手术器械低温锻造常见缺陷原因分析

采用外观和金相方法,对止血钳和手术剪锻坯出现的型腔填充不满、裂纹、重皮和切边撕裂等缺陷进行分析。结果表明:锻坯缺陷是由钢材低温流动性差和锻坯未进行锻后高温回火处理引起,提高锻造温度,增加钢的流动性,可避免或减少型腔填充不满、开裂和重皮缺陷,锻后高温回火可避免切边撕裂,选用合适的模具材料降低锻造应力可提高模具寿命。

Al-Zn-Mg合金超低温高速大变形中超细晶组织演化行为的研究

利用透射电子显微镜研究了Al-Zn-Mg铝合金在低温(液氮)高速多向大变形条件下的显微组织演化,分析了合金在不同变形条件下的变形及组织形貌特征,讨论了低温及几何动态再结晶对显微组织演化过程的影响。结果表明:在超低温、高速、大形变量、约束变形条件下,7075铝合金能够不经过退火实现连续的大变形而不会失效,并且获得了均匀的超细晶组织,晶粒尺寸小于200nm;超细晶组织随着变形量增加而明显细化,相邻晶粒的取向差增大。

大型环件表面孔洞类缺陷性质及原因分析

某公司制造的大型环件,粗加工后表面发现孔洞类缺陷,对其进行解剖分析。结果表明,大型环件表面孔洞类缺陷系环件内部大量孔洞缺陷外漏所致,环件内部缺陷系低温冷锻造成。

Mechanical properties and microstructural evolution of ultrafine grained zircaloy-4 processed through multiaxial forging at cryogenic temperature

The mechanical properties and microstructural evolution of zircaloy-4 subjected to cumulative strains of 1.48,2.96,4.44 and 5.91 through multiaxial forging（MAF） at cryogenic temperature（77 K） were investigated.The mechanical properties of the MAF treated alloy were measured through universal tensile testing and Vickers hardness testing equipment.The zircaloy-4 deformed up to a cumulative strain of 5.91 showed improvement in both ultimate tensile strength and hardness from 474 MPa to 717 MPa and from HV 190 to HV 238,respectively,as compared with the as-received alloy.However,there was a noticeable decrement in ductility（from 18%to 3.5%） due to the low strain hardening ability of deformed zircaloy-4.The improvement in strength and hardness of the deformed alloy is attributed to the grain size effect and higher dislocation density generated during multiaxial forging.The microstructural evolutions of deformed samples were characterized by optical microscopy and transmission electron microscopy（TEM）.The evolved microstructure at a cumulative strain of 5.91 obtained after MAF up to 12 cycles depicted the formation of ultrafine grains with an average size of 150-250 nm.

超低温轧制大变形量加工3004铝合金机械性能的改善

对于改善铝合金的机械性能，晶粒细化是有效的方法之一。在本研究中，3004铝合金的晶粒通过可引入大量积蓄应变能的加工－热锻或超低温锻予以细化，利用以锻造为前工序加工的超低温轧制，压下率可达98％，最后在再结晶温度下于盐溶炉中进行退火，以实现快速再结晶。压下率达98％的试样的维氏硬度、抗拉强度和屈服应力分别达Hv160,450MPa和390MPa。研究发现，不考虑锻造条件，屈服应力和抗拉强度分别达初始试样的1．6倍和1．2倍，在缩短退火时间的情况下（即30s)，粒度达3－4μm，屈服应力提高到2．5倍。这种加工方法对提高铝合金机械性能是一种比较实用易行的方法。