材料成型金属学ch08 金属组织性能控制

• Mg
– – AM 100A AZ80A
Rene' 41 Inconel 700
Sand Castings Extruded products
High Temperature up to 1800F
• Ni
– –
• Fe
–
–
A-286 17-10P
High Strength Stainless
Precipitation Hardening
• • •
Microstructure hardening
2.形变强化 work hardening
• 形变位错受到阻碍 interaction 加工硬化——古老又普遍的现象 理论仍不完善
•
Some applications of physical metallurgy
• Work (dislocation density) hardening
8.3 冲压性能的控制
冷轧深冲板
汽车板：超深冲冷轧板、IF钢电镀锌钢板、IF钢深冲电镀锌钢 板、烘烤硬化钢、汽车摩擦片用钢。 家电用钢：家电用电镀锌、耐指纹板、热镀锌板、彩涂板、彩 电框架用钢、冰箱内板、侧板和面板。
热冲压成形：
高强度汽车钢板的进展－DP外板
Exposed quality dual phase with GI, GA, EG coatings
第二相弥散质点 dispersed second phase particle ⑴位错切过第二相质点. ⑵位错饶过第二相质点 Orowan机制 质点尺寸↑
451º C 340º C
Step 1: Solution-treat at a temperature between 340 to 451º C to form a single-phase a solid solution Step 2: Quench to room temperature fast enough to prevent the precipitate phase from forming Step 3: Age at a temperature below 340º C to from a fine dispersion of phase
80
-140 -120 -100
-80
-60
-40
-20
0
20
40
60
T/℃
脆性转变温度曲线
ຫໍສະໝຸດ Baidu
工业生产Super-SS400钢组织性能分析
(a) 1#20℃
(b) 1#-100℃
(c) 3#20℃
(d) 3#-70℃
(e) 3#-100℃
实验钢冲击断口形貌
影响强韧性能的因素
• 合金成分控制 • 气体、夹杂物 • 晶粒尺寸
– Quenching or rapid
cooling to room temperature to form a nonequilibrium supersaturated solid solution
(to prevent diffusion and the accompanying formation of any second phase)
Microstructure of Copper-Beryllium before and after Precipitation Hardening
(x 750)
(a) Solution heattreated
(b) Precipitation hardened
8.2 强韧性能的控制
• 强韧性 strength and toughness 金属的韧性与韧化. • 强度指标：屈服极限、抗拉强度 yield strength tensile strength • 韧性指标：冲击韧性、 脆性转变温度. 材料承受载荷时在破坏前单位横截面吸 收的变形功。
晶粒尺寸 d↓ ↑ DBTT↓ ductile brittle traction T 晶界↑－ 位错塞积在晶界处引起的应力集中程 度小/分散 － 脆性↓
晶粒细化 同时提高强韧性的唯一方式
形变热处理
• 提高铝合金的韧性 －脱溶沉淀
根据相变与形变发生的顺序，调整热处理工艺：
1 加工始态－是固溶还是时效，决定了是相变 前还是相变后进行形变； 2 加工温度－形变过程是否伴随相变； 3 加工后时效－形变后相变。
Limitation: only being produced by drawing wire to a reduction in area of over 90%fine wires 细丝
Description
UTS Range (MPa)
Piano wire 1790~2400 Mandolin wire 2000~2760 Wire cables 2210 Galvanized suspension cable wire 1380~1590 Mechanical spring wires 2960
冲压性
冲压变形过程中不产生裂纹等缺陷的变形极限。
条件：板料沿厚度方向的强度>沿板面方向的强度 板料沿厚度方向不易变形，沿板面方向容易变形。
改善冲压性能
冲压性能的测定
• 1）模拟法 杯突法 压入的深度值－杯突值
杯突值
冲压性能？
2）拉伸试验法 －屈强比
－加工硬化系数
Q：1.屈强比与加工硬化指数？
• Precipitation Hardening is a thermodynamic reaction that involves creation of a new phase change
– Precipitation Heat Treatment:
• precipitates form on grain boundaries • lower fracture toughness compared to strain hardening
Hardness of Steel vs. Interstitial Carbon Content
金属的拉拔－高强度金属丝
high – strength steel wire (p69)
