std::mutex not locking properly for std::cout

I'm learning about multithreading in C++11 and I tried this simple test but the output is not what I expected.

#include <thread>
#include <iostream>
#include <mutex>

int main() {
    auto function = [](int x) {
        std::mutex m;
        m.try_lock();
        std::cout << "Hello" << x << std::endl;
        m.unlock();
        return;
    };
    std::thread t1(function , 1);
    std::thread t2(function, 2);
    std::thread t3(function, 3);
    std::thread t4(function, 4);    

    t1.join();
    t2.join();
    t3.join();
    t4.join();

    std::cin.get();
    return 0;
}

I expected the output to be:

Hello1
Hello2
Hello3
Hello4

(maybe not in that order but each hello and number in a separate line)

Instead I got something like this:

HelloHello21
Hello3
Hello4

Or

HelloHello2
1
Hello3
Hello4

What puzzles besides the mutex aparently not locking properly is that it's always the Hello1 the one that gets cut in half.

EDIT: done in VS2015 if it makes any difference (should not because it's all standard?)