1、AECMA STANDARD NORME AECMA AECMA NORM prEN 31 14-1 Edition P 1 July 1997 PUBLISHED BY THE EUROPEAN ASSOCIATION OF AEROSPACE INDUSTRIES (AECMA) Gulledelle 94 - 6-1 200 BRUXELLES - Tel. (+32) 2 775 81 10 - Fax. (+32) 2 775 81 11 ICs : Descriptors : ENGLISH VERSION Aerospace series Test method Microstr
2、ucture of (a + ) titanium alloy wrought products Part 1 : General requirements Srie arospatiale Mthode dessai Microstructure des produits corroys en alliage de titane (a + ) Partie 1 : Exigences gnrales Luft- und Raumfahrt Prfverfahren Mikrostruktur von geschmiedeten Erzeugnissen aus Titaniegierung
3、(a + ) Teil 1 : Allgemeine Anforderungen This “Aerospace Series“ Prestandard has been drawn up under the responsibility of AECMA (The European Association of Aerospace Industries). It is published on green paper for the needs of AECMA-Members. It has been technically approved by the experts of the c
4、oncerned Technical Committee following comment by the Member countries. Subsequent to the publication of this Prestandard, the technical contentshall not be changed to an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. After examinat
5、ion and signature of the AECMA Standard Checking Centre (NPSI and formal agreement of the Official Services of the Member countries it will be submitted as a draft European Standard to CEN (European Committee for Standardization) for formal vote. NOTE : images of higher quality for the prints in thi
6、s standard are available from BNAE. Nota - Extra copies can be supplied by B.N.A.E. - Technopolis 54 - 199, rue Jean-Jacques Rousseau - 921 38 ICCY-LEC-MOULINEAUX CEDEX I Comments should be sent within six months 1- after the date of publication to - Edition approved for publication 1997-07-31 AECMA
7、 Gulledelle 94 C5 Chairman Mr Odorico I 6-1 200 BRUXELLES I aecma 1997 - STD-AECMA PREN 3134-3-ENGL 1777 3032333 0033087 512 Page 2 prEN 31 14-1 : 1997 Contents list Page O Introduction 3 3 1 2 Normative references 3 3 3 4 Preparation of the microsections 3 5 Assessment 5 6 Description of microstruc
8、tures 5 STD-AECMA PREN 333q-L-ENGL 3997 R 303i2333 0033088 459 Page 3 prEN 31 14-1 : 1997 O Introduction This standard is part of the series of EN metallic material standards for aerospace applications. The general organization of this series is described in EN 4258. 1 Scope This standard specifies
9、the conditions for micrographic examination of (a + ) titanium alloy wrought products and description of terms used. Specific microstructures applicable to each type of product are defined in EN 31 14-2 to EN 31 14-4. This standard shall be applied in conjunction with EN material standards, which de
10、fine the acceptance criteria unless otherwise specified on the order. It is applicable to : - bars, sections, forging stock and forgings (EN 31 14-2) ; - plate (EN 31 14-3) ; - sheet for superplastic forming (EN 31 14-4). 2 Normative references This European Standard incorporates by dated or undated
11、 reference provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when inco
12、rporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN 31 14-2 Aerospace series - Microstructure of (a + ) titanium alloy wrought products - Part 2 : Microstructure of bars, sections, forging stock and forgings 1) Aerospace serie
13、s - Microstructure of (a + ) titanium alloy wrought products - Part 3 : Microstructure of plate 1) Aerospace series - Microstructure of (a + ) titanium alloy wrought products - Part 4 : Microstructure of sheet for super-plastic forming 1) Aerospace series - Metallic materials - General organization
14、of standardization - Links between types of EN standards and their use 1) EN 31 14-3 EN 31 14-4 EN 4258 3 Sampling The sampling and its frequency shall be as defined in the relevant technical specification and/or order. The sampling sections shall be at least 10 mm, in thickness or length. Samples s
15、hall preferably be taken by sawing. Cold work hardened zones shall be avoided or removed. If the sampling material is taken by abrasive cut off or flame cutting, the resulting heat affected zone shall be completely removed in the course of sample preparation. 4 Preparation of the microsections The s
16、urface of the sample sections to be examined shall be prepared by machining and grinding and polishing to ensure that the microstructure is clearly defined after etching. In the case of electrolytic polishing, grinding may be omitted. The method of preparation shall not change, contaminate or deform
