Abstract: The discharge capacity of Ti0.8Zr0.2Mn0.5V0.5Ni1.0 alloy was greatly improved by rapid-quenching, and its peak value can be achieved at certain rapid rate. The microstructure of as-quenching alloy was observed by XRD, SEM and TEM. The results show that: 1) the dendritic crystal will be finer with increasing rapid rate; 2) small quantity of amorphous appears only at the quench rate of 32m/s, the main of alloy still consists of microcrystallite and nanocrystal; 3) both of as-cast alloy and low rate as-quenching alloy are polyphase structure(larger quantity of C14, a little of TiNi), and C15 phase appears under the rate above 8m/s, and more content of C14+C15 phases greatly improves the discharge capacity. With the quenching rate changing, the relative content of each phase is changed, so the relationship between the content of C14+C15 and the rapid quenching rate is not simply lineal.
Discharge capacity and microstructure of cast and quenching Ti-based hydrogen-storage alloy
Abstract:
The discharge capacity of Ti 0.8Zr 0.2Mn 0.5V 0.5Ni 1.0 alloy was greatly improved by rapid-quenching, and its peak value can be achieved at certain rapid rate. The microstructure of as-quenching alloy was observed by XRD, SEM and TEM. The results show that: 1) the dendritic crystal will be finer with increasing rapid rate; 2) small quantity of amorphous appears only at the quench rate of 32 m/s, the main of alloy still consists of microcrystallite and nanocrystal; 3) both of as-cast alloy and low rate as-quenching alloy are polyphase structure (larger quantity of C14, a little of TiNi) , and C15 phase appears under the rate above 8 m/s, and more content of C14+C15 phases greatly improves the discharge capacity. With the quenching rate changing, the relative content of each phase is changed, so the relationship between the content of C14+C15 and the rapid quenching rate is not simply lineal.
Table1 Components of as-cast alloy: main phase and second-phase (%)
Point in Fig.2
Ti
Zr
V
Mn
Ni
Si
Phase
1
27.04
8.67
15.12
27.01
21.24
0.91
TiMn2
2
27.15
9.88
15.73
25.47
20.02
1.75
TiMn2
3
31.48
9.16
6.87
11.56
40.93
—
TiNi
4
25.115
7.128
15.740
25.613
23.369
3.036
TiMn2
5
37.381
4.903
5.726
11.331
40.694
—
TiNi
图2 铸态和快淬态贮氢合金的SEM形貌
Fig.2 SEM images of as-cast alloy and as-quenched alloy (a) —Cross section of as-cast alloy; (b) —Longitudinal section of as-cast alloy; (c) , (d) —Cross sections of 2 m/s, 8 m/s solidification rate.