Experimental investigations of machining characteristics and removal mechanisms of advanced ceramics in high speed deep grinding

Machining characteristics and surface integrity of advanced ceramics, including alumina, alumina–titania, and yttria partially stabilized tetragonal zirconia, were studied under high speed deep grinding conditions. Material removal mechanisms involved in the grinding processes were explored. The material removal in the grinding of alumina and alumina–titania was dominated by grain dislodgement or lateral cracking along grain boundaries. The removal for zirconia was via both local micro fracture and ductile cutting. It was found that under a feed rate of 500 mm/min and for all the wheel speeds used, an increase in the wheel depth of cut (DOC) from 0.1–2 mm slightly improved the ground surface finish, but greatly prolonged the wheel life. This increase did not deepen the subsurface damage layer for the alumina and alumina–titania, but resulted in a slightly deeper damage layer for the zirconia.     

叔胺萃取分离精炼铂的新工艺

用三烷基胺（Ｎ２３５）萃取分离铂，考察了稀释剂、改质剂浓度、料液酸度对分配系数的影响，从复杂的工业料液中，用Ｎ２３５萃取、洗涤、反萃、再生及精炼铂的工艺技术。     

时效对接触线用Cu-Ag-Cr合金性能的影响

分析了固溶温度、时效及时效前冷变形量对Cu - 0 1 %Ag - 0 1 %Cr接触线用合金性能的影响 ,结果表明 :经 870℃固溶、 40 %～ 5 0 %冷变形及 480℃× 1 5h时效处理后 ,合金可获得良好的综合性能。     

管理史对MBA的边际效用

近年来 ,我国MBA的社会评价不高 ,其根本原因是MBA毕业生不能满足市场要求。本文通过分析管理史的功能 ,得出学习管理史对MBA的边际效用大 ,MBA培养方案中有必要增设管理史类的课程。     

Microstructural Investigation of Protective and Non-Protective Oxides on 11% Chromium Steel

FIB, SEM and STEM/EDX were used to investigate X20 stainless-steel samples exposed to dry O₂, or O₂ containing 40% H₂O, with a flow velocity of 0.5 cm/s or 5 cm/s, for 168 hr or 336 hr at 600°C. Thin protective Cr-rich (Cr,Fe)₂O₃ was maintained on the samples exposed to dry O₂, even after 336 hr, and on the sample exposed to O₂/H₂O mixture with the low-flow velocity (0.5 cm/s) for 168 hr. The oxide scale formed in the latter environment contained less Cr, due to Cr loss through CrO₂(OH)₂ evaporation. Breakaway oxidation occurred on the samples exposed in high-gas-flow velocity for shorter time (168 hr) or in low-gas-flow velocity (0.5 cm/s) for longer time (336 hr). The breakaway scales featured a two-layered structure: an outward-growing oxide “island” consisting of almost pure hematite (α-Fe₂O₃), and an inward-growing oxide “crater” consisting of (Cr,Fe)₃O₄. The transition from a thin protective (Cr,Fe)₂O₃ scale to a non-protective thick scale on this martensitic/ferritic steel originated locally and was followed by rapid oxide growth, resulting in a thick scale that covered the whole sample surface.     

Ag-Cu-In-Sn合金的结构特性

借助金相、X光衍射及SEM方法研究Ag-Cu-In-Sn合金的结构特性及合金各组元在合金相中的分布规律,还讨论了某些相结构对合金力学性能的影响。四元合金的化学成分是(wt％)57～63Ag,17～23Cu,(20—x)In,xSn,其中:Ag+Cu=80wt％,In+Sn=20wt％,2≤x≤16。     

中厚板在线30通道超声波探伤方法及应用

介绍了柳钢公司在生产锅炉板、压力容器板过程中，曾试用了６种探伤方法；而研制的３０通道在线超声波探伤法不仅可满足国家标准要求，而且能适应生产节奏，并具有快速、准确、简便的特点。     

Sr对高铁Al-Si合金组织和性能的影响

研究了Sr元素（加入量分别为0．03％、0．06％、0．09％、0．12％和0．18％）对含Fe量为1．2％的ZL102合金的组织和性能的影响。研究发现，随着Sr元素的加入，合金中粗大的针状Fe相开始出现断裂分叉现象，同时针状Fe相的长度也随Sr元素加入量的增加而减小，但Sr对Fe相的针状形貌没有明显改变。随着Sr元素加入量逐渐增加，合金的抗拉强度和伸长率均呈现出先增后减的变化趋势。当Sr元素加入量达到0．12％时，合金材料的综合力学性能最佳。