奥氏体不锈钢321合金不同应变速率下动态再结晶分析

以奥氏体不锈钢321合金为研究对象,通过EBSD和TEM等方法,分析在950～1250℃变形温度和0. 001～1 s~(-1)应变速率条件下的不连续动态再结晶(DDRX)行为。研究结果表明:当变形温度上升后,合金中更多晶粒发生了再结晶转变的过程,同时,再结晶晶粒的尺寸也显著增大;当应变速率上升后,再结晶晶粒的数量发生了降低的现象,并且其尺寸也明显减小。在温度较高而应变速率较小的情况下,晶粒将会在三叉晶界部位发生形核,此时晶界也很容易发生迁移的现象;而在较低温度以及应变速率很大的情况下,稠密位错墙也会对再结晶形核过程造成较大影响。当真应变逐渐增大后,小角晶界随之减少,同时形成了更多大角晶界与孪晶。与传统DDRX相比可以发现,此时的孪晶在初始变形阶段出现了降低的现象。     

基于塑性异化比值的金属板冲压加工性能研究

目的:研究塑性异化比值与金属板冲压加工性能之间的关系。方法:选取某金属板作为实验试样,分别在温度为350℃、400℃、430℃和450℃以及应变速率为10^-4/s、10^-3/s、10^-2/s的条件下,改变金属板试样的塑性异化比值,并计算试样冲压应变大小,比较塑性异化比值与冲压应变之间的关系。结果:当金属板塑性异化比值超出一定范围时,试样冲压应变为零,金属板出现断裂。结论:在对金属板生产加工过程中,应保证金属板的塑性异化比值控制在适当范围内,并采用爆炸焊接方法制备金属板,从而避免金属板断裂,保证金属板生产加工的质量。     

基于混合电极两步键合工艺的阳极键合研究

提出了一种基于新型混合电极的两步键合工艺。阳极键合工艺是在自行设计的多功能键合系统中完成,分析了不同电极配置对键合时间,键合强度以及键合界面的影响,并详细分析了键合界面和键合强度。借助于新型混合电极结构,能够在15-20min内实现无气泡晶圆级阳极键合,其键合强度高于10MPa。 以上结果表明,该种键合方法有非常好的应用价值,能应用于绝大多数晶圆级MEMS封装。     

板料辊弯成形数值模拟中回弹的影响因素

分析了诸因素对第一道次辊弯成形回弹的影响;利用Marc软件对其成形过程进行数值模拟,获得关于辊弯成形过程的各种信息,据此对轧辊设计及工艺方案的优化提供指导。     

沉积、退火条件以及刻蚀液对PECVD氮化硅薄膜湿法刻蚀速率的影响

The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition （PECVD） silicon nitride thin film is studied. The deposition source gas flow rate and annealing temperature were varied to decrease the etch rate of SiNx：H by HF solution. A low etch rate was achieved by increasing the SiH4 gas flow rate or annealing temperature, or decreasing the NH3 and N2 gas flow rate. Concentrated, buffered, and dilute hydrofluoric acid were utilized as etchants for Sit2 and SiNx：H. A high etching selectivity of Sit2 over SiNx：H was obtained using highly concentrated buffered HE     

板料辊弯成形数值模拟中纵向弯曲的影响因素

分析辊弯成形与普通弯曲成形的区别,研究诸因素对第一道次纵向弯曲的影响及机架间距对纵向弯曲的影响;利用Marc软件对其成形过程进行数值模拟,获得关于辊弯成形过程的各种信息,据此对轧辊设计及工艺方案的优化提供指导。     

均匀设计和遗传算法在板料成形数值模拟中的应用

介绍了均匀设计和遗传算法各自的特点,分析它们在板料成形数值模拟中的应用,并以方盒件成形为例,以凸模的运动速度凸模和压边圈与板料的摩擦系数凹模与板料的摩擦系数为决策变量,进行均匀实验设计,以成形后的最大减薄率为目标,优化成形工艺参数,提高成形质量,取得了令人满意的效果。     

表面修饰法制备大面积石墨烯

We develop a novel and convenient method to prepare large area single-layer and multi-layer graphene through surface modification with oxygen plasma.The obtained large area single-layer graphene is dozens of microns wide in the lateral dimension and characterized by optical microscopy,atomic force microscopy.Raman spectroscopy show multilayer graphene has less disorder density than single-layer graphene.X-ray photoelectron spectroscopy（XPS） analysis shows that hydroxyl groups are formed on the HOPG surface during oxygen plasma pre-treatment.Hydrogen bonds develop between hydroxyl groups on HOPG surface and silanol groups on hydroxylated SiO₂/Si substrate,which facilitate the transfer process.This study may provide a potential approach to develop graphene-based devices by using the large area lithographic printing process.     

板料成形数值模拟中回弹问题的处理

在分析了板料成形回弹特性的基础上,列出了回弹的影响因素,提出了回弹计算方法,最后运用自主开发的三维板料成形数值模拟软件SHEET3D对盒形件回弹进行了数值模拟。     

应力和电阻率可控的适用于高品质因子MEMS器件的原位掺硼LPCVD多晶硅薄膜

The simultaneous control of residual stress and resistivity of polysilicon thin films by adjusting the deposition parameters and annealing conditions is studied. In situ boron doped polysilicon thin films deposited at 520 ℃ by low pressure chemical vapor deposition （LPCVD） are amorphous with relatively large compressive residual stress and high resistivity. Annealing the amorphous films in a temperature range of 600-800 ℃ gives polysilicon films nearly zero-stress and relatively low resistivity. The low residual stress and low resistivity make the polysilicon films attractive for potential applications in micro-electro-mechanical-systems （MEMS） devices, especially in high resonance frequency （high-f） and high quality factor （high-Q） MEMS resonators. In addition, polysilicon thin films deposited at 570 ℃ and those without the post annealing process have low resistivities of 2-5 mΩ·cm. These reported approaches avoid the high temperature annealing process （〉 1000 ℃）, and the promising properties of these films make them suitable for high-Q and high-f MEMS devices.