1.2熔池的凝固过程-焊缝横断面结晶模式 centerline equlaxed fusion zone welding dendritic direction weld columnar dendritic pool dendritic pool boundary cellular ccllular planar planar fusion base line <100> <100> <100> metal 50μm base metal Variation in solidification mode Planar-to-cellular and cellular-to- across the fusion zone dendritic transitions in 1100 Al welded with 4047 filler
Variation in solidification mode across the fusion zone Planar-to-cellular and cellular-todendritic transitions in 1100 Al welded with 4047 filler 1. 2 熔池的凝固过程-焊缝横断面结晶模式
1.3晶粒结构 ·熔合线附近的外延生长： ①不填丝情况下的焊接o焊丝成分与母材相当 ②以母材为形核基体不改变晶粒取向 ·熔合线附近的非外延生长： ①填丝情况下的焊接or异种金属的焊接 ②化学成分差异导致晶粒取向发生改变
1. 3 晶粒结构 ▪ 熔合线附近的外延生长: ① 不填丝情况下的焊接or焊丝成分与母材相当 ② 以母材为形核基体不改变晶粒取向 ▪ 熔合线附近的非外延生长: ① 填丝情况下的焊接or异种金属的焊接 ② 化学成分差异导致晶粒取向发生改变
weld metal 外延生长 uoisny Cu 詈 Grain (crystal) base metal (a) GB1 GB2 weld metal m Base Metal Weld Pool GB 1 (substrate) (liquid) base 6u!pleM (b) metal 100μm GB 2 FL resolidified zone Al Epitaxial Stainless Steel Growth 20μm
外延生长 Cu Al Stainless Steel
非外延生长 Weld Metal Equiaxed Region B Base Metal 40m Acc.V Spot Magn Det WD 20m 20.0 kV 4.0 1600x SE 10.0 409-Monel (WF=30ipm Fusion boundary microstructure in 409 ferritic stainless steel (bcc)welded with Monel filler wire (fcc):(a) optical micrograph;(b)scanning electron micrograph
非外延生长 Fusion boundary microstructure in 409 ferritic stainless steel (bcc) welded with Monel filler wire (fcc): (a) optical micrograph; (b) scanning electron micrograph
竞争生长 uoisny 晶粒易长大方向与散热方向 Base Weld 一致时，优先生长 Metal Pool 不一致，生长缓慢 > 取向不利生长，且与散热最快 方向不一致时，停止生长 Competitive Growth Epitaxial Growth Crystal Structure Easy-Growth Direction Examples Face-centered-cubic(fcc) <100> Aluminum alloys, austenitic stainless steels Body-centered-cubic (bcc) <100> Carbon steels,ferritic stainless steels Hexagonal-close-packed (hcp) <1010> Titanium,magnesium Body-centered-tetragonal(bct) <110> Tin
晶粒易长大方向与散热方向 一致时，优先生长 不一致，生长缓慢 取向不利生长，且与散热最快 方向不一致时，停止生长 竞争生长