• The strongest known metal (disregarding whisker filament) is drawn pearlitic wire. Not only with extremely high strength , but also with an amazing ductility at this strength level. 珠光体钢丝－超高强度、高塑性
加工硬化
位错密度与应力的关系
0 k 1/ 2 : flow stress : measured dislocation density
=> 加工硬化与位错有直接关系
0 k 1/ 2
k = b
Stress
0
½ -cm
3.固溶强化 solid solution hardening
• Al
– 2014 – 2024 – 7075 Forged Aircraft Fittings, Al Structures High strength forgings, Rivets Aircraft Structures, Olympic Bikes
• Cu
Beryllium Bronze: Surgical Instruments, Non sparking tools, Gears
Patenting 铅浴
Patenting
奥氏体化－ 淬火（熔融 铅池）－空 冷－拉拔
The purpose of heat treatment: to achieve the finest possible pearlite spacing prior to drawing
4.弥散强化
Particle hardening
– at this temperature

diffusion rates become appreciable
– The precipitates of the
second phase form as finely dispersed particles. (aging)
Typical Precipitation Hardened Alloys
500 DP GA
0.6 mm 600 DP GI, EG
Ferrite-martensite DP600 GI
成形效果的比较
• TRIP(transformation induced plasticity) • +B+ R retained austenite
4.5 4 3.5 3
32
德国采用薄规格镀锡板生产易拉罐
Precipitation hardening is accomplished by two different heat treatments
1. Solution heat treatment
– During solution heat
treatment all solute atoms are dissolved to form a single-phase solid solution
冲击试验：摆锤法
脆性转变温度
• 以冲击试样断口上开始出现脆性特征或断 口上出现50％脆断面积时的温度； • 冲击值为完全韧性断裂于完全脆性断裂试 样冲击值的平均值时的温度。
工业生产Super-SS400钢组织性能分析
40
30
20
Ak/J
1#带钢 3#带钢
10
0
1号和3号带钢的脆 性转变温度（Tk） 分别为： -37.2℃，-70.8℃。
Grain Boundaries
Microstructure of A 7150-T651 Aluminum Alloy after Precipitation Hardening
Fig. 11.24 A transmission electron micrograph showing the microstructure of a 7150-T651 aluminum alloy (6.2Zn-2.3Cu-2.3Mg0.12Zr-balanced Al) that has been precipitation hardened. The light matrix phase is an Al solid solution.
Chap.8 金属组织性能控制 (1) 8.1 金属的强化机制 strengthening mechanism
1.晶界强化 microstructure hardening
• 原子排列的正常结构遭到破坏/大量晶格缺陷 /第二相 夹杂物 晶界能 晶界两侧晶粒取向不同,滑移难以连续进行. 易滑移/难滑移 ——需满足变形连续性. 单晶体晶粒 克服晶格阻力 杂质原子对位错阻力 多晶体晶粒 克服晶界阻力
Precipitation hardening is accomplished by two different heat treatments
2. Precipitation heat
treatment (aging)
– The supersaturated
solid solution is heated to an intermediate temperature within the two-phase region
2.n~冲压性能？
•加工硬化系数 材料不容易出现细颈 杯突性能 冲压性能
塑性变形比R
B0 B0 ln ln b B1 B1 R h ln H ln B1 L1 h B0 L0
28 22
35 30 25 20 15 10 5 0
万吨
2.5 2 1.5 1 0.5 0 1983 0.3 1993 0.26 镀锡板厚度，mm 生产一亿个易拉罐所耗镀锡板数量 每个罐重量 2003 0.2
g
深冲 deep drawing
板料 中心部位
受冲头的作用产生拉延
外缘部位
受冲模的作用产生模压
固溶体强度>基体金属 固溶体 solution
溶质 溶剂 固溶度 solubility
有限互溶 /完全互溶
solute solvent
• ⑵流变应力～溶质浓度 • 稀固溶体 理论
– 位错钉扎 pinning effect
• 摩擦机制 不动的溶质原子应力 场，—↑位错运动阻力.
固溶强化
Solid-solution hardening