17、 the surface microstructure. 1) Published as AECMA Prestandard at the date of publication of this standard STD-AECMA PREN 33L4-L-ENGL 1777 = 1012311 0033089 395 W Page 4 prEN 31 14-1 : 1997 Reagent Nitric acid (65 %) Water up to Nitric acid (65 %) Water up to Benzalkonium chloride Methyl alcohol Gly
18、cerol Water up to Nitric acid (65 %) Glycerol up to 6 Potassium hydroxide 1 Hydrofluoric acid (40 %) 2 Hydrofluoric acid (40 %) 3 Hydrofluoric acid (40 %) 4 Hydrofluoric acid (40 %) 5 Hydrofluoric acid (40 %) Hydrogen peroxide (30 %) Water up to 7 Hydrofluoric acid (40 %) Nitric acid (65 %) Lactic a
19、cid 8 Hydrochloric acid (40 %) Nitric acid (65 %) Lactic acid Nitric acid (65 %) Water up to 10 Nitric acid (65 %) Water up to 11 Hydrofluoric acid (40 %) Nitric acid (65 %) Hydrogen peroxide (30 %) Water up to 9 Hydrofluoric acid (40 %) 4.1 Grinding Resin bonded alumina, zirconia or silicon carbide
20、 paper shall be used for grinding. The pressure shall be as low as possible in order to avoid any cold work hardening of the surface of the microsection. Table 1 : Etching of titanium alloys Vol. % Remarks Use 8 Swab or immerse Micro etch 40 Macro etch (Etching time 2 Swab or immerse Bright grain bo
21、undary etch 1 O0 up to several minutes) 10 1 O0 2-6 Swab Stain etch 19 Avoid overetching Stain a or depending on 35 Avoid water in etch solution the heat treatment condition 40 0,5 Swab or immerse Stain etch 1 O0 2-20 Swab Bright etch 5-25 Glycerol acts as inhibitor Slower etch than 1 1 O0 10 Immers
22、e (70-80) OC Grain boundaries, subgrain 15 boundaries. Stains a and 1 O0 transformed , retained not stained. Orientation sensitive, develops contrast between grains. 20 Swab rigorously Chemical polish and etch 20 60 10 Swab General etch 25 65 10 Swab or immersion + Etch for segregation 15 1 min in a
23、mmonium 25 Swab or immersion Removal of copper surface 1 Spray wash Removal of tin surface layer 2 50 1 O0 1 O0 bifluoride 20 g/l 1 O0 layer 4.2 Polishing Polishing may be accomplished mechanically and/or electrolytically. The following solution is recommended for electrolytic polishing : - 700 ml m
24、ethanol ; - 200 ml butylglycol ; - 60 ml perchloric acid. STD.AECMA PREN 3LLq-L-ENGL L7 m LO123LL OOL3090 O07 I Page 5 prEN 3114-1 : 1997 5 Assessment The prepared surface shall be examined at the same magnification as that of the reference photomicrograph. 6 Description of microstructures 6.1 Acicu
25、lar a A transformation product arising, during cooling, by nucleation and growth on preferred planes of the primary phase, or by martensitic transformation and growth. It appears in acicular form, as pointed lamellae, or plates. 6.2 a enriched zone (Blocky a) A coarse area of a by comparison with th
26、e primary a grain of the matrix. Such a areas are frequently accompanied by grain boundary a. Microhardness is not significantly different from that of the matrix. 6.3 a phase (a) The stable sub- transus a phase with close packed hexagonal crystal structure. 6.4 a + structure Microstructure containi
27、ng a and phases in various forms. 6.5 Zone of higher a stabilized content, significantly harder than the surrounding structure. Normally caused through local oxygen andlor nitrogen enrichment. a stabilized hard zone High Interstitial Defect (HID) 6.6 a stabilized surface (a case) A surface zone enri
28、ched mainly by oxygen or less often by nitrogen or carbon, in which the a phase is stabilized. The a case result from elevated temperature exposure to environments containing these elements. a case is hard, brittle and considered detrimental. 6.7 a stabilizer Element preferentially dissolving in the
29、 a phase, and which increases the a and transus temperatures. 6.8 a stringer In comparison with the fine a + matrix, clearly defined coarse elongated a phase. 6.9 a transus The temperature which determines the boundary between a and a + fields - also known as a/a + transition temperature. 6.1 O Alum
30、inium enriched zone Zones in which an increased amount of a-stabilizing aluminium leads to higher percentage of a-phase compared with the matrix. In comparison with the matrix structure, such areas show relatively little hardness increase, also called soft a. STD-AECMA PREN 3114-1-ENGL 1997 m 101231
