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Part 4 Writing (15 points)Imagine you are on holiday in your favorite Chinese town or city. Write a postcard to your friend. In your postcard, you have to mention:· the weather· who you are with· what you are doing· what you are eatingHi _____________________________,Greetings from _____________________________! We’re having a _____________________________ holiday here and the weather is _____________________________. We arrived _____________________________ and on our first day we _____________________________.We’ve been _____________________________. And of course, we’ve _____________________________.We’ve been enjoying some _____________________________ is my favorite!See you soon,Li

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碳溶解在γ-Fe中所形成的固溶体是_____。

A. 铁素体
B. 奥氏体
C. 渗碳体
D. 珠光体

渗碳体在钢中是强化相,组织中渗碳体量越多,强度越高。

A. 对
B. 错

纯铁在降温过程中,912℃时发生同素异构转变,由面心立方晶格的γ-Fe转变为体心立方晶格的α-Fe。这种转变也是结晶过程,同样遵循晶核形成和晶核长大的结晶规律。

A. 对
B. 错

金属的晶体结构不同,机械性能也不同,如γ-Fe比α-Fe的塑性好,强度低。

A. 对
B. 错

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