塑料螺栓的注塑模具設(shè)計(jì)

塑料螺栓的注塑模具設(shè)計(jì),塑料螺栓的注塑模具設(shè)計(jì),塑料,螺栓,注塑,模具設(shè)計(jì) Investigations on Ti6Al4V with gadolinium addition fabricated by metal injection moulding M. Holm a, , T. Ebel a , M. Dahms a,b a Magnesium Innovation Centre, Helmholtz-Zentrum Geesthacht, Max-Planck-Strae 1, 21502 Geesthacht, Germany b Flensburg University of Applied Sciences, Faculty of Engineering, Kanzleistrae 91-93, 24943 Flensburg, Germany article info Article history: Received 9 January 2013 Accepted 3 May 2013 Available online 14 May 2013 Keywords: Titanium alloy Gadolinium Powder metallurgy Sintering abstract Thisstudypresents theresultsofinvestigations onTi6Al4Valloyedwith15wt.%gadolinium.TheTi 6Al4V+Gd samples are fabricated by metal injection moulding (MIM) using Ti6Al4V and elemental gadolinium powder. In previous investigations, it is shown that TiB precipitates in Ti6Al4V fabricated by MIM result in a microstructurerenement,whiletheremovalofoxygenimprovestheductility.Thus,rareearthelements could possibly combine both effects in one, by reacting with oxygen from the titanium matrix and by forming small oxides leading to grain renement. Because thereareactuallynoinvestigations concerningTi6Al4V alloyed withgadolinium,thisstudy mainly gives a rst overview to show how the microstructure and mechanical features of Ti6Al4V change. In order to provide this overview, this study shows that it is possible to prepare a reasonable homoge- neous powder metallurgical Ti6Al4V alloy with Gd additions by using the MIM-technique. Adding Gd to Ti6Al4V alloy powder and processing the blend by MIM leads to signicant grain renement and a slight change in pore size and shape. However, strength and ductility are reduced by the addition of Gd. 2013 Elsevier Ltd. All rights reserved. 1. Introduction Rare earthelementscan be found ina steadily expandingnum- ber of applications in modern materials, enhancing their perfor- mance or even being the basis for their functionality. Often they areusedonlyinsmallquantitiesasalloyadditions,buteffectasig- nicantchangeinthematerialsproperties.Examplesaretheusage incarexhaustcatalysts1,specialsteels2,nickelmetalhydride accumulators 3 and high-performance permanent magnets 4. Rare earth elements are also found in compounds in luminescent materials, special glasses and hard-drives. Furthermore, rare earth elements can be used to remove impurities like nitrogen, oxygen, sulphur, hydrogen and other elements from molten metal. Addi- tionally, they can change the morphology of the sulphide and graphite in steel and cast iron. If rare earth elements are added to stainless steel, they can increase the machinability. In alumin- ium and magnesium alloys, they improve strength and ductility 5. Powder metallurgy methods and especially metal injection moulding (MIM) offer a cost-effective approach to fabricate titanium alloys for a wide range of applications 6. Today, it is possible to process Ti6Al4V powders by MIM to components with tensile properties in the range of wrought material 7. How- ever,inordertofurtherimprovethemechanicalproperties,e.g.the fatigue properties, of Ti6Al4V fabricated by MIM, two main problems have to be solved: grain coarsening and contamination by oxygen, nitrogen and carbon during the sintering process. In 8 it is shown that TiB precipitates in Ti6Al4V fabricated byMIMresultinamicrostructurerenement,while9showsthat removal of oxygen improves the ductility. Thus, rare earth elements could possibly combine both effects in one, by reacting with oxygen from the titanium matrix and by formingsmalloxidesleadingtograinrenement.Earlierinvestiga- tions on titanium alloys with gadolinium addition 1012 exhibit renedgrainsthatimprovethestrengthofthe alloys,anditisalso well known that gadolinium is an oxygen getter 10,12. Thus, in this study gadolinium was chosen as a possible addition to Ti6Al4V. Because there are actually no investigations about Ti6Al4V alloyed with gadolinium, this study mainly gives a rst overview to show how the microstructure of Ti6Al4V changes. 2. Experimental procedure For the specimen preparation spherical, gas-atomised Ti6Al 4VGrade5powderwithadiameterlessthan45lmsuppliedfrom TLSTechnik,Germany,wasused.TheGdpowderwasmadefroma 0261-3069/$ - see front matter 2013 Elsevier Ltd. All rights reserved. http:/dx.doi.org/10.1016/j.matdes.2013.05.003 Corresponding author. Tel.: +49 4152 87 1941. E-mail address: Martin_Holmgmx.de (M. Holm). Materials and Design 51 (2013) 943948 Contents lists available at SciVerse ScienceDirect Materials and Design journalhomepage: