Effect of Pre-forming Process of Tailor Rolled Blank on Al-Si Coating

doi:10.12068/j.issn.1005-3026.2025.20240044

Abstract

Abstract:

Indirect hot forming process needs to preform raw materials before hot stamping. Tailor rolled blanks （TRBs）have different work hardening degrees after variable thickness rolling， so annealing treatment is needed before preforming. The preforming process of Al-Si coated TRB was studied. The results show that the elongation increases to 16.0%~26.2% after annealing at 600~620 ℃. The total thickness of the coating has little change， and its structure changes from the three-layer structure consisting of Al base， alloy diffusion layer and Fe₂Al₅+FeAl₃ （from outer to inner） into a four-layer structure comprising τ₅-Fe₂SiAl₇， thin band structure containing τ₁-Fe₃Al₂Si₃， η-Fe₂Al₅， and alloy compound with a layer of 1~2 μm between η-Fe₂Al₅ and substrate. With increasing annealing temperature， the ribbon region containing τ₁-Fe₃Al₂Si₃ changes from τ₁-Fe₃Al₂Si₃+τ₂-FeAl₃Si+θ-FeAl₃ to τ₁-Fe₃Al₂Si₃+θ-FeAl₃+η-Fe₂Al₅， and with increasing annealing time， the region changes from τ₁-Fe₃Al₂Si₃+τ₂-FeAl₃Si+θ-FeAl₃ to τ₁-Fe₃Al₂Si₃+θ-FeAl₃+η-Fe₂Al₅. The layered structures of the coatings with 10% and 30% reduction ratios are the same， τ₅-Fe₂SiAl₇， τ₁-Fe₃Al₂Si₃+τ₂-FeAl₃Si+θ-FeAl₃ and η-Fe₂Al₅ from outer to inner. When the reduction ratio is 50%， the layered structure consists of τ₅-Fe₂SiAl₇， τ₁-Fe₃Al₂Si₃+τ₂-FeAl₃Si+η-Fe₂Al₅ and η-Fe₂Al₅ from outer to inner.

Key words: tailor rolled blank（TRB）, pre-forming, Al-Si coating, annealing, mechanical property

CLC Number:

TF 046

Xian-lei HU, Peng HAN, Qin-cheng XIE, Ying ZHI. Effect of Pre-forming Process of Tailor Rolled Blank on Al-Si Coating[J]. Journal of Northeastern University(Natural Science), 2025, 46(9): 65-72.

Figures/Tables 13

Table 1 Chemical composition of 22MnB5 steel(mass fraction)

C	Si	Mn	P	S	Ti	Cr	V	B	Fe
0.214	0.226	1.142	0.011	0.002	0.039	0.173	0.003	0.003	余量

Fig.1 Experimental process path

Fig.2 Dimensions of tensile specimens

Fig.3 Morphology of Al-Si coating with different reduction ratios

Fig.4 Tensile properties with different reduction ratios

Fig.5 SEM, element line scan and surface scan of Al-Si coating

Table 2 Element content and phases of annealed Al-Si coating (atomic fraction)

检测点	Al	Si	Fe	物相
A₁	66.80	10.50	22.71	τ₅-Fe₂SiAl₇
A₂	48.80	18.26	32.94	τ₁-Fe₃Al₂Si₃+τ₂-FeAl₃Si+θ-FeAl₃
A₃	71.57	0.75	27.69	η-Fe₂Al₅
B₁	62.94	8.02	29.04	τ₅-Fe₂SiAl₇
B₂	50.55	21.83	27.62	τ₁-Fe₃Al₂Si₃+τ₂-FeAl₃Si+η-Fe₂Al₅
B₃	68.81	1.82	29.37	η-Fe₂Al₅

Fig.6 SEM, element line scan and surface scan of Al-Si coating

Table 3 Element content and phases of annealed Al-Si coating(atomic fraction)

检测点	Al	Si	Fe	物相
C₁	68.29	9.30	22.41	τ₅-Fe₂SiAl₇
C₂	61.62	18.56	19.82	τ₁-Fe₃Al₂Si₃+τ₂-FeAl₃Si+θ-FeAl₃
C₃	72.40	0.77	26.83	θ-FeAl₃
C₄	68.85	1.71	29.44	η-Fe₂Al₅
D₁	71.97	5.49	22.54	η-Fe₂Al₅
D₂	41.54	24.09	34.36	τ₁-Fe₃Al₂Si₃+θ-FeAl₃+η-Fe₂Al₅
D₃	69.46	1.49	29.05	η-Fe₂Al₅

Fig.7 SEM, element line scan and surface scan of Al-Si coating

Table 4 Element content and phases of annealed Al-Si coating（atomic fraction）

检测点	Al	Si	Fe	物相
E₁	69.60	9.79	20.61	τ₅-Fe₂SiAl₇
E₂	55.48	13.17	31.35	τ₁-Fe₃Al₂Si₃+τ₂-FeAl₃Si+θ-FeAl₃
E₃	70.73	1.36	27.91	η-Fe₂Al₅
F₁	65.35	10.28	24.37	τ₅-Fe₂SiAl₇
F₂	56.41	21.46	22.13	τ₁-Fe₃Al₂Si₃+τ₂-FeAl₃Si+η-Fe₂Al₅
F₃	69.69	1.09	29.22	η-Fe₂Al₅

Fig.8 XRD results

Table 5 Tensile properties of different annealing

工艺参数	$抗拉强度 M P a$	$屈服强度 M P a$	$延伸率 %$
10%-600 ℃-2 h	590	512	22.1
30%-600 ℃-1 h	615	528	15.3
30%-600 ℃-2 h	601	505	16.4
30%-620 ℃-2 h	587	490	17.8
30%-600 ℃-4 h	568	446	18.2
50%-600 ℃-2 h	474	348	26.2

Table 5 Tensile properties of different annealing

工艺参数	$抗拉强度 M P a$	$屈服强度 M P a$	$延伸率 %$
10%-600 ℃-2 h	590	512	22.1
30%-600 ℃-1 h	615	528	15.3
30%-600 ℃-2 h	601	505	16.4
30%-620 ℃-2 h	587	490	17.8
30%-600 ℃-4 h	568	446	18.2
50%-600 ℃-2 h	474	348	26.2

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