melt-back interface at the seed perimeter could be suppressed using the mold with small surface roughness.The isolated un-melted dendrite stem at semi-solid mushy of the seed with the large original primary dendrite spacing transfer to complex network structure,suppressing the formation of the stray grains,when the primary dendrite spacing of seed decreased or the seed underwent so-lution heat treatment.Then,the formation mechanisms of the stray grains at the melt-back region are discussed based on above results,and a method is proposed to suppress the formation of the stray grains for preparing single crystal components by re-used seed.
其他文献
1 会议概况rn高校智库是中国特色新型智库建设体系中具有独特优势的主力军,在“双一流”建设背景下,高校智库建设正当其时.为加强中国特色新型智库核心能力建设,探索解决中国特色新型智库建设理论与实践发展中面临的新问题,2021年11月11日,由中国科学院文献情报中心主办,西南交通大学公共管理学院、《智库理论与实践》编辑部联合承办的第七届新型智库建设学术研讨会顺利举办.本次研讨会以“\'双一流\'建设与高校智库发展”为主题,来自全国的智库学者、智库工作者以及高校师生共500多人,围绕“智库的影响力与国际
[目的/意义]中南海法制讲座是我国最高领导集体重视法治、规划法治、厉行法治的生动范例,在依法治国历史实践中具有重要的地位和作用,然而,目前仍缺乏从智库层面上对其展开研究,阐释其具有的重大意义、地位和作用等.[方法/过程]本文通过历史分析方法,考察中南海法制讲座的演变,以制度理论的视角来解读该讲座的地位、性质、内容和主要功能.[结果/结论]概括地说,中南海法制讲座是一项推动我国法治发展的复合型优良制度,是一种普法宣传教育的形式,是一项领导干部学法制度,是中央政治局集体学习的一部分,是加强法治建设的重要机制,
As two important members of complex hydrides,Mg(BH4)2 and NaBH4 have a high gravimetric capacity (14.9 and 10.8 wt％,respectively).In this study,the Mg(BH4)2 was synthesized by the ion exchange method.Afterwards,the Mg(BH4)2 and NaBH4 composites with diffe
As a hydrogen storage material,palladium nanoparticle decorated nitrogen doped graphene (Pd/N-rGO) has drawn much attention owing to its high absorption capacity at moderate conditions.However,its hydrogen absorption-desorption cycle performance,which is
Anatase TiO2 nanotubes array (ATONA) has attracted tremendous attention owing to its promising applications in solar cells,water splitting and organic pollutants photocatalytic degradation.However,the activity of ATONAs was greatly suppressed by the grain
Biogenic hydroxyapatites from mammalian bones naturally contain traces of ions,like Mg,which play a vital role in the bone remodeling process.In this way,synthetic hydroxyapatites should include this kind of mineral.In this work,hydroxyapatite added with
The increasing demand for portable and flexible energy storage devices drives the development of flexible electrodes and electrolytes.The aim of this work is to fabricate the flexible free-standing polyaniline/poly (vinyl alcohol) (PANI/PVA) composite ele
To promote substantially the performances of red phosphorous (P) anode for lithium and sodium-ion batteries,a simple plasma assisted milling (P-milling) method was used to in-situ synthesize SeP2/C composite.The results showed that the amorphous SeP2/C co
The influence of alloying elements and heat treatment on the microstructure and mechanical behaviors of extruded Mg Gd Nd ternary alloys was investigated in this study.The grain sizes dramatically decreased after extrusion,and the particles which distribu
The manganese sulfide (MnS) has attracted more attention as anode material on energy storage and conversion field,owing to its high theoretical capacity (616 mA h g-1) and good electrochemical activity.However,low electronic conductivity and large volume