31、1 DO13091 T43 m Page 6 prEN 3114-1 : 1997 6.1 1 Banded structure Structure in which the components are orientated in the direction of maximum work in a fibrous plate- like form. 6.12 Basket weave a plates or lamellae with or without phase between them. In this case the a phase is oriented in “groups
32、“ like a woven basket (figure 1). 6.13 eutectoid stabilizer Alloying element which dissolves preferentially in the phase and lowers the transus temperature. The phase may decompose via an eutectoid reaction, into a + intermetallic compound. 6.14 fleck Zones of low or zero primary a in an a + structu
33、re. They have a noticeably lower transus temperature than surrounding structure. 6.1 5 grain size After transformation from the field, grain size can be retained as the macro grain size. With a + working, the shape of the original grains may be changed. 6.16 soluble isomorphous element An element sh
34、owing continuous solubility in the phase. The transus temperature is lowered, without an eutectoid reaction. 6.17 phase C) The stable phase above the transus, having body centered cubic crystal structure. 6.18 stabilizer Element dissolving preferentially in the phase, and which lowers the transus te
35、mperature. 6.19 transus The temperature which specifies the boundary between the a + range and the range, also designated as the a + / transformation temperature. 6.20 Colonies Zones within prior grain boundaries, and having parallel a plates. 6.21 Elongated a a phase in fibrous form, arising primar
36、ily from unidirectional deformation. 6.22 Equiaxed a a with a rounded or polygonal appearance with similar dimensions in all directions. 6.23 Globular a a phase, primarily showing circular shape. STD-AECMA PREN 3114-1-ENGL 1997 20123L1 0013092 98T I Page 7 prEN 3114-1 : 1997 6.24 Grain boundary a Th
37、e M phase appearing at prior grain boundaries. It can encompass the complete prior grain. 6.25 Hydride phase Brittle intermetallic compound of composition TiH,. It can appear when the solubility limit for hydrogen is exceeded. 6.26 Intermetallic compound A compound formed between alloying elements i
38、n an alloy system with at least one field of limited solubility. 6.27 Interstitial element Element of relatively small atomic diameter (e.g. oxygen, nitrogen, carbon, hydrogen) which can occupy sites between the titanium lattice. 6.28 Lamellar a Parallel orientation of elongated phase. 6.29 Lean a a
39、rea See 6.14 fleck. 6.30 Martensitic a A supersaturated a phase, not in equilibrium, arising from diffusionless transformation of the phase (Hexagonal a or orthorhombic a). It is often difficult to distinguish martensitic a from acicular a. 6.31 Matrix Matrix is the uniformly distributed microstruct
40、ural background. The matrix can be single or multiphase. 6.32 Omega phase (o) Omega is an intermediate phase which can arise from transformation of metastable into equilibrium a. It cannot be seen under an optical microscope. In alloys with content or in metastable alloys it can occur at ageing temp
41、eratures and lead to a decrease in formability. 6.33 Primary a M phase arising through recrystallisation or growth following hot forming or annealing in the a + field. 6.34 Plate-like a Coarse a phase which precipitates on preferred planes of the phase during transformation from to a + , frequently
42、in colonies or a Widmannsttten structure. 6.35 “Serrated“ grains Irregular a grains with grain boundaries of a sawtooth nature. STD-AECMA PREN 3L14-2-ENGL 3977 LOL23LL 0033093 BLb D Page 8 prEN 31 14-1 : 1997 6.36 Substitution element An element which by virtue of a similar atomic diameter similar t
43、o titanium, can replace titanium atoms in the lattice. 6.37 Transformed structure This refers to a + structures produced by nucleation and growth via transformation from the phase. Transformation occurs during cooling from temperature above the transus. The transformed structure consists of a platel
44、ets or in multiphased structures, of a platelets with phase between them. 6.38 Widrnannsttten structure A structure of a - or c1 and platelets in a crystallographically orientated geometrical arrangement, arising under particular conditions during cooling from temperatures above the transus (see figure 2). STD-AECMA PREN 3114-1-ENGL 1777 lDL2311 OOL309Li 752 W Page 9 prEN 31 14-1 : 1997 200: 1 Figure 1 : Basket weave 200 : 1 Figure 2 : Widmannsttten